Effect Of Rhamnolipid Bioleaching Of Tannery Sludge

With the rapid development of the China’s leather industry, the production of tannery sludge increased rapidly in recent years., it is a very key element for sustainable development of China’s leather industries that how to handle the trannery sludge reasonably. Tannery sludge is one of the superior soil fertilizers for its richness in nutrients like organic matter, nitrogen, phosphorus,potassium and so on. So, the agricultural utilization of tannery sludge is a very promising disposal method. But there are certain limitations such as presence of heavy metals in sludge, which is the major factor. Therefore, how to lower the concentration of heavy metals effectively in tannery sludge is a hot issue among researchers nowadays.In this paper, the tannery sludge from Binyang Country was selected as the research object which was regarded as a culture medium. The thiooxidans domesticated and isolated from the sludge was inoculated with the tannery sludge mixed indigenous thiobacilli, which was cultivated by biosurfactants rhamnolipid this method could investigate the effects of rhamnolipid of different concentration on the oxidation capacity for sulfur of mixed thiobacilli, and also explore the effects of different concentrations of rhamnolipid on nutrients and the dissolution and fractions changes of Cr, Cu and Zn, and the nutrients in tannery sludge.The results showed that:(1) when the concentration of rhamnolipid was among0～1.5g/L, the rhamnolipid could promote mixed thiobacilli to oxidate the elemental sulfur, and the oxidation rate of elemental sulfur increased with the growth in the rhamnolipid dose.(2)In the tannery sludge bioleaching system, it was also shown that the optimum dosage of rhamnolipid was l.Og/L. After the leaching of14days, dissolution rate of Cr and Cu reached98.0%and7.0%, respectively, while the dissolution rate of Zn was20.3%after leaching of10days.(3)Heavy metals like Cr, Cu and Zn presented in stable oxidizable and residual fractions after leaching. The concentration of sulfate ion was the highest in the group in which the dosage of rhamnolipid was1.0g/L. Meanwhile the utilization rate of elemental sulfur was the highest exceeding100percent among the inorganic element The loss of phosphorus was much in tannery sludge while the loss of nitrogen was little, However, the tannery sludge can still use in agricultural for possessing certain manurial effects.