The Effect Of Pretreatment On The Preparation Of Cationic Starch Flocculant

In the production and processing, a large amount of high concentrated organic wastewater is produced, which mainly contains micro fiber, starch, sugar, protein,etc. They are generally non-toxic and fill of higher recycling value. However, the commonly used flocculants, such as PAC, PFS and PAM will produce a large number of iron sludge , the residual monomer of PAM even causes the secondary pollution. Cationic starch is a natural and biodegradable green water treatment agent,that can flocculates suspended solids and partial colloids, reduces the COD and SS.Meanwhile, the flocculation products can be recycled and utilized for fertilizer,aquaculture and other industries. In this thesis,the NCS was pretreated with DMSO/NaOH and modified by 3-chloro-2-hydroxypropyltrimethylammonium under the catalysis of NaOH by dry process. The results obtained are as follows:(1)The NCS was pretreated with DMSO/NaOH at a certain temperature and the P-CS was characterized by SEM,FT-IR,XRE,TG,etc. The results indicates that the surface of the original starch granule was needle like, and the specific surface area increased after pretreatment. The crystalline structure of starch was damaged, the crystallinity and thermal stability decreased, the cold water solubility of starch increased greatly and the starch paste became more transparent.(2)Using P-CS,CHPTMA and NaOH as catalyst,the PCS was synthesized by dry process and the PCS was characterized by SEM, FT-IR,TG,etc. The optimum conditions were: m(P-CS): m(CHPTMA): m(NaOH)=2.80: 2.83: 1, the water content of the system was 25% and reacted at 60 ? for 3h, the DS,RE of PCS was 0.3912,44.98%. The P-CS can reacted more efficiently with CHPTMA. The thermal stability of PCS increased, the starch became not sticky and soluble in cold water.(3)Using kaolin simulated wastewater as the target water samples, the flocculation effect of PCS on wastewater was investigated and the optimal experimental conditions were: pH=4.5, dosage of PCS was 60mg/L, DS=0.36, the PCS had better flocculation effect on kaolin simulated wastewater. PCS was used in the starch wastewater of the plant and the experimental results demonstrated that the removal rate of COD, SS was 37.5%, 61.0?67.4% after added the PCS. There were about 2%of the nitrogen content of the flocculated sediment, which indicated that there also contained a certain amount of protein that can be processed into protein feed for fertilizer and aquaculture industry, made waste profitable and this not only reduced the processing load of the subsequent wastewater, but also could be used to achieved the maximization of the resource.