关键词: 环境工程；生物质炭；吸附；砷

Abstract: In order to study the removal effect and adsorption mechanism of arsenic in water by Fe3O4 modified biochar, wheat straw was selected as raw material to prepare raw biochar (BC), and two modified biochar (MBC-1 and MBC-2) with different iron-to-carbon ratios （MFe3O4∶MBiochar=1∶4, 1∶2） was designed by co-precipitation method. SEM, BET, FT-IR, and XRD spectrogram were applied to determine the surface morphology, specific surface area, porous structures, and functional groups of BC, MBC-1 and MBC-2; and XPS and EDS were used to analyze physical and chemical properties of MBC-1. The influence of biochar dosage and solution pH value on the adsorption was investigated. The adsorption kinetics and isothermal adsorption experiments were carried out to study the adsorption characteristics of As on BC, MBC-1 and MBC-2, and the adsorption mechanism of As on Fe3O4 modified biochar was discussed. The results show that Fe3O4 is successfully loaded onto biochar, and the specific surface areas of MBC-1 and MBC-2 are 1.69 and 2.26 times as much as that of BC, respectively. The removal rate of As by BC, MBC-1 and MBC-2 increases with the increase of biochar dosage and decreases with the increase of solution pH value. The adsorption of As by BC, MBC-1 and MBC-2 accords with the pseudo-second-order kinetic model, and the adsorption isotherm curve accords with the Freundlich adsorption model. The maximum adsorption capacity of MBC-1 and MBC-2 for arsenic fitted by Langmuir model are 141 and 184 times higher than that of BC, respectively. The more Fe3O4 loaded, the better the adsorption effect. The adsorption of As by MBC-1 and MBC-2 includes electrostatic attraction, coordination reaction and ion exchange. Fe3O4 loaded in biochar participates in the redox reaction of As, changes the occurrence form of As and affects the adsorption and fixation of As.

Key words: environmental engineering; biochar; sorption; arsenic（As）