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Article

Facile Synthesis of Fe(0)@Activated Carbon Material as an Active Adsorbent towards the Removal of Cr (VI) from Aqueous Media

by
Mohammed J. Almujaybil
1,
Dania Fathi Mohammed Abunaser
2,
Mohamed Gouda
1,*,
Mai M. Khalaf
1,3,
Ibrahim M. A. Mohamed
3 and
Hany M. Abd El-Lateef
1,3,*
1
Department of Chemistry, College of Science, King Faisal University, Al-Ahsa 31982, Saudi Arabia
2
Anwar Al-Wafa Pharmacy, Jerash 26150, Jordan
3
Department of Chemistry, Faculty of Science, Sohag University, Sohag 82524, Egypt
*
Authors to whom correspondence should be addressed.
Catalysts 2022, 12(5), 515; https://doi.org/10.3390/catal12050515
Submission received: 11 April 2022 / Revised: 29 April 2022 / Accepted: 2 May 2022 / Published: 4 May 2022
(This article belongs to the Special Issue Frontiers in Graphene-Based Electrocatalysts)
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Abstract

:
A novel adsorbent substrate based on zero-valent iron in activated carbon (Fe(0)@AC) was introduced in this work, and was evaluated as a cheap adsorbent for the removal of Cr(VI) from aqueous solutions. The as-prepared Fe(0)@AC material was chemically prepared via NaBH4 reduction in the presence of ferric chloride as an iron source, followed by the addition of powdered activated carbon. The different physicochemical tools confirm the successful preparation of Fe(0) composite with activated carbon as a heterogeneous composite with heterogeneous morphology of the rock-shape structure, which could play a role in the metal adsorption application. Interestingly, the removal efficiency (RE) of Cr(VI) was increased from 52% to 84% due to the Fe(0)@AC adsorbent being changed from 0.2 to 0.4 g/100 mL. Following this, the increase rate was stabilized, and the RE reached 95% in the case of 0.8 g/100 mL from Fe(0)@AC adsorbent. This result could be due to the increase in the sorbent active sites with more contents from Fe(0)@AC. The adsorption model based on the Langmuir approach could successfully describe the experimental outcomes for Cr(VI) removal by Fe(0)@AC with the correlation coefficient of 0.977. To conclude, Fe(0)@AC heterogeneous material is an active adsorbent for Cr(VI) removal from aqueous solutions.

1. Introduction

Currently, high concentrations of heavy metals–above the permitted level–could be considered a global pollution concern, especially in aqueous environments. This presents a threat to human health and environmental sustainability [1,2]. One of these heavy metals, Cr(VI), is of significant concern due to its high toxicity at high concentrations [3]. The maximum permissible contents of Cr(VI) in wastewater is 0.1 mg/L [4], however, the expected content of Cr(VI) in traditional wastewater is very high [5]. Therefore, Cr(VI) contents should be controlled under the permissible ratios before using water for human uses. To overcome this pollution issue, different chemical and engineering technologies were introduced to remove Cr(VI) from wastewater, including adsorption, extraction, and electrochemical method [6,7,8,9,10]. Among the reported approaches, selective adsorption is one of the most promising approaches for the removal of metallic pollutants from wastewater. The chemistry of the reported adsorbents used to remove Cr(VI) includes polymers [11,12], MOFs [10], transition metal embedded 3D hydrogel [13], metal sulphides [14,15], 3D porous carbon [16], iron oxide composites [17], TiO2 nanofibers [18] that could be prepared by electrospinning technique [19,20], amino-functionalized MXenes [21], PANI-WO3 [22], transition metals ferrites [23], nanosized Fe(0) [24,25], and so on. Although these reported substrates have an acceptable Cr(VI) removal performance, they were still plagued with some disadvantages during process, such as high cost, limited chemical or thermal stability, and poor regeneration. Therefore, this study focuses on the design of novel adsorbents for Cr(VI) removal, paying specific attention to low cost and significant regeneration properties.
Zero-valent iron (Fe(0))-based nanomaterials have been utilized to adsorb or remove toxic metals from wastewater media because of surface area, small size, reactivity, and reducing power [26]. Different metallic and organic pollutants including CCl4, nitrates, arenites, chromates, and so on, were reported to be removed by Fe(0) materials [27]. However, a possible agglomeration or oxides formation could cause a rapid loss in activity and limit the commercial application. To overcome these problems, polymers like chitosan [28] and carboxymethyl cellulose [29] have been applied to increase the chemical stability of Fe(0) material. Additionally, zeolites were utilized to enhance the dispersibility of Fe(0) material [30]. Furthermore, a few reports focused on protecting Fe(0) material with carbon substrates including graphene, carbon nanotubes, carbon nanofibers, and activated carbon which will be focused on in this work.
In this study, modified Fe(0) material with activated carbon (AC) was evaluated to separate and remove Cr(VI) from wastewater media. The presence of AC as a chemical substrate could provide the sufficient surface area and porosity during the adsorption of precious metals. Additionally, the existence of Fe(0) could enhance the favoured interaction between the adsorbate and the adsorbent. The prepared composite of Fe(0)@AC was characterized using microscopic, spectroscopic, and physicochemical techniques. Then, it was investigated under different environmental factors on Cr(VI) removal, followed by additional characterization after Cr(VI) adsorption to confirm the nature of Cr(VI) adsorption.

2. Results and Discussion

2.1. Material Characterization

In this work, Fe(0)@AC material was prepared and studied via characterization techniques and adsorption performance for Cr(VI) removal. The morphology of the prepared Fe(0)@AC was studied at two magnifications; 1 KX and 3 KX (Figure 1A,B, respectively). The SEM morphology of the Fe(0)@AC material is micro rock shape, with a porous and heterogeneous character that could be attributed to the formation of zero-iron over the traditional activated carbon. The activated carbon was reported to have a homogeneous rock shape character [20,31]. This morphological image confirmed the heterogeneity of the formed rock shape, which might play a role in the metal adsorption application. The presence of Fe in zero-state was confirmed by XRD analysis of the Fe(0), as shown in Figure S1 (Supplementary Material). A clear peak was found around 2θ~44.8°, with a sharp intensity that indicates a high degree of crystallinity. The position of the highest peak was in accordance with the reported Fe(0) XRD card JCPDS 00-003-1050. Based on the studied XRD analysis, it is obvious that the formation of iron is in the zero-valence state. Additionally, the TEM of the Fe(0) was shown in Figure S2 (Supplementary Material). The TEM image indicates a network particle with an estimated average particle size lower than 120 nm. The connected network particles could be due to the agglomeration and interaction between the Fe(0) particles during the experimental preparation of the Fe(0) material. Chemical bonds at the surface of the Fe(0)@AC material were investigated by FT-IR, as shown in Figure 2A, which showed different peaks at 1560 and 453 cm−1, which could be due to the vibration mode of C=C bonding in activated carbon [32] and Fe-C bond, respectively [33]. The peak centered at 2104 cm−1 is assigned to the adsorbed CO2 gas [34].
The Raman spectral was studied at a range of 200–2100 cm−1 in order to identify the synthesized Fe(0)@AC. Two sharp peaks were seen in the Raman spectra of the Fe(0)@AC material (Figure 2B) at 1601.80 cm−1 and 1341.05 cm−1. The first peak could be due to the G-peak, which is the graphite scattering peak of the graphite carbon structure. Another sharp peak could be attributed to the D-peak, which is interpreted by lattice defects or disordered arrangement [35]. In conclusion, it can be understood that the AC in the prepared Fe(0)@AC has a graphitic character after modification by zero-valent iron [36].
In this work, Fe(0)@AC material was prepared and studied via characterization techniques and adsorption performance for Cr(VI) removal. The morphology of the prepared Fe(0)@AC was studied at two magnifications; 1 KX and 3 KX (Figure 1A,B, respectively). The SEM morphology of Fe(0)@AC material is micro rock shape, with porous and heterogeneous character that could be attributed to the formation of zero-iron over the traditional activated carbon; activated carbon was reported to have a homogeneous rock shape character [20,31]. This morphological image confirmed the heterogeneity of the formed rock shape, which might play a role in metal adsorption application. The chemical bonds at the surface of the Fe(0)@AC material were investigated by FT-IR, as shown in Figure 2A, which showed different peaks at 1560 and 453 cm−1 that could be caused by the vibration mode of C=C bonding in activated carbon [32] and Fe-C bond, respectively [33]. The peak centered at 2104 cm−1 is assigned to the adsorbed CO2 gas [34].
The Raman spectral was studied at a range of 200–2100 cm−1 in order to identify the synthesized Fe(0)@AC. Two sharp peaks were seen in the Raman spectra of Fe(0)@AC material (Figure 2B) at 1601.80 cm−1 and 1341.05 cm−1. The first peak could be due to the G-peak, which is the graphite scattering peak of the graphite carbon structure. Another sharp peak could be attributed to the D-peak, which is interpreted by lattice defects or disordered arrangement [35]. In conclusion, it can be understood that the AC in the prepared Fe(0)@AC has a graphitic character after modification by zero-valent iron [36].

2.2. Cr(VI) Adsorption Study

The Cr(VI) adsorption at the investigated Fe(0)@AC was carried out by UV–vis spectra at the optimum wavelength. The impact of the Fe(0)@AC amount as an adsorbent amount on the removal efficiency (RE) of Cr(VI) at room temperature was investigated, as shown in Figure 3A. The RE was calculated from the following reported equation [37]:
RE / % = C i − C e C i × 100
where RE, Ce, and Ci are the removal efficiency, Cr(VI) equilibrium concentration, and initial concentration, respectively. The amount of Fe(0)@AC adsorbent was studied from 0.2 to 0.8 g/100 mL. As the introduced amount of Fe(0)@AC adsorbent goes up, the RE (%) grows at the fixed condition from Cr(VI) concentration or temperature, or the utilized conditions. Interestingly, the RE was increased from 52% to 84% because the Fe(0)@AC adsorbent was changed from 0.2 to 0.4 g/100 mL. After that, the increase rate was stabilized, and the RE reached 95% on the 0.8 g/100 mL from Fe(0)@AC adsorbent. This result could be due to the increase in the sorbent active sites with more contents from Fe(0)@AC. To conclude, the amount of 0.8 g/100 mL of Fe(0)@AC adsorbent is the optimum sorbent content for Cr(VI) adsorption experiments.
Catalysts 12 00515 g003 550
Figure 3. Influence of the sorbet weight (100 mL solution of 100 mg/L Cr(VI)) (A), contact time (0.6 g Fe(0)@AC; 100 mg/L Cr(VI),) (B), initial [Cr (VI)] (0.6 g FE(0)@AC) (C), and shaking rate 100 mg/L Cr(VI), 0.6 g Fe(0)@AC, adsorption time 90 min) (D) on the removal efficiency (adsorption) of Cr (VI) by Fe(0)@AC; pH = 2, at 25 °C.
Figure 3. Influence of the sorbet weight (100 mL solution of 100 mg/L Cr(VI)) (A), contact time (0.6 g Fe(0)@AC; 100 mg/L Cr(VI),) (B), initial [Cr (VI)] (0.6 g FE(0)@AC) (C), and shaking rate 100 mg/L Cr(VI), 0.6 g Fe(0)@AC, adsorption time 90 min) (D) on the removal efficiency (adsorption) of Cr (VI) by Fe(0)@AC; pH = 2, at 25 °C.
Catalysts 12 00515 g003
The suitable adsorption time is a significant factor in introducing novel adsorbents. Therefore, it was studied and described in Figure 3B. Different contact times were recorded from 30 min to 180 min and drawn against RE (%). Firstly, the RE sharply increased from 44% to 90% solely due to the increase in adsorption time from 30 min to 60 min. Following this, time slightly affected the RE %, with an increasing trend up to 180 min. The effect of the elapsed time confirms the time required for equilibrium is 90 min, as no considerable change could be detected after 90 min.
The effect of Cr(VI) contents on the RE % value was investigated from 25 mg/L to 200 mg/L at fixed conditions from the adsorbent amount (0.8 g/100 mL), room temperature, and contact time (180 min). The obtained adsorption data were organized in Figure 3C. Firstly, the RE ranged between 97% and 80% for all investigated Cr(VI) concentrations. Secondly, the RE % slightly decreased as the Cr(VI) content increased. Therefore, the Cr(VI) adsorption by Fe(0)@AC adsorbent had a slight dependence on the Cr(VI) concentration. The shaking rate of adsorbent with adsorbate could enhance the physical or chemical interaction between Cr(VI) and adsorbent, in addition to the improvement of the mass transfer rate, by decreasing the diffusion layer thickness [37]. Figure 3D depicts the effect of shaking speed from 200 rpm to 400 rpm on the RE %. Generally, the RE % goes up with the increase in shaking speed. For example, the RE % improved from 86% to 96% solely due to the shaking speed changing from 200 rpm to 400 rpm. The enhancement of RE with an increase in shaking speed could be due to the increase in the physical interaction and mass transfer between Cr(VI) and Fe(0)@AC adsorbent.
Figure 4A shows the temperature impact on Cr(VI) removal (RE %) at temperatures from 25 °C to 55 °C. The RE % values were decreased and found at 97, 93, 90, and 88% of Cr(VI) at 25 °C, 35 °C, 45 °C, and 55 °C, respectively, indicating the Cr(VI) adsorption at Fe(0)@AC adsorbent is exothermic [38]. The RE % value is still in an acceptable range even at high temperature such as 55 °C, which indicates the ability of the investigated Fe(0)@AC adsorbent to remove Cr(VI) at different temperature conditions. The pH of the studied solution is one of the most significant parameters in the chemistry of the adsorption, which could be related to the ionic character of the functional groups and their interaction with the adsorbate [39]. Figure 4B displays that the Cr(VI) RE value decreases with the pH increase from 2.0 to 11.0. At the lower pH 2, the RE % was increased with the increase in the pH. The RE is the most optimal at pH 2, which could be due to the existence of Cr(VI) in monovalent form, which is gradually transferred to divalent form as pH goes up. This result was in accordance with the reported Cr(VI) adsorption studies [39,40,41,42,43]. At a low pH, a high concentration of hydronium ions (H3O+) could be found, providing a positive partial charge at the surface of Fe(0)@AC adsorbent, and leading to a better adsorption process of Cr(VI) in the solution due to the binding of anionic CrO42- ion with the surface of the Fe(0)@AC adsorbent. The decline of adsorption performance at a high pH is attributed to the competition between the same negative ions (OH- and CrO42-) to be adsorbed. In short, the adsorption performance of Cr(VI) at Fe(0)@AC adsorbent should be at a low pH–around pH 2. A desorption regeneration study could help to understand the adsorption stability and to evaluate the ability of commercialization. The results of the sorption regeneration experiments were shown in Figure 5. No big difference was seen between the sorption RE first cycle and fifth cycle, which indicates the ability of Fe(0)@AC adsorbent to remove Cr(VI) from aqueous solutions for up to at least five cycles.

2.3. Adsorption Isotherm Studies

In order to assess the adsorption ability of the Fe(0)@AC material, the Cr (VI) adsorption findings onto 0.6 g nano- Fe(0)@AC/100 mL Cr(VI) at equilibrium were examined based on the Freundlich and Langmuir isotherm models [44]. The Langmuir isotherm model assumes the existence of assembly of the sorbate ions on the sorbent homogeneous surface. The Freundlich model was usually utilized to designate the inhomogeneity of the interface. The Langmuir and Freundlich models were expressed by the following Equations [45]:
Langmuir   model     1 q e = 1 q m + 1 q m K L 1 C e
Freundlich   model   log q e = log K f + 1 n log C e
where qe represent the adsorption effectiveness at equilibrium (mg/g), n is the Freundlich exponent consistent to adsorption capacity, Ce is the equilibrium concentration of Cr (VI) in (mg/L), Kf signifies the Freundlich constant (mg/g), 1/n describe the adsorption density, qm designates the maximum adsorption efficiency (mg/g), and KL is the constant of Langmuir (L/mg). The above-exposed parameters are calculated from the relation of log qe vs. log Ce and Ce/qe vs. Ce diagrams. The Linear plots of the Freundlich and Langmuir isotherm models for Cr (VI) removal at sorbent weight = 0.6 g/100 mL Cr(VI), pH = 2 are depicted in Figure 6A,B, respectively. The value of n should be 10 < n > 1 for favorable adsorption situations. The value of n in the current study was found to be 8.33, which demonstrates that the Cr(VI) sorption onto Fe(0)@AC material is favorable. The calculated parameters of the examined adsorption models are reported in Table 1. According to the association coefficient values (R2), the findings are more suitable when fitted to the Langmuir model (R2 = 0.977) in comparison to those obtained by the Freundlich isotherm model (R2 = 0.971). The possibility and features of the Langmuir model based on the dimensional separation factor RL is defined by the next Equation [46]:
R L = 1 1 + K L C i
where Ci is the Cr (VI) initial concentration. The RL value approves the adsorption to be favorable (0 < RL < 1), linear (RL = 1), irreversible (RL = 0), and disapproving (RL > 1). The RL value for the studied sorbent Fe(0)@AC material was found to be 0.31 (in the range of 0 < RL < 1). This value confirms an appropriate isotherm adsorption of Cr (VI) ions onto the Fe(0)@AC interface in the scrutinized concentration range.

2.4. Adsorbent Characterization after Adsorption

Fe(0)@AC adsorbent was characterized via variable techniques after Cr(VI) adsorption, and compared without adsorption experiments. The morphology of the prepared Fe(0)@AC adsorbent was studied with and without adsorption experiments, as shown in Figure 7. The SEM morphology of the Fe(0)@AC adsorbent was not changed after Cr(VI) adsorption; it remained a micro rock shape, with porous and heterogeneous character. This morphological image confirmed the heterogeneity of the formed rock shape, which could play a role in the metal adsorption application. Next, the chemical bonds at the surface of Fe(0)@AC adsorbent were investigated with and without adsorption experiments by FT-IR, as shown in Figure 8A. The same peaks were found at 1560 and 453 cm−1, which could be due to the vibration mode of C=C bonding in activated carbon [32] and Fe-C bond, respectively [33]. The intensity of the peaks declined after adsorption, which confirms the interaction between Cr(VI) and the investigated adsorbent. Additionally, the Raman spectral was studied at a range of 200–2100 cm−1 with and without adsorption experiments, as displayed in Figure 8B. Two sharp peaks were seen in the Raman spectra of Fe(0)@AC adsorbent at 1601.80 cm−1 and 1341.05 cm−1. The first peak could be due to the G-peak, which is the graphite scattering peak of the graphite carbon structure. The other sharp peak could be attributed to the D-peak, which is interpreted by lattice defects or disordered arrangement. The peaks after adsorption become wider, which could be attributed to the interaction between the adsorbed Cr(IV) and the Fe(0)@AC adsorbent. In conclusion, it can be understood that the designed Fe(0)@AC material could be utilized to remove Cr(VI) from aqueous solutions.

2.5. The Adsorption Capacity Comparison and pH of Solution for Cr (VI) Removal of with Some Reported Adsorbent Materials

Although a comparative study of the studied Fe(0)@AC sorbent with other described adsorbents is hard owing to the portable test conditions related to each study, the comparison results of the solution pH and the adsorption capacity for removal of Cr (VI) with some previous described adsorbents are recorded in Table 2 [47,48,49,50,51,52,53,54]. For the prepared Fe(0)@AC material, the adsorption capacity (qm; mg g−1) was found to be 38.4 mg g−1. These findings demonstrate that this Fe(0)@AC material shows a very noteworthy uptake adsorption ability compared to other types of materials and composites, for example, hydrous stannic oxide with a qm of 3.48 mg g−1 [47], modified groundnut hull with a qm of 31.0 mg g−1 [53], and Nano-Al2O3 with a qm of 17.7 mg g−1 [54], as shown in Table 2. Additionally, the mechanism of Cr(VI) adsorption over the prepared Fe(0)@AC material could be suggested by the physical adsorption followed by chemical interaction [55]. The physical adsorption starts at the pores of the activated carbon and then interacts with the zero-valent iron by chemical interaction between the Cr(VI) and Fe(0). To conclude, the composition of Fe(0)@AC could be applied as a substrate towards Cr(VI) adsorption in aqueous solutions.

3. Materials and Methods

The source of zero-iron is ferric chloride in addition to sodium borohydride as a reducing agent. Zero-iron and powdered activated carbon were purchased from Sigma-Aldrich (St. Louis, MO, USA) and Fisher (Waltham, MA, USA), and were utilized in experimental work without further analysis or purification.

3.1. Synthesis of Fe(0)@Activated Carbon Material

All materials in this report were of analytical grade and used directly, without any further purification. All the reagents were delivered from Chemical Reagent Co., Ltd. (Darmstadt, Germany) and Sigma-Aldrich (St. Louis, MO, USA).
The preparation of Fe(0) by NaBH4 reduction is shown in the following reaction:
4 Fe ( aq ) 3 + + 9 H 2 O + 3 BH 4 - → 4 Fe ( s ) 0 + 12 H ( aq ) + + 3 H 2 BO 3 - + 6 H 2 ( g )
In a representative process, 0.1 M of sodium borohydride in a certain volume of bidistilled H2O was gradually added into 0.2 M of FeCl3.6H2O in an equivalent ratio of ethanol absolute. Next, all the NaBH4 was added. Then, 0.75 g of powdered activated carbon (AC) was inserted, followed by strong stirring (400 rpm) for 25 min. Consequently, the mix was left to settle for 40 min. The product was isolated through centrifugation, then washed three times carefully with bidistilled H2O and ethanol. Finally, the solid product was dried under vacuum to prepare it for further use.

3.2. Material Categorization

FTIR study was carried out in the range of 400–4000 cm−1 using the FTIR spectrometer (model BRUKER, Lemböckgasse, Wien, Austria). The morphology of the solid prepared material was investigated by a SEM (Model-JEOL, JSM-5410, Tokyo, Japan). Raman spectroscopy was employed to examine the steadiness of the chemical construction of the prepared Fe(0)@AC material, using a Raman spectrometer (HORIBA SCIENTIFIC, California SUA) before and after the Cr(VI)adsorption. Transmission electron microscopy (TEM) using a Jeol TEM-1230 as a TEM model operating at acceleration voltage 120 kV was used to study the morphology of the Fe(0) material (Tokyo, Japan). The XRD of the prepared Fe(0) material was investigated with the use of a TD-3500 diffractometer at room temperature with Ni filtered CuKα radiation and λ = 0.15418 nm, at 25.0 mA and 35.0 kV in the range 2θ = 10–80° at scan steps 0.02°( Dandong Tongda Science & Techn Co., Ltd., Liaoning, China).

3.3. Batch Adsorption Experimentations

All tests were carried out at the temperature range 25–55 °C. The adsorption experiments were accomplished in batches. The experimentations of adsorption batch were completed by 0.6 g of Fe(0)@AC shaking with 100 mL solutions of Cr (VI). The flasks were stirred in a THERMOLAB Shaking Water Bath at a shaking speed of 200, 300, and 400 rpm. The Cr (VI) dose in the test solution was measured spectrophotometrically by a UV/vis-spectrophotometer (UV-1800-JAPAN -MODEL SHIMADZU) at a wavelength range from 200 to 800 nm and supplied with a 1.0 cm quartz-cell. After the accomplishment of the adsorption testing, the values of absorbance were recorded at the λmax = 360.0 nm. The effect of the Fe(0)@AC catalyst mass (0.2–0.8 g/100 mL) on the removal of Cr (VI) was scrutinized. The contact time effect on the adsorption of Cr (VI) was examined from 25 to 180.0 min. The values of pH of the medium were adjusted from 1.0 to 11.0 using 0 0.01 M nitric acid or 0.1 M potassium hydroxide.

4. Conclusions

Removal of Cr(VI) from wastewater was studied via a novel synthesized adsorbent substrate based on zero-valent iron and activated carbon (Fe(0)@AC). The SEM images of the as-prepared Fe(0)@AC material confirm the successful chemical design of Fe(0) with activated carbon as a heterogeneous composite with a heterogeneous morphology of the rock shape structure, which could play a role in the metal adsorption application. Additionally, the effect of pH, adsorbent weight, adsorbate concentration, and regeneration performance were studied. The removal efficiency (RE) of Cr(VI) reached 95% in the case of 0.8 g/100 mL from Fe(0)@AC adsorbent. In short, the adsorption performance of Cr(VI) at Fe(0)@AC adsorbent should be at low pH of around 2. Langmuir adsorption isotherm is well-suited, due its higher correlation coefficients (R2). Adsorption regeneration was confirmed as a stable performance up to the fifth cycle, which indicates the ability of Fe(0)@AC adsorbent to remove Cr(VI) from aqueous solutions for up to at least five cycles.

Supplementary Materials

The following supporting information can be downloaded at: https://www.mdpi.com/article/10.3390/catal12050515/s1, Figure S1: XRD analysis of the prepared Fe(0) material; Figure S2: TEM micrograph of the prepared Fe(0) material.

Author Contributions

M.J.A.: Investigation, Methodology, Resources, Formal analysis, Data curation. D.F.M.A.: Investigation, Methodology, Resources, Formal analysis, Data curation. M.G.: Investigation, Supervision, Methodology, Resources, Formal analysis, Data curation, Funding acquisition, Writing-original draft, Writing-review & editing. M.M.K.: Conceptualization, Investigation, Methodology, Resources, Formal analysis, Data curation, Funding acquisition, Writing-original draft, Writing-review & editing. I.M.A.M.: Conceptualization, Investigation, Resources, Formal analysis, Data curation, Writing-original draft, Writing-review & editing. H.M.A.E.-L.: Conceptualization, Investigation, Methodology, Resources, Formal analysis, Data curation, Funding acquisition, Writing-original draft, Writing-review & editing. All authors have read and agreed to the published version of the manuscript.

Funding

The authors acknowledge the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research at King Faisal University, Saudi Arabia for financial support under research group project track [GRANT-550].

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The raw/processed data generated in this work are available upon request from the corresponding author.

Acknowledgments

The authors acknowledge the Deanship of Scientific Research, Vice Presidency for Graduate Studies and Scientific Research at King Faisal University, Saudi Arabia for financial support under research group project track [GRANT-550].

Conflicts of Interest

The authors declare no conflict of interest.

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Catalysts 12 00515 g001 550
Figure 1. SEM images of the introduced Fe(0)@AC at two different magnifications; 1 KX (A), and 3 KX (B).
Figure 1. SEM images of the introduced Fe(0)@AC at two different magnifications; 1 KX (A), and 3 KX (B).
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Catalysts 12 00515 g002 550
Figure 2. FT-IR; (A), and Raman spectroscopy; (B) of the prepared Fe(0)@AC.
Figure 2. FT-IR; (A), and Raman spectroscopy; (B) of the prepared Fe(0)@AC.
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Catalysts 12 00515 g004 550
Figure 4. Effect of temperature (pH = 2) (A) and pH (B) on the on the removal efficiency (adsorption) of Cr (VI) by Fe(0)@AC; 0.6 g of Fe(0)@AC, 100 mg/L Cr(IV), adsorption time = 90 min.
Figure 4. Effect of temperature (pH = 2) (A) and pH (B) on the on the removal efficiency (adsorption) of Cr (VI) by Fe(0)@AC; 0.6 g of Fe(0)@AC, 100 mg/L Cr(IV), adsorption time = 90 min.
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Figure 5. Regeneration of ZVI@AC (Fe(0)@AC) sorbent (100 mL of 100 ppm Cr(VI), 25 °C, 0.6 g sorbent and).
Figure 5. Regeneration of ZVI@AC (Fe(0)@AC) sorbent (100 mL of 100 ppm Cr(VI), 25 °C, 0.6 g sorbent and).
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Figure 6. Linear diagrams of (A) Freundlich and (B) Langmuir models for Cr (VI) removal; pH = 2, sorbent weight = 0.6 g/100 mL Cr(VI).
Figure 6. Linear diagrams of (A) Freundlich and (B) Langmuir models for Cr (VI) removal; pH = 2, sorbent weight = 0.6 g/100 mL Cr(VI).
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Catalysts 12 00515 g007 550
Figure 7. SEM images of the prepared Fe(0)@AC adsorbent after adsorption experiment (A) and before adsorption experiment (B).
Figure 7. SEM images of the prepared Fe(0)@AC adsorbent after adsorption experiment (A) and before adsorption experiment (B).
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Figure 8. FT-IR (A) and Raman spectroscopy (B) of the prepared Fe(0)@AC adsorbent with (red lines) and without (black lines) adsorption experiments.
Figure 8. FT-IR (A) and Raman spectroscopy (B) of the prepared Fe(0)@AC adsorbent with (red lines) and without (black lines) adsorption experiments.
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Table
Table 1. Adsorption isotherm parameters for Cr(VI) adsorption on 0.6 g/100 mL Fe(0)@AC material.
Table 1. Adsorption isotherm parameters for Cr(VI) adsorption on 0.6 g/100 mL Fe(0)@AC material.
ModelLangmuirFreundlich
Parametersqmax (mg/g)KL (L/mg)R2KfnR2
Values38.40.0380.9776.328.330.971
Table
Table 2. Comparison of adsorption capacity and pH of solution for Cr (VI) removal of with reported different adsorbents.
Table 2. Comparison of adsorption capacity and pH of solution for Cr (VI) removal of with reported different adsorbents.
SorbentsOptimum pHSorbent/Solution Ratio (g L−1)Adsorption Capacity
qm (mg g−1)		References
Fe(0)@AC2638.4This study
Hydrous stannic oxide243.48[47]
Treated sawdust of sal tree3.50.19.55[48]
Dictyopteris polypodioides11021.78[49]
Banana peel2-10.42[50]
Henna Leaves4-0.078[51]
banana peel powder3-7.35[52]
modified groundnut hull2-31.0[53]
Nano-Al2O34517.7[54]
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Almujaybil, M.J.; Abunaser, D.F.M.; Gouda, M.; Khalaf, M.M.; Mohamed, I.M.A.; Abd El-Lateef, H.M. Facile Synthesis of Fe(0)@Activated Carbon Material as an Active Adsorbent towards the Removal of Cr (VI) from Aqueous Media. Catalysts 2022, 12, 515. https://doi.org/10.3390/catal12050515

AMA Style

Almujaybil MJ, Abunaser DFM, Gouda M, Khalaf MM, Mohamed IMA, Abd El-Lateef HM. Facile Synthesis of Fe(0)@Activated Carbon Material as an Active Adsorbent towards the Removal of Cr (VI) from Aqueous Media. Catalysts. 2022; 12(5):515. https://doi.org/10.3390/catal12050515

Chicago/Turabian Style

Almujaybil, Mohammed J., Dania Fathi Mohammed Abunaser, Mohamed Gouda, Mai M. Khalaf, Ibrahim M. A. Mohamed, and Hany M. Abd El-Lateef. 2022. "Facile Synthesis of Fe(0)@Activated Carbon Material as an Active Adsorbent towards the Removal of Cr (VI) from Aqueous Media" Catalysts 12, no. 5: 515. https://doi.org/10.3390/catal12050515

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