Chlortetracycline hydrochloride removal by different biochar/Fe composites: A comparative study

Abstract In the last years, the synthesis and applications of biochar/Fe composites have been extensively studied, but only few papers have systematically evaluated their removal performances. Herein, we successfully synthesized and structurally characterized Fe0, Fe3C, and Fe3O4-coated biochars (BCs) for the removal of chlortetracycline hydrochloride (CH). Evaluation of their removal rate and affinity revealed that Fe0@BC could achieve better and faster CH removal and degradation than Fe3C@BC and Fe3O4@BC. The removal rate was controlled by the O–Fe content and solution pH after the reaction. The CH adsorption occurred on the O–C groups of Fe0@BC and the O = C and O–Fe groups of Fe3C@BC and Fe3O4@BC. Electron paramagnetic resonance analysis and radical quenching experiments indicated that HO• and 1O2/ O2•− were mainly responsible for CH degradation by biochar/Fe composites. Additional parameters, such as effects of initial concentrations and coexisting anions, regeneration capacity, cost and actual wastewater treatment were also explored. Principal component analysis was applied for a comprehensive and quantitative assessment of the three materials, indicating Fe0@BC is the most beneficial functional material for CH removal.