IJSRD - International Journal for Scientific Research & Development| Vol. 2, Issue 09, 2014 | ISSN (online): 2321-0613 All rights reserved by www.ijsrd.com 241 Study on Effect of Soil Washing with Different Washing Cycles on Particle Size of Contaminated Soil Bibhabasu Mohanty 1 1 Assistant Professor 1 Department of Civil Engineering 1 SAL Institute of Technology & Engineering Research Ahmedabad, Gujarat, India Abstract— Soil contamination by heavy metals is a major problem at many contaminated sites now a day. According to EPA’s list of priority pollutants cadmium, chromium, copper, lead, mercury, nickel, and zinc are the most hazardous heavy metals found at many soil contaminated sites. Many techniques are employed for the decontamination of soils. This consists of various physiochemical as well as biological methods. Among these process soil washing is a physiochemical method, which has a very high efficiency for heavy metal removal from contaminated soils. It is a simple, ex situ remediation technology. In this process by the addition of washing water, heavy metals can be transferred from the degraded sediment to wash solution. This process can be enhanced by addition of acid washing, chelating agents or surfactants. Particle size always plays an important role in the removal of heavy metals. In this research paper an attempt has made to soil washing technology for removal of Pb and Cr from contaminated soil with the help of different combination of EDTA and DI water cycle. Another attempt has also made to find out the effect of particle size i.e. soil, silt and clay on the soil washing. Key words: Remediation, Heavy metals, Soil washing, EDTA, Particle size I. INTRODUCTION Soil, one of the important elements of the environment is at threat because of various pollutants. Soils are mostly contaminated by volatile organics, hydrophilic and hydrophobic organics, heavy metals, and radioactive materials [1]. Among all the pollutants heavy metals plays a significant role. The most common heavy metals found at contaminated sites are lead, chromium, arsenic, zinc, cadmium, copper and mercury. These heavy metals are non degradable therefore, persist for ever in the environment. These heavy metals are one of the major sources of environmental pollution. They affect the human health, animal’s life by means of bioaccumulation. Heavy metal pollution can arise from many sources, but most commonly arise from the purification of metals, e.g. the smelting of copper and the preparation of nuclear fuels. Electroplating is the primary source of chromium and cadmium. Heavy metals also generated from industrial discharge energy production, chemical used in agricultural industry, construction activity, from vehicles exhaust, burning of fossil fuels etc. The E.P.A estimated over 20 million cubic yards of soil at current national priority list (NPL) sites are contaminated with metals. Metal is relatively immobile in sub surface system because of precipitation or adsorption reaction. The decontamination of soil includes the in- situ. The E.P.A estimated that over 20 million cubic yards of soil at current national priority list (NPL) sites are contaminated with metals. Metal s is relatively immobile in sub surface system because of precipitation or adsorption reaction. The decontamination of soil includes the in-situ as well as ex- situ remediation technique. The in-situ treatment mainly increases the stabilization of metals in sediment particles. The Ex-situ process achieved by extracting or separating metals from the contaminated sediment. Soil washing is a relatively simple and useful ex-situ remediation technology. In this technique washing water are added and heavy metal can be transferred from degraded sediment to wash solution. [2] The performance of soil wash is increase by addition of various additives such as, acid (H2SO4, HNO3), chelating agents (EDTA, EDDS, DTPA) or surfactants (eg. Rhamnolipid). Among all this additives chelating agents are most popular. Chelating agents such as Ethylenediamine Tetraacetic Acid (EDTA) can form stable and soluble complexes with heavy metal and increases metal removal from contaminated soil. Soil washing is useful for treatment of soil contaminated with heavy metals, hydrocarbons but it is less effective for VOC and pesticides [3]. Particle size also plays an important role in soil washing it is easy to remove heavy metal for larger size particle due to less molecular attraction between soil particles and heavy metals. But removal efficiency for very fine particles such as silt and clay is less compared to larger size particle due to strong molecular attraction. II. MATERIALS AND METHODS A. Soil The soil sample was collected from VIT University campus. The samples were air dried at room temperature to remove excess moisture. Then the air dried samples were sieved by using 2.36mm sieve to remove stones, large particles and other unwanted things. Then the soil samples were completely mixed with hand. Thoroughly mixed samples were kept in airtight plastic bag at room temperature for further use in experiments. B. Soil Contamination Procedure From the stored soil about 5 Kg of sample was taken. That sample was mixed with a solution of deionized water (DI), dissolved salts of lead nitrate Pb (NO3)2, potassium dichromate K2Cr2O7. The aim of mixing is to artificially contaminate the soil with Pb and Cr heavy metals. The conc. of heavy metals was kept around 5000ppm. For 10 days, the soil and heavy metals were properly mixed. Then particle size distribution of contaminated soil was performed with the help of 1700 microns – 53 microns sieve size. Concentration of heavy metals at each particle size was determined by soil digestion method. For soil digestion process was performed according to EPA 3050B method. The physicochemical properties of soil are shown on Table 1. The pH of soil was determined by using 1:5 soils to water ratio by using pH meter. With the help of Walkley and Black rapid titration method total organic carbon was