Adsorption of lead on organo-mineral complexes isolated from loess in Northwestern China

Four types of organo-mineral complex (OMC) samples with different sizes were extracted from loess in northwestern China. OMC, which has a size less than 2 μm, was used to investigate the adsorption behavior of lead. The OMC sample had a porous structure with a surface area of 147.49 m2/g, and the adsorption capacity changed with different conditions of OMC content, pH values of the solution, temperature, and ionic strength. The adsorption isotherms suggested that the adsorption process was favorable, and the maximum adsorption capacity of lead on OMC was 1.5877 mg/g, which was calculated by using Langmuir equation. The reaction fits better the pseudo-second-order kinetic equation, and the adsorption behavior could be divided into two sections, thereby indicating that the reaction involved physical and chemical adsorption. The adsorption of lead on OMC was spontaneous and exothermic in nature, and the randomness of the system decreased slightly throughout the entire process. The desorption efficiency was acceptable with purified water and with ultrasonic assistance.