Next Article in Journal
α-L-Arabinofuranosidases of Glycoside Hydrolase Families 43, 51 and 62: Differences in Enzyme Substrate and Positional Specificity between and within the GH Families
Previous Article in Journal
Facile Synthesis of Ni(OH)2 through Low-Temperature N-Doping for Efficient Hydrogen Evolution
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Catalysts
Volume 14
Issue 8
10.3390/catal14080535
catalysts-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst

by
Ju Gao
1,
Fucheng Sun
2,
Pei Liu
3,
Jizhi Zhou
1,* and
Yufeng Zhang
1,*
1
School of Environmental Science and Engineering, Nanjing Tech University, Nanjing 211816, China
2
Key Laboratory of Environmental Pollution Control Technology of Zhejiang Province, Zhejiang Environmental Science & Design Institute, 109 Tianmushan Rd., Hangzhou 310000, China
3
Shanghai Solid Waste Disposal Co., Ltd., 2491 Jiazhugong Rd., Shanghai 201807, China
*
Authors to whom correspondence should be addressed.
Catalysts 2024, 14(8), 535; https://doi.org/10.3390/catal14080535 (registering DOI)
Submission received: 4 July 2024 / Revised: 14 August 2024 / Accepted: 15 August 2024 / Published: 17 August 2024
(This article belongs to the Special Issue Homogeneous and Heterogeneous Catalytic Oxidation and Reduction)
Browse Figures
Versions Notes

Abstract

:
Catalysts for the selective catalytic reduction (NOX SCR) of nitrogen oxides can be obtained from sludge in industrial waste treatment, and, due to the complex composition of sludge, NOX SCR shows various SCR efficiencies. In the current work, an SCR catalyst developed from the sludge produced with Fe/C micro-electrolysis Fenton technology (MEF) in wastewater treatment was investigated, taking into account various sludge compositions, Fe/C ratios, and contaminant contents. It was found that, at about 300 °C, the NOX removal rate could reach 100% and there was a wide decomposition temperature zone. The effect of individual components of electroplating sludge, i.e., P, Fe and Ni, on NOX degradation performance of the obtained solids was investigated. It was found that the best effect was achieved when the Fe/P was 8/3 wt%, and variations in the Ni content had a limited effect on the NOX degradation performance. When the Fe/C was 1:2 and the Fe/C/P was 1:2:0.4, the electroplating sludge formed after treatment with Fe/C MEF provided the best NOX removal rate at 100%. Moreover, the characterization results show that the activated carbon was also involved in the catalytic reduction degradation of NOX. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P effectively reduces the catalytic reaction temperature, and the formation of phosphate promotes the generation of adsorbed oxygen, which in turn contributes to improvements in catalytic efficiency. Therefore, our work suggests that controlling the composition in the sludge is an efficient way to modulate SCR catalysis, providing a bridge from contaminant-bearing waste to efficient catalyst.

1. Introduction

Electroplating is widely used for the surface treatment of metals and plastics [1]. However, the electroplating industry produces a large amount of wastewater containing heavy metals (Ni, Cu, Cr, etc.) during the pretreatment or washing process [2]. If these components are not effectively treated, they will form some metal–organic complexes that are toxic and harmful to the environment [3]. Electroplating sludge (ES) is the sediment produced by the treatment of electroplating wastewater [4]. It has been reported that approximately 10 million tons of electroplating sludge is generated annually in China, with about 1.3 million and 150,000 tons generated in the USA and Europe, respectively [5,6]. As the various transition metals in electroplating sludge are also valuable elements, the handling of electroplating sludge has gradually evolved from simple landfill and coagulation treatment to the recovery of valuable metals from the sludge [7,8]. Therefore, the safety and recyclability of electroplating sludge have become current research hotpots. In addition, as a heavy metal sludge rich in iron, electroplating sludge is expected to be used in the construction of a new catalytic system.
Selective catalytic reduction (SCR) is the predominant catalytic method in industry, owing to its high applicability and broad compatibility [9,10]. The essence of this catalytic technology lies in the use of efficient and durable catalysts [11]. The majority of SCR catalysts possess an acidic surface, meaning that ammonia, as an alkali, is a strong adsorptive reducing agent. The adsorbed ammonia reacts with nitrogen oxides to form nitrogen [12,13,14,15]. To enhance the reaction efficiency, the iron-based material with carbon is commonly used as the catalyst carrier, which is due to its good thermal stability at medium to high temperatures, enhancing the low-temperature sulfur resistance and water resistance of catalysts [16,17,18]. Therefore, iron-based catalysts with carbon have been developed from waste sludge, which exhibit superior redox capabilities and acid sites, providing more surface active sites than conventional materials and enabling faster molecular transit through the pores [19].
Yu et al. [20] prepared an iron-based catalyst for SCR using iron from Fenton sludge (FS) and treated this sludge using acid leaching. Their research highlighted the role of oxygen-containing functional groups (-COOH, ·OH, etc.) present in Fenton sludge, which significantly improved the catalytic efficiency for NOX removal. Moreover, increasing the surface acidity of the catalyst can promote the adsorption of NH3, and the increased electronegativity of Fe3+ improves the activity and migration rate of Fe3+. Additionally, a study has demonstrated that catalysts prepared with activated carbon loaded with relevant heavy metals have good catalytic activity for NOX, and that they can achieve the catalytic degradation of NOX pollution gas at 300 °C [21]. Xu et al. [22] introduced active components into the catalyst materials, and the obtained carbon-based catalyst materials achieved a catalytic efficiency of more than 77% for 600 ppm of NO in the temperature range of 250–400 °C. Thus, these catalysts derived from micro-electrolytic sludge can potentially serve as low-cost and high-performance SCR catalysts.
However, the composition of sludge is very complex, which causes the efficiency of NOX degradation to vary. Electroplating sludge generally contains a variety of transition metal ions [23,24]. For example, as a byproduct of treating electroplating wastewater using Fe/C micro-electrolysis Fenton technology, this sludge contains Fe, Cu, Ni, Zn, and other elements. These elements can be synthesized into crystalline spinels, such as FeCr2O4, CuCr2O4, NiCr2O4, and ZnCr2O4, resulting in highly selective catalysts [25]. Furthermore, it has been demonstrated that adding the element P can further enhance the catalytic performance. For instance, Wang et al. [26] have revealed that the addition of phosphate promotes the low-temperature SCR induced by Cu/SAPO-34 catalysts. The introduction of P to the reaction induced more metal complexes and inhibited the adsorption of SO2 on the surface of the catalyst, thereby preventing the interaction of SO2 with active Cu2+ sites. Therefore, it is necessary to investigate the complex effect of the sludge composition in the SCR process.
Recent studies have shown that Fe/C micro-electrolysis Fenton technology (MEF) can also be used for treating organic wastewater containing heavy metals. The use of MEF in wastewater treatment often produces a large amount of sludge. The main components of these sludges usually include Fe, P, S, and other ions [27,28]. The sludge is commonly treated as electroplating sludge [4]. The utilization of MEF sludge for SCR catalyst has become a current research hotspot, which provide insights into how the complex composition of the solid-waste-derived catalyst contributes to NOX degradation.
NOX catalyst should include, among others, the following beneficial properties: (i) good NOX catalytic activity and N2 selectivity at temperatures of 100–300 °C [29]; (ii) good resistance to sulfur poisoning; (iii) good anti-water poisoning performance [30]; and (iv) good alkali resistance for metals, heavy metal poisoning. Alkali metals and heavy metals are prone to causing catalyst agglomeration, pore clogging, or the direct destruction of surface active sites, which in turn impair the catalyst’s redox performance and acidic sites. Future work on the mechanism of sulfur and water resistance would be worthwhile [31,32].
Therefore, this study explored the feasibility and effectiveness of re-engineering electroplating sludge into a NOX SCR catalyst through Fe/C micro-electrolysis Fenton technology. A bridge was established from sludge to a NOX SCR catalyst by introducing Fe/P content. Through simulation experiments, the preparation pathway for electroplating sludge-derived catalysts was identified by adjusting the concentration of electroplating wastewater, as well as the proportion of external components. Our work demonstrated the high efficiency of electroplated sludge-derived catalysts for NOX removal in NH3 SCR systems.

2. Results and Discussion

2.1. Effect of Fe/C Micro-Electrolysis Fenton Technology for Wastewater Removal

The application of Fe/C micro-electrolytic Fenton technology efficacy in the removal of total phosphorus (TP) and nickel (Ni) from Ni-plated wastewater has been evaluated by our research team [33]. As illustrated in Figure 1, the concentrations of TP and Ni exhibited a gradual reduction as the reaction time increased. Notably, the TP and Ni removal efficiencies were 100 and 78%, respectively, after 180 min of reaction. A subsequent rise in the solution’s pH and an increase in the Fe2+ corresponded with a decrease in TP and Ni concentrations. The integration of carbon into the reaction system stimulated electron transfer and accelerated the formation of Fe2+ during the Fe/C + H2O2 process, thereby improving the oxidation removal efficiency [34]. Moreover, the introduction of H2O2 led to the degradation of the Ni–EDTA structure due to ·OH oxidation, which then released Ni2+, facilitating its removal in the Fe/C + H2O2 system [35]. These free metal ions (Ni2+) are easily adsorbed and removed during Fe/C + H2O2.
The mechanism underpinning the removal of TP and Ni primarily involves adsorption, oxidation, and precipitation processes, as delineated by Equations (1)–(3) [36,37]. The Fe/C micro-electrolysis system generates Fe2+, which then reacts with H2O2 to form ·OH. At the same time, Fe2+ is oxidized to Fe3+ by H2O2. The hypophosphite in the system is oxidized into phosphate by ·OH, and the structure of Ni–EDTA is also oxidized by ·OH to form Ni2+. Finally, the Fe3+ generated in the system generates FePO4 due to the reaction with phosphate, so that the total phosphorus in the wastewater can be removed. The Ni2+ generated is mainly removed through adsorption and precipitation mechanisms.
H2PO2− +·OH→HPO2−→HPO2−→H2PO3−→H2PO4−
Ni–EDTA +·OH→Ni2+
PO43− + Fe3+→FePO4↓

2.2. Analysis of Components in Sludge

Figure S1 shows the XPS spectra of the composites precipitation, and the results indicate that the composites contain elements of P and Ni. Figure S1a shows that the P 2p XPS spectrum of two intense peaks centered at 133.00 and 133.74 eV correspond respectively to the P 2P3/2 and P 2p1/2 signals of POX [38]. Combined with XRD results, this also proves that the P in the precipitate is mainly in the form of PO43− [39]. The spectrum of Ni 2p was shown in Figure S1b, the Ni 2p spectrum of precipitates exhibits two well-defined peaks at 865.17 and 873.84 eV, corresponding respectively to the Ni 2p3/2 and Ni 2p1/2 of Ni2+, and accompanied by two respective satellite peaks at 861.90 and 879.60 eV [40]. In this work, sensible Fe 2p spectra could not be obtained with our X-ray source, due to the Ni LMM auger signal.

2.3. Comparison of SCR Catalytic Performance of Sludge with Different Compositions

Figure 2 shows the NOX catalytic degradation rates achieved utilizing electroplating sludge with different compositions. An increase in reaction temperature enhanced the catalytic degradation rate of the sludge composed of four varying ingredients. The compositions in terms of NOX removal rates were, in descending order, Fe/Ni/P/C, Fe/Ni/P, Fe/Ni, and Fe. When the sludge contained only Fe, the NOX removal rate increased from 9.33 to 35.04% as the temperature increased from 100 to 400 °C. When the ingredients of the sludge were Fe and Ni, there was no significant increase in NOX removal rate, and the NOX degradation efficiency was 12.07 and 44.29% at 100 and 400 °C, respectively. This indicates that the addition of Ni had little effect in terms of improving the catalyst’s activity and therefore had little effect on the NOX removal rate. These results are consistent with other reports [41].
On the other hand, the introduction of P into the sludge prompted, along with a temperature increase from 100 to 400 °C, an increase of NOX removal rate from 48.02 to 76.36%. This indicates that the catalytic activity was markedly improved by the addition of P. Phosphorus can also slow down the carbon build-up behavior on the surface of Ni-based catalysts by modulating the catalyst surface’s acidity [42]. This may be attributed to the fact that the P in electroplating sludge mainly occurs in the form of phosphate, which possesses excellent thermal stability, proton conductivity, ion exchange, and acidity, thereby accelerating the transfer of surface oxygen and the regeneration of active sites. Thus, it is conducive to NH3 activation and promotes the activity of NOX SCR [43]. When the sludge contained Fe, Ni, P, and C, the NOX removal rate was 67.42% at 100 °C. When the temperature rose to 300 °C, the NOX removal efficiency reached 98.65%. This indicates that the addition of carbon could potentially enhance the catalytic activity of the sludge as well as the activity of the catalyst at low temperatures. Xie et al. [44] believe that there is no direct link between the specific surface area of activated carbon and the denitrification performance of the NH3 SCR reaction. NOX adsorption is the first step in the SCR reaction, so the pore structure of the activated carbon may have an effect on the NH3 SCR reaction. In many catalytic areas, compared with microporous activated carbons, activated carbons with rich micro- and macroporous structures exhibit superior catalytic performance [45,46]. This can be attributed to the fact that micropores provide active sites, while mesopores and macropores reduce the diffusion resistance and increase the diffusion rates. Therefore, the effect of pore structure on the oxidation performance of NO is also worth investigating. As a result, the processed electroplating sludge composed of Fe/Ni/P/C has a high NOX degradation efficiency.

2.4. Comparison of SCR Catalytic Performance with Different Composition Ratios

2.4.1. Effect of P on SCR Catalytic Performance

As shown in Figure 3a, the concentration of P had a significant influence on the NOX degradation efficiency. For instance, when the temperature reached 400 °C, the NOX degradation rate was more than 95% at all P levels. When the P content was 3 wt% and the temperature was 300 °C, the NOX degradation rate could reach more than 95%, while, when the P content continued to increase to 4 wt%, the NOX degradation rate started to decrease at certain temperatures. Therefore, the best NOX degradation efficiency was achieved when the P content was 3 wt%. This may be due to the addition of P leading to the generation of adsorbed oxygen, the transfer of surface oxygen, and the acceleration of the regeneration of the active site [43].

2.4.2. Effect of Ni on SCR Catalytic Performance

The effect of the Ni composition on SCR catalytic performance is shown in Figure 3b, illustrating that variations in Ni content had almost no effect on the NOX removal efficiency regardless of the percentage of Ni when it ranged from 1 to 5 wt%. This was probably due to the low percentage of Ni2+ in Fe-dominated catalysts, which had less impact on the overall catalytic reaction. Zhao et al. [47] have revealed that the incorporation of Ni weakened the adsorption of NO in the Ni0.2Fe0.8/TiO2 framework. Combined with the NO TPD results, this study showed that the reduction of Fe also weakened the adsorption of NO. Therefore, it can be inferred that Fe is the adsorption site for NO, explaining why there was no significant change in the removal of NOX with an increasing content of Ni in this work.

2.4.3. Effect of Fe on SCR Catalytic Performance

As shown in Figure 3c, the activity of the catalyst increased slightly with an increase in iron content. When the iron content achieved 8 wt%, at 400 °C, the NOX degradation efficiency could reach 99.9%. Conversely, an increment of iron content to 10 wt% slightly decremented the NOX decomposition efficacy, presumably due to the agglomeration phenomena induced by the excessive iron content on the catalyst’s surface, thereby detrimentally impacting catalyst activity [48]. Yang et al. [49], in their study of the effects of Fe2O3 on the NH3 SCR-promoting activity of MoTiOX catalysts, showed that the presence of ferric oxide species increased the surface oxygen activity, thereby enhancing the SCR performance at lower temperatures. Moreover, Fe2O3 provided rich acid sites. Jin et al. [50] investigated the effects of different tungsten additions on the NH3 SCR activities of iron-based catalysts at medium-to-low temperatures. The XRD, SEM, and BET results indicate that defect sites and heterophase interfaces can significantly increase Fe2O3 and WO3 dispersion, consequently boosting the catalyst’s specific surface area and pore volume.

2.5. Effects of Iron-to-Carbon Ratio and Ni Plating Effluent Concentration on SCR Catalytic Performance

2.5.1. Effect of Different Fe/C Ratios on SCR Catalytic Performance

Both iron and carbon are important to micro-electrolytic systems, with Fe serving as the anodic material. When carbon was added to the wastewater in contact with iron, it resulted in the formation of a large number of microscopic primary cells, which catalyzed the degradation of NOX. This study investigated the effect of various Fe/C ratios (3:1, 2:1, 1:1, 1:2, and 1:3) on the catalytic degradation of NOX. Our findings indicate that, under conditions where the P content in the wastewater was roughly 2500 ppm, the catalyst exhibited the highest rate of NOX decomposition at an Fe/C ratio of 1:2, achieving full decomposition at 400 °C (Table 1a and Figure 4a). The content of Fe in the plating sludge was 16.2%, while the content of P was 7.5% at 400 °C. When the Fe/C ratio was adjusted to 1:3, the NOX catalytic degradation efficiency decreased. This may have been due to the low level of C in the Fe/C micro-electrolysis system, which impaired the progress of the cell reaction. When the Fe/C ratios were 1:1, 2:1, and 3:1, the primary cells were saturated and the excess iron ions accumulated in the primary cells led to the depletion of ·OH in the system, thus making the catalytic degradation of NOX inefficient [51]. Therefore, the sludge product formed had the highest NOX degradation efficiency at an Fe/C ratio of 1:2.

2.5.2. Effect of Pollutant Concentration on the Catalytic Performance of SCR

Table 1b and Figure 4b show that, with an increase in P concentration in pollutants, the amount of P in the product gradually increased and the amount of Fe gradually decreased. When the P concentration reached 2000 ppm in the pollutant, the highest NOX degradation efficiency was achieved, with 100% degradation. At this P concentration, the Fe content of the electroplated sludge was 15.6% and the P content was 6.2%. It is important to note that extremely high or low concentrations of P can negatively affect the catalytic efficiency of NOX. This can be explained by the fact that, when the Fe content/P content is close to 8/3 wt%, the product has a large specific surface area, which is good for the degradation of NOX. Thus, when the Fe/C ratio was 2:1 and the P concentration in the Ni-plated wastewater was 2000 ppm, the product formed after treatment with Fe/C micro-electrolysis Fenton technology was most favorable for NOX degradation.

2.6. Microstructural Transformation of Sludge Catalyst

The changes in gas-phase components before and after reaction are shown in Table 2a. The decrease in carbonaceous content within the sludge suggests that carbon components participated in the reduction and decomposition of NO, which is similar to the role of the reducing agent in the general catalytic decomposition process of NO. As listed in Table 2a, NO was completely removed except at 300 °C, which could be attributed to an excessively high gas hourly space velocity. The predominant gaseous products were N2 and CO2, with trace amounts of N2O (only at 300 °C) and CO.
To elucidate the influences of Fe, Ni, and P on the morphology of catalysts, SEM analysis was performed on Fe8/P4/Ni/C and Fe10/P5/Ni/C catalysts. The SEM results reveal that the surface size of the Fe8/P4/Ni/C catalyst particles was uniform with an excellent particle dispersion, as depicted in Figure 5a,b. In comparison, the Fe10/P5/Ni/C sample exhibited an irregular surface particle size (Figure 5c), large particle size, and visible surface reunification (Figure 5d), indicating that the excessive loading of Fe/P led to a reduction in the specific surface area of the catalyst.
The XRD spectra of the crystal phase structure of Fe8/P4/Ni/C samples before and after the catalytic reaction are shown in Figure S2a. The visible diffraction peaks at 2θ of 12.4°, 22.3°, 25.4° and 26.2° correspond to FePO4 patterns of (101), (200), (012), and (210) respectively, in accordance with the standard (JCPDS: No. 84-0876). The visible diffraction peaks at 2θ of 35.2°, 42.7°, 58.1° and 62.7° correspond to Fe2O3 patterns of (311), (511), (400) and (440), respectively, in accordance with the standard (JCPDS: No. 47-1409). However, after a prolonged reaction, the FePO4 phase in the catalyst weakened and the strongest peak gradually changed to Fe3O4. This was reflected by the visible diffraction peaks of Fe3O4 (JCPDS: No. 89-0688) at 2θ of 27.3°, 44.1°, 63.3° and 65.8°, which correspond to (220), (511), (322) and (533), respectively. This indicates a significant reduction of the iron valence state in the catalyst after the reaction. This phenomenon could be interpreted as FePO4 exhibiting good redox properties, which enables it to have a potent oxygen enrichment effect, consequently elevating the redox potential of the catalyst surface and ultimately improving the catalytic degradation of NOX [52].
As can be seen from Table 2b, the specific surface areas of the products with different P and iron contents, in descending order, were Fe/Ni/C, Fe6/P4/Ni/C, Fe6/P3/Ni/C, Fe8/P4/Ni/C, Fe10/P4/Ni/C, and Fe6/P5/Ni/C. Upon the introduction of P, the specific surface area of the FeX/PX/Ni/C system began to gradually decrease. This was probably because of the formation of phosphates on the catalyst’s surface, subsequently leading to the blockage of pore channels, which in turn led to a decrease in specific surface area. When the P content reached 4 wt%, with an increase in Fe content, the total pore volume and average pore diameter of the sample gradually increased, while the specific surface area gradually decreased. Combined with the SEM results, the particle distribution on the sample surface appeared non-uniform, and agglomeration occurred, which can be attributed to a decrease in specific surface area and an increase in pore volume and pore diameter. As demonstrated by the assessment of catalyst activities, the addition of certain elements, such as P and iron, to the catalyst was not directly linked to improvements in the surface properties of the catalyst. Upon combining the physical adsorption and desorption curves with the pore size distribution curves of the Fe8/P4/Ni/C sample N2 in Figure S2b, it is observed that the catalytic reaction is well aligned with a type IV isothermal adsorption and desorption curve [53]. The pore size distribution of the catalysts is mainly in the range of 2–50 nm, so the electroplated sludge-derived catalysts can be categorized as mesoporous materials.

2.7. Mechanism Discussion

TPD was used to investigate the types of adsorption centers on the catalyst surface. Figure 6a shows the distribution of acidic sites on the surface of Fe, Fe/Ni, and Fe/Ni/P/C samples. The NH3 TPD curve shows that, at 100 °C, there was a clear desorption peak for Fe/Ni/P/C samples, which can be attributed to the desorption of NH3 by the carboxylic acid groups present on the carbon surface of the sample. There was also a strong desorption peak at around 270 °C, representing the acidic site of NH3. It is notable that the Fe/Ni/P/C sample also has an NH3 desorption peak at around 400 °C, suggesting that the introduction of Fe might have generated Lewis acidic sites [54,55].
Figure 6b shows the curves of NH3 desorption from Fe/Ni/P/C catalysts at around 270 °C. It can be seen that, as the amount of P doping increases, the adsorption capacity of NH3 decreases significantly. In addition, as the P content increases, the desorption peak shifts to lower temperatures. It has been reported that P doping can increase the acidity of samples by increasing the number of Brønsted acidic sites [56]. It has also been documented that P doping can reduce the Lewis acidic sites and increase Brønsted acid sites. The adsorption of NH3 on Lewis acid sites is more stable than that on Brønsted acid sites and therefore requires a higher-temperature desorption [57]. Figure 6c shows the NO2 TPD curve of the sample before and after the catalytic reaction, clearly indicating the loss of active adsorption sites following the catalytic degradation reaction.
The comprehensive characterization results show that the main gas products of NOX catalyzed by the electroplating sludge-derived catalyst system, after Ni-plating wastewater treatment with Fe/C micro-electrolysis Fenton technology, are CO2 and N2, essentially adhering to the conservation of N and O. The degradation pathways may be as follows: NH3 was adsorbed in the Lewis acid. Then, the intermediate NHX + NOX was generated by direct reaction with gaseous NO and NO2 through the Eley–Rideal (E–R) mechanism. Finally, it was decomposed into N2 and H2O, enabling the catalytic degradation of NOX [58,59]. In this work, the schematic of the reaction is shown in Figure 7.

3. Experimental Section

3.1. Materials

The materials used in this experiment include the following: iron chips (Fe, 99.5%, 100 mesh); activated carbon (AC, granular, spherical, coconut shell); hydrogen peroxide (H2O2, 0.5 mol/L, AR); potassium persulfate (K2S2O8, AR); calcium hydroxide (Ca(OH)2, AR); sodium hydroxide (NaOH, AR); ammonium molybdate tetrahydrate ((NH4)2MoO4, AR); nitric acid (HNO3, AR); potassium dihydrogen phosphate (KH2PO4, AR); and hydrochloric acid (HCl, AR); nitrogen (N2, 500 ppm); ammonia (NH3, 10%); nitric oxide (NO, 500 ppm); argon (Ar, 99.9992%); oxygen (O2, 99.9999%); helium (He, 99.9992%).

3.2. Preparation of Sludge-Derived Catalyst

Initially, the scrap iron was immersed in a 10% sodium hydroxide solution for 2 h to remove surface grease, followed by a 30 min soak in a 5% hydrochloride acid solution to remove the surface oxidation products. Subsequently, the iron was rinsed with deionized water until a neutral pH was attained. Electroplating wastewater and argon gas were then introduced into the reactor, with the controlled addition of H2O2 via a peristaltic pump. Additionally, iron powder, activated carbon, and sodium phosphate were introduced into the Ni sulfate solution to adjust the composition of the sludge. The ratio of sludge composed of P, Ni, and Fe, as well as the concentration of electroplating wastewater were adjusted to obtain varied catalysts, while maintaining the total mass of Fe and activated carbon content constant. Furthermore, the ratio of exogenous components was manipulated to achieve catalysts with different elemental compositions. After 3 h of treatment, the electroplating sludge was collected using centrifugal separation. Following drying, the sludge was calcined in a muffle furnace at 300 °C for 6 h to eliminate volatile substances and increase the fixed carbon content, producing the final sludge catalyst.
The sludge produced through the Fe/C micro-electrolysis Fenton treatment of Ni-plated wastewater primarily contained P, Ni, C, and Fe. The mass content (Fe, Ni, C, P) of all tested catalysts in this work are shown in Table 3. The content of Fe, P, C and Ni listed in Table 3 are theoretical concentrations of elements.

3.3. SCR Catalysis

SCR catalysts were prepared using electroplating sludge. Ammonia, serving as a reducing agent, demonstrated strong affinities, as shown in Equations (4)–(7). The apparatus for the NOX gas catalytic decomposition and monitoring is depicted in Figure 8. The SCR reactor was made of quartz glass with a 500 mm length and a 4 mm inner diameter. Mess flow were used to control inflow gases, including 30.0 mL/min of NO (500 ppm), 0.3 mL/min of NH3 (10%), 1.0 mL/min of O2 (99.9999%), and 1.0 mL/min H2O (5%). The gas hourly space velocity (GHSV) was adjusted to 14,400 h−1.
The detailed operational steps are as follows: The dried catalyst samples whose preparation is described in Section 3.2 were milled to a particle size of 100 mesh. A powder form catalyst sample weighing 0.1 g was added to the glass reaction tube, which was connected to the reactor. For a duration of 30 min prior to the commencement of the reaction, the apparatus and associated piping were purged with Ar. Subsequently, the valves controlling the flow of NO and NH3 were opened, with the flow rate of NO set at 30 mL/min. When the incoming nitrogen was diluted to 51.2 ppm with the incoming Ar gas, the monitoring and heating were then commenced according to the set temperature. The gas NO, O2, and NH3 were passed into the quartz tube for catalytic reaction at a certain ratio and flow rate, making the response airspace (GHSV) reach 14,400 h−1. The ratio of NO and NH3 was calculated to maintain a 1:1 concentration, each accounting for 0.1% of the total gas volume. Once the NO, NH3 and O2 flowed into the reactor and stabilized, the NO concentration was monitored using a NO–NO2–NOX analyzer. By tracking the NO concentration in real time, the concentration of NOX at different temperatures was recorded, and the NOX removal efficiencies at each temperature were calculated to evaluate the catalytic performance of the catalyst product.
4NO + 4NH3 + O2→4N2 + 6H2O
6NO + 4NH3→5N2 + 6H2O
2NO + 4NH3 + O2→3N2 + 6H2O
NO + NO2 + 2NH3→2N2 + 3H2O

3.4. Characterization

A UV spectrophotometer (UV, Techcomp Instrument Ltd., Shanghai, China) was utilized to determine the concentrations of various substances before and after the reaction. The pH of the solution was measured using a pH meter (INESA Scientific Instrument Co., Ltd., Shanghai, China). The phosphate content in the sample was determined using an ion chromatograph (MIC, Oudrey Industrial Equipment Co., Ltd., Shanghai, China). The composition of the sludge was determined through X-ray fluorescence spectrometer (XRF, Verder Instruments and Equipment Co., Ltd., Shanghai, China) and the elemental valence was measured by X-ray photoelectron spectroscopy (XPS, Thermo Fisher Scientific, Shanghai, China). Scanning electron microscopy (SEM, JEOL Ltd., Tokyo, Japan) was used to study the surface composition and morphology of the sludge and X-ray diffraction (XRD, Rigaku CO., Tokyo, Japan) analysis was used to determine the crystal phase and its oxidation state before and after the sample reaction. The scanning rate was set to 8°/min in the 2θ range of 5–90° and Brunauer–Emmett–Teller (BET, Thermo Fisher Scientific, Shanghai, China) analysis was conducted to determine the specific surface area and pore size of the sample. The NH3 temperature-programmed desorption (TPD) curves of samples containing different concentrations of substances were studied using TPD (Verder Instruments and Equipment Co., Ltd., Shanghai, China).

4. Conclusions

In this study, a derivative catalyst was prepared using Fe/C micro-electrolysis Fenton technology, using electroplating sludge generated after the treatment of electroplating wastewater. The catalyst was utilized to examine the effect of the components of electroplating sludge on the catalytic efficiency of NOX, and then to determine the pathway for the preparation of electroplating sludge-derived catalysts by adjusting the concentration of electroplating wastewater, as well as the proportion of external components. The results show that, when the sludge contained the four components of Fe, P, Ni, and C, the contents of P and Fe in the ingredients were 3 and 8 wt%, respectively; Fe:C = 1:2 and Fe/C/P was 1:2:0.4; the NOX removal rate could reach 100%; and that there was a wide decomposition temperature zone. Moreover, a series of characterizations (SEM, XRD, BET, TPD) showed that the introduction of P and Fe to improve the denitrification activity of the catalyst was not directly related to the specific surface area, pore volume, and pore diameter of the catalyst. An excessive Fe content may cause agglomeration on the catalyst surface and thus affect the catalytic efficiency. The addition of P decreased the catalytic reaction temperature, and the formation of phosphate promoted the production of adsorbed oxygen, thereby improving catalytic efficiency. The above results demonstrate the potential of electroplating sludge as a NOX SCR catalyst. However, at present, the catalytic degradation of NOX by electroplating sludge is still in the experimental stage. In the future, it can further research the catalysis of electroplating sludge generated by actual wastewater.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal14080535/s1, Figure S1: The X-ray photoelectron spectroscopy of the precipitate (a) P 2p1/2 and P 2p2/3; (b) Ni 2p1/2 and Ni 2p2/3; Figure S2: (a) The XRD comparison of Fe8/P4/Ni/C samples before and after reaction; (b) The Fe8/P4/Ni/C adsorption curve and pore size distribution curve.

Author Contributions

J.G.: Methodology, Writing—original draft, Writing—review & editing. F.S.: Data curation, Investigation. P.L.: Methodology, Writing—review & editing. J.Z.: Investigation, Resources, Formal analysis, Writing—review & editing. Y.Z.: Data curation, Visualization. All authors have read and agreed to the published version of the manuscript.

Funding

This research has no funding.

Data Availability Statement

Date will be made available on request.

Conflicts of Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

References

  1. Li, S.; Dai, M.; Ali, L.; Bian, H.Z.; Peng, C.S. Recovery of nickel from actual electroplating wastewater by integrated electrodeposition with adsorption pretreatment technique. Process. Saf. Environ. 2023, 172, 417–424. [Google Scholar] [CrossRef]
  2. Luo, Z.J.; Hong, Y.X.; Qu, L.L.; Luo, H.; Ganiyu, S.O.; Ayala, P.C.; Mohamed Gamal El Din, M.G. Decomplexation of copper complexes from synthetic and real electroplating wastewater by alkaline-thermal synergistic activation of persulfate and stabilization of generated sludge by Fe3O4 coating. Chem. Eng. J. 2024, 484, 149323. [Google Scholar] [CrossRef]
  3. Rajoria, S.; Vashishtha, M.; Sangal, V.K. Treatment of electroplating industry wastewater: A review on the various techniques. Environ. Sci. Pollut. Res. 2022, 29, 72196–72246. [Google Scholar] [CrossRef]
  4. Yue, Y.; Zhang, J.; Sun, F.C.; Wu, S.M.; Pan, Y.; Zhou, J.Z.; Qian, G.R. Heavy metal leaching and distribution in glass products from the co-melting treatment of electroplating sludge and MSWI fly ash. J. Environ. Manag. 2019, 232, 226–235. [Google Scholar] [CrossRef]
  5. Xiao, Y.; Li, L.; Huang, M.; Liu, Y.; Xu, J.; Xu, Z.; Lei, Y. Treating waste with waste: Metals recovery from electroplating sludge using spent cathode carbon combustion dust and copper refining slag. Sci. Total Environ. 2022, 838, 156453. [Google Scholar] [CrossRef]
  6. Yu, Y.; Huang, Q.; Zhou, J.; Wu, Z.; Deng, H.; Liu, X.; Lin, Z. One-step extraction of high-purity CuCl2·2H2O from coppercontaining electroplating sludge based on the directional phase conversion. J. Hazard. Mater. 2021, 413, 125469. [Google Scholar] [CrossRef] [PubMed]
  7. Pinto, F.M.; Pereira, R.A.; Souza, T.M.; Saczk, A.A.; Magriotis, Z.M. Treatment, reuse, leaching characteristics and genotoxicity evaluation of electroplating sludge. J. Environ. Manag. 2020, 280, 123706. [Google Scholar] [CrossRef]
  8. Sun, Z.H.; Xu, Z.H.; Zhou, Y.W.; Zhang, D.F.; Chen, W.F. Effects of different scrap iron as anode in Fe-C micro-electrolysis system for textile wastewater degradation. Environ. Sci. Pollut. Res. Int. 2019, 26, 26869–26882. [Google Scholar] [CrossRef] [PubMed]
  9. Minestrini, G. Primary techniques for NOx containment. Aiming for a more sustainable glass industry. Glass. Technol. Part-A 2018, 59, 153–156. [Google Scholar] [CrossRef]
  10. Wen, J.W.; Wang, X.L.; Yu, F.S.; Tian, M.L.; Wang, C.X.; Huang, G.Y.; Xu, S.M. Recovery and value-added utilization of critical metals from spent catalysts for new energy industry. J. Clean. Prod. 2023, 419, 138295. [Google Scholar] [CrossRef]
  11. Zhao, J.H.; Wen, Z.Z.; Zhu, R.S.; Li, Z.; Ding, R.; Zhu, Y.J.; Gu, T.K.; Yang, R.; Zhu, Z.Y. In/H-Beta modified by Co3O4 and its superior performance in the presence of H2O and SO2 for selective catalytic reduction of NOx with CH4. Adv. Chem. Eng. 2020, 3, 100029. [Google Scholar] [CrossRef]
  12. Zhao, B.; Wang, S.X.; Liu, H.; Xu, J.Y.; Fu, K.; Klimont, Z.; Hao, J.M.; He, K.B.; Cofala, J.; Amann, M. NOx emissions in China: Historical trends and future perspectives. Atmos. Chem. Phys. 2013, 13, 9869–9897. [Google Scholar] [CrossRef]
  13. Li, S.Y.; Song, L.Y.; Zhan, Z.C.; Qiu, W.G.; Li, J.; Fan, X.; He, H. Redox and acid properties of MnV2Ox/TiO2 catalysts synthesized by assistance of microwave for NO selective catalytic reduction by ammonia. Adv. Chem. Eng. 2021, 8, 100156. [Google Scholar] [CrossRef]
  14. Garcia-Cortes, J.M.; Illan-Gomez, M.J.; Solano, A.L.; de Lecea, C.S.M. Low temperature selective catalytic reduction of NOx with C3H6 under lean-burn conditions on activated carbon-supported platinum. Appl. Catal. 2000, 25, 39–48. [Google Scholar] [CrossRef]
  15. Busca, G.; Lietti, L.; Ramis, G.; Berti, F. Chemical and mechanistic aspects of the selective catalytic reduction of NOx by ammonia over oxide catalysts: A review. Appl. Catal. 1998, 18, 1–36. [Google Scholar] [CrossRef]
  16. Shen, S.Y.; Liu, Y.; Zhai, D.; Qian, G.R. Electroplating sludge-derived spinel catalysts for NO removal via NH3 selective catalysis reduction. Appl. Surf. Sci. 2020, 528, 146969. [Google Scholar] [CrossRef]
  17. Shi, J.; Zhang, Y.; Zhu, Y.; Chen, M.; Zhang, Z.; Shangguan, W. Efficient Fe-ZSM-5 Catalyst with Wide Active temperature Window for NH3 Selective Catalytic Reduction of NO: Synergistic Effect of isolated Fe3+ and Fe2O3. J. Catal. 2019, 378, 17–27. [Google Scholar] [CrossRef]
  18. Huang, J.J.; Chen, J.Y.; Yao, J.Z.; Zhao, S.Y.; Wu, X.B.; Xia, Q.B. Novel regenerated V- and Ce-mixed oxide modified catalysts for the NH3-SCR of NOx displaying a distinctive broad temperature window. J. Clean. Prod. 2023, 382, 135384. [Google Scholar] [CrossRef]
  19. Kilic, M.Y.; Yonar, T.; Mart, B.K. Landfill leachate treatment by Fenton Fenton-like oxidation processes. Clean-Soil Air Water 2014, 42, 586–593. [Google Scholar] [CrossRef]
  20. Yu, Z.Y.; Zhao, G.J.; Yu, H.W.; Liu, Q.; Zhang, Z.Y.; Sun, R.F.; Wang, L.Y.; Geng, W.G.; Yuan, D.L. Application of Fenton sludge coupled selective acid leaching in selective catalytic reduction of NOx: Performance and mechanisms. Fuel 2022, 236, 125058. [Google Scholar] [CrossRef]
  21. Huang, R.; Huang, K.L.; Lin, Z.Y.; Wang, J.W.; Lin, C.T.; Kuo, Y.M. Recovery of valuable metals from electroplating sludge with reducing additives via vitrification. J. Environ. Manag. 2013, 129, 586–592. [Google Scholar] [CrossRef]
  22. Xu, Z.C.; Wu, S.; Zhou, M.D.; Zang, S.L. The enhancement for SCR-NO by H2 in C3H6-SCR over Ag/Al2O3 catalyst. Appl. Chem. Ind. 2016, 45, 207. [Google Scholar] [CrossRef]
  23. Gong, J.; Tan, R.; Wang, B.J.; Wang, Z.B.; Gong, B.C.; Mi, X.; Deng, D.; Liu, X.N.; Liu, C.L.; Deng, C.J.; et al. Process and mechanism of strengthening chlorination cascade recovery of valuable metals from electroplating sludge. J. Clean. Prod. 2022, 376, 134330. [Google Scholar] [CrossRef]
  24. Liang, X.; Tang, J.J.; Li, L.S.; Wu, Y.S.; Sun, Y. A review of metallurgical processes and purification techniques for recovering Mo, V, Ni, Co, Al from spent catalysts. J. Clean. Prod. 2022, 376, 134108. [Google Scholar] [CrossRef]
  25. Li, C.Y.; Ding, S.Y.; Zhang, J.; Wu, J.Z.; Yue, Y.; Qian, G.R. Ball milling transformed electroplating sludges with different components to spinels for stable electrocatalytic ammonia production under ambient conditions. Chemosphere 2022, 296, 134060. [Google Scholar] [CrossRef] [PubMed]
  26. Wang, H.M.; Xu, X.H.; Hao, J.M.; Ning, P.; Zhang, Q.L. Unravelling the phosphorus-induced effect on NH3-SCR catalytic performance, hydrothermal stability and SO2 resistance of Cu/SAPO-34. Appl. Catal. A-Gen. 2022, 646, 118888. [Google Scholar] [CrossRef]
  27. Tian, B.Y.; Cui, Y.C.; Qin, Z.J.; Wen, L.K.; Li, Z.H.; Chu, H.C.; Xin, B.P. Indirect bioleaching recovery of valuable metals from electroplating sludge and optimization of various parameters using response surface methodology (RSM). J. Environ. Manag. 2022, 312, 114927. [Google Scholar] [CrossRef]
  28. Mao, L.Q.; Tang, R.Z.; Wang, Y.C.; Guo, Y.N.; Su, P.; Zhang, W.Y. Stabilization of electroplating sludge with iron sludge by thermal treatment via incorporating heavy metals into spinel phase. J. Clean. Prod. 2018, 187, 616–624. [Google Scholar] [CrossRef]
  29. Guo, K.; Ji, J.W.; Song, W.; Sun, J.F.; Tang, C.J.; Dong, L. Conquering ammonium bisulfate poison over low-temperature NHsub3/sub-SCR catalysts: A critical review. Appl Catal B-Environ. 2021, 297, 120388. [Google Scholar] [CrossRef]
  30. Chen, Y.X.; Li, C.; Chen, J.X.; Tang, X.F. Self-Prevention of Well-Defined-Facet Fe2O3/MoO3 against Deposition of Ammonium Bisulfate in Low-Temperature NH3-SCR. Environ. Sci. Technol. 2018, 52, 11796–11802. [Google Scholar] [CrossRef]
  31. Chen, S.W.; Zhao, Y.L.; Zhang, R.Q. Formation Mechanism of Atmospheric Ammonium Bisulfate: Hydrogen-Bond-Promoted Nearly Barrierless Reactionsof SO3 with NH3 and H2O. Chemphyschem 2018, 19, 967–972. [Google Scholar] [CrossRef] [PubMed]
  32. Kang, L.; Han, L.P.; Wang, P.L.; Feng, C.; Zhang, J.P.; Yan, T.T.; Deng, J.; Shi, L.Y.; Zhang, D.S. SO2-Tolerant NOx Reduction by Marvelously Suppressing SO2 Adsorption over FeδCe1-δVO4 Catalysts. Environ. Sci. Technol. 2020, 54, 14066–14075. [Google Scholar] [CrossRef] [PubMed]
  33. Zhou, J.Z.; Liu, P.; Liu, Z.Y.; Zhang, J.; Huang, X. Simultaneous recovery of phosphorus with nickel purification in nickel-plating wastewater via Fe/C activated H2O2 oxidation. Chem. Eng. J. 2019, 381, 122702. [Google Scholar] [CrossRef]
  34. Zhang, Q. Treatment of oilfield produced water using Fe/C micro-electrolysis assisted by zero-valent copper and zero-valent aluminium. Environ. Technol. 2015, 36, 515–520. [Google Scholar] [CrossRef] [PubMed]
  35. Fu, F.L.; Xie, L.P.; Tang, B.; Wang, Q.; Jiang, S.X. Application of a novel strategy—Advanced Fenton-chemical precipitation to the treatment of strong stability chelated heavy metal containing wastewater. Chem. Eng. J. 2012, 189, 283–287. [Google Scholar] [CrossRef]
  36. Guan, W.; Tian, S.C.; Ma, N. An electrochemical method through hydroxyl radicals oxidation and deposition of ferric phosphate for hypophosphite recovery. J. Colloid Interface Sci. 2018, 516, 529–536. [Google Scholar] [CrossRef] [PubMed]
  37. Liu, P.; Li, C.L.; Liang, X.G. Recovery of high purity ferric phosphate from a spent electroless nickel plating bath. Green Chem. 2014, 16, 1217–1224. [Google Scholar] [CrossRef]
  38. Zeng, L.B.; Li, X.Y.; Shi, Y.R.; Qi, Y.F.; Huang, D.Q.; Tade, M.; Wang, S.B.; Liu, S.M. FePO4 based single chamber air-cathode microbial fuel cell for online monitoring levofloxacin. Biosens. Bioelectron. 2017, 91, 367–373. [Google Scholar] [CrossRef] [PubMed]
  39. Tan, P.L. Active phase, catalytic activity, and induction period of Fe/zeolite material in nonoxidative aromatization of methane. J. Catal. 2016, 338, 21–29. [Google Scholar] [CrossRef]
  40. Yuan, H.; Song, W.B.; Wang, M.; Chen, Y.B.; Gu, Y.J. Lithium-ion conductive coating layer on nickel rich layered oxide cathode material with improved electrochemical properties for Li-ion battery. J. Alloys Compd. 2019, 784, 1311–1322. [Google Scholar] [CrossRef]
  41. Lei, Y.; Ding, J.J.; Yu, P.F.; He, G.Y.; Chen, Y.Y.; Chen, H.Q. Low-temperature preparation of magnetically separable Fe3O4 @ZnO-RGO for high-performance removal of methylene blue in visible light. J. Alloys Compd. 2020, 821, 153366. [Google Scholar] [CrossRef]
  42. Bang, S.; Hong, E.; Baek, S.W.; Shin, C.H. Effect of acidity on Ni catalysts supported on P-modified Al2O3 for dry reforming of methane. Catal. Today 2018, 303, 100–105. [Google Scholar] [CrossRef]
  43. You, Y.C.; Shi, C.N.; Chang, H.Z.; Guo, L.; Xu, L.W.; Li, J.H. The promoting effects of amorphous CePO4 species on P-doped CeO2/TiO2 catalysts for selective catalytic reduction of NOx by NH3. Mol. Catal. 2018, 453, 47–54. [Google Scholar] [CrossRef]
  44. Xie, W.; Liang, D.; Li, L.; Qu, S.J.; Tao, W. Surface chemical properties and pore structure of the activated coke and their effects on the denitrification activity of selective catalytic reduction. Int. J. Coal. Sci. Technol. 2019, 6, 595–602. [Google Scholar] [CrossRef]
  45. Zhang, Q.; Han, K.; Li, S.J.; Li, M.; Li, J.X.; Ren, K. Synthesis of garlic skin-derived 3D hierarchical porous carbon for high-performance supercapacitors. Nanoscale 2018, 10, 2427–2437. [Google Scholar] [CrossRef] [PubMed]
  46. Zhu, Y.W.; Miao, Y.F.; Li, H.Y. Enhancement effect of ordered hierarchical pore configuration on SO2 adsorption and desorption process. Processes 2019, 7, 173. [Google Scholar] [CrossRef]
  47. Zhao, K.W.; Li, Z.F.; Yan, T.; Gao, Z.J.; He, Q.; Wang, Q.F.; Liu, W.Q.; Zhang, J.Y.; Zhao, X.Z.; Liu, L.; et al. Ni enhanced reactivity of Fe/TiO2 for selective catalytic reduction of NO with CO and the mechanism investigation. J. Environ. Chem. Eng. 2023, 11, 109757. [Google Scholar] [CrossRef]
  48. Ellmers, I.; Velez, R.P.; Bentrup, U.; Schwieger, W.; Bruckner, A.; Grunert, W.G. SCR and NO oxidation over Fe-ZSM-5—The influence of the Fe content. Catal. Today 2015, 258, 337–346. [Google Scholar] [CrossRef]
  49. Yang, Z.W.; Lang, L.; Yuan, H.; Meng, D.J.; Sun, Y.; Li, S.Y. Promotional effects of Fe2O3 additive on the NH3-SCR activity and alkali resistance of MoTiOx catalysts. Sep. Purif. Technol. 2024, 351, 128026. [Google Scholar] [CrossRef]
  50. Jin, Y.Y.; Fan, K.H.; Hu, B.; Li, J.Y.; Hu, B.Y.; Jin, L.Y.; Li, J.Y.; Liu, X.S. Highly synergistic effects of Fe-W catalysts to enhance medium-low temperature NH3-SCR activity. Mol. Catal. 2024, 563, 114271. [Google Scholar] [CrossRef]
  51. Zhang, C.; Zhou, M.H.; Yu, H.M.; Ma, L.; Yu, F.K. Modified iron-carbon as heterogeneous electro-Fenton catalyst for organic pollutant degradation in near neutral pH condition: Characterization, degradation activity and stability. Electrochim. Acta 2015, 160, 254–262. [Google Scholar] [CrossRef]
  52. Han, L.P.; Cai, S.X.; Gao, M.; Hasegawa, J.; Wang, P.L.; Zhang, J.P.; Shi, L.Y.; Zhang, D.S. Selective Catalytic Reduction of NOx with NH3 by Using Novel Catalysts: State of the Art and Future Prospects. Chem. Rev. 2019, 119, 10916–10976. [Google Scholar] [CrossRef]
  53. Naderi, M. Chapter Fourteen-Surface area: Brunauer-Emmett-Teller (BET). Progress in Filtration and Separation; Academic Press: Cambridge, MA, USA, 2015. [Google Scholar]
  54. Xu, F.; Chen, W.; Walenta, C.A.; O’Connor, C.R.; Friend, C.M. Dual Lewis site creation for activation of methanol on Fe3O4 (111) thin films. Chem. Sci. 2020, 11, 2448–2454. [Google Scholar] [CrossRef] [PubMed]
  55. Deng, J.; Wang, S.; Lan, T.S.; Guo, S.Q.; Zhang, K.; Zhang, D.S. Precise regeneration of NOx reduction catalysts poisoned by metal ions via Sabatier principle of antidote-active center interaction. J. Clean. Prod. 2023, 417, 137967. [Google Scholar] [CrossRef]
  56. Castellino, F.; Rasmussen, S.B.; Jensen, A.D.; Johnsson, J.E.; Fehrmann, R. Deactivation of vanadia-based commercial SCR catalysts by polyphosphoric acids. Appl. Catal. B Environ. 2008, 83, 110–122. [Google Scholar] [CrossRef]
  57. Peng, Y.; Qu, R.Y.; Zhang, X.Y.; Li, J.H. The relationship between structure and activity of MoO3-CeO2 catalysts for NO removal: Influences of acidity and reducibility. Chem. Commun. 2013, 49, 6215–6217. [Google Scholar] [CrossRef]
  58. Jiang, L.Y.; Xu, Y.C.; Jiang, W.J.; Pu, Y.J.; Yang, L.; Dai, Z.D.; Yao, L. The promotion of NH3-SCR performance by AC addition on Mn-Fe/Z catalyst. Sep. Purif. Technol. 2023, 322, 124274. [Google Scholar] [CrossRef]
  59. Li, R.; Yue, T.; Zheng, Y.; Li, G.L.; Gao, J.J.; Tong, Y.L.; Wang, J.Q.; Ma, M.Y.; Su, W. Promotional mechanism of La-Mn-Fe modification on activated coke for NH3-SCR of NOx at low temperatures. Fuel 2024, 371, 132016. [Google Scholar] [CrossRef]
Catalysts 14 00535 g001
Figure 1. Fe/C + H2O2 treatment of electroplating wastewater effluent in (a) TP, Ni, and Fe2+ and (b) pH change.
Figure 1. Fe/C + H2O2 treatment of electroplating wastewater effluent in (a) TP, Ni, and Fe2+ and (b) pH change.
Catalysts 14 00535 g001
Catalysts 14 00535 g002
Figure 2. The effect of composition on NOX removal efficiency.
Figure 2. The effect of composition on NOX removal efficiency.
Catalysts 14 00535 g002
Catalysts 14 00535 g003
Figure 3. The effects of (a) P, (b) Ni, and (c) Fe on NOX removal efficiency.
Figure 3. The effects of (a) P, (b) Ni, and (c) Fe on NOX removal efficiency.
Catalysts 14 00535 g003
Catalysts 14 00535 g004
Figure 4. The effects of (a) Fe/C and (b) P concentration in the pollutants on NOX removal efficiency.
Figure 4. The effects of (a) Fe/C and (b) P concentration in the pollutants on NOX removal efficiency.
Catalysts 14 00535 g004
Catalysts 14 00535 g005
Figure 5. SEM images of (a) Fe8/P4/Ni/C (10.0 μm); (b) Fe8/P4/Ni/C (1.0 μm); (c) Fe10/P5/Ni/C (10.0 μm); and (d) Fe10/P5/Ni/C samples (1.0 μm).
Figure 5. SEM images of (a) Fe8/P4/Ni/C (10.0 μm); (b) Fe8/P4/Ni/C (1.0 μm); (c) Fe10/P5/Ni/C (10.0 μm); and (d) Fe10/P5/Ni/C samples (1.0 μm).
Catalysts 14 00535 g005
Catalysts 14 00535 g006
Figure 6. (a) The NH3 TPD curves of Fe, Fe/Ni and Fe/Ni/P/C; (b) the NH3 TPD curves of Fe/Ni/P/C samples with different P contents; and (c) the NO2 TPD curves of the sample before and after reaction.
Figure 6. (a) The NH3 TPD curves of Fe, Fe/Ni and Fe/Ni/P/C; (b) the NH3 TPD curves of Fe/Ni/P/C samples with different P contents; and (c) the NO2 TPD curves of the sample before and after reaction.
Catalysts 14 00535 g006
Catalysts 14 00535 g007
Figure 7. Schematic of the reaction.
Figure 7. Schematic of the reaction.
Catalysts 14 00535 g007
Catalysts 14 00535 g008
Figure 8. The NOX catalytic experimental device and technological process.
Figure 8. The NOX catalytic experimental device and technological process.
Catalysts 14 00535 g008
Table 1. (a) The content compositions of iron and P in products after reactions with different iron/carbon ratios. (b) The content compositions of iron and P in products after reactions with different pollutant concentrations.
Table 1. (a) The content compositions of iron and P in products after reactions with different iron/carbon ratios. (b) The content compositions of iron and P in products after reactions with different pollutant concentrations.
(a)
Fe/C ratioFe content (wt%)P content (wt%)
Fe:C = 1:312.609.60
Fe:C = 1:216.207.50
Fe:C = 1:120.305.10
Fe:C = 2:121.504.20
Fe:C = 3:121.604.30
(b)
P concentration in wastewater (ppm)Fe content in the product (wt%)P content in the product (wt%)
50018.603.40
100017.104.30
150016.205.10
200015.606.20
250015.007.50
300014.508.30
Table 2. (a) The changes in gas-phase composition at different reaction temperatures (GHSV = 14,400 h−1). (b) The BET-specific surface area and pore size of Fex/Py/Ni/C samples.
Table 2. (a) The changes in gas-phase composition at different reaction temperatures (GHSV = 14,400 h−1). (b) The BET-specific surface area and pore size of Fex/Py/Ni/C samples.
(a)
NON2CO2CON2ONtOt
R.T51.30--------51.3051.30
300 °C15.6019.1013.300.141.4355.9542.38
400 °C--23.1722.502.06--46.1147.25
500 °C--26.0224.500.62--51.8649.52
(b)
SampleSpecific surface area (m2/g)Total pore volume (cm3/g)Average pore size (nm)
Fe/Ni/C47.700.0418.5
Fe6/P3/Ni/C37.90.1021.3
Fe6/P4/Ni/C40.10.1523.6
Fe6/P5/Ni/C32.70.1826.9
Fe8/P4/Ni/C35.80.2029.6
Fe10/P4/Ni/C33.60.2531.8
“--”: not detected. Total N (Nt) = NO + 2N2 + 2N2O; total O (Ot) = NO + 2CO2 + CO. In theory, Nt = Ot = initial NO concentration (51.30 ppm).
Table 3. The mass content (Fe, Ni, C, P) of all tested catalysts.
Table 3. The mass content (Fe, Ni, C, P) of all tested catalysts.
CatalystsFe (wt%)P (wt%)C (wt%)Ni (wt%)
Fe/Ni/C1.00--1.001.00
P1/Fe/Ni/C1.001.001.001.00
P2/Fe/Ni/C1.002.001.001.00
P3/Fe/Ni/C1.003.001.001.00
P4/Fe/Ni/C1.004.001.001.00
Ni1/Fe/P/C1.003.001.001.00
Ni2/Fe/P/C1.003.001.002.00
Ni3/Fe/P/C1.003.001.003.00
Ni4/Fe/P/C1.003.001.004.00
Ni5/Fe/P/C1.003.001.005.00
Fe2/Ni/P/C2.003.001.001.00
Fe4/Ni/P/C4.003.001.001.00
Fe6/Ni/P/C6.003.001.001.00
Fe8/Ni/P/C8.003.001.001.00
Fe10/Ni/P/C10.003.001.001.00
“--”: not added.
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Gao, J.; Sun, F.; Liu, P.; Zhou, J.; Zhang, Y. Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst. Catalysts 2024, 14, 535. https://doi.org/10.3390/catal14080535

AMA Style

Gao J, Sun F, Liu P, Zhou J, Zhang Y. Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst. Catalysts. 2024; 14(8):535. https://doi.org/10.3390/catal14080535

Chicago/Turabian Style

Gao, Ju, Fucheng Sun, Pei Liu, Jizhi Zhou, and Yufeng Zhang. 2024. "Sludge Recycling from Non-Lime Purification of Electrolysis Wastewater: Bridge from Contaminant Removal to Waste-Derived NOX SCR Catalyst" Catalysts 14, no. 8: 535. https://doi.org/10.3390/catal14080535

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop