In - Situ Rapid Repair Of Cadmium Contaminated Soil Based On Competitive Adsorption

With the rapid development of industry and urbanization, soil contaminated with heavy metals has become increasingly serious. Among all heavy metals, cadmium has high mobility and bioavailability, is considered the most harmful for human health. Moreover, the cadmium pollution in soil has become a very terrible problem. It is urgent to address and remedy the cadmium contaminated soils. Soil washing is a time-efficient and versatile method, and attracts increasing attentions in recent years. After a novel functionalized nonwovens(PP-g-AA-ASA nonwovens)was prepared, we constructed an in situ remediation of cadmium contaminated soil, which was based on the competitive adsorption and learn from soil washing remediation. The remediation was done by spreading the chelating agents on the soil surface and subsequently mixing it, so that cadmium transfer from the soil solid phase to the aqueous phase and then the PP-g-AA-ASA nonwovens can be used to exchange chelated metals from the solution to the solid support and achieve the recycling of chelating agents at the same time, which has a significant economic advantages.After a series of extractant was used to washing cadmium contaminated soil, the PP-g-AA-ASA nonwovens was put into the leacheate to study the efficiency of competitive adsorption. In the selection of extractant, the amount of desorption, the efficiency of competitive adsorption, degradation and price are taken into account. The migration routes of cadmium and cycle path of extractant was also studied. After the extractant is selected, the influences of various variables were examined, including extractant concentration, pH, contact time, and the dose of PP-g-AA-ASA nonwovens. Batch extractions were conducted to washing cadmium contaminated soil under the best conditions. The results show that the the optimal conditions for washing cadmium from the pollution soil were as follows:citric acid used as washing agent; the concentration was 20 g/L, the pH value was 2, and the soil/water ratio was 1:1.5, the contact time was 10 min.Then, put into 1g PP-g-AA-ASA nonwovens for 400 g contaminated soil and the contact time is 20 min. The removal rate can reach 57.5% in the optimal conditions. Under the above test condition, the light contaminated soil was washed only twice to meet the required environmental standards. The cleaning process only need 1 hour, and the complexing agent was unnecessary to add in the followed circulating cleaning system.