Sorption of lead on variable-charge soils in China as affected by initial metal concentration, pH and soil properties

Six variable-charge soils locally referred to as Yellow brown soil (YBS), Latosol soil (LS), Red soil (RS). Lateritic red soil (LRS), Paddy soil (PS) and Yellow soil (YS) and classified as Alfisol. Oxisol, Ultisol, Oxisol, Alfisol and Oxisol, respectively, in the American classification system, were collected from Hubei, Hainan, Guangxi. Jiangxi and Guizhou provinces of China. The adsorption of Pb2+ was studied as a function of metal ion concentration and solution pH. The results showed that the amount of Pb adsorbed increased with the increasing concentration of Pb and solution pH, the relationship could be well described by Freundlich isotherm equation. Pb2+ showed stronger affinity to paddy soil (PS) at all concentrations and pH. The adsorption capacity of the soils was in the order PS>YS>YBS>RS>LS>LRS. A significant positive correlation (r = 0.91; 0.88; 0.51; 0.77; p <= 0.05) was found between the Freundlich Kf and pH, organic matter. CEC and amorphous Al, respectively. A significant negative correlation (r = -0.88, p <= 0.05) was found between the Freundlich Kf and clay. The Freundlich n was positively correlated with amorphous Fe (r = 0.91, p <= 0.05) and negatively correlated with crystalline Al (r = -0.63, p <= 0.05). Soil pH, organic matter. CEC, clay and amorphous Al and Fe are the important soil properties controlling the adsorption of lead in the studied soils.