Ecology, Environment and Conservation Paper

LEACHABILITY BEHAVIOR OF HEAVY METALS BY CONTAMINATED SOIL WITH ADDITIVES

G Venkata Ramaiah, S. Krishnaiah and Shankara

Abstract

Batch leaching, Toxicity Characteristics Leaching Procedure (TCLP) and Extended TCLP tests have been conducted to study the leaching behavior of Ni2+and Pb2+ on Mavallipura soil (MP soil) amended with fly ash and bentonite in small percentages. The tests were performed based on different load ratios of 50 mg/kg and 100 mg/kg. Sub-samples were drawn at different curing periods of 7, 28 and 45 days to study the leaching behaviour. It was found that higher the load ratio, higher is the percentage of leaching in soil alone and also for soil with admixtures. MP soil leached to a maximum of 0.65 and 1.05 mg/g for a load ratios of 50 and 100 mg/kg respectively for Ni. Whereas MP soil leached to a maximum of 0.85 and 1.1 mg/g for a load ratios of 50 and 100 mg/kg respectively. It is observed that the leaching of Ni and Pb has considerably reduced for a soil mixture with 30% fly Ash, 20% fly Ash and 6% bentonite. Curing period had a noticeable effect on the retention capacity of the contaminants. While precipitation effect is not influenced by curing period, but formation of complexes appears to be affected by the curing period. It was found that the both the heavy metals were adsorbed well for short term period but for a long term period, the metal ion was desorbed back to the soil media. Mechanism and behavior of leaching were studied by means of Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) confirmatory tests of micro structural characteristics on leached samples showed that MP soil amended with fly ash and bentonite retained lead and nickel effectively.