AN EFFICIENT SCREENING SYSTEM OF CLAY SOIL PARTICLES IN THE SOIL WASHING REMEDIATION PROCESS

The traditional leaching technology for heavy metal contaminated soil remediation efficiency was low, and the contaminated soil could be classified and reduced to improve the leaching efficiency. Through the development of an efficient soil classification system, soil particles could be quickly screened to improve the efficiency of soil pollution leaching remediation. The system used the principle of filtration separation, through the active pressure of the pump and the rotation of the screen surface, the particles accumulated on the screen surface were subjected to centrifugal force, gravity and liquid shear force, and the solid-liquid system was fully disturbed, which greatly reduced the bridging accumulation of soil particles on the screen surface, strengthened the screening process, and then classified the particles in the soil water solution according to the target particle size. Through the practical verification of multi-stage particle size(250~35 μm), compared with the conventional air separation system, the screening rate of the system was significantly improved, the screening efficiency and yield could be guaranteed, and the purpose of soil particle size classification was well achieved. In addition, based on the screening system, the grading leaching experiment was carried out, and the quality of the soil leached after particle size classification was reduced by about 20%. The optimal process parameters of EDTA leaching Pb contaminated soil were determined as follows:leaching solution concentration of 0.01~0.05 mol/L, pH value of 7, and leaching time of 10 h.