Study On The Preparation Of Modified Starch Flocculant And The Application On Treatment Of Potato Starch Wastewater

In this paper, the study was mainly on the preparation of the cationic modified starch (CMS) flocculants with high degree of substitution (DS) which were prepared by potato starch as raw materials and the application of it in the treatment of wastewater caused by the potato starch processing industry.Firstly, the main ingredients and main pollution emission indexes of potato starch wastewater were measured. It can be seen from results that the high protein content (2.17%) of starch wastewater is the main reason for the high COD (49000mg/l) of wastewater.The results by using the conventional flocculants to treat potato starch wastewater were compared. It is shown that it is better to use the flocculant mix Polymerization Aluminum Chloride (PAC) and Cationic Polyacrylamide (CPAM) and lower rate with using Polyferric Sulfate (PFS) and Cationic Polyacrylamide (CPAM).Through the orthogonal tests, the optimal potato wastewater treatments were:The concentration of cationic CPAM was 1.0‰, the concentration of PFS was 2.0‰, and the PH of the water was 6.0. The removal rate of COD in the wastewater was up to 53.16%.Secondly, the cationic modified starch (CSM) was prepared via the reaction of potato starchwith3-chloro-2-hydroxypropyl-trimethyl ammonium chloride (CHPTMA) using pre-drying dry process. Through orthogonal tests, the optimal reaction conditions of preparing high DS CMS were confirmed as follows:the amount of CHPTMA was 55% of mass of starch, the molar ratio of NaOH to CHPTMA was 1.0, reaction temperature was 85℃and reaction time was 5h. With the optimal conditions it would get the flocculant of CMS with DS 0.3903.The product gained in the experiment was characterized by Scanning Electron Microscope(SEM) and FTIR Spectrometer.The flocculant of CMS was studied to be used in the treatment of wastewater. It is shown that it's better to use the flocculant mix CMS with Poly Ferric Sulfate (PFS). The optimal conditions by using CMS and PFS were as follows:the concentration of CMS was 1.2‰, the concentration of PFS was 1.5‰and the PH of the water was 7.0.By using the above optimal conditions, the removal rate of COD in the wastewater was up to 64.31%.By comparing the effects of the treatment of potato wastewater with CPAM and CMS,it can be seen that the effect by using PFS is better than using CPAM.Finally, the preparation of the copolymerization of CMS and Acryl amide (AM) and the flocculating test of potato wastewater were preliminarily studied in this paper. It was found that an even better effect could be got when the DS of CMS-AM was 0.0697. The removal rate of COD in the wastewater came up to 68.21% with the conditions as the concentration of CMS-AM was 0.2‰, the concentration of PFS was 1.5‰and the PH of the water was 6.0.