SOIL WASHING WITH SURFACTANTS TO REMOVE HEAVY METALS CONTAMINANTS OF AGRA DISTRICT, UP INDIA

The purpose of this work was to remove heavy metal contaminants (Cr3+, Mn2+, Fe2+, Ni2+, Zn2+, C2+ and Pb2+) from soil samples using micellar wash liquids. Five contaminated soil samples from Kitham, St. John's, Shahganj, Shahadra and Nunhai areas with low, moderate, high, higher and highest metal concentrations respectively were collected from top horizons (0-20 cm deep). Three types of the wash liquid were 4 CMC (above critical micelle concentration, CMC) of each of sodium dodecyl sulfate (SDS), Criton X-100, i.e., isooctylphenoxy-hexaethoxyethanol (CTX) and N-cetyl N, N, N-trimethyl ammonium bromide (CTAB). Total metal content in the sample (before and after 1, 4, 7 and 10 washings) extracted with 60% perchloric acid was determined with a Perkin-Elmer AAnalyst 100 AAS. The micellar enhancement in removal was entirely different for various types of surfactants as well as different chemical species. However, surfactants were able to enhance the removal of contaminants 2-3 times greater than filtration without surfactants. Anionic surfactants removed more cationic contaminants and vice versa. The order of metal removal by surfactants was SDS > CTX > CTAB. In case of A and B type soils the order of removal % was Zn > Cr > Fe > Ni > Cu > Pb > Cd > Mn. The removal order for C, D and E with 4 CMC of all the three surfactants was Cr > Fe > Ni > Cu > Pb > Zn > Cd > Mn. Since SDS had higher removal, it should be preferred for metal removal from soil or water. Investigations at below and above CMCs are suggested.