Persulfate Activation Process Research Articles

2,3-pyridinedicarboxylic acid-modified MIL-88A(Fe) for enhanced peroxymonosulfate activation to degrade organic contaminants

Metal-organic framework (MOF)-based composites have shown a great application potential in photoassisted persulfate activation process and environmental remediation. Herein, 2,3-pyridinedicarboxylic acid (PDA) is firstly used to improve the catalytic activity of MIL-88A(Fe). The composite catalysts are effectively synthesized using a solvothermal method. At an 80.2 mg modification level of PDA, the catalyst [MIL-88A(Fe)-PDA-3] could achieve 98.20 % removal of AR18 (acid red 18) through the visible-light-assisted peroxymonosulfate (PMS) activation. It is 7.8-fold increase than pristine MIL-88A(Fe). The suitable conditions for AR18 elimination are 0.4 g/L MIL-88A(Fe)-PDA-3, 1.5 mM PMS and pH = 10. The interplay between influencing factors is explored by a response surface methodology. The quenching studies and EPR tests indicate the generation of active species such as ·OH, SO4·−, 1O2, O2·−, and FeIVO in the reaction system, with ·OH playing a significant role for AR18 degradation. A potential mechanism is proposed based on the above results. This study offers a fresh perspective for the development of efficient MOFs materials.

Remediation of polycyclic aromatic hydrocarbons polluted soil by biochar loaded humic acid activating persulfate: performance, process and mechanisms

The remediation for polycyclic aromatic hydrocarbons contaminated soil with cost-effective method has received significant public concern, a composite material, therefore, been fabricated by loading humic acid into biochar in this study to activate persulfate for naphthalene, pyrene and benzo(a)pyrene remediation. Experimental results proved the hypothesis that biochar loaded humic acid combined both advantages of individual materials in polycyclic aromatic hydrocarbons adsorption and persulfate activation, achieved synergistic performance in naphthalene, pyrene and benzo(a)pyrene removal from aqueous solution with efficiency reached at 98.2%, 99.3% and 90.1%, respectively. In addition, degradation played a crucial role in polycyclic aromatic hydrocarbons remediation, converting polycyclic aromatic hydrocarbons into less toxic intermediates through radicals of ·SO4-, ·OH, ·O2–, and 1O2 generated from persulfate activation process. Despite pH fluctuation and interfering ions inhibited remediation efficiency in some extent, the excellent performances of composite material in two field soil samples (76.7% and 91.9%) highlighted its potential in large-scale remediation.

Single Atom Catalyst in Persulfate Oxidation Reaction: From Atom Species to Substance.

With maximum utilization of active metal sites, more and more researchers have reported using single atom catalysts (SACs) to activate persulfate (PS) for organic pollutants removal. In SACs, single metal atoms (Fe, Co, Cu, Mn, etc.) and different substrates (porous carbon, biochar, graphene oxide, carbon nitride, MOF, MoS2 , and others) are the basic structural. Metal single atoms, substances, and connected chemical bonds all have a great influence on the electronic structures that directly affect the activation process of PS and degradation efficiency to organic pollutants. However, there are few relevant reviews about the interaction between metal single atoms and substances during PS activation process. In this review, the SACs with different metal species and substrates are summarized to investigate the metal-support interaction and evaluate their effects on PS oxidation reaction process. Furthermore, how metal atoms and substrates affect the reactive species and degradation pathways are also discussed. Finally, the challenges and prospects of SACs in PS-AOPs are proposed.

Utilizing Self‐Floating Cu3BiS3 Polydopamine Polyurethane Sponges for Enhanced Water Purification: Harnessing the free radical and non‐radical in persulfate system

AbstractThe advanced oxidation process based on persulfate group is a promising technology for water purification. However, the synergistic effect of free radical and non‐free radical degradation is still not feasible in the persulfate activation process, which consumes a large amount of external energy. The self‐floating Cu3BiS3/polydopamine/polyurethane sponge was prepared using a simple method, resulting in high catalytic performance when activated by peroxydisulfate (PDS). The experiments conducted to identify free radicals showed that the degradation process of tetracycline (TC) involved the synergistic action of non‐radical 1O2 and free radicals (SO4⋅− and • OH) and the conversion of Cu+/Cu2+. The addition of Cl−, HCO3−, PO43−, and SO42− to the solution did not significantly affect the high degradation rate of TC. Furthermore, the interfacial evaporation process achieved a remarkable evaporation rate of 1.53 kg m−2 h−1 and produced reclaimed water without any detectable TC contaminants. The sponge also exhibited excellent salt resistance and chemical stability. This study provides valuable insights into the degradation of antibiotics and the desalination of seawater.

Flexible regulation of persulfate activation mechanisms through tuning Cu valence in CuBTC-derived copper oxide catalysts for improved pollutant degradation

Radical and nonradical dominated persulfate activation processes have pros and cons in the degradation of pollutants. It is challenging to flexibly tune the contribution ratios of radicals and nonradicals in a persulfate activation process for improved pollutant degradation. Herein, we successfully synthesize copper oxide catalysts derived from metal-organic frameworks. By varying the annealing temperature, valence states of copper can be regulated in the catalyst, thereby enabling the switching between radical and nonradical mechanisms for persulfate activation. Copper oxides annealed at 300 °C (CuBTC-300) demonstrate high performance in peroxydisulfate (PDS) activation for the degradation of bisphenol A (BPA), with the synergy of radical and nonradical mechanisms. The surface activated PDS-catalyst complex and OH are identified as the reactive oxidative species involved in this process. On one hand, PDS undergoes a one-electron transfer reaction with Cu(I) sites in Cu2O, generating SO4−, which subsequently converts into OH for BPA degradation. On the other hand, the combination of PDS molecules with CuO forms surface-activated complexes, depriving electrons from BPA. The increased content of Cu(II) in the catalyst gradually directs PDS activation towards the nonradical pathway. As the annealing temperature increases from 300 °C to 500 °C, the contribution of nonradical oxidation to BPA degradation increases from 58.65 % to 100 %. This work provides new insights into flexibly regulating persulfate activation mechanisms via rational catalysts design.

Rapid PFOS mineralization with peroxydisulfate activation process mediated by N modified Fe-based catalyst

As the cheap and efficient catalysts, the iron-based catalysts have been considered as one of the most promising catalysts for peroxydisulfate (PDS) activation and the development of high-performance iron-based catalysts are attracting growing attentions. In this work, a magnetic Fe-based catalysts (Fe/NC-1000) was obtained by using Fe modified ZIF-8 as the precursor and used to activate the PDS for the degradation of perfluorooctane sulphonate (PFOS). Morphology and structure analysis showed that the resulted Fe/NC-1000 catalyst was displayed porous spheres (40–60 nm) and mainly composed of Fe0, FeNx and carbon. When Fe/NC-1000 was employed to activate the PDS (0.1 g/L of catalyst dosage, 0.5 g/L of PDS dosage and at initial pH of 4.6), the Fe/NC-1000/PDS system exhibited excellent efficiency (97.9 ± 0.1) % for PFOS (10 mg/L) degradation within 30 min. The quenching tests and EPR results revealed that the Fe/NC-1000/PDS system degraded PFOS primarily through singlet oxygen (1O2) evolution and electron-transfer process. Besides, based on the degradation byproducts determined by LC-MS-MS, the PFOS first occurred de-sulfonation to form PFOA, and then the resulted PFOA underwent stepwise defluorination in the Fe/NC-1000/PDS system. Density Functional Theory (DFT) calculations and electrochemistry tests strongly confirmed that Fe/NC-1000 exhibited high electron transfer efficiency, resulting in promoted performance on activating PDS. Importantly, the results of Ecological Structure-Activity Relationship (ECOSAR) analysis showed that the intermediates were lowly toxic during the PFOS degradation, manifesting a green process for PFOS removal. This study would provide more understandings for the persulfate activation process mediated by Fe-based catalysts for Perfluorinated alkyl substances (PFAS) elimination.

In-situ degradation of phenol using CuMgFe-LDO catalyst and assessment of its service life in the persulfate activation process

Layered double oxides (LDOs) have been proven effective and reusable materials in removing phenols. However, the service life of LDOs in an application remains unclear. This study optimized the properties of CuMgFe-LDO and assessed its service life for in-situ groundwater remediation. Phenol degradation in CuMgFe-LDO-activated persulfate (PS) system with various groundwater matrix was analyzed. Results showed improved phenol degradation with increasing Cu content and calcination temperature in LDO production, with a decrease in degradation beyond a certain level of Cu. Phenol removal was slightly influenced by fulvic acid and sodium humate below 20.0 mg/L but strongly affected by 1.0 mmol/L of SO42− and HCO3−. A high TOC removal of 80 % in all three recycled tests was found within 30 min, with intermediate products identified as benzoquinone, fumaric/maleic acid, and finally, oxalic and acetic acid. The CuMgFe-LDO showed demonstrated exemplary performance in a continuously flowing phenol and PS solution column, with a long service life of 12 days and low copper leaching (1.8 mg/L) at pH 6.55. This study supports the potential of the CuMgFe-LDO-activated PS system for remediating groundwater contaminated with phenolic compounds and mitigating acidification from PS use.

Evaluation of atrazine degradation by iron persulfate activation process in aqueous phase using Taguchi approach

Atrazine (ATZ) is one of the most widely used herbicides for the control of annual broadleaf and grassy weeds in the world. Its residual in the environment is of great concern. This research work primarily focused on examining ATZ degradation by the ferrous ion activated persulfate (PS) oxidation process (Fe2+-AP process) and the influence of oxidative parameters on the degradation of ATZ in aqueous phase. The Taguchi Design of Experiment methodology was used to explore the effects of various operational parameters, including ATZ concentration, dosage of Fe2+, dosage of PS, and pH condition (Taguchi L9 orthogonal array). The optimal operational conditions were then determined based on the results of ANOVA statistical analysis. Operational conditions included ATZ at an initial concentration of 5 mg/L, with initial concentrations of 1 mM Fe2+, 10 mM PS, and pH = 3, at 20oC, for a reaction time period of 3 h. The sensitivity of factors for the ATZ degradation followed the decreasing order: PS concentration, pH, ATZ concentration and Fe2+ dosage. The results of this study provide useful operational conditions for the Fe2+-AP process, for application to field remediation of ATZ contamination.

Optimized fabrication of Cu-doped ZnO/calcined CoFe‒LDH composite for efficient degradation of bisphenol a through synergistic visible-light photocatalysis and persulfate activation: Performance and mechanisms

A novel magnetically separable Cu/ZnO/CoFe‒CLDH composite, whose synthesis was optimized using the Taguchi approach, was optimally synthesized by hydrothermally coupling Cu-doped ZnO and calcined CoFe–LDH. The synthesized Cu/ZnO/CoFe‒CLDH was applied to construct a synergistic process of integrating visible-light photocatalysis (VPC) with persulfate activation (PSA) and to degrade bisphenol A (BPA). Various characterizations proved that Cu/ZnO/CoFe‒CLDH possessed excellent physicochemical, optoelectronic and magnetic properties, thereby enhancing the catalytic performance. The Cu/ZnO/CoFe‒CLDH composite achieved highly efficient BPA degradation during the synergistic VPC‒PSA process, and its reaction rate constant (0.74 h−1) was 6.17-, 4.11-, and 2.85-fold higher than that of Cu/ZnO, CoFe‒CLDH, and Cu/ZnO/CoFe‒CLDH (VPC only), respectively. Moreover, the effects of the catalyst dosage, initial pollutant concentration, solution pH, persulfate dosage and coexisting ions on BPA degradation were comprehensively investigated. Radical-trapping experiments revealed that the contributions of ·OH, SO4·‒, ·O2−, and 1O2 involved in BPA degradation. Based on the intermediates identified by LC/MS, the main BPA degradation pathways were determined, the overall trend of which reflects a decreasing ecotoxicity. This study verified the effectiveness of the synergistic VPC‒PSA process with Cu/ZnO/CoFe‒CLDH, which could be used as a new reference for removing organic micropollutants from water.

Role of trace TEMPO as electron shuttle in enhancing chloroquine phosphate elimination in UV-LED-driven persulfate activation process

Chloroquine Phosphate (CP) is an antiviral drug used for treatment of COVID-19. It is released into wastewater and eventually contaminates natural water. This study reports an effective homogeneous catalysis way for CP degradation by the 2,2,6,6-Tetramethylpiperidine-N-oxyl (TEMPO) enhanced persulfate (PDS) activation under UVB-LEDs irradiation at 305 nm. TEMPO at a low concentration (0.1 μM) enhanced CP degradation in UV305/PDS process in deionized water at different pHs, in different anions and different molecular weight dissolved organic matter solutions and in real surface water. The enhancement was verified to be attributed to the electron shuttle role of TEMPO, which promoted the yield of SO4•– by enhancing electron donating capacity of the reacting system. The degradation products of CP and their acute toxicities suggested that UV305/PDS/TEMPO process has better performance on CP detoxification than UV305/PDS process. This study provides a new way to tackle the challenge of pharmaceutical pollutions in homogeneous photocatalysis process for natural water and sewage restoration.

Asymmetric enhancement of persulfate activation by N-doped carbon microelectrode: Electro-adsorption and activation pathway regulation

N-doped activated carbon as particle electrode was applied to form a three-dimensional persulfate electro-activation system (ACN/PS/EC) for p-chlorophenol (4CP) removal. The synergy between electro-catalysis (EC) and ACN/PS not only greatly accelerated the PS activation and 4CP degradation processes, but also markedly changed the activation mechanism. Basing on the results of radicals scavenging and electro-adsorption experiments, it is demonstrated that the radical pathway rather than the non-radical pathway was significantly strengthened by using EC owing to the asymmetric electro-adsorption of persulfate ions and 4CP. By quantitative structure-activity relationship analysis, the vital function of graphitic N was unveiled, which exerted action as an active center for PS activation. The effects of operation parameters (including PS concentration, current density, pH, etc.) on the persulfate activation process were also investigated, and the results suggest that the ACN/PS/EC system is a flexible and efficient oxidative system for pollutant degradation, even in complicated wastewaters.

Electron transfer-based peroxydisulfate activation by waste herb residue biochar: Adsorption versus surface oxidation

Waste herb residue biochar (WBC) was synthesized to activate peroxydisulfate (PDS) for the removal of different micropollutants. WBC prepared at 700 °C (WBC700) exhibits discrepant adsorption and PDS catalytic performance to three pharmaceuticals and four phenolic compounds. At 60 min reaction time, the adsorptive removal by 0.5 g/L WBC700 varied from 31.3% (clofibric acid) to 97.6% (4-chlorophenol), while the apparent removal ranged from 36.1% (clofibric acid) to 99.5% (4-chlorophenol) when 0.5 g/L WBC700 and 1.0 mM PDS were applied. The oxidation of the micropollutants involves electron transfer mechanism via the surface-confined metastable reactive complexes (WBC-PDS*), which was verified by electrochemical tests, quenching experiments, electron paramagnetic resonance, Fourier transform infrared and in-situ Raman spectroscopy. The observed pseudo first-order kinetic constant (kobs) of organic removal did not exhibit a good correlation with its electrochemical redox descriptor (half-wave potential, φ1/2, for example) as reported in the previous studies. Instead, the surface oxidation rate constant (koxid), determined from a dynamic model considering liquid-solid mass transfer of micropollutant and the sequent surface oxidation by WBC-PDS* complexes, was highly related to φ1/2. In parallel, the liquid-solid mass transfer coefficient (KLa) of micropollutant was obtained from a similar model excluding the surface oxidation, and kobs showed a more significant association with KLa than with adsorption capacity (Qe). This study provides a promising approach to understand the role of adsorption and surface oxidation in an electron transfer-dominated persulfate activation process.

Insight into the roles of microenvironment and active site on the mechanism regulation in metal-free persulfate activation process coupling with an electric field

The regulation of the persulfate activation mechanism is highly desirable and meaningful for the treatment of different wastewaters. The role of active sites for mechanism regulation in carbon-driven persulfate activation is still ambiguous due to the complex and easily neglected microenvironment (concentration distributions of organics and oxidants) nearby carbon catalyst. This work aims to reveal the critical roles of active site and microenvironment on the activation mechanism through N-doped modification and application of an electric field (AC/PS/EC). Several N-doped activated carbon catalysts were prepared by activating for different times to adjust the surface active center and adsorption selectivity under an electric field. The contribution ratio of radical pathway and non-radical pathway for organic elimination significantly varied with the concentration distribution of organics and oxidants nearby the microelectrodes. The increased electro-adsorption of persulfate anion was found to be the primary promoting factor for the radical pathway for organic oxidation, resulting in a synergistic increase in degradation rate in the AC/PS/EC system. The quantitative structure-activity relationships analysis also revealed that the electro-adsorption selectivity was dominated by the surface graphitic N and pore structure of catalyst. This study sheds new light on the oxidative pathway regulation to deal with complex wastewater in a flexible and efficient manner.

Flow line of density functional theory in heterogeneous persulfate-based advanced oxidation processes for pollutant degradation: A review

Persulfate-based advanced oxidation processes (P-AOPs), as the commonly used technologies, attract intensive attention, because persulfate is stable and safe with various activation methods, and the generated reactive oxygen species (ROS) are highly active. Density functional theory (DFT) calculations can analyze the intrinsic mechanism and specific pathways of P-AOPs at microscopic level, which is difficult to be realized in experiments. Recent DFT discoveries for P-AOPs have induced tremendous interest in persulfate activation or pollutant degradation pathways, and the corresponding mechanism. However, there is no systemic and comprehensive flow line for DFT calculations to evaluate the performance and understand the mechanism of P-AOPs. In this review, flow line of DFT calculations on heterogeneous P-AOPs is systematically summarized in the following aspects: (i) sites for persulfate activation or pollutant degradation; (ii) persulfate activation process; (iii) pollutant degradation process; and (iv) influential factors. Specially, primary evaluation criteria of radical or nonradical mechanism of persulfate activation are ultimately proposed, aiming to boost the development of P-AOPs. It not only provides systemic flow line to utilize DFT calculations to explore heterogeneous P-AOPs at microscopic level, but also guides and helps more researchers to instantly analyze their results and interpret the phenomena occurred in experiments or DFT calculations.

A novel polydopamine-modified metal organic frameworks catalyst with enhanced catalytic performance for efficient degradation of sulfamethoxazole in wastewater

In this study, a novel polydopamine (PDA)-modified metal organic frameworks (MOFs) catalyst (MIL/PDA) was successfully fabricated to activate persulfate (PS) for the degradation of sulfamethoxazole (SMX) in wastewater. The experimental results indicated that PDA-modified catalyst exhibited superior catalytic performance and enhanced the degradation of SMX (91.5%) compared to pure MOFs. The physical-chemical properties of the MIL/PDA catalyst were comprehensively characterized, and the applications in the catalytic degradation of SMX were evaluated. It was found that the modification of PDA enhanced the electron transfer, while promoting the redox cycle of Fe(III)/Fe(II), which in turn boosted the production of active oxygen species. Furthermore, MIL/PDA showed high stability and reusable performance over multiple cycles. Both radical and non-radical pathways were jointly involved in the activation process of PS were confirmed by quenching experiments combined with electron paramagnetic resonance (EPR). Based on this, the possible mechanism of the catalytic reaction was investigated. Finally, five degradation pathways of SMX degradation were proposed according to the results of liquid chromatography-mass spectrometry (LC-MS). This work provided a new insight into the design of novel and efficient heterogeneous catalysts for advanced wastewater treatment.

Activation of persulfate using CuS synthesized by ultrafast solid-state reaction for removal of organic pollutants from wastewater: Economical synthesis, catalytic performance, and mechanism

The article presents a simple, ultrafast, economical, and efficient method for the synthesis of CuS with designed morphologies via solid-state reaction at room temperature. The morphology and structure of CuS were investigated using XRD, Raman spectra, FE-SEM, and HRTEM. Using different precursors as a sulfur source produced CuS samples with different morphologies. The prepared CuS was successfully used for catalytic activation of persulfate (PS) and applied for degradation of RhB as a model organic pollutant. The efficiency was significantly affected by the sample morphology where CuS prepared by Na2S displayed a superior PS activation performance with RhB degradation. Complete removal of RhB over CuS-Na2S/PS system was obtained within 5 min with a rate constant of 0.25 min−1 which is 10.86 and 5.20 times larger than that CuS-Tu/PS and CuS-S2O32−/PS, respectively. The impact of operating parameters, such as PS dosage, catalyst dosage, the initial pH, and interfering ions on the CuS-Na2S/PS system was optimized in detail. The potential mechanism for the catalytic activity of CuS was confirmed via using different radical quenchers, and the results indicated that both the OH. and SO4− radicals were generated during the PS activation process, while the OH. radical played a crucial role in the degradation process. Further, CuS-Na2S/PS system showed excellent efficiency for the removal of different cationic and anionic organic pollutants. The sample showed acceptable efficiency and good stability after 3 consecutive runs. Finally, the XRD patterns of CuS-Na2S/PS system before and after the recycling process are similar which confirmed its stability and reusability.

Efficient catalytic degradation of trichloroethylene in persulfate system by Ca-Fe2O3 and Cu-Fe2O3 nanoparticles: Mechanistic insights

M-metal (Ca and Cu) doped Ca-Fe2O3 and Cu-Fe2O3 catalysts were synthesized using solvothermal method. The Ca-Fe2O3 and Cu-Fe2O3 catalysts were characterized by XRD, Raman spectroscopy, SEM, TEM and XPS spectroscopy. The catalytic performance of 6%Ca-Fe2O3 and 5%Cu-Fe2O3 catalysts for trichloroethylene (TCE) removal were improved by M-metal doping leading to TCE removal at 99.8% in 1 h, which were three folds greater than by simple a-Fe2O3 in the presence of persulfate (PS). Ca and Cu doping formed defective structure and created more oxygen vacancies thereby generating abundant active species during PS activation process. Further, the influence of catalysts’ dosage, oxidant dosage, solution pH, inorganic anions, and dissolved oxygen were evaluated. Complete removal of TCE was also obtained at weak alkaline pH condition. The greater specific surface area and the improved electrical conductivity was attributed to the huge generation of O2•– and 1O2 species which played major part in TCE removal. Scavenging tests and ESR spectroscopy confirmed the dominant role of O2•– and 1O2 in TCE degradation. The stability and viability of 6%Ca-Fe2O3 and 5%Cu-Fe2O3 catalysts were evaluated by repetition tests and in the presence of surfactants, TCE removal in real water matrix, and in the degradation of multi-pollutants.

UV-light assisted activation of persulfate by rGO-Cu3BiS3 for the degradation of diclofenac

Reduced graphene oxide (rGO)-Cu3BiS3 composites were synthesized via a solvothermal process. The Cu3BiS3 nanoparticles were successfully distributed on rGO at different weight percentages of 5, 10, 15 and 20%, and were characterized for their physicochemical, morphological, structural and optical properties. Fourier transformed infra-red spectroscopy confirmed the incorporation of Cu3BiS3 on rGO, and also confirmed the reduction of GO during the solvothermal process. X-ray diffraction study confirmed the destruction of the layered structure of GO as a result of the compositing process. Photoluminescence studies of the composites, showed that the quenching ability of rGO on Cu3BiS3 was optimal with the composite containing 15% nanoparticles. The photocatalytic activity of the composite was explored in a UV-assisted persulfate (PS) activation process for the degradation of diclofenac, and the effect of process parameters such as pH, catalyst dosage, and PS dosage were explored. The degradation efficiency of the process reached 85% after 60 min using 30 mg of catalyst, PS concentration of 5 mM and solution pH of 7. Radical scavenging experiments showed that the degradation process proceeded significantly through a non-radiative process and the re-usability study confirmed the stability of the composite after three process cycles. The wide applicability of the process was further studied for the degradation of other organic pollutants such as tetracycline, bisphenol, methyl orange and methylene blue. The UV-light assisted rGO-Cu3BiS3 persulfate activation process could therefore be an important, cost effective and highly efficient process for the degradation of a wide range of water contaminants.

Evaluation of the photocatalytic and persulfate activation properties of GO-CuSbS2 composite

The photocatalytic and persulfate activities of graphene oxide composited with copper antimony sulfide (CuSbS2) nanoparticles have been explored in this study. Pure phase CuSbS2 obtained by the co-thermolysis of metal dithiocarbamate complexes was composited with graphene oxide (GO) and explored as catalysts in a photocatalytic and persulfate activation processes. The charge carrier separation efficiency study, used in screening the different ratio of CuSbS2-GO composite, showed the optimum level of CuSbS2 in the composite to be at 10 wt.% of the catalyst. The photocatalytic and persulfate activation activities of the composites for tetracycline degradation reached 94% and 74% efficiency respectively after 60 min, confirming the potential of the catalyst for both processes. The reaction rate constant for the photocatalytic process was 5.0 0 × 10−2 min−1, while the persulfate activation process recorded a rate constant of 1.6 × 10−2min−1. Compositing of CuSbS2 with GO resulted in enhancement of the photocatalytic activity by 59 and 23 times compared to CuSbS2 and GO alone. Confirming a high synergistic effect between the materials. The radical scavenging experiment showed that photogenerated holes (h+) were the most significant radical species in the photocatalytic process, while in the persulfate activation process, electron transfer between GO-CAS(10%) and PS was the most significant process in the degradation process. Thus, in this study, the enhancement of the catalytic activity of CuSbS2 through its incorporation within the matrices of graphene oxide has been established.

New insights into the effect of adsorption on catalysis in the metal-free persulfate activation process for removing organic pollutants

• Sucrose-derived N-doped CXs were prepared by a simple hydrothermal method. • Pollutants degradation were mainly by nonradical pathway in CXs/PS system. • High adsorption capacity was beneficial to organic pollutants degradation in Mode 1. • Inhibitory effect of adsorption on catalytic PS activation was found in Mode 2. • The sulfonic group on pollutants might play a crucial role in the inhibitory effect. Coupling adsorption and advanced oxidation processes (AOPs), two widely used wastewater treatment technologies, has been an attractive idea pursued by many researchers. Although many studies have demonstrated that adsorption could facilitate AOPs such as persulfate (PS) activation, the inhibitory effect of adsorption on PS activation was ignored. In this work, both as adsorbents and catalysts, sucrose-derived carbon xerogels (CXs) were prepared to investigate the effect of adsorption on PS activation. The results showed that the specific surface areas (SSAs) and N contents of CXs varied with the HCl concentration. Among different CXs, CX-0.5 with the highest SSA and N content exhibited the highest adsorption capacity and catalytic activity for acid orange 7 (AO7) degradation by simultaneously adding CXs and PS, where the promoting effect of adsorption on catalysis was found. Quenching tests demonstrated that degradation of pollutants in the CX-0.5/PS system were mainly by nonradical pathway. However, the catalytic activities of CXs were inhibited after the pre-adsorption of AO7 on CXs. Comparing the molecular structures of several compounds, the sulfonic group on chemicals might play a crucial role in the inhibitory effect. We concluded that if CXs have the same adsorption sites for pollutants and PS, adsorption of pollutants would inhibit the catalytic PS activation. These findings provided a comprehensive understanding of the effect of adsorption on AOPs, which had a significant guidance for future researches and applications.