[Adsorption and Interaction of Cu2+ and Pb2+ on BS-12 Amphoteric Modified Bentonites].

Amphoteric modification can simultaneously improve the adsorption of organic pollutants and heavy metals on clay minerals. Study of the adsorption and interaction of multiple heavy metals on amphoteric modified soils is therefore of practical significance. Here, bentonite-(CK) and 150BS-12-modified bentonites (150BS-12) were characterized both before and after metal ion adsorption using Fourier-transform infrared spectroscopy (FTIR). The equilibrium adsorption characteristics and differences of Cu2+ and Pb2+ in single and binary systems were studied by batch methods. The interaction mechanism of the metals on modified bentonites is also discussed. The results showed that the adsorption capacity of Cu2+ and Pb2+ in single and binary systems was ranked, in descending order, as 150BS-12 > 100BS-12 > 50BS-12 > CK, and that the adsorption isotherm could be described by the Langmuir and Freundlich equations. Although the modification of BS-12 was more beneficial for the adsorption of Cu2+, the adsorption capacity and selectivity coefficient of Pb2+ on BS-12-modified bentonites were larger than for Cu2+. Cu2+ and Pb2+ had a mutually antagonistic effect on each other; modification with BS-12 enhanced the effect of Cu2+ on Pb2+ and weakened the effect of Pb2+ on Cu2+, which was always stronger than the effect of Cu2+ on Pb2+. Increases in temperature and pH, and a reduction in ionic strength, can increase the adsorption of Cu2+ and Pb2+; however, the influence of these factors varied between the two metals, which also affected the interaction between the metals.