Singlet oxygen-dominated peroxymonosulfate activation by layered crednerite for organic pollutants degradation in high salinity wastewater

Advanced oxidation processes have been widely studied for organic pollutants treatment in water,but the degradation performance of radical-dominated pathway was severely inhibited by the side reactions between the anions and radicals,especially in high salinity conditions.Here,a singlet oxygen(^(1)O_(2))-dominated non-radical process was developed for organic pollutants degradation in high salinity wastewater,with layered crednerite(CuMnO_(2))as catalysts and peroxymonosulfate(PMS)as oxidant.Based on the experiments and density functional theory calculations,^(1)O_(2)was the dominating reactive species and the constructed Cu-O-Mn with electron-deficient Mn captured electron from PMS promoting the generation of^(1)O_(2).The rapid degradation of bisphenol A(BPA)was achieved by CuMnO_(2)/PMS system,which was 5-fold and 21-fold higher than that in Mn_(2)O_(3)/PMS system and Cu_(2)O/PMS system.The CuMnO_(2)/PMS system shown prominent BPA removal performance under high salinity conditions,prominent PMS utilization efficiency,outstanding total organic carbon removal rate,wide range of applicable pH and good stability.This work unveiled that the^(1)O_(2)-dominated non-radical process of CuMnO_(2)/PMS system overcame the inhibitory effect of anions in high salinity conditions,which provided a promising technique to remove organic pollutants from high saline wastewater.

Different non-radical oxidation processes of persulfate and peroxymonosulfate activation by nitrogen-doped mesoporous carbon

Activated persulfate oxidation is an emerging advanced oxidation process for organic pollutant degradation.Own to different molecular structures and oxidation potentials,persulfate(PDS)and peroxymonosulfate(PMS)may show different degradation performances due to various catalytic mechanisms even by the same catalysts.In this study,the nitrogen-doped mesoporous carbon(N-OMC)was applied to activate PDS and PMS for degrading a model organic pollutant phenol to reveal their activation mechanisms.Re sults show that both PDS and PMS could be efficiently activated by N-OMC.The degradation of phenol fitted well with pseudo-first-order kinetics,whose kinetic constants increased with the increase of pH,PDS/PMS dosage,and N-OMC dosage.Based on quenching experiments and electron spin resonance spin-trapping technique,the N-OMC was found to activate PDS and PMS via nonradical process of electron transfer and singlet oxygen formation,respectively,instead of the commonly observed radical process.This wo rk will be useful to understand the activation processes of PDS and PMS,and benefit for the development of catalysts for pollutant degradation.

Extremely efficient electro-Fenton-like Sb(Ⅲ) detoxification using nanoscale Ti-Ce binary oxide: An effective design to boost catalytic activity via non-radical pathway

Environmental risks posed by discharge of the emerging contaminant antimony(Sb) into water bodies have raised global concerns recently.The toxicity of Sb has been shown to be species-dependent,with Sb(Ⅲ) demonstrating much greater toxicity than Sb(V).Here,we proposed an electrochemical filtration system to achieve rapid detoxification of Sb(Ⅲ) via a non-radical pathway.The key to this technology was an electroactive carbon nanotube filter functionalized with nanoscale Ti-Ce binary oxide.Under an electric field,in situ generated H_(2) O_(2) could react with the Ti-Ce binary oxide to produce hydroperoxide complexes,which enabled an efficient transformation of Sb(Ⅲ) to the less toxic Sb(V)(τ<2 s) at neutral pH.The impact of important operational parameters was assessed and optimized,and system efficacy could be maintained over a wide pH range and long-term operation.An optimum detoxification efficiency of> 90% was achieved using lake water spiked with Sb(Ⅲ) at 500 μg/L.The results showed that Ti/Ce-hydroperoxo surface complexes were the dominant species responsible for the non-radical oxidation of Sb(Ⅲ) based on extensive experimental evidences and advanced characterizations.This study provides a robust and effective strategy for the detoxification of water containing Sb(Ⅲ) and other similar heavy metal ions by integrating state-of-the-art advanced oxidation processes,electrochemistry and nano-filtration technology.

Hollow Co/CoO/Carbon nanofibers promoted PMS decomposition for the degradation of Rhodamine B

Carbon nanofibers with hollow structures have an excellent application prospect in various fields be-cause of their high specific surface area and abundant active sites.PAN-based hollow carbon nanofiber doped with Co/CoO(H-Co/CoO-CNF)was successfully prepared and used as a catalyst to activate perox-ymonosulfate(PMS)and degrade Rhodamine B(RhB).The catalyst showed a surprising degradation rate(98.89%)of RhB within 15 min and had good degradation performance in a wide pH range(pH 1.5-11.2).Compared with solid fibers,H-Co/CoO-CNF shows better cyclic characteristics.The catalyst is also mag-netic and recoverable easily due to the addition of Co/CoO.Two pathways of both radical(SO_(4)·^(−))and non-radical(^(1)O_(2))exist during the RhB degradation process are confirmed through electron paramagnetic resonance(EPR)analysis and radical quenching experiments.This work provides a new idea for hollow fibers loaded with metals and their oxides and can guide the development of catalysts for advanced oxi-dation processes in the future.

Insights into the electron transfer mechanisms of permanganate activation by carbon nanotube membrane for enhanced micropollutants degradation

Numerous reagents have been proposed as electron sacrificers to induce the decomposition of permanganate(KMnO_(4))by producing highly reactive Mn species for micropollutants degradation.However,this strategy can lead to low KMnO_(4) utilization efficiency due to limitations associated with poor mass transport and high energy consumption.In the present study,we rationally designed a catalytic carbon nanotube(CNT)membrane for KMnO_(4) activation toward enhanced degradation of micropollutants.The proposed flow-through system outperformed conventional batch reactor owing to the improved mass transfer via convection.Under optimal conditionals,a>70%removal(equivalent to an oxidation flux of 2.43 mmol/(h·m^(2)))of 80μmol/L sulfamethoxazole(SMX)solution can be achieved at single-pass mode.The experimental analysis and DFT studies verified that CNT could mediate direct electron transfer from organic molecules to KMnO_(4),resulting in a high utilization efficiency of KMnO_(4).Furthermore,the KMnO_(4)/CNT system had outstanding reusability and CNT could maintain a long-lasting reactivity,which served as a green strategy for the remediation of micropollutants in a sustainable manner.This study provides new insights into the electron transfer mechanisms and unveils the advantages of effective KMnO_(4) utilization in the KMnO_(4)/CNT system for environmental remediation.

Cobalt/nitrogen co-carved carbon nanorod for efficient Fenton-like reaction:Degradation efficacy,reaction mechanism and singlet oxygen generation

The Fenton-like process shows promising potential to generate reactive oxygen species for the reme-diation of increasingly environmental pollutants.However,the slow development of high-activity cata-lysts with strong stability and low leaching of metal ions has greatly inhibited scale-up application of this technology.Here,cobalt(Co)/nitrogen(N)atom co-curved carbon nanorod(CoNC)containing highly uniform CoN_(x)active sites is developed as a Fenton-like catalyst for the effective catalytic oxidation of various organics via peroxymonosulfate(PMS)activation with high stability.As confirmed by the exper-imental results,singlet oxygen(^(1)O_(2))is the dominant active species for the degradation of the organ-ics,with a proportion of 100%.Furthermore,density functional theory calculations indicate that CoN_(2)C_(2)is the most effective ligand structure with more negative adsorption energy for PMS and the shortest length Co-O bond,while the most reasonable generation pathway for^(1)O_(2)was CoN_(2)C_(2)-PMS→CoN_(2)C_(2)-OH∗→2O∗→^(1)O_(2).Further studies demonstrate that the electron can be transferred from the highest occupied molecular orbitals of the organics to the lowest unoccupied molecular orbitals of the PMS via CoN_(2)C_(2)action.In addition,the CoNC presents strong resistance to inorganic ions and natural organic matter in the Fenton-like catalysis process.The presence of CoN_(2)C_(2)active centre can significantly shorten the migration distance of the^(1)O_(2)generated from PMS activation,which further enhances the Fenton-like catalytic activity in terms of mineralising various organic contaminants with high efficiency over a wide pH range.

Phenol degradation in waters with high iodide level by layered double hydroxide-peroxodisulfate:Pathways and products

Recently, layered double hydroxide-peroxodisulfate(LDH-PDS) as an advanced oxidation system can effectively remove organics by the pathway of free radical. However, little has been known if there is a potential risk regarding the formation of high toxic iodine byproducts through another pathway when LDH-PDS is used in high iodide waters at coastal areas.Therefore, this study investigated phenol degradation pathways and transformation products to evaluate both removal mechanism and potential risk by LDH-PDS in high iodide waters. The results showed that in LDH-PDS system, with the degradation of PDS, phenol degraded till below detection limit in 1 hr in the presence of iodide, while PDS and phenol were hardly degraded in the absence of iodide, indicating iodide accelerated the transformation of PDS and the degradation of phenol. What is more, it reached the highest phenol removal efficiency under the condition of 100 mg/L LDH, 0.1 mmol/L PDS and 1.0 mmol/L iodide. In LDH-PDS system, iodide was rapidly oxidized by the highly active interlayer PDS, resulting in the formation of reactive iodine including hypoiodic acid, iodine and triiodide instead of free radicals, which contributed rapid degradation of phenol. However, unfortunately toxic iodophenols were detected. Specifically, 2-iodophenol and 4-iodophenol were formed firstly,afterwards 2,4-diiodophenol and 2,6-diiodophenol were produced, and finally iodophenols and diiodophenols gradually decreased and 2,4,6-Triiodophenol were produced. These results indicated that LDH-PDS should avoid to use in high iodide waters to prevent toxic iodine byproduct formation although iodide can accelerate phenol degradation.

Biochar with self-doped N to activate peroxymonosulfate for bisphenol-A degradation via electron transfer mechanism:The active edge graphitic N site

Environmental endocrine disruptors,represented by bisphenol A(BPA),have been widely detected in the environment,bringing potential health risks to human beings.Nitrogen-containing biocarbon catalyst can activate peroxymonosulfate(PMS)to degrade BPA in water,but its active sites remain opaque.Herein,in this work,nitrogen-containing biochar,i.e.,C–Nedge,enriched with graphitic-N defects at the edges was prepared by one-pot co-pyrolysis of chitosan and potassium carbonate.The results showed that the C–Nedge/PMS system can effectively degrade 98%of BPA(50 mg/L).The electron transfer based non-radical oxidation mechanism was responsible for BPA degradation.Edge graphitic-N doping endows biochar with strong electron transfer ability.The catalyst had good recovery and reuse performance.This catalytic oxidation was also feasible for other refractory pollutants removal and worked well for treating practical wastewater.This work may provide valuable information in unraveling the N doping configurationactivity relationship during activating PMS by biochar.