Lignocellulosic Biomass Derived Nitrogen And Cobalt Co-doped Biochar As Highly Efficient Peroxymonosulfate Activator For Ciprofloxacin Degradation

Burning lignocellulosic biomass wastes,like stalks,in an outdoor atmosphere has placed heavy burden on ecological environment and increased risk on human health.How to convert solid agricultural wastes into functional materials has always been a key issue to be explored.In recent years,advanced oxidation processes（AOP）,which can generate free radicals with higher oxidation-reduction potentials and can efficiently degrade or even completely mineralize organic pollutants in water bodies,has shown great development potential and broad application prospects in the treatment of environmental organic contaminants.Compared to various AOPs involving hydroxyl radical（·OH）reported,sulfate radical(SO₄^·-)-based advanced oxidation process（SR-AOP）has been regarded as a promising alternative due to its higher reaction activity,lower requirements on p H and environmentally friendly.In this study,biochar derived from cotton stalk biomass was utilized as a raw material to successfully synthesize nitrogen and cobalt co-doped carbon catalyst（N/Co-BC）through impregnation and carbonization process.To explore its catalytic performance,N/Co-BC was applied to activate peroxymonosulfate（PMS）for ciprofloxacin（CIP）degradation.Based on this,the activation mechanism and degradation pathway was illuminated according to characterization analysis and experimental results.In terms of morphology and structure,the characterization results of FESEM and BET showed that N/Co-BC has mesoporous structure characteristic,and its specific surface area and pore size were significantly improved.Additionally,it could be found from XRD,Raman spectra that nitrogen and cobalt co-doped biochar introduced defects as active sites on the well-organized carbon network,thereby produced directional flow of electrons,accelerated electron migration and improved electron conduction ability.It was found that the CIP adsorption capacity of N/Co-BC increased by nearly 10 times compared with the pristine biochar（BC）.Meanwhile,N/Co-BC also presented excellent catalytic performance in activating PMS to degrade CIP,and its degradation rate was 16 times that of BC/PMS system.Based on results of radical quenching experiment and EPR experiment,it was apparent that both radical and non-radical process conjointly led to the stepwise decomposition of CIP.Singlet oxygen（¹O₂）mediated non-radical pathway was found to play a dominant role during the decomposition of CIP.This work provides a brand-new strategy for the disposition of lignocellulosic biomass wastes and illuminates the underlying mechanism of heterogeneous catalysis by nitrogen and cobalt co-doped biochar.