Abstract
This study presents the experimental remediation studies of diesel contaminated soil with Sodium Deducible Sulfate (SDS) as surfactants using column tests. Sandy selected soil had the grain size distribution of # 40 meshes to the # 200 mesh range. The soil columns were contaminated with adequate diesel amount to achieve the concentration of 10000 and 20000 ppm in soil. 0.1, 0.2, 0.3, 0.4 percent of surfactants and pH values of 4, 7, 9 and 11, were examined. After 72 h, washing began and all tests were continued up to 10 pore volume and the trend of remediation and permeability of soil during the test was investigated. pH and TPH of outlet solution measured during 2, 4, 6 and 10 pore volumes. Times were recorded during 0.67, 1, 1.33, 2, 3.33, 4, 5.67, 6, 7.33, 8, 8.67, 9.33 and 10 pore volumes, in order to calculate permeability values.Results showed that in all states the quantity of remediation for acidic states was very low and efficiency of remediation when using only water was about (1:3) of maximum amount. For soil with initial contaminant concentration of 10000 ppm the maximum efficiency is for surfactant in the concentration of 0.3 and pH = 11 and for soil with initial contamination amount of 20000 ppm the maximum efficiency is for surfactant in the concentration of 0.1 and pH = 11. By increasing the amount of surfactant concentration, the permeability of soil decreased and in pH = 11 the amount of permeability is maximum. With increasing initial contamination quantity rate of increasing of remediation and permeability decreased. Consequently in the low level of contamination the effect of washing solution pH value in soil remediation and permeability is more in comparing with high level of contamination. For initial contamination of 10000 ppm optimum removal efficiency obtained 35% for surfactant of 0.3% and pH = 11. For initial contamination of 20000 ppm, optimum removal efficiency is obtained as 45% for 0.1% of surfactant and pH = 11. Using of higher soil column, sampling from different elevation for investigating remediation trend in height and surveying temperature effect on diesel contaminated soil remediation can help to modification procedure and improvement of efficiency.
Highlights
Iran is subjected to oil pollution because of its oil resources, petrochemical productivity and transportations
For initial contamination of 20000 ppm, optimum removal efficiency is obtained as 45% for 0.1% of surfactant and pH = 11
Initial contamination of 10000 ppm: Soil columns were contaminated with 10000 ppm diesel, washing was performed under different conditions
Summary
Iran is subjected to oil pollution because of its oil resources, petrochemical productivity and transportations. Finding a solution for soil remediation is one of high importance. Soil remediation methods are presented in three main parts; biological, physical and chemical and all other methods are related to these three main methods. Soil contamination by hydrophobic components is a main type of pollution. (Khalladi et al, 2009). The washing processes with surfactants is themost used. The main items of these methods consists of the mobilization the solubilization of hydrocarbons by lowering the interfacial tension at the soil and water phase interfaces. Surfactant soil remediation is done by removing organic molecules adsorbed on soil and catched in the pores, continued by their encapsulation within micelles formed at a concentration greater than the Critical Micelle Concentration (CMC) (Khalladi et al, 2009)
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