Effect of different surfactants on the remediation of a clay soil contaminated with ‎Dimethyl phthalate by electrokinetic method

Electrokinetic technique is one of the common methods that can be used for removal of ‎organic contaminants in soil. There are some of organic contaminants with low solubility ‎in water. In order to improve the efficiency of remediation in this method it is possible to use appropriate ‎surfactants as flushing solution.‎ In this work SDS, Poloxamer 407 and Brij 35 surfactants were selected for improving the ‎remediation of a clay soil contaminated with Dimethyl phthalate (DMP). The contaminated ‎soil was prepared artificially with the concentration of 40 mg/kg in the laboratory. ‎Experimental tests were conducted in a special apparatus. It was consisted of a Plexiglas ‎with 1 cm thickness as the main cell. The main cell dimensions were 30 cm in length, 10 ‎cm in width and 30 cm in height. Two reservoirs as anode and cathode were added on ‎the two sides of the main cell and they were connected to the main cell. The prepared ‎contaminated soil after saturated was poured into the main cell of apparatus. The anode ‎and cathode reservoirs were filled with desired solution of surfactant and distilled water ‎respectively. A constant voltage of 50 V was applied to the soil for duration of 7 days for all tests. ‎A reference test was also conducted with distilled water in anode and cathode reservoirs ‎under the same voltage and duration. During each test the pH, EC (electrical ‎conductivity) and volume of outflow liquid discharge were measured. At the end of each test, ‎the shear strength of soil was measured by shear van at the distance of 4, 12, 19 and 26 ‎cm from anode. A number of soil samples were also extracted from these points for pH ‎measurement and removal of DMP by using GC (Gas Choromatography) ‎apparatus. The results showed that the shear strength of soil is increased with increasing ‎the distance from anode. The values of shear strength around the cathode were measured ‎as 7, 5.5, 8 and 42 kPa for distilled water and solutions of Brij 35, Poloxamer 407 and ‎SDS respectively. It was revealed that by increasing the distance from anode the value of ‎pH was also changed from acidic to alkaline. In addition, the results indicated that the ‎percentage of remediation at the distance of 4, 12, 19 and 26 cm from anode for solution ‎of SDS were 73, 70.5, 14 and 20.12 and for Brij 35 they were changed to 69.55, 66 ,21 ‎and 17 % respectively. The percentage of remediation for solution of Poloxamer 407 were ‎also determined 68.94, 65.89, 10.97 and -1.24 and for distilled water as 55, 53.3, 7.77 and -20 % at the ‎same distance from anode respectively. The results showed that the effectiveness of ‎solution surfactants in removal of DMP was SDS>Brij 35> Poloxamer ‎‎407.‎‎