Adsorption of tetrakis(hydroxymethyl)phosphonium chloride on pomelo peel biochar and its antimicrobial ability

Abstract

In this study, potassium hydroxide (KOH), aluminum chloride (AlCl3), and zinc chloride (ZnCl2) were co-pyrolyzed with pomelo peel biomass (according to different pyrolysis conditions, abbreviated in order as KOH-BC, AlCl3-BC, and ZnCl2-BC) to enhance the original biochar (BC) adsorption performance of an emerging contaminant tetrakis(hydroxymethyl)phosphonium chloride (THPC). The adsorption experiments indicated that the adsorption capacity for THPC of KOH-BC reached 438 mg·g–1, which showed much higher adsorption properties than those of BC (239.6 mg·g–1), AlCl3-BC (301.6 mg·g–1) and ZnCl2-BC (278.9 mg·g–1) due to its better developed pore structures. The adsorption process of THPC by BC, KOH-BC, AlCl3-BC, and ZnCl2-BC, a spontaneous endothermic process that had been analyzed, according with the second-order kinetic model and Langmuir isotherm model. And the adsorption mechanisms of THPC removal (i.e., pore filling, cation-π interaction, hydrogen bonding, and ion exchange) were summarized. Targeting Escherichia coli, the antibacterial activity of BC (THPC-BC) and KOH-BC (THPC-KOH-BC) of THPC after adsorption was explored. Antibacterial activity experiments have shown that THPC-BC and THPC-KOH-BC could effectively inhibit the growth of E. coli. Therefore, BC and modified BC can not only be used to remove THPC but also be recycled for secondary utilization, which provides a novel idea for the emission reduction and resource recycling of THPC with great practical value.