Cr (¢ö) In Chromium Residue Dissolved The Release Of Its Study Of The Migration Of Soil

China is one of major country to produce chromate. A large amount of chromium-containing slag was annually discharged from chromate industries. For lacking of appropriate disposal facilities, the deposition of chromium-containing slag will result in serious soil and groundwater pollution. A Ferro-Alloy Plant in Hunan province produced a large amount of chromium-containing slag, resulting in soil contamination with quantity of 12 500 thousand tons and this trend will increase due to continuous leaching of Cr(VI) from the salg.In this thesis, the slag sampled from a waste heap at a ferroalloy manufacturing plant in Hunan, China was used to investigate the main factors influencing the dissolution-release of Cr(VI) by making soaking and dynamic leaching. The results showed that the main factors were the solid-liquid ratio, soak time, agitation, acidity, particle size and water dynamic flow. Based on the parameters gained from dynamic leaching experiment, a Cr(VI) release and leaching model was developed and applied to predict the annual average releasing concentration of Cr(VI) in chromium slag under atmospheric precipitation. The minimum Cr(VI) concentration was 31.04mg/L which exceeded the limit of Chinese Drinking Water Quality Standard (GB5749-2006) by 620 times. As a result, the slag is a major source of soil and groundwater pollution.In this work, the kinetic and isothermal adsorption models of Cr(VI) in soils were investigated. The results showed that the adsorption equilibrium was reached within the 5h and Cr(VI) adsorption kinetics at different temperatures was well fit with pseudo-second-order model within a correlation coefficient of 0.999; Thermodynamic analysis showed that Cr(VI) adsorption process was a spontaneous and endothermic reaction. Moreover the random disorder in the solid/liquid interface between Cr(VI) and soil phase occured in the internal soil.The adsorption capacity of Cr(VI) in soil decreased with the pH of the solution increasing. Especially, The adsorption capacity of Cr(VI) was very low in strong alkaline environment. With the Cr(VI) initial concentration of solution increased, the adsorption capacity of Cr(VI) increased. A Langmuir isothermal model was much better to describe Cr(VI) adsorption phenomena under different temperatures than Freundlich isotherm model.In addition, the parameters of soil media model were determined by the column dynamic simulation experiment on the transfer of Cr(VI) in the soil, which provided the measured parameters to the simulation transfer of Cr(VI) in soil and groundwater system. The results showed that the transfer of Cr(VI) was obviously delayed in soil comparing to that of the conservative matter(Cl-). In the stable penetration, the permeability coefficient Kt in the soil was 63.36 mm/d. The adsorption distribution coefficient Kd was 1.17×10-3m3/kg and the retard factor Rd could not be calculatated because of unstable constant of soil moisture in the unsaturated soil. The adsorption distribution coefficient Kd was 0.054×10-3m3/kg and the retard factor Rd was 1.17 in saturated soil.According to the simulation results of Cr(VI) release and leaching model and the drilling data of underground water level in study area, Cr(VI) translocation model in soil depths was established by using HYDRUS-1D (V3.00) software and convection-dispersion equation. The results showed that the breakthough time of Cr(VI) penetrating soil depths of 50cm,100cm and 150cm were 175 days, 700 days and 1800 days, respectively.