Adsorption studies of organochlorine pesticides on humic acid colloids

It is well known that colloids can effectively adsorb contaminants in groundwater, and therefore significantly influence their migration behaviors. The current study, applying laboratory simulation experiments, systematically investigated humic acid colloids (HACs) adsorption of benzene hexachlorides (BHCs) on different effects from adsorption time, BHC concentrations, HAC concentrations, etc. The results show that, when a true solution phase, a colloid phase and a suspension phase co-existed in aqueous solution, the presences of BHCs are in the order of colloid phase>; suspension phase>; true solution phase. Adsorptions of BHCs by HACs are consistent to the Henry isotherm. HACs with adsorbed BHCs have smaller colloidal sizes than the pristine ones, possibly due to the increased hydrophobicity of HACs and structure shrinkages under pressures from surrounding waters. The UV-Vis spectra show that the adsorption peak of BHCs at 203nm disappeared because of the physical adsorption of BHCs by HACs and aromatic and aliphatic hydrocarbons in HACs.