Addition Of Peroxymonosulfate Research Articles

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.

Catalytic degradation of carbamazepine by surface modified zerovalent copper via activation of peroxymonosulfate: Mechanism, degradation pathways and ecotoxicity

ABSTRACT In this research work, surface modified nano zerovalent copper (nZVC) was prepared using simple borohydride reduction method. The spectroscopic and crystallographic results revealed the successful synthesis of surface modified nano zerovalent copper (nZVC) using solvents i.e., ethanol (ETOH), ethylene glycol (EG) and tween80 (T80). The as-synthesized material was fully characterized for morphological surface and crystal structural properties. The results indicated that EG provides excellent synthesis environment to nZVC compared to ETOH and T80 in terms of good dispersion, high surface area and excellent catalytic properties. The catalytic efficiency of nZVC/EG was investigated alone as well as with the addition of peroxymonosulfate (PMS) in the absence of light. The degradation results demonstrated that the involvement of PMS synergistically boosted the catalytic efficiency of synthesized nZVC/EG material. Furthermore, the degradation products (DPs) of CBZ were determined by GC−MS and subsequently the degradation pathways were proposed. The ecotoxicity analysis of the DPs was also explored. The proposed (nZVC/EG/PMS) system is economical and efficient and thus could be applied for the degradation of CBZ from aquatic system after altering the degradation pathways in such a way that results in harmless products formation.

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.

Fe-loaded alginate hydrogel beads activating peroxymonosulfate for enhancing anaerobic fermentation of waste activated sludge: Performance and potential mechanism

The recovery of volatile fatty acids (VFAs) through anaerobic fermentation (AF) is usually restricted by the poor biodegradability of waste activated sludge (WAS). This study proposed a novel strategy, i.e. peroxymonosulfate (PMS) activated by Fe-loaded sodium alginate hydrogel beads (Fe-SA), to enhance AF performance. Experimental results demonstrated that the as-synthesized Fe-SA and PMS co-pretreatment synergistically enhanced WAS solubilization and VFAs production. The maximal VFAs yield of 2013 mg COD/L was achieved at the Fe-SA dosage of 4.0 mM/g TSS, which was 93.7% higher than that with sole PMS addition and 8.82 times higher than that of the control. Mechanistic studies elucidated that the generation of reactive radicals such as SO4•− and •OH from PMS was greatly induced by Fe-SA, which contributed to WAS disintegration and degradation of refractory compounds. Additionally, analysis of the key enzyme activities indicated that the Fe-SA could strengthen biological hydrolysis and acidogenesis of sludge during AF. Microbial analysis illustrated that Fe-SA evidently improved the abundances of fermentative microorganisms as well as functional gene expression via creating a favorable environment for microbial growth. This study demonstrated the applicable potential of Fe-SA hydrogel beads activating PMS for VFAs production and provides an important reference for developing advanced oxidation processes-based application in AF.

Inhibition caused by adsorption of organic micropollutants (MPs) on PES@CoFe2O4 polymeric ultrafiltration membranes and the enhanced MPs degradation by a continuous pH regulation

In this work, catalytic membranes were fabricated by blending CoFe2O4 catalysts into polyethersulfone (PES) and then used to treat naproxen with the addition of peroxymonosulfate (PMS). It was found that the addition of PMS results in a decrease in pH, which increases the adsorption of naproxen. This often overlooked phenomenon is demonstrated here to have an important role since the adsorption of naproxen on the polymeric matrix and catalytic particles decreases the degradation efficiency of naproxen. To verify this hypothesis and rule out the decrease in pH after the addition of pH, two ways of controlling the pH of the naproxen solution were compared: adjusting pH before and after the addition of PMS, respectively. Our results indicate that in the batch experiment, adjusting the pH of naproxen solution after adding PMS led to a dramatic 23-fold increase in the kinetic constant of the naproxen oxidation (0.42/min, pH6) compared to when pH was adjusted before adding PMS (0.018/min, pH 6). This enhancement in the overall kinetics was attributed to the elimination of the inhibition caused by MPs adsorption at low pH. In a dead-end cell, the catalytic membranes with 2.0 % of CoFe2O4 achieved quantitative conversion of naproxen, bisphenol A, and atrazine, with values of 98 %, 97 %, and 74 %, respectively, demonstrating the efficacy of this approach to convert multitype of MPs in wastewater streams. In a reusability study, the naproxen removal of the catalytic membranes with 2.0 % of CoFe2O4 decreased by 81 % and 45 % after 5 rounds in the batch experiment and dead-end cell, respectively. However, with a chemical cleaning process between each round, the degradation efficiency can be effectively recovered, proving the negative effects of the adsorption of MPs or their intermediates during the SR-AOPs. Our work demonstrates that pH in SR-AOP-based catalytic membrane processes determined both the reaction rate and the adsorption of MPs or their intermediates on the membrane and its reactive sites. We envision that these results will be valuable in developing efficient catalytic membranes for the treatment of MPs in wastewater streams.

Degradation of methylene blue by ellipsoidal β-FeOOH@MnO2 core-shell catalyst: Performance and mechanism

An ellipsoidal β-FeOOH@MnO2 core-shell catalyst was synthesized and used to degrade methylene blue (MB). The ultra-thin less-crystalline MnO2 nanosheets loaded on the surface of ellipsoidal β-FeOOH were similar to corn-bracts, and the specific surface area of this catalyst has been significantly improved than β-FeOOH. β-FeOOH@MnO2 exhibited a certain removal rate of MB without peroxymonosulfate (PMS). Then, with the addition of PMS, the degradation rate of MB rapidly increased to 99% after 10 min in β-FeOOH@MnO2/PMS system, which is much higher than that in β-FeOOH/PMS system (51%). LC-MS/MS was used to investigate the degradation products, and a probable degradation pathway was proposed. According to FTIR, XPS and quenching studies, the redox processes of Fe3+/Fe2+ and Mn4+/Mn3+, as well as 1O2, O2−, OH and SO4− produced by catalyst-activated PMS, were found to be primarily responsible for the quick degradation of MB. However, 1O2 plays a key role. Generally, this research indicated that β-FeOOH@MnO2 was an efficient catalyst and had a potential application in practical wastewater treatment.

Dispersed cobalt embedded nitrogen-rich carbon framework activates peroxymonosulfate for carbamazepine degradation: cobalt leaching restriction and mechanism investigation

Metal leaching is a key issue in cobalt-based catalysts/PMS systems, which results in the decline of catalytic ability and serious secondary pollution. Hence, a nitrogen-rich carbon framework with cobalt node (Co-NC-920) with low cobalt leaching was synthesized based on zeolite imidazole framework (ZIF) and g-C3N4 to activate peroxymonosulfate (PMS) for the degradation of carbamazepine (CBZ). With the restriction of nitrogen-rich carbon framework, cobalt can disperse better and form stable cobalt-nitrogen bonds, thus only 0.09 mg/L cobalt ions were leached in the solution. More than 99.9% of CBZ can be removed within 30 min of PMS addition. Further investigation revealed that 1O2, SO4•− and high-valent cobalt species were primarily responsible for CBZ degradation in the Co-NC-920/PMS system and different reactive oxygen species (ROS) were distinguished and quantified, finding 1O2 was predominant. The degradation process was realized by the coexistence of free radicals and non-free radicals. Moreover, CBZ degradation capacity of the catalyst was evaluated under the influence of common anions and in actual waterbody. Finally, the possible degradation pathways of CBZ were proposed and the toxicity of the intermediates was analyzed. This work provides a new approach for the synthesis of cobalt-based nitrogen-rich carbon catalysts with low leaching and high efficient.

Activation of peroxymonosulfate by Co-Mg-Fe layered doubled hydroxide for efficient degradation of Rhodamine B.

Reactive species serve as a key to remediate the contamination of refractory organic contaminants in advanced oxidation processes. In this study, a novel heterogeneous catalyst, CoMgFe-LDH layered doubled hydroxide (CoMgFe-LDH), was prepared for an efficient activation of peroxymonosulfate (PMS) to oxidize Rhodamine B (RhB). The characterization results showed that CoMgFe-LDH had a good crystallographic structure. Correspondingly, the CoMgFe-LDH/PMS process exhibited good capacity to remove RhB, which was equivalent to degradation performance as homogeneous Co(II)/PMS process. The RhB oxidation in the CoMgFe-LDH/PMS process was well described with pseudo-first-order kinetic model. Additionally, the oxidation process presented an excellent stability, and only 0.9% leaching rate was detected after six sequential reaction cycles at pH 5.0. The effects of initial pH, CoMgFe-LDH dosage, PMS concentration, RhB concentration, and inorganic anions on the RhB degradation were discussed in detail. Quenching experiments showed that sulfate radicals (SO4•-) acted as the dominant reactive species. Further, the removal of RhB from simulated wastewater was explored. The removal efficiency of RhB (90μM) could reach 94.3% with 0.8g/L of catalyst and 1.2mM of PMS addition at pH 5.0, which indicated the CoMgFe-LDH/PMS process was also effective in degrading RhB in wastewater.

Isoporous catalytic ceramic membranes for ultrafast contaminants elimination through boosting confined radicals

Catalytic membrane based oxidation-filtration processes (AOP-CM), a derivative concept of membrane process that combines physical separation and chemical oxidation, offers a high-efficient water purification strategy. However, the application of AOP-CM was still hampered by the low heterogeneous AOPs efficiency of catalytic membranes. In order to improve the heterogeneous AOP efficiency, an isoporous AlOx/La2CoMnO6-δ ceramic membrane (IAPCM) with nano-confinement characteristics was prepared via sol–gel based block copolymer self-assembly route. Benefiting from the well-designed pore structure, IAPCM exhibited excellent pure water permeance (313 L·m−2·h−1·bar−1) and size-exclusion performance (complete rejection of MS2 phages with a diameter of ∼ 20 nm). With the addition of peroxymonosulfate (PMS), IAPCM achieved ultrafast degradation of organic micropollutants (e.g. atrazine, carbamazepine and sulfamethazine) at 0.5 bar (equivalent to a retention time of 4.3 × 10−4 s). Finite-Element analysis confirmed that high-concentration radical fields were generated in the confined nanoscale-pores within the isoporous La2CoMnO6-δ layer. The boosted mass transfer rates and high-concentration radical fields induced ultrafast degradation of micropollutants in IAPCM based oxidation-filtration system. This work highlights the significance of pore structure design for high-performance AOP-CM processes.