Enhanced Washing Effect Of Ddts Contaminated Site Soil With Single And Compound Surfactants

With the course of industrialization and urbanization being accelerated, batch of old pesticide manufacturing enterprises of our country frontage closes, use field function to happen change, the problem of DDTs producing enterprise leaving over space soil after moving contaminating is demanding prompt solution, and the repairation technology studying and developing speedy and high-effect of DDTs contaminated soil is very urgent. This studying used high concentration DDTs contaminated site soil as material, and soil washing experiments had been taken off, the washing effects of DDTs in soil by different kinds of single and compound surfactants and the influencing factor in progress of wasing were studied, and the following conclusions can be got:In this paper, deionized water, non-ionic surfactant Tween60and TritionX100, anionic surfactant SDS on the role of soil DDTs elution have been studied; results showed that the deionized water, little or no elution of DDTs effect, Tween60, TritionX100and SDS three single surfactants on DDTs were eluted with a certain role. With increasing of Tween60concentration, the total elution efficiency of DDTs in soil increased gradually. With increasing of TritionX100concentration, the total elution efficiency of DDTs increased first, then reduced, and increased again. With increasing of SDS concentration, the total elution efficiency of DDTs increased gradually. In the selected solution concentrations, the maximum total elution efficiencies of Tween60, TritionX100, and SDS were43.60%,20.85%and34.62%. To the high concentration of DDTs contaminated site soil used in this study, Tween60should be adopted as eluant.On the base of single surfactants research, the elution effect of DDTs in soil with anionic and non-ionic compound surfactants were studied. On the concentration ratio of the selected compound surfactant TritionX100-SDS, DDTs elution efficiency was increased first and then decrease with increase of SDS concentration. DDTs elution efficiency was gradually increased with increase of SDS concentration in Tween60-SDS compound surfactants, and it reached maximum62.08%when the concentration of SDS was2500mg·L-1. The efficiencies of total DDTs eluted by TritionX100-SDS and Tween60-SDS two compound surfactants were greater than the total elution corresponds to two single surfactant, and has demonstrated synergistic solubilization of aionic and non-ionic surfacttants, resulting in a1+1>2elution effect. Tween60-SDS has the better elution efficiency than TritionX100-SDS, and has better prospects for practical application.Influencing factors and determination of the optimal elution conditions in the process of contaminated soil washing have an important guiding significance for practical engineering applications. This paper selected the best-performing elution Tween60-SDS and studied the adsorption of Tween60, liquid soil ratio, elution times, time and temperature on the elution effect respectively.The study results of soil particles on the adsorption of Tween60showed that with SDS concentration increased in Tween60-SDS, the adsorption amount of Tween60to the soil particles was a first-order exponential decay function and was gradually reduced. When SDS concentration was2500mg·L-1, Tween60adsorption capacity by soil was the smallest, and DDTs elution efficiency was the best.The study results of liquid soil ratio on elution efficiency of DDTs in soil showed that the increase of liquid soil ratio, the total concentration of DDTs in elution was the third-order exponential decay function, and was gradually increased. Taking into account the cost of the practical application of contaminated soil repairing, selecting liquid soil ratio of30:1is more appropriate.The results of several consecutive elutions on elution efficiency of DDTs in soil showed that with the increase of the number elution, DDTs in a single elution showed a significant first-order exponential decay function, and was gradually reduced. The former three-eluting elution of DDTs accounted for most of the total elution volume of five times. With increase of the number eluted, elution efficiency of soil DDTs accumulated gradually increased. Three times elution is more appropriate for contaminated soil DDTs studied.The results of elution time on the elution effect of DDTs in soil showed that with the elution time extended, the total concentration of DDTs elution showed a second-order exponential decay function. The total elution efficiency of DDTs could be achieved maximum61.93%when shock-eluting7hours, which elution efficiency was only1.16%higher than shocking5hours, so we choose5hours as the best shock-eluting elution time. The results of elution temperature on the elution effect of DDTs in soil showed that with the elution temperature rised, the elution efficiency of soil DDTs showed a exponential growth function of gradually increasing, and reached maximum at50℃. Therefore, the elution temperature of50℃is more suitable for actual remediation of contaminated soils.This study selected the best soil-eluting repair surfactant type, concentration and elution conditions suitable for DDTs contaminated sites soil washing, and had great significance to the initial development of contaminated sites complete soil remediation technologies and equipments.