Co_(3)O_(4)-ZnO/rGO catalyst preparation and rhodamine B degradation by sulfate radical photocatalysis

The development of a combined photocatalytic system with peroxymonosulfate (PMS) has great potential applications in the degradation and treatment of aqueous organic pollutants. Herein, a Co_(3)O_(4)-ZnO/rGO was prepared by a hydrothermal method using cobalt acetate, zinc acetate, and reduced graphene oxide (rGO) as the main raw materials. The physical and chemical characteristics of the obtained catalyst were analyzed using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS),scanning electron microscopy (SEM), and Fourier transform infrared (FT-IR). The photocatalytic features and capacities of the catalytic materials to activate PMS were investigated. Co_(3)O_(4)-ZnO/rGO exhibited stronger photocatalytic activity and ability to activate PMS than Co_(3)O_(4)/rGO or ZnO/rGO, and significantly improved the ability of PMS and photocatalysis to synergistically degrade rhodamine B (RhB), with a degradation rate of 90.40% within 40 min. The mechanism of RhB degradation was proposed based on characterization of materials, evaluation of RhB degradation efficiency, and analysis of the active species involved. The unique particle/sheet structure of Co_(3)O_(4)-ZnO/rGO provides a large number of active sites, and the formation of heterojunctions between Co_(3)O_(4) and ZnO improves carrier separation and transport in the reaction system. Our study offers a reference for designing more effective heterojunction catalysts based on the combination of PMS and photocatalytic technology.

Effects of acid,acid-ZVI/PMS,Fe(Ⅱ)/PMS and ZVI/PMS conditioning on the wastewater activated sludge(WAS)dewaterability and extracellular polymeric substances(EPS)

The effects of four conditioning approaches:Acid,Acid-zero-valent iron(ZVI)/peroxydisulfate(PMS),Fe(Ⅱ)/PMS and ZVI/PMS,on wastewater activated sludge(WAS)dewatering and organics distribution in supernatant and extracellular polymeric substances(EPS)layers were investigated.The highest reduction in bound water and the most WAS destruction was achieved by Acid-ZVI/PMS,and the optimum conditions were pH 3,ZVI dosage 0.15 g/g dry solid(DS),oxone dosage 0.07 g/g DS and reaction time 10.6 min with the reductions in capillary suction time(CST)and water content(Wc)as 19.67%and 8.49%,respectively.Four conditioning approaches could result in TOC increase in EPS layers and supernatant,and protein(PN)content in tightly bound EPS(TB-EPS).After conditioning,organics in EPS layers could migrate to supernatant.Polysaccharide(PS)was easier to migrate to supernatant than PN.In addition,Acid,Acid-ZVI/PMS or Fe(Ⅱ)/PMS conditioning promoted the release of some polysaccharides containing ring vibrations v P=O,v C-O-C,v C-O-P functional groups from TB-EPS.ESR spectra proved that both radicals of SO4-·and·OH contributed to dewatering and organics transformation and migration.CST value of WAS positively correlated with the ratios of PN/PS in LB-EPS and total EPS,while it negatively correlated with TOC,PN content and PS content in TB-EPS,as well as PS content in supernatant and LB-EPS.BWC negatively correlated to zeta potential and TOC value,PN content,and HA content in supernatant.

Magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering(MPEOD) of activated sludge： Role and behavior of moisture and organics

In this study, a magnetic micro-particle conditioning–pressurized vertical electro-osmotic dewatering（MPEOD） process with magnetic micro-particle conditioning–drainage under gravity–mechanical compression–electrical compression（MMPC–DG–MC–EC） stages was established to study the distribution and migration of water, extracellular polymeric substances（EPS）, and other organic matter in the activated sludge（AS） matrix at each stage.Results showed that the MPEOD process could attain 53.52% water content（WC） in dewatered AS with bound water（BW） and free water（FW） reduction rates of 82.97% and 99.67%,respectively. The coagulation and time-delayed magnetic field effects of magnetic microparticles（MMPs） along the MMPC–DG–MC stages initiated the transformation of partial BW to FW in AS. EC had a coupling driving effect of electro-osmosis and pressure on BW, and the changes in pH and temperature at EC stage induced the aggregation of AS flocs and the release of partial BW. Additionally, MMPs dosing further improved the dewatering performance of AS by acting as skeleton builders to provide water passages. Meanwhile, MMPs could disintegrate sludge cells and EPS fractions, thereby reducing tryptophan-like protein and byproduct-like material concentrations in LB-EPS as well as protein/polysaccharide ratio in AS matrix, which could improve AS filterability. At EC stage, the former four Ex/Em regions of fluorescence regional integration analysis for EPS were obviously reduced, especially the protein-like substances in LB-and TB-EPS, which contributed to improvement of AS dewaterability.

Corrigendum to ‘Effects of acid, acid-ZVI/PMS, Fe(Ⅱ)/PMS and ZVI/PMS conditioning on the wastewater activated sludge (WAS) dewaterability and extracellular polymeric substances (EPS)' [J. Environ. Sci. 91 (2020) 73-84]

The authors regret'In the acknowledgments of this manuscript,the Nos.51678035 and 51478041 of the National NaturalScience Foundation of China are wrong.The correct Nos.are 51678053 and 51478041'.The authors would like to apologize for any inconvenience caused.

Reversibility of the structure and dewaterability of anaerobic digested sludge

The reversibility of the structure and dewaterability of broken anaerobic digested sludge（ADS）is important to ensure the efficiency of sludge treatment or management processes.This study investigated the effect of continuous strong shear（CSS）and multipulse shear（MPS）on the zeta potential,size（median size,d（50））,mass fractal dimension（DF）,and capillary suction time（CST）of ADS aggregates.Moreover,the self-regrowth（SR）of broken ADS aggregates during slow mixing was also analyzed.The results show that raw ADS with d（50） of 56.5μm was insensitive to CSS–SR or MPS–SR,though the size slightly decreased after the breakage phase.For conditioned ADS with d（50） larger than 600μm,the breakage in small-scale surface erosion changed to large-scale fragmentation as the CSS strength increased.In most cases,after CSS or MPS,the broken ADS had a relatively more compact structure than before and d（50） is at least 200μm.The CST of the broken fragments from optimally dosed ADS increased,whereas that corresponding to overdosed ADS decreased.MPS treatment resulted in larger and more compact broken ADS fragments with a lower CST value than CSS.During the subsequent slow mixing,the broken ADS aggregates did not recover their charge,size,and dewaterability to the initial values before breakage.In addition,less than 15%self-regrowth in terms of percentage of the regrowth factor was observed in broken ADS after CSS at average velocity gradient no less than 1905.6 sec^（-1）.