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.

Biomass derived Fe-N/C catalyst for efficiently catalyzing oxygen reduction reaction in both alkaline and neutral pH conditions

Fe-N/C is a promising oxygen reduction reaction(ORR)catalyst to substitute the current widely used precious metal platinum.Cost-effectively fabricating the Fe-N/C material with high catalytic activity and getting in-depth insight into the responsible catalytic site are of great significance.In this work,we proposed to use biomass,tea leaves waste,as the precursor to prepare ORR catalyst.By adding 5%FeCl3(wt%)into tea precursor,the pyrolysis product(i.e.,5%Fe-N/C)exhibited an excellent four-electron ORR activity,whose onset potential was only 10 m V lower than that of commercial Pt/C.The limiting current density of 5%Fe-N/C(5.75 m A/cm^(2))was even higher than Pt/C(5.44 m A/cm^(2)).Compared with other biomass or metal organic frameworks derived catalysts,5%Fe-N/C showed similar ORR activity.Also,both the methanol tolerance and material stability performances of as-prepared 5%Fe-N/C catalyst were superior to that of Pt/C.X-ray adsorption fine structure characterization revealed that the FeN4O2might be the possible catalytic site.An appropriate amount of iron chloride addition not only facilitated catalytic site formation,but also enhanced material conductivity and reaction kinetics.The results of this work may be useful for the Fe based transition metal ORR catalyst design and application.

Advances and challenges of sulfur-driven autotrophic denitrification(SDAD)for nitrogen removal

Sulfur-driven autotrophic denitrification(SDAD),a process suited for the treatment of nitrogen and sulfur-polluted wastewater without extra supplement of organic carbon,is a promising biological nitrogen removal process.However,the SDAD process was affected by many factors such as various electron donors,organic carbon and exogenous substances(e.g.,antibiotics and heavy metal),which prevent further application.Thus,we conducted a detailed review of previous studies on such influence factors and its current application.Besides,a comparative analysis was adopted to recognize the current challenges and future needs for feasible application,so as to ultimately perfect the SDAD process and extend its application scope.