Preparation Of Rhamnolipid And Its Application In Sludge Cleaning

Due to its excellent inter-facial activity,rhamnolipid as a biosurfactant has been widely used in environment,petroleum,cosmetics,medicine industries.However,large-scale production of rhamnolipid has been limited due to the high cost and low yield.How to improve the yield and reduce the economic cost have become a hot topic.The purpose of this paper was to explore the fermentation process to improve the yield and reduce the cost.Then,the application of rhamnolipid on the oil sludge cleaning was studied.The research contents and results were as follows:(1)Through the shaking culture,the type of carbon source,nitrogen source concentration and pH of fermentation medium components were optimized,with optimal carbon source type of kitchen waste oil,yeast extract concentration of 2.00g/L and pH of 8.00,respectively.The physical and chemical analysis results of rhamnolipid from kitchen waste oil showed six rhamnolipid congeners,among which Rha-C10-C10 and Rha-Rha-C10-C10 were the main components,with mass fraction of approximately 50.86%and 34.20%,respectively.In addition,the critical micelle concentration of rhamnolipid obtained was 55.87mg/L,the stability of rhamnolipid test result showed that its interfacial tension and emulsification index can maintain stability under the temperature 20-100?,pH=6.00-12.00,and salinity 2-20%(w/v)in a wide range.(2)Based on the optimized conditions,the experiment of rhamnolipid fermentation coupled with foam fractionation was carried out.The results showed that the stable period of cell growth in the coupling fermentation was 4.67 times than that in the batch fermentation,and its rhamnolipid yield reached 5.29g/L which was 2.21 times than that of the batch fermentation.Besides,the highest recovery rate and enrichment ratio of rhamnolipid in the coupling fermentation were 69.05%and 13.33,respectively.The results indicated that the foam fractionation coupling with fermentation technology not only could compress rhamnolipid to reduce separation cost,but also improve its production.(3)With the excellent inter-facial activity of rhamnolipid,the single factor experiment,Plackett-Burman and response surface method were applied for oil sludge cleaning by rhamnolipid.It was concluded that the best cleaning conditions were rhamnolipid concentration of 325mg/L,pH=10.70,temperature of 63?,speed of 450r/min,time of 35min,liquid-solid ratio of 5:1.The oil removal rate of the sludge was 70.92%,reducing its oil content from 10.18%to 2.96%.