Search Results (59)

Amitriptyline (AMT), a widely prescribed antidepressant, and its metabolites have emerged as significant environmental contaminants, posing substantial risks to aquatic organisms and human health. Systematic and in-depth investigations into advanced anode materials, coupled with a profound elucidation of their electrochemical mechanisms, are imperative for the development of efficacious technologies for AMT removal. In this study, a series of amorphous carbon-encapsulated zinc oxide (C@ZnO) modified anodes were systematically synthesized and incorporated into a persulfate-based electrochemical system (CZ-PS) to comprehensively elucidate the catalytic mechanisms and mass transfer efficiencies governing the degradation of AMT via electroperoxidation. Notably, the CZ-PS system achieved a 97.5% degradation for 5.0 mg/L AMT within 120 min under optimized conditions (200 C@ZnO electrode, pH 7.0, current density 20 mA/cm², PS concentration 0.5 mM), significantly outperforming the single PS system (37.8%) or the pure electrocatalytic system. Quenching experiments and EPR analysis confirmed hydroxyl radicals (•OH) and sulfate radicals (SO₄•⁻) as the dominant reactive species. Both acidic and neutral pH conditions were demonstrated to favorably enhance the electrocatalytic degradation efficiency by improving adsorption performance and inhibiting •OH decomposition. The system retained >90% degradation efficiency after 5 electrode cycles. Three degradation pathways and 13 intermediates were identified via UPLC–MS/MS analysis, including side-chain demethylation and oxidative ring-opening of the seven-membered ring to form aldehyde/carboxylic acid compounds, ultimately mineralizing into CO₂ and H₂O. It demonstrates strong engineering potential and provides a green, high-efficiency strategy for antibiotic wastewater treatment. Full article

The widespread contamination of aquatic systems by ciprofloxacin (CIP)—a persistent fluoroquinolone antibiotic—poses severe ecological risks due to its antibacterial resistance induction. Conventional sulfate radical-based advanced oxidation processes (SR-AOPs) suffer from inefficient catalyst synthesis, exemplified by low-yield ZIF-67 precursors (typically <25%). To address this, a nitrogen-doped carbon composite Co₃O₄/N@C was synthesized via ammonia-assisted ligand exchange followed by pyrolysis, using N-doped ZIF-67 as a self-sacrificial template. The ammonia incorporation quadrupled precursor yield compared to ammonia-free methods. This catalyst activated peroxydisulfate (PDS) to degrade 95% CIP within 90 min under the optimized conditions (0.5 g/L catalyst, 2 mmol/L PDS, pH 5), representing a 30% enhancement over non-ammonia analogs. Mechanistic studies identified singlet oxygen (¹O₂) as the dominant reactive species, facilitated by N-doped carbon-mediated electron transfer. This strategy overcomes the scalability barrier of MOF-derived catalysts for practical antibiotic wastewater remediation. Full article

The continuous increase in solid waste poses a significant environmental challenge. Pyrolysis represents a crucial technology for the valorization of solid waste. As the primary product, biochar has found applications in numerous fields and garnered significant scientific interest. This study investigated the potential of NH₄Cl and FeCl₃ for modifying biochar. The resultant modified biochar achieved over 70% sulfamethoxazole (SMX) degradation within 30 min. The incorporation of NH₄Cl and FeCl₃ facilitated the formation of pyridinic nitrogen (N), graphitic nitrogen (N), and Fe(II) 1/2p, while the concomitant increase in persistent free radicals facilitated enhanced electron transfer rates. Notably, NH₄Cl/FeCl₃-modified biochar demonstrated superior efficacy compared with alternative activation techniques for real wastewater treatment. This study presents a novel material for persulfate (PDS)-based advanced oxidation processes, while also offering a cost-effective strategy for solid waste disposal. Full article

The continuous occurrence of steroidal pharmaceutical dexamethasone (DXM) in aqueous environments indicates the need for an efficient removal technology. The frequent detection of DXM in surface water could be substantially reduced by the application of photo-induced advanced oxidation technology. In the present study, Fe²⁺ and UVA-light activated peroxo compounds were applied for the degradation and mineralization of a glucocorticoid, 25.5 µM DXM, in ultrapure water (UPW). The treatment efficacies were validated in real spring water (SW). A 120 min target pollutant degradation followed pseudo first-order reaction kinetics when an oxidant/Fe²⁺ dose 10/1 or/and UVA irradiation were applied. Acidic conditions (a pH of 3) were found to be more favorable for DXM oxidation (≥99%) regardless of the activated peroxo compound. Full conversion of DXM was not achieved, as the maximum TOC removal reached 70% in UPW by the UVA/H₂O₂/Fe²⁺ system (molar ratio of 10/1) at a pH of 3. The higher efficacy of peroxymonosulfate-based oxidation in SW could be induced by chlorine, bicarbonate, and carbonate ions; however, it is not applicable for peroxydisulfate and hydrogen peroxide. Overall, consistently higher efficacies for HO^•-dominated oxidation systems were observed. The findings from the current paper could complement the knowledge of oxidative removal of low-level DXM in real water matrices. Full article

Fe-doped BiOBr nanomaterials with varying Fe concentrations were synthesized using a solvothermal method. Paracetamol (APAP) was selected as the target pollutant to evaluate the visible-light-driven peroxydisulfate (PDS) activation performance of the prepared catalysts. Among all samples, 5% Fe-doped BiOBr (5% Fe-BOB) exhibited the highest catalytic efficiency, which can completely degrade APAP in 30 min under visible light irradiation. The degradation kinetics of APAP, PDS consumption, and the dominant reactive species in the 5% Fe-BOB/PDS/visible light system were systematically investigated. Results revealed that both photocatalyst dosage and PDS concentration significantly influenced activation efficiency. The primary active species responsible for APAP degradation were identified as photogenerated holes (h⁺) and singlet oxygen (¹O₂). Furthermore, cycling tests and control experiments confirmed that the 5% Fe-BOB/PDS/visible light system maintained high stability and effectively degraded APAP across a wide pH range. This work provides an efficient and stable photocatalytic system for pharmaceutical wastewater treatment through PDS-based advanced oxidation processes. Full article

Carbonaceous materials (CMs) have gained great attention as heterogeneous catalysts in water treatment because of their high efficiency and potential contribution to achieving carbon neutrality. Expanded graphite (EG) is ideal for studying CMs because the reactivity in CMs largely depends on graphitic structures, and most surface of EG is exposed, minimizing mass transfer resistance. However, EG is poor in adsorption and catalysis. In this study, EG was modified by simple thermal treatment to investigate the effects of characteristics of graphitic structures on reactivity. Tetracycline (TC) removal rate via activating peroxydisulfate (PDS) by the EG treated at 550 °C (EG550) was more than 10 times that of EG. The thermal modification did not significantly increase surfaces but led to increases in damaged, rough surfaces, graphitization degree, C content, defects, and C=O. Radical and non-radical pathways, such as SO₄^•−, O₂^•−, ¹O₂, and electron transfer, were involved in TC removal in EG550+PDS. TC degradation in EG550+PDS was initiated by hydroxylation, followed by demethylation, dehydroxylation, decarbonylation, and ring-opening. The ions ubiquitous in water systems did not significantly affect the performance of EG550+PDS, except for H₂PO₄⁻ and HCO₃⁻, suggesting the high potential of practical applications. This study demonstrated that graphitic structure itself and surface area are not detrimental in the catalytic reactivity of CMs, which is different from previous studies. Rather, the reactivity is governed by the characteristics, i.e., defects and functional groups of the graphitic structure. It is thought that this study provides valuable insights into the development of highly reactive CMs and the catalytic systems using them. Full article

Tetracycline (TC) contamination in wastewater presents a significant global environmental challenge, with conventional water treatment methods often proving ineffective at eliminating antibiotic pollutants. As a result, there is an urgent need for cost-effective and efficient remediation technologies. In this study, we utilized the abundant and low-cost Eichhornia crassipes as a precursor to prepare sulfuric acid-modified functional biochar (SC-Fe) through a two-step pyrolysis process. This SC-Fe was then employed to activate peroxydisulfate (PDS) for the removal of TC from wastewater. The structural and physicochemical properties of SC-Fe were extensively characterized, and its efficiency in activating PDS for TC degradation was evaluated. The results demonstrated that the SC-Fe/PDS system effectively removed 99.36% of TC within 60 min under optimal conditions (0.3 g/L SC-Fe, 5 mM PDS, initial pH 7.09, and 25 °C). The outstanding removal efficiency can be attributed to the high specific surface area, large porosity, and defect-rich structure of SC-Fe. Furthermore, during the TC removal process, the SC-Fe/PDS system generated SO₄^•−, •OH, and ¹O₂, with SO₄•⁻ and •OH acting as the primary reactive species. The high catalytic efficiency and low consumption of the SC-Fe/PDS system present a promising strategy for effective wastewater treatment. Full article

Extensive utilization of the herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) has resulted in contamination of the aquatic environment; this situation requires effective treatment technology. Ultraviolet-based advanced oxidation processes (UV-AOPs) are widely employed for the removal of organic contaminants from water. This study’s aim was to compare the degradation of the pesticide 2,4-D in UV-C-activated peroxide and peroxydisulfate systems. UV-C irradiation alone exhibited a negligible effect on pesticide degradation, whereas the addition of oxidants significantly enhanced the degradation efficiency relative to 2,4-D. Complete pesticide removal was achieved after 15 min of UV/H₂O₂ treatment, while twice as much time was required with the UV/S₂O₈²⁻ process. COD decreased by 74% and 28% for UV-C-activated peroxide and peroxydisulfate, respectively. Both investigated systems demonstrated good performance for 2,4-D dechlorination. Pesticide degradation rates increased with increasing dosages of the applied oxidants. Acidic conditions were more favorable for degradation of 2,4-D, compared to neutral and basic conditions, for both systems studied. The degradation efficiency relative to 2,4-D decreased in the presence of HA, Cl⁻ and HCO₃⁻ in water matrices. The predominant radical for the UV-C-activated peroxydisulfate was determined to be a sulfate radical. These findings are of fundamental and practical significance in understanding UV-C-activated 2,4-D degradation, paving the way for the selection of preferred processes for the optimal removal of pesticides from various aqueous matrices. Full article

Electroless nickel plating is a chemical deposition process in which nickel ions within a plating solution are reduced by a chemical reducing agent and subsequently deposited onto the surface of a solid substrate. Chemical nickel-plating wastewater contains substantial amounts of phosphorus as well as abundant nickel resources. In this study, electrodialysis coupled with advanced oxidation techniques was utilized for the efficient recovery of nickel and phosphorus from spent nickel-plating solutions. The end-of-life tank solution from chemical nickel plating was treated via electrodialysis to remove harmful phosphite and sulfate ions, enabling the purified solution to be reused in plating production by supplementing it with appropriate amounts of sodium hypophosphite and nickel sulfate. Subsequently, the concentrate generated from electrodialysis was treated using peroxydisulfate (PDS)-based advanced oxidation technology to break nickel complexation and simultaneously promote the oxidation of hypophosphite and phosphite ions. Finally, Ca(OH)₂ was employed as a precipitating agent to effectively recover phosphorus from the treated concentrate. From an economic perspective, optimal process conditions were determined as follows: a current density of 20 mA/cm², concentrate-to-dilute water volume ratio of 1:1, current speed of 1.0 m³/h, and a sodium sulfate concentration in concentrate of 20 g/L. Under these conditions, the migration rates of H₂PO₂⁻ and HPO₃²⁻ ions reached 67.3% and 62.53%, respectively, whereas Ni²⁺ exhibited significantly lower mobility at only 6.77%. The purified wastewater recovered approximately 60% of its initial plating activity. Regarding the concentrate—which is a by-product of electrodialysis—the hypophosphite ions were nearly completely oxidized using a PDS dosage of 0.3 mol/L. Furthermore, when the Ca/P molar ratio was adjusted to 2.0, total phosphorus (TP) and nickel (Ni) removal efficiencies exceeded 98% and 93%, respectively. Full article

In the present study, cellulose and lignin with different weight ratios were mixed and pyrolyzed to prepare biochars for organic dye pollutant removal in water via Fenton-like catalysis. The results indicated that a higher cellulose content in a biomass precursor could result in a lower biochar yield with a lower carbon content in the biochar. Moreover, with the increase in cellulose content, the resulting biochar had a higher graphitization degree with higher levels of crystallinity, as well as a richer porosity. When using Rhodamine B (RhB) as the dye probe, the biochar derived from a higher cellulose/lignin ratio precursor exhibited better adsorptive performance. It was further found that the biochar could act as a Fenton-like catalyst to activate peroxydisulfate (PDS) and accelerate RhB removal via a degradation route, in which single oxygen (¹O₂) was identified as the active species. Therefore, the biochar/PDS catalytic system exhibited prominent RhB removal stability in various water matrices with a wide pH application range. This study develops a new approach to prepare biomass-derived biochar with high organic removal capacity via Fenton-like catalysis assisted with adsorption synergy. Full article

In this study, the catalytic performance of the Fenton sludge iron-based biochar catalyst (Fe@BC700), generated during the Fenton process, was investigated regarding its role in oxidizing 2,4-dichlorophenol (2,4-DCP) and As(III) from aqueous solutions in peroxymonosulfate (PMS), peroxydisulfate (PDS), and hydrogen peroxide (H₂O₂) systems. The characteristics of the as-prepared catalyst, operational parameters of H₂O₂/UV/Fe@BC700, PDS/UV/Fe@BC700, and PMS/UV/Fe@BC700 systems, and the kinetics of 2,4-DCP degradation were evaluated. Fe@BC700 exhibited excellent capabilities for activating persulfate and an outstanding oxidant performance as a heterogeneous photocatalyst under UV irradiation. Among the tested systems, PMS/UV/Fe@BC700 showed the highest oxidation capabilities for both 2,4-DCP and As(III) within 40 min. The total organic carbon (TOC) removal efficiency for 2,4-DCP was up to 95.9% in the PMS/UV/Fe@BC700 system. The presence of free radicals in the PMS/PDS system included ·OH, SO₄^·−, and ·O₂⁻, which were facilitated by both UV irradiation and the catalyst. The by-products generated during the PMS/UV/Fe@BC700 treatment were identified via LC-MS analysis, which showed that catalytic degradation substantially reduced the chronic and acute toxicity of 2,4-DCP intermediates. The present study demonstrates that the iron-based biochar derived from Fenton sludge exhibited remarkable persulfate activation capabilities and was highly effective in removing 2,4-DCP and As(III). Full article

Advanced oxidation processes based on either peroxydisulfate (PDS) or peroxymonosulfate (PMS), collectively termed persulfate-based advanced oxidation processes (PS-AOPs), show potential in wastewater treatment applications. In this work, the nitrogen (N) and sulfur (S) co-doped biochar (NSBC) was prepared via a one-step pyrolysis of coffee grounds at 400 to 800 °C as a PMS activator for degrading paracetamol (PCT). The non-metallic NSBC demonstrated exceptional catalytic activity in activating PMS. In the NSBC-800/PMS system, 100% of PCT was completely degraded within 20 min, with a high reaction rate constant (k_obs) of 0.2412 min⁻¹. The system’s versatility was highlighted by its degradation potential across a wide pH range (3–11) and in the presence of various background ions and humic acids. The results of various experiments and characterization techniques showed that the system relied on an NSBC-800-mediated electron transfer as the main mechanism for PCT degradation. Additionally, there was a minor involvement of ¹O₂ in a non-radical degradation pathway. The graphitic N and thiophene-S (C-S-C) moieties introduced by N/S co-doping, as well as the carbonyl (C=O) groups of the biochar, were considered active sites promoting ¹O₂ generation. The total organic carbon (TOC) removal rate reached 37% in 120 min, while the assessment of the toxicity of the degradation products also affirmed the system’s environmental safety. This research provides a novel method for preparing environmentally friendly and cost-effective carbon-based catalysts for environmental remediation. Full article

The persistence of peroxydisulfate anion (S₂O₈²⁻) in soil is a key factor influencing the effectiveness of in situ chemical oxidation (ISCO) treatments, which use S₂O₈²⁻ (S₂O₈²⁻ based ISCO) to remediate contaminated groundwater. However, only a few studies have addressed aspects of S₂O₈²⁻ persistence, such as the effect of temperature and the fate of sulfates (SO₄²⁻) generated by S₂O₈²⁻ decomposition in real soil and/or aquifer materials. Additionally, there are no studies comparing batch and dynamic column tests. To address these knowledge gaps, we conducted batch tests with varying temperatures (30–50 °C) and initial S₂O₈²⁻ concentrations (2.7 g/L and 16.1 g/L) along with dynamic column experiments (40 °C, 16.1 g/L) with comprehensively characterized real soil/aquifer materials. Furthermore, the principal component analysis (PCA) method was employed to investigate correlations between S₂O₈²⁻ decomposition and soil material parameters. We found that S₂O₈²⁻ decomposition followed the pseudo-first-order rate law in all experiments. In all tested soil materials, thermal dependence of S₂O₈²⁻ decomposition followed the Arrhenius law with the activation energies in the interval 65.2–109.1 kJ/mol. Decreasing S₂O₈²⁻ concentration from 16.1 g/L to 2.7 g/L led to a several-fold increase (factor 2–11) in bulk S₂O₈²⁻ decomposition rate coefficients (k′) in individual soil/aquifer materials. Although k′ in the dynamic column tests showed higher values compared to the batch tests (factor 1–3), the normalized S₂O₈²⁻ decomposition rate coefficients to the total BET surface were much lower, indicating the inevitable formation of preferential pathways in the columns. Furthermore, mass balance analysis of S₂O₈²⁻ decomposition and SO₄²⁻ generation suggests the ability of some systems to partially accumulate the produced SO₄²⁻. Principal Component Analysis (PCA) identified total organic carbon (TOC), Ni, Mo, Co, and Mn as key factors influencing the decomposition rate under varying soil conditions. These findings provide valuable insights into how S₂O₈²⁻ behaves in real soil and aquifer materials, which can improve the design and operation of ISCO treatability studies for groundwater remediation. Full article

In this work, the decomposition of bisphenol S (BPS) by biochar derived from banana peel (BPB) promoted by copper phosphide (Cu₃P) was examined. Different materials with Cu₃P loadings from 0.25 to 4.00 wt.% on biochar were synthesized, characterized using the Brunauer–Emmett–Teller (BET) method, X-ray diffraction (XRD) and a scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS), and evaluated. Nearly all of the synthesized materials exhibited low to moderate adsorption capacity, attributable to their limited surface area (<3.1 m²/g). However, in the presence of sodium persulfate (SPS), the 2%Cu₃P/ΒPB/SPS system was capable of removing 90% of 500 μg/L BPS in less than 10 min. The system’s performance was enhanced under inherent pH, and the reaction rate followed pseudo-first-order kinetics with respect to BPS and persulfate concentrations. Interestingly, the presence of 250 mg/L of sodium chloride had a negligible effect, while low to moderate inhibition was observed in the presence of bicarbonates and humic acid. In contrast, significant retardation was observed in experiments performed in real matrices, such as secondary effluent (WW) and bottled water (BW). According to scavenging experiments, both radical and non-radical mechanisms participated in the BPS degradation. Four transformation products were identified using the UHPLC/TOF-MS system in negative ionization mode, with two of them having higher molecular weights than BPS, while the other two TBPs involved the ring-opening reaction, and a BPS decomposition pathway was proposed. Full article

Persulfate-based advanced oxidation processes have emerged as a promising approach for the degradation of organic pollutants in aqueous environments due to their ability to generate sulfate radicals (SO₄^−·) within catalytic systems. In this study, peroxydisulfate (PDS) and peroxymonosulfate (PMS) were investigated with the natural vanadium–titanium magnetite (VTM) as the activator for the degradation of acid orange II. The degradation efficiency increased with higher dosages of VTM or persulfate (both PDS and PMS) at lower concentrations (below 10 mM). However, excessive PMS (higher than 10 mM) in the PMS/VTM system led to the self-consumption of free radicals, significantly inhibiting the degradation of acid orange II. The VTM-activated PDS or PMS maintained an effective degradation of acid orange II in a wide pH range (3~11), suggesting remarkable pH stability. The SO₄^−· was the main active species in the PDS/VTM system, while hydroxyl radical (·OH) also contributed significantly to the PMS/VTM system. In addition, PMS exhibited better thermal stability during VTM activation. Coexisting ions in an aqueous environment such as bicarbonate (HCO₃^–), carbonate (CO₃^2–), and hydrogen phosphate (HPO₄^2–) had obvious effects on persulfate activation. Our study systematically investigated the different activation processes and influencing factors associated with PDS and PMS when the natural VTM was used as a catalyst, thereby providing new insights into the persulfate-mediated degradation of organic pollutants in aqueous environments. Full article