Removal Of Copper From Contaminated Soil With Potassium Pyrophosphate Rhamnose And Rhamnolipid

With the properties of poor mobility and bioaccumulation, excess heavy metals in soil not only inhibit the growth of crop and destruct soil microbial communities, but also threat the human health badly through food chain. Soil washing is an important technique in soil remediation with thorough restoration and short operation cycle both for heavy metals and organic matter.The Cu contaminated soil was researched in this study, with the method of shaking extraction. The copper removal was analyzed after the extraction by potassium pyrophosphate, rhamnose and rhamnolipid, regard of leaching time, the chelant concentration, eluent pH and other important conditions. At the same time, the changes of copper distribution before and after leaching were studied. Compared to the removal of copper with pyrophosphate alone, the combination of chelants was processed too. The results of this study were shown as follows:(1) With the extension of reaction time, the copper removal increased, and reached 20.99% when the leaching time was 24h, followed by essentially flat. While the pH of pyrophosphate was 7.0, leaching of copper is maximized for 34.49%. Considering the costs and copper removal, a molar ratio of 7:1 as the optimal concentration of leaching experiments was selected; BCR sequential extraction before and after soil washing indicated that potassium pyrophosphate mainly remove copper of acid-extractable and had little effect on oxidizable and residual fraction.(2) the kinetic of copper removal by potassium phosphate was analyzed, regard of different times. The results showed that:double constant equation was the most suitable equation to descripte copper desorption process. R2 was 0.9614 and SE was 0.0062, indicating a non-homogeneous diffusion process.(3) As the concentration increases, the removal of copper by rhamnose and rhamnolipid continued to increase. Rhamnose concentration of 4% for copper removal rate was 49.99%, followed by removal rate increases slowly. Rhamnolipid in the range of concentration of the copper removal rate continued to increase, but the increase is small. Alkaline environment conducive rhamnose and rhamnolipid the removal of copper in soil. Rhamnose leaching of copper in soil mainly in the acid-extractable and residual fraction.(4) The contribution values of potassium pyrophosphate combine rhamnose and rhamnolipid to remove copper were positive, indicating that pyrophosphate was in favour of the removal of copper by rhamnose and rhamnolipid.(5) the copper removal effect of chelants group had better expression than which was used alone. Mixed 2% of rhamnose and 4% of rhamnolipid with pyrophosphate of 7:1 can remove 57.25% and 45.02% of copper, respectively. Rhamnose group removed mainly acid-extractable Cu and reduced state-based, compared with the previous two forms of leaching were reduced by 35.49% and 20.46%. Rhamnolipid group removed mainly copper-based acid-extractable, reducible partially reduced, two forms were reduced by 31.70% and 11.60%. With respect to rhamnose and rhamnolipid separate leaching, potassium pyrophosphate promoted rhamnose and rhamnolipid removing acid-extractable and reducible fraction mainly.The use of environmentally friendly chelants, potassium pyrophosphate, rhamnose and rhamnolipid to repair copper in contaminated soil achieved good results, which indicated this technical well application prospect.