Effect of the Molecular Weight of Humic Acids on the Adsorption of As(V) on Goethite
摘要
The migration of arsenic in groundwater is controlled by the adsorption of iron-containing minerals, and natural organic matter also has a great influence on arsenic adsorption during the adsorption process. The effects of humic acids with different molecular weights on the isotherms and adsorption kinetics of arsenic adsorption on goethite, as well as the mechanism of these effects, were studied via zeta potential, Fourier transform infrared spectroscopy, and three-dimensional fluorescence analysis. The results showed that the adsorption of arsenic in the low molecular weight inhibited the adsorption capacity from 25.1 to 14.5 mg.g−1, while the medium molecular weight promoted the adsorption capacity from 25.6 to 32.3 mg.g−1, and the high molecular weight humic acid had little effect on arsenic adsorption. The surface charge analysis revealed that there was competitive adsorption between arsenic and humic acid, and as the molecular weight of the humic acid increased, the amount of negative charge on the surface of the goethite increased. The infrared spectroscopy results showed that an arsenic-goethite-organic matter ternary complex was formed. The three-dimensional fluorescence spectroscopy indicated that the humic acid fluorescence was quenched after the addition of arsenic.