Sorption and desorption behaviors of heavy metal Mn(II) on loess soil

Manganese is a trace heavy metal. Toxic effect will be caused by excessive intake of manganese. The control of manganese discharge into environment has been attracted much attention recently. Loess soil is used to study the behaviors of removing Mn(II) from aqueous solutions due to its low cost and easy availability. Factors including reaction time, concentration of Mn(II), temperature and complexing agent nitriletriacetic acid (NTA) are studied. The adsorption of Mn(II) on loess soil is a fast process and can reach equilibrium within 1 h. The kinetic data fit the pseudo-second order kinetics model very well, and the reaction rate decreases with the increasing initial concentration of Mn(II). The adsorption capacity of Mn(II) on loess soil is determined to be 7.829 mg/g, and high temperature favors the adsorption process. NTA has contribution on the desorption of Mn(II) from loess soil. The higher concentration of NTA, the more Mn(II) is desorbed. When the amount of Mn(II) laden in loess soil is small, nearly all Mn(II) can be desorbed from loess soil. Clay minerals and organic matter in loess play important roles in Mn(II) adsorption, and ion exchange is the main adsorption mechanism. The results provide an evidence for loess soil as containment barrier system and as adsorbent removing heavy metal contamination in aquatic environment. The introducing of NTA has a certain reference value for remediation of contaminated soil.