Study On Characters Of Zinc Adsorption-Desorption Of The Principal Types Soil At Yangtze River Delta

Heavy metal was an universal pollutant in soil. The chemical behavior character of heavy metal was mostly decided by soil character and the environment factors. After the heavy metal entered the soil, the inevitable process must be that the heavy metal was adsorbed by soil firstly, and desorbed from soil, then achieved balance at last. The mobility, the distribution and the accumulation of heavy metal were depend on that firm degree for adsorbing and whether the heave metal was adsorbed by the soil colloid to a great extent.The adsorption-desorption of heavy metal in the soil-water system was one of main functions that controlled heavy metal concentration in soil solution and influenced the behavior and trend of heavy metal in soil. It also decided that the heavy metal buffering ability and capacity of soil and the amount of heavy metal entered the food chain. According to the data of the soil adsorbed or released heavy metal, the trend of heavy metal entering the soil solution and the degree of the migration in the soil could be predicted. In other words, the adsorption-desorption of soil controlled the level and vertical movement of heavy metal in soil on a certain degree. Therefore, studding the character of heavy metal adsorbed by the soil was significant to predicting the environment effect of heavy metals.Zinc adsorption-desorption characteristics of soil that originated from four kinds of parent material at Yangtze River delta were studied via kinetics experiments and thermodynamics experiments. Through the investigation of the relation between adsorption quantity and concentration of equilibrium solution, then related with the national soil quality standard and the water quality standard, the author evaluated whether soil at Yangtze River delta matched with national standards.Results are list as follow: I . The results of kinetics experiment:1. The soil in the experiment adsorbed zinc fast. The adsorption nearly accomplished in 10 min. System achieved adsorption equilibrium in 4h, and achieved desorption equilibrium in 8h.2. Zinc adsorption-desorption reaction time varied with soil type. When the soil was alkalescent, the time to achieve equilibrium was longer than that of acid soil, because the neutralization reaction between soil and liquor delayed the equilibrium.3. The adsorption kinetic curves of two types soil were similar, and the process was same. Zinc was adsorbed and desorbed at different rates. According to the rate, the reaction of adsorbing-desorbing could be divided into two types: fast and slow reactions.