Addition Of Peroxymonosulfate Research Articles

Assessment of hydrogen peroxide, persulfate, and peroxymonosulfate as oxidizing agents in electrochemical oxidation of pyridine

The removal of pyridine, a toxic and refractory nitrogen heterocyclic compound from coal chemical wastewater, has been examined using electrochemical oxidation (EO) processes in the presence of hydrogen peroxide (H2O2), persulfate (PDS), and peroxymonosulfate (PMS). Degradation of pyridine was observed in EO/H2O2, EO/PDS, and EO/PMS systems with removal efficiencies of 41.3, 40.6, and 93.5 %, respectively. The energy consumption for the EO/H2O2, EO/PDS, and EO/PMS processes was calculated to be 1.4, 1.3, and 0.56 KWh g−1, respectively. The yield of ClO3- in the EO/PMS system was relatively higher than that in the EO/PDS system. Additionally, the overall concentration of total organic chlorine was lower in the EO/PDS (292.1 mg/L) and EO/PMS (120.1 mg/L) systems when SO4•– radicals were present. The contribution of reactive species were quantified. Specially, in the EO/H2O2 system, the ratio of OH• was 44 %. In the EO/PDS system, the ratios of OH•, SO4•–, and other reactive species were 31 %, 22 %, and 47 %, respectively. In the EO/PMS system, the ratios of OH•, SO4•–, and other reactive species were 18 %, 71 %, and 11 %, respectively. Specifically, in the EO/PMS system, while CCl3 was detected, no other chlorinated organic intermediates were observed. Compared to EO/H2O2 and EO/PDS systems, the EO/PMS system shows better suitability for high Cl– conditions. The pH had a negligible impact on the EO/H2O2 system. Under acid conditions, degradation rate constants for pyridine were highest in the EO/PMS and EO/PDS systems. Notably, the addition of PMS to coal chemical wastewater achieved a 30 % removal of ultraviolet light absorbance at 254 nm (UV254), indicating effective inhibition of trihalomethane formation. This study provides critical insights into optimizing the EO process for the effective removal of refractory pollutants like pyridine from coal chemical wastewater, enhancing environmental safety and treatment efficiency.

Visible light-driven photocatalytic degradation of atrazine in aqueous phase: impact of the g-C3N4/TiO2/NiFe2O4 nanocomposite activated by potassium peroxymonosulfate.

The present investigation focused on the photocatalytic degradation of aqueous atrazine over g-C3N4/TiO2/NiFe2O4 composite in the presence of peroxymonosulfate (PMS) under visible light irradiation. The ternary photocatalyst was synthesized and characterized using XRD, FTIR, nitrogen sorption, SEM, UV-Vis, and photoluminescence spectroscopy. This catalyst exhibited full absorption in the visible spectrum at 815nm and a high specific surface area of 105 m2/g. The effect of operating conditions encompassing atrazine initial concentration, photocatalyst loading, PMS concentration, and temperature on the degradation reaction extent was investigated. The obtained findings highlighted the efficiency of the ternary composite in the photocatalytic degradation of this widely used and environmentally harmful pesticide. The strategic addition of PMS was shown to be crucial to improving this efficiency. Indeed, in the presence of PMS at a concentration of 5mM, atrazine conversion reached 97.2% within 300min of reaction at ambient temperature with a photocatalyst loading of 0.3g/L. Furthermore, the activation energy of the reaction was evaluated to be 37.3kJ/mol. The present study showed the promising potential of the g-C3N4/TiO2/NiFe2O4 photocatalyst for environmental remediation, offering important perspectives in the fight against pesticide pollution.

Reversible surfactant combined with micro-nano bubbles and peroxymonosulfate: A method for cyclic remediation of PAHs contaminated soil and groundwater

The persistent presence of highly hydrophobic polycyclic aromatic hydrocarbons (PAHs) in low-permeability soils represents a continuous hazard to the environment. Surfactant-enhanced remediation (SER) can effectively solubilize PAHs adsorbed on the soil particles and efficiently removing them from the subsurface environment. Nevertheless, the adsorption of surfactants by soil particles and the potential for secondary contamination resulting from dissolved PAHs in the eluent have hindered the application of this technology. In this study, we propose and demonstrate a new method of enhancing the transfer of surfactant N1, N2-bis[4-[4-[(4-butylphenyl) azo] phenoxy] butyl]-N1, N2-tetramethylethane-1,2-diammonium bromide (AzoPBT) in soil by micro-nano bubbles (MNBs). Peroxymonosulfate (PMS) is added directly to the AzoPBT/MNBs mixed solution following the completion of the extraction, UV irradiation, and filtration processes. After being irradiated with visible light and treated with AzoPBT, the solution is reinjected into the soil to effectively remediate both soil and groundwater contaminated with PAHs. The AzoPBT/MNBs mixed solution has been demonstrated to be able to fully remediate soil and groundwater contaminated with phenanthrene (99.8 %) within a period of 38 days. The addition of MNBs can effectively reduce the surface properties such as CMC, γCMC, contact angle, and viscosity of AzoPBT solution, which enhances its diffusion in soil. Furthermore, the distinctive morphology of the micelles formed by MNBs and AzoPBT exhibits a diminished Zeta potential, which mitigates the adsorption of AzoPBT by soil in solution (8.4 %). The addition of PMS effectively eliminates the residual Phe in the mixed solution, facilitates secondary utilization, and mitigates the risk of secondary contamination. The AzoPBT/MNBs mixed solution is recycled to treat soil and groundwater contaminated with Phe, resulting in a 77.6 % decrease in the amount of surfactant. These results suggest that the new technique proposed by the study has significant potential in addressing soil and groundwater pollution caused by PAHs.

Preparation and performance of g-C3N4/g-C3N5 homojunction photocatalyst activated peroxymonosulfate for ceftriaxone sodium degradation

As the overuse of antibiotics increasingly contaminates the environment, one of modern chemistry's objectives is to identify high-performance photocatalytic materials to degrade antibiotics. This study initially utilized NH4Cl as a gas template to synthesize porous lamellar g-C3N4 (CNS) through a high-temperature calcination process. Building upon this, a homojunction catalyst, CNS/g-C3N5 (S-CN), was developed via a secondary sintering technique using different amount of 3-amino-1,2,4-triazole addition to evaluate its efficacy in activating peroxymonosulfate (PMS) for degrading the antibiotic ceftriaxone sodium. Under neutral conditions, the photocatalytic system composed of S-CN catalysts prepared by 50 mg of 3-amino-1,2,4-triazole addition and PMS (S3-CN/PMS) exhibited degradation rates that were 3.37 and 8.11 times higher than those of the CNS/PMS and g-C3N5/PMS, respectively. At a pH of 8, the S3-CN/PMS system attained a 99.7 % degradation efficiency within 75 min. Based on results from UV–visible diffuse reflectance spectroscopy (DRS), transient photocurrent response, electrochemical impedance spectroscopy (EIS), photoluminescence spectroscopy and radical scavenging experiments, this high efficiency is attributed to a homojunction Z-type charge transfer mechanism that enhances the separation of photogenerated carriers. Furthermore, the study found that the optimal PMS addition was 20 mg and the optimal pH was 8. Chloride ions promoted the reaction, while other ions decreased the reaction rate. In conclusion, this paper provides valuable insights for the morphological modification of carbon nitride homojunction materials and the efficient activation of PMS for pollutant degradation.

Chemical oxidation co-coagulation-flocculation for the flotation wastewater treatment of lead-zinc oxide ore from Lanping mine

The flotation wastewater produced by "lead preferred flotation-zinc flotation" all-open process with aids of mixed depressants and cationic-anionic collectors has a high turbidity and multitude of reagent contaminants, and fails to meet the discharge standards. This study objective is to remove fine solid particles and flotation reagents in this wastewater by chemical oxidation co-coagulation-flocculation process. Results of chemical oxidation tests indicate peroxymonosulfate (PMS) exhibits superior performance on decreasing COD, and the COD remarkably decreases to 71.8 mg·L<sup>-1</sup> with 100 mg·L<sup>-1</sup> PMS addition after 120 min. Moreover, the combined oxidation of radicals (SO<sub>4</sub><sup>•-</sup> and •OH) are responsible for degradation of flotation reagents (Na<sub>2</sub>S, DCCH, xanthates and amine) in the wastewater. Results of experimental factors confirm that the turbidity of wastewater decreases significantly from 124796 to 71.4 NTU, and the yield of water reaches above 90% with combined usage of lime (500 mg·L<sup>-1</sup>) and polyacrylamide (PAM, 50 mg·L<sup>-1</sup>). Besides, the contents of S, P, N, Zn Pb and Fe decrease, and meet the discharge standards. Results of zeta potential analysis suggest lime reduces the electrostatic repulsion between particles, and PAM plays a bridge link role between particles, accelerating the precipitation of suspended particle.

Enhanced perfluorooctanoic acid (PFOA) degradation by electrochemical activation of peroxydisulfate (PDS) during electrooxidation for water treatment

Improved treatment of per- and polyfluoroalkyl substances (PFAS) in water is critically important in light of the proposed United States Environmental Protection Agency (USEPA) drinking water regulations at ng L−1 levels. The addition of peroxymonosulfate (PMS) during electrooxidation (EO) can remove and destroy PFAS, but ng L−1 levels have not been tested, and PMS itself can be toxic. The objective of this research was to test peroxydisulfate (PDS, an alternative to PMS) activation by boron-doped diamond (BDD) electrodes for perfluorooctanoic acid (PFOA) degradation. The influence of PDS concentration, temperature, and environmental water matrix effects, and PFOA concentration on PDS-EO performance were systematically examined. Batch reactor experiments revealed that 99 % of PFOA was degraded and 69 % defluorination was achieved, confirming PFOA mineralization. Scavenging experiments implied that sulfate radicals (SO4–) and hydroxyl radicals (HO) played a more important role for PFOA degradation than 1O2 or electrons (e−). Further identification of PFOA degradation and transformation products by liquid chromatography-mass spectrometry (LC-MS) analysis established plausible PFOA degradation pathways. The analysis corroborates that direct electron transfers at the electrode initiate PFOA oxidation and SO4– improves overall treatment by cleaving the CC bond between the C7F15 and COOH moieties in PFOA, leading to possible products such as C7F15 and F−. The perfluoroalkyl radicals can be oxidized by SO4– and HO, resulting in the formation of shorter chain perfluorocarboxylic acids (e.g., perfluorobutanoic acid [PFBA]), with eventual mineralization to CO2 and F−. At an environmentally relevant low initial concentration of 100 ng L−1 PFOA, 99 % degradation was achieved. The degradation of PFOA was slightly affected by the water matrix as less removal was observed in an environmental river water sample (91 %) compared to tests conducted in Milli-Q water (99 %). Overall, EO with PDS provided a destructive approach for the elimination of PFOA.

In situ-growth of Fe2S3 ultrathin layer on CdS nanorod through cation-exchange for efficient photocatalytic degradation of organic pollutants under visible light coupled oxidant activation

A new core-shell structure CdS@Fe2S3 material was synthesized by in situ cation exchange method to enhance the degradation of organic pollutants in water under visible light. It is proved that Fe2S3 nanolayer is successfully loaded on CdS nanorods by TEM and UV-Vis spectra and other means. The representative Rhodamine B was selected as the target pollutant and the results of degradation experiment showed that after 60 min of exposure to LED visible light with a low energy (25 W), the removal efficiency for this dye could reach 98 % in the presence of peroxymonosulfate (PMS) forming free radicals, which displayed a observed kinetic rate constant exceeding 0.62 min−1 that is approximately 5 times higher than the system without PMS addition and 10 times than the system with original CdS as catalyst. The result of inhibition experiments shows that sulfate radical (SO4·-) and singlet oxygen (1O2) play as important roles during the photocatalytic process. In addition, this core-shell material can be recycled at least four times. Generally, this study can make full use of visible light which can be easily obtained and effectually resolve the organic pollution problems.

Metal-free g-C3N5 photocatalysts with defect sites as efficient peroxymonosulfate activators for antibiotic removal in aqueous media

Nitrogen-rich graphitic carbon nitride (g-C3N5) has emerged as a promising and fascinating photocatalyst for tackling problems related to antibiotic pollution. Herein, porous O-doped g-C3N5 with N vacancy (g-C3N5-x-O) was fabricated via a facile two-step pyrolysis technique using 3-amino-1,2,4-triazole and oxalic acid as precursors. The sample modified with 2.0 mol.% oxalic acid (CN-2.0) exhibits a porous structure with a specific surface area of 249.78 m2. g−1, 2.77 times greater than that of pristine g-C3N5 (CN-0). In addition, the existence of O-doping and N vacancies in g-C3N5 framework not only promotes charge transfer properties but also suppresses photogenerated electron-hole recombination according to the results of transient photocurrent responses, photoluminescence and electrochemical impedance spectra. The CN-2.0 sample displays the highest photocatalytic activity, which eliminates 77.3% sulfamethoxazole (SMX, 20 mg. L−1) after 60 min irradiation under UV 365 nm light source. The addition of peroxymonosulfate (PMS, HSO5-) significantly accelerates SMX photodegradation rate as well as reduces the influence of pH solution during treatment process. The reactive oxygen species including •O2−, 1O2, SO4•−, •OH, h+ contribute to SMX removal. The efficient degradation of numerous antibiotic classes highlights the possible applicability of g-C3N5-x-O. Interestingly, the catalyst retains its high activity and stability even after four consecutive reuse cycles. The intermediates of SMX degradation were determined and plausible SMX degradation pathways were proposed. Toxicity assessments demonstrated that the overall toxicity of the solution decreased after treatment. This work provides a feasible strategy to design and modulate g-C3N5 photocatalyst activated by PMS for antibiotic removal in wastewater.

Synergistic oxidative removal of sulfamethoxazole using Ferrate(VI) and peroxymonosulfate

The synergic effect of Ferrate(VI) (Fe(VI)) and peroxymonosulfate (PMS) on sulfamethoxazole (SMX) oxidative removal was investigated in this study. The sulfate radicals (SO4−), generated through Fe(VI)-mediated activation of PMS, have been demonstrated as an effective oxidant for the removal of SMX. However, the scavenging experiments have suggested that various iron species, i.e., Fe(VI), Fe(V), and Fe(IV) play a vital role in facilitating efficient SMX oxidation. pH is a crucial parameter in this system because the involved species, including Fe(VI), PMS, and SMX, have acid-base dissociation points. Accordingly, the optimal pH value for the SMX removal was achieved at pH = 6, and the addition of PMS enhanced the degradation efficiency of Fe(VI) at all pH-operating conditions. Several oxidation products of SMX were identified, including sulfanilamide (SAM), 3-amino-5-methylisoxazole (AMI), and other potentially hydroxylated byproducts. Characterization studies on solid particles collected after the Fe(VI)/PMS treatment revealed structural changes during SMX oxidation, and the potential contributions of Fe2O3 or Fe(OH)3 to the oxidation mechanism were evaluated accordingly. While the removal efficiency in a river matrix was slightly reduced, the presence of inorganic ions had minimal impact on SMX removal, which confirms the high potential of the Fe(VI)/PMS technology to operate in environmentally relevant conditions.

Performance and mechanism of magnetic Fe3O4@MnO2 catalyst for rapid degradation of methylene blue by activation of peroxymonosulfate

A flower ball shaped magnetic Fe3O4@MnO2 core-shell catalyst has been synthesized and the average diameter is about 135–180 nm. The Fe3O4@MnO2 (140.6 m2 g−1) showed a larger specific surface area than Fe3O4 (64.6 m2 g−1) due to the thin film like nature of MnO2. The Fe3O4@MnO2 exhibited a great degradation performance for methylene blue (MB, 20 mg L−1, pH=7) after the addition of peroxymonosulfate (PMS, 0.18 g L−1) when the dosage of Fe3O4@MnO2 is 0.3 g L−1, which reached 98% within 20 min. Additionally, the influences of catalyst dosage, PMS concentration and initial pH value of MB solution have been studied to maximize the catalytic performance of Fe3O4@MnO2. Results showed that the increase of catalyst dosage and PMS concentration have improved the degradation efficiency and reaction rate of MB. However, the effect of pH on MB removal was complex and has been analyzed. According to XPS and quenching studies, the degradation effects of free radicals produced by catalyst-activated PMS on MB followed the order 1O2> •OH> SO4•−. This research demonstrates that Fe3O4@MnO2 is an effective catalyst for the degradation of organic dye MB.

Zinc oxide@citric acid-modified graphitic carbon nitride nanocomposites for adsorption and photocatalytic degradation of perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) is a highly persistent organic pollutant of global concern. A novel nanocomposite composed of ZnO nanoparticles and citric acid-modified g-C3N4 was synthesized by ball milling process. The synthesized nanocomposite was more efficient than pure ball-milled ZnO nanoparticles for PFOA elimination under visible light irradiation. The optimal hybrid photocatalyst, produced by the addition of 5 wt% of citric acid-modified g-C3N4, demonstrated significantly better performance for PFOA removal than pure ZnO nanoparticles under UV irradiation, with the apparent rate constants of 0.468 h−1 and 0.097 h−1, respectively. The addition of peroxymonosulfate (0.53 g L−1) significantly increased PFOA removal, clarifying the crucial effect of sulfate radicals on PFOA photodegradation. In comparison, citric acid-modified g-C3N4 was not effective for PFOA elimination under visible light irradiation, even with the addition of peroxymonosulfate. Further experiments under dark conditions identified surface adsorption on hybrid photocatalyst as a key process in total PFOA removal. In summary, PFOA removal by ZnO@citric acid-modified graphitic carbon nitride nanocomposites is due to the combined action from adsorption and photodegradation, with adsorption as the dominating mechanism.

Photocatalytic Degradation of Neonicotinoids—A Comparative Study of the Efficacy of Hybrid Photocatalysts

This study deals with the synthesis and characterization of a series of hybrid photocatalysts consisting of different loadings of TiO2, Cd, and Fe on mesoporous SBA-15 material. The prepared samples were characterized by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM), and tested for the removal of the neonicotinoid insecticide imidacloprid. The results showed that uncalcined 10% Cd-SBA-15 catalyst exhibited the best photocatalytic activity. The photocatalytic degradation of the imidacloprid was carried out in a batch photoreactor at different pH values, and in the presence or absence of additional compounds such as peroxymonosulfate (PMS) and peroxydisulfate (PDS). The best degradation results were achieved at a pH value of 6.5 with 10% Cd/SBA-15. The degradation performance increased with the addition of PMS and PDS. Based on the results of the experimental measurements, Cd/SBA-15 is a good candidate that can show a reasonable degradation efficiency and reactivity, especially in the presence of PDS or PMS.

Table Olive Manufacturing Wastewater Treatment Using the Peroxymonosulfate/Fe(III) System

Wastewater generated in table olive manufacturing processes (WWTOMP) is a seasonal waste difficult to manage due to the high salinity content. The treatment of WWTOMP has been accomplished by including a precoagulation stage with aluminum sulfate, oxidation using the peroxymonosulfate/Fe(III) system, and a final aerobic biological stage. The optimum conditions of precoagulation led to a chemical oxygen demand removal rate of roughly 30–35% without the need for pH adjustment. The peroxymonosulfate(PMS)/Fe(III) system was thereafter applied to the effluent after coagulation. The addition of PMS lowered the initial pH to acidic conditions (pH = 1.5–2.0). Under these operating conditions, the initial PMS concentration and the initial Fe(III) dose showed optimum values. An excess of the oxidant and/or the catalyst partially inhibited the process efficiency, and pH exerted a significant influence. COD removal was substantially increased as the pH of the solution was moved toward circumneutral values in the interval 5–4. Moreover, at pH values of 5 and 7, PMS was capable of reducing COD without the need for Fe(III) presence. The direct oxidation of organics by PMS or the generation of chloride-based oxidants (Cl2 or HClO) is suggested to occur in parallel to the radical attack from PMS decomposition. An attempt to biologically reduce the final COD to discharge limits failed, mainly due to the high salinity content; however, the 1:2 dilution led to the reduction in COD from 6 to 2 g L−1. Acclimated sludges or saline content reduction should be first considered.

Highly graphitized biochar as nonmetallic catalyst to activate peroxymonosulfate for persistent quinclorac removal in soil through both free and non-free radical pathways

To explore highly effective and nonmetallic advanced oxidation process system to alleviate the persistent herbicides contamination in agricultural soils is of great importance. In this study, a significantly graphitized biochar with abundant C = O structure is prepared as non-metallic catalyst (WCGBC800). Different from other traditional amorphous pristine biochar, WCGBC800 can accelerate the electron transfer in the system and then effectively activate peroxymonosulfate (PMS) to produce free (OH, O2–, SO4−, etc.) and non-free radicals (1O2, electron transfer, etc.). Consequently, WCGBC800 can degrade 100 % the persistent organic herbicide quinclorac (QNC, with a content of 50 mg·kg−1) in soil within 20 min after PMS addition. The T.E.S.T-QSAR software simulation evidence that the toxicity of degradation intermediates is much lower than QNC. The stress of QNC on rice seedlings was directly described through rice cultivation experiment. The stress of rice seedlings was relieved after WCGBC800 + PMS treatment. The growth experiment of rice seedlings also shows that with an original QNC concentration of 7 mg·kg−1 in soil, the root length, root surface area, leaf length, leaf area, and leaves perimeter of rice increase of 255.30 %, 148.38 %, 207.64 %, 204.19 %, and 63.69 % respectively after detoxification by WCGBC800 + PMS system. This functional material and the WCGBC800 + PMS system provide new solutions for solving the problem of herbicide residues in soil with promising safety.

Underwater bubbling plasma assisted with persulfate activation for the synergistic degradation of tetracycline hydrochloride

The performance and mechanism of persulfate consisting of peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation by underwater bubbling plasma (UBP) for the synergistic removal of tetracycline hydrochloride (TCH) were comparatively investigated. Both PMS and PDS addition significantly promoted the removal of TCH in UBP system, indicating persulfate exhibited highly synergistic effect with UBP. Furthermore, enhancing the persulfate dosage, peak voltage and pulse frequency, as well as reducing initial TCH concentration were favorable for the elimination of TCH. Compared with neutral condition, acidic and alkaline condition were advantageous to TCH removal. The presence of coexisting substances including Cl−, SO42− and humic acid (HA) had an adverse effect on TCH degradation, while Fe2+ could improve the removal of TCH. The degradation of ciprofloxacin and metronidazole proved the applicability for other antibiotics degradation of the reaction system. SO4−·, ·OH, ·O2−, hydrated electrons, O3 and H2O2 were the active substances responsible for TCH removal. The reduction of aqueous O3 concentration and enhancement of H2O2 concentration were observed after persulfate addition. UV–vis spectra and TOC analysis illustrated the addition of PMS or PDS facilitated the degradation and mineralization of TCH. 3D-EEMF spectra visually displayed the degradation process of TCH. Plausible degradation routes were deduced based on LC-MS and the toxicities of TCH and its intermediates were evaluated by Toxicity Estimation Software Tool.

Decomposition of the antibiotic sulfamethoxazole by the liquid-phase plasma process enhanced by peroxymonosulfate

In this study, sulfamethoxazole (SMZ) was successfully degraded using the liquid phase plasma (LPP) method, a new advanced oxidation process (AOPs). The effects of LPP process variables and side reactions on SMZ decomposition reactions were evaluated, and optimal LPP process conditions were determined based on these data. To increase the efficiency of the SMZ decomposition reaction, peroxymonosulfate (PMS) was added to the LPP reaction. The optimal addition amount was derived by tracking the change in the amount of oxidation radicals produced according to the addition of PMS. By analyzing the reaction intermediates generated in the SMZ decomposition reaction, the decomposition pathway of SMZ by the LPP method was proposed.

Coupled sorptive and oxidative antimony(III) removal by iron-modified biochar: Mechanisms of electron-donating capacity and reactive Fe species

Sorption and oxidation are two potential pathways for the decontamination of trivalent antimony (Sb(III))-bearing water, using iron (Fe)-modified biochar (FeBC). Here we investigated the sorption and oxidation behavior of FeBC for Sb(III) in aqueous solutions. Results revealed that Sb(III) removal by FeBC was significantly improved showing the maximum Sb(III) sorption (64.0 mg g−1). Density functional theory (DFT) calculations indicated that magnetite (Fe3O4) in FeBC offered a sorption energy of −0.22 eV, which is 5 times that of non-modified biochar. With the addition of peroxymonosulfate (PMS), the sorption of Sb(III) on FeBC was 7 times higher than that on BC, indicating the sorption capacity of FeBC for Sb(III) could be substantially increased by adding oxidizing agents. Electrochemical analysis showed that Fe modification imparted FeBC higher electron-donating capacity than that of BC (0.045 v. s. 0.023 mmol e− (g biochar)−1), which might be the reason for the strong Sb(III) oxidation (63.6%) on the surface of FeBC. This study provides new information that is key for the development of effective biochar-based composite materials for the removal of Sb(III) from drinking water and wastewater. The findings from this study have important implications for protecting human health and agriculture.

Peroxymonosulfate based in situ chemical oxidation: An efficient strategy for mitigation of membrane fouling in real seawater reverse osmosis desalination

Persulfate based advanced oxidation processes (AOPs) is an emerging method to assist the pretreatment to prevent membrane fouling for seawater desalination. However, the present strategies which adopt activators (e.g., UV, heat, Fe) to generate kinds of free radicals, are energy-consuming and enhance the concerns of disinfection by-products (DBPs). Here, peroxymonosulfate (PMS) is adopted as a green, effective and economical pretreatment chemical for simultaneous microorganic pollutants degradation and microorganism inactivation in seawater reverse osmosis (SWRO) desalination without any external energy input. After adding into the seawater, 53% PMS could be activated by Cl- in situ to generate HClO at most with no other active species generated, which is verified by stoichiometric analysis and quenching experiments. Benefited from the residual PMS, not only could up to 89.6% of total organic carbon be removed in the real seawater, but also nearly 80% of DBPs could be degraded by simply adjusting pH from neutral to alkaline conditions. Meanwhile, all bacteria could be killed completely and hardly any regrowth appeared, which further proved the anti-fouling ability of the PMS/Cl- system. Consequently, the addition of PMS could maintain the flux for a long time in the practical SWRO application with significantly reducing the RO membrane fouling. Moreover, the operating cost of PMS is only 0.024 $/ton, which is comparable to NaClO. This study demonstrated the excellent performance of PMS in SWRO pretreatment, supplying a promising scheme in practical desalination processes.

Critical role of Photo-electrode with Ce-g-C3N4 in multi-stage microbial fuel cells cascade reactor treating diluted hyper-saline industrial wastewater rich in amines

Treatment of chemical industrial wastewater often faces problems of large volume occupation, high cost, and long processing time. In this study, low-content Ce-modified g-C3N4 was prepared and used as a catalyst on stainless steel mesh photo-cathode in constructing a multi-stage cascade microbial fuel cell system to reduce treatment costs in an energy-saving way. The large specific surface area (332.5 m2 g−1) and mesoporous structure of the material, is favorable for catalytic reactions, in which Ce elements were mainly present in single atoms. The characterized catalyst indicated a pronounced effect of Ce species in increasing photo-current and the synergistic pollutant removal, microbial bio-degradation and cascade operation stability. In Batch-mode (light illumination, aeration, total HRT (hydraulic residence time) of 54 h) treatment through three cascade reactors, removed 88% COD (Chemical Oxygen Demand). With 0.5 mM PMS (peroxymonosulfate), 94% COD and 86% NH4+-N of the system were removed. The cascade net average COD removal capacity reached 16.04 kg per kg catalyst per day. The addition of PMS also enhanced the electricity generation. In continuous-mode, in totally 18 h treatment through the three-stages cascade reactors without PMS, overall, 83% COD and 78% TOC (Total Organic Carbon) were removed, reaching a net calculated system average COD removal capacity of 19.29 kg per kg catalyst per day. With Ce-g-C3N4 catalyst, the batch or continuous multi-stage cascade system demonstrated great technical flexibility and economic potential in treating high-strength, high-salinity amine-rich industrial wastewater.

Titania/reduced graphene oxide nanocomposites (TiO2/rGO) as an efficient photocatalyst for the effective degradation of brilliant green in aqueous media: effect of peroxymonosulfate and operational parameters.

This study is focused on synthesis of highly efficient Titania/reduced Graphene Oxide (TiO2/rGO) nanocomposites by means of simple hydrothermal technique. The TiO2/rGO were synthesized in different ratios of 0.5, 1.0, 2.0, and 3% by varying the concentration of rGO while the concentration of TiO2 was kept constant and the obtained samples were designated as TrG0.5, TrG1, TrG2, and TrG3 respectively. Different characterization techniques (SEM, TEM, HRTEM, XRD, EDX, TGA, UV-DRS, PL, EIS, and BET) showed high crystallinity, small crystallite size (18.4 nm), high thermal stability, high purity, low band gap energy (Eg = 3.12 eV), and high surface area (65.989 m2/g) for the as-synthesized TiO2/rGO nanocomposite. The efficiencies of TiO2/rGO were determined in terms of brilliant green (BG) dye degradation in aqueous media under UV light. The results revealed that 2% TiO2/rGO (TrG2) showed high efficiency for BG degradation with the kapp of 0.023 min-1 compared to TiO2 alone (kapp of 0.006 min-1). The rate of BG degradation was further synergised by the addition of peroxymonosulfate (PMS) to the system. The degradation of BG was improved to 99.4% by the incorporation of PMS in aqueous media compared to TrG2 alone. Furthermore, the degradation of BG was also examined in various media (neutral, acidic, and basic). The results revealed that by increasing pH of the medium from 3.85 to 8.2 the degradation of BG was enhanced from 99.4 to 99.9% with the corresponding kapp of 0.0602 min-1. Moreover, the photocatalytic degradation of BG followed the pseudo-first-order kinetics. Radical scavenging experiments showed that ●OH and SO4●- were the main species responsible for the degradation of BG under UV light. Besides, for determining the efficiency of as-synthesized TrG2/PMS system, the degradation of BG was also performed in various water types (distilled water, tape water, synthetic wastewater, and industrial wastewater). The degradation products (DPs) of BG and their corresponding pathways were proposed, accordingly.