Natural Hematite-algal Biochar Composites As Sulfite Activator For The Removal Of Tetracycline Hydrochloride

The pollution caused by the abuse of antibiotics and the risk of antibiotic resistance put a certain pressure on water environmental remediation.Advanced oxidation process is a promising technology for water remediation.Among them,advanced oxidation technology based on persulfate activation has developed rapidly in recent years,and the research and development of heterogeneous composite activator has gradually become a new research focus.In this study,with natural hematite and spirulina residue as feedstocks,novel hematite-algal derived biochar composite（HBC）was synthesized via one-step pyrolysis successfully combining the two modification methods of iron ore combination and endogenous nitrogen-doping.And the performance of HBC in persulfate（PDS）activation and tetracycline hydrochloride（TCH）degradation was evaluated.Detailed characterization results indicated that graphitic-N,pyrrolic-N and pyridinic-N structures were introduced by endogenous N-doping,which enhanced the dispersion of hematite on biochar.Hematite combination enriched the pore structure of HBC and introduced effective active site of iron species.Additionally,the synergistic effect of iron species and nitrogen deficiency promoted the transformation of sp³ C to sp² C and improved the graphitization degree of HBC.Remarkably,the optimized HBC presented excellent catalytic performance in PDS activation for TCH removal.HBC/PDS systems degraded 20 mg/L TCH close to 100%with in 20min,applied with 0.1 g/L catalyst,0.1 m M oxidant and the initial p H=4.6.Compared with the results of pure algal derived biochar（BC）and other relevant research results,HBC significantly removed high-concentration TCH more effectively with the competitive advantage of less dosage and shorter time.Radical quenching experiment and EPR test showed that the free radical degradation pathway involving·OH,SO₄^·-and O₂^·-and the non-free radical pathway mediated by ¹O₂ co-participated in the HBC/PDS system for the TCH degradation.The iron species introduced by hematite,the rich nitrogen deficiency and the graphite-carbon structure formed under the synergistic action of the two may be the main catalytic active sites of HBC.Based on the active structure,HBC played multiple roles in removing pollutants,such as pollutants and PDS adsorption,PDS actiation and electron transfer mediation for reactive removal of pollutants.Exploring the influencing factors showed that the HBC activated PDS system preferred acidic conditions and showed relatively stable performance in the p H range of 3-9.This work proposed an economical and green biochar-based material modification method and provided a new idea for the synthesis of efficient PDS heterogeneous iron-based catalyst and its efficient application in removing TCH from water.