Green synthesis of natural limonite-modified biochar catalyst for peroxymonosulfate activation in efficient degradation carbamazepine in water

Emerging contaminants in water pose a severe threat to the ecological environment, thus there is an urgent need to develop a cost-effective remediation method. To effectively remove emerging contaminants from water, this study involves one-step pyrolysis synthesis of a sustainable limonite-modified corn straw biochar (LCS-750-200) to activate peroxymonosulfate (PMS) for degradation of carbamazepine (CBZ) in water. The physicochemical properties of biochar were analyzed by SEM-EDS, FTIR, XRD, and XPS, various factors influencing degradation of CBZ were investigated. Degradation mechanisms and pathways of CBZ were explored by quenching reaction, EPR analysis, XPS, and LC-MS. The results indicated that LCS-750-200 with microporous and mesoporous structures facilitated adsorption of CBZ and PMS. The goethite and hematite of limonite were reduced to magnetite under 750 degrees C pyrolysis temperature, becoming active site for PMS activation. The LCS-750-200 exhibited high performance for PMS activation, achieving a 82.3 % removal of CBZ (10 mg/L) within 120 min (3.0 g/L LCS-750-200, 5.0 mM PMS, with no initial pH adjustment). The CO2- degradation of CBZ, but 83.0 % of CBZ could be removed within 40 min when Cl- coexistence. Free radical (SO center dot- and center dot OH) and non-radical pathways (1O2) were jointly involved in CBZ degradation by quenching experiments and EPR analysis. The primary active sites were Fe(II) of iron minerals, oxygen-containing functional groups, and sp2-carbon. Furthermore, CBZ was degraded via deamination, dehydroxylation, and amide cleavage, which were further mineralized to inorganic substances. This study provides novel insights into iron-based biochar for activating persulfate in degrading organic pollutants.