[Copper sorption and desorption by loess in water-sediment systems]

A series of experiments were designed to investigate copper sorption and desorption by loess in hyper-concentrated sediment systems. The results demonstrate that loess had large copper sorption capacity because of its specific adsorption and precipitation of carbonate and hydroxide. Copper sorption decreased with increasing ionic strength of solution, but the effects of varying cationic charge of supporting electrolyte were still detected. Less than 4% of copper was desorbed in the neutral saline solution, and increased with increasing ionic strength of solution. The pH was the most dominant factor on copper desorption. More than 70% of copper can be desorbed in the acid solution, and copper desorption increased with the decrease of solution pH. When pH of solid-liquid system was fixed, copper desorption from equivalent loess increased with the increase of solution volume, and copper desorption in the same sediment concentration increased with the adsorptive capacity.