Preparation And Structure-activity Relationship Analysis Of Bioflocculant

Now,the wastewater and the waste activated sludge have increased sharply,and the untreated sludge would produce a series impact on the ecosystem and threaten human health.At the same time,the underutilized beneficial ingredients in the sludge would cause the waste of resources.So the combination of pollution control and resource utilization is the trend of solid waste treatment.According to the analyses above,this paper puts forward a new way of sludge recycle which is the preparation of biological flocculent by waste activated sludge.This method not only can realize sludge recycling,but also add a new way to prepare bioflocculant.Sludge bioflocculant preparation method was determined by comparing the flocculating activity of hydrolysates under different conditions.The activities and applied range of the sludge bioflocculant were characterized.And the flocculating mechanism was investigated.The following findings were made:(1)Respectively using ultrasonic technology,using microwave technology,using sodium hydroxide solution and dilute hydrochloric acid solution to extract the ingredients with flocculating activity in the sludge,results showed that the flocculant which was extracted by dilute hydrochloric acid had a better flocculating activity.The effect of the dosage of the extraction agent on the preparation of flocculant was investigated.The results showed that the flocculation rate was above 90%,when the amount of 18% dilute hydrochloric acid in 10ml-40 ml,mixed with 30 g activated sludge.Studies indicated that the suitable pH regions for flocculation was from 4.0 to 11.0,and when the rough flocculant dosage was 2 ~ 10 mL,98% of flocculating rate for 4 g/L kaolin clay was achieved.(2)The crude flocculant was purified and dried,and its main components were analyzed and determined.The content of polysaccharide was determined by phenol sulfuric acid method,results show that the average content of total sugar was 66.8%(w/w).The protein content were determined by the method of Coomassie brilliant blue,results show that the average protein content was 3.2%(w/w).Scanning electron micrograph of flocculant displayed that the geometrical appearance was round-like,particle size was relatively uniform,and the particles were intertwined,mutual adhesion.Infrared spectrum analysis showed that the flocculant may contain hydroxyl(-OH),amino(-NH-),and ester group(-COOC-).(3)The flocculant was used in the treatment of particulate wastewater,dye wastewater,oily wastewater,and heavy metal waste water.the flocculation ability and application scope were investigated.The flocculating rate of the flocculant for kaolin wastewater was 99.5%,the flocculating rate of the flocculant for starch wastewater was 93.2%;the Congo red dye wastewater by maximum decolorization rate was 98.9%;for 300 ml simulative oily wastewater,adding flocculant 4ml,flocculation rate and the highest removal rate of COD were 86.2% and 94.4%;the removal rate of mercury in reservoir water can reach 100%.(4)The flocculation mechanism of the purified flocculant was studied.Scanning electron microscopy images showed that the effect of adsorption and bridging was also exist.Zeta potential test results show that the positively charged flocculant added to kaolin suspension with negative charge and the Congo red solution will make Congo red kaolin and the negative charge quantity is reduced,so that the suspension of kaolin and the Congo red instability,and indicate the existence of electric flocculation process.