Influence of Humic Acid Colloid on Adsorption of DDT in the Riverbed Sediments

Static experiments were conducted to investigate the influence of humic acid on adsorption of DDT in the Wei river sediments. The results of kinetics experiments showed that adsorptive equilibrium time of DDT in sediments without humus was 120 h and its adsorption kinetics conformed to the first-order kinetics equation; with humic acid colloid, the DDT equilibrium time was shortened to 48 h and the adsorption kinetics fitted the second-order kinetics equation. The results of adsorption thermodynamics experiments indicated that the forms of the adsorption isotherms of o,p'-DDT, p,p'-DDD and p,p'-DDE without humus were S-, L-and L-shaped and the correspondingly adsorption models accorded with Freundlich, Langmuir and Langmuir equation, respectively. The adsorption isotherms forms of o,p'-DDT, p,p'-DDD and p,p'-DDE with humus were L-, S- and L-shaped and the correspondingly adsorption models were Langmuir, Freundlich and Langmuir equation, respectively. Concentration of humic acid had a silght impact on adsorption kinetics and thermodynamics experiments.