Studies On The Separation Of A Polysaccharide Bioflocculant And Its Application In Wastewater Treatment

Polysaccharide bioflocculant is an extracellular polymer isolated from microbial fermentation broth.Due to its biodegradability,non-toxicity,harmlessness and no secondary pollution,polysaccharide bioflocculant has a wide range of applications.In this study,Bacillus licheniformis CGMCC 2876 was used as the starting strain,and the extracellular polymer---polysaccharide bioflocculant was isolated,purified and analyzed.Finally,it was used in Congo red wastewater and Pb2+ wastewater treatment.The conclusions are as follows:(1)The cell-free supermatant was mixed with three folds the volume of ethanol,adjusted to pH=9 and left for 4 hours at 4℃.Fast Flow ion exchange chromatography and Sephacryl S-400 High Resolution gel chromatography were followed for purification.Mw of the polysaccharide product was 4.47 × 105 Da,with 96.4%purity,7.74%final extraction rate.It contains 32.43%neutral sugar,5.16%amino sugar and 1.22%uronic acid.The monosaccharide components and molar ratio is glucuronic acid:galactose:glucosamine = 1:5:1.7.(2)To treat Congo red wastewater,the optimum dosage of polysaccharide bioflocculant is 100 mg/L,with an addition of cationic salt FeCl3 · 6H2O,the decolorization rate of Congo red is as high as 98.4%,which is better than polyacrylamide.In addition,with the condition of 10 mg/L polysaccharide bioflocculant,pH=7,the adsorption of Pb2 is 1473.7 mg/g.Adding cationic salt KCl and CaCl2 solution promoted the adsorption of Pb2+ by bioflocculant.