Innovative Sludge Dehydrating Reagent Preparation By Hydrotalcite As Backbone And Its Sludge Dewatering Ability

Along with the acceleration of urbanization process, urban sewage is increasing every year. The urban sewage treatment plants are large range constructed, and large number of sewage sludge are centralized and discharged, so the problem of sludge is very conspicuous. The high water content sludge needs to add sludge dehydrating agent and mechanical dewatering to increase the interstitial water dewatering. Currently, polyacrylamide is widely used as sludge dehydrating agent, it is relatively expensive, hard to be diluted, easy to paste on container wall and difficult to degrade, thus causing secondary pollution, also the dehydration efficiency is limited (the cake moisture content is 80~85%), this lead to high cost of secondary treatment, and the large sludge volume and not environment friendly, based on these problems, this thesis prepared novel sludge dehydrating agents.Compared with normally used active inorganic material montmorillonite and rectorite, this research proposed to use the natural and has been large-scale industrial production of hydrotalcite, and its chemical modifier as new inorganic active materials. For the characteristics of the main laminates'second-dimensional size with a positive charge, and the two-dimensional nanosize of the main laminate was ordered arrangement along the third dimension direction, at this time the talcum was formed by small hydrogen bonding force and easily peeling. Through the carbonation reaction and dialysis membranes chemically modified to obtain the dual-core aluminum hydroxide magnesium chloride laminated sheet cluster (Mg3Al-Cl-LDH) and dual-core positively charged Mg-Al hydroxide sol multilayer cluster (Mg3Al-LDHEPCL), both of them continue the high density of positive charge. Under the molecular design, as the normalized crystal structure and high dispersion, Mg3Al-Cl-LDH can be used as inorganic backbone. Its alkaline hydroxyl reacted with and acrylic acid/sodium acrylate, and control the acrylic acid ratio, when the ester bond formed, the high-energy implement intercalation, the laminated film divided into 7~9 cluster, and formed intercalation precursor monomer, and then reacted with acrylamide monomer intercalation copolymerization. By the grafted polymerization and intercalated polymerization, the hydrotalcite with normalized structure and excellent crystal can be polymerized with acrylamide-based high performance functional group together. The hydrotalcite was first applied in polymer field, two new technologies of acrylamide kinds of monomer and inorganic crystal layer cluster were developed.To realize two molecular amalgamation technologies of the grafted polymerization and intercalate polymerization, after the study of the existing aggregation methods, hydrotalcite's layer with a positive charge cluster can stabilize the concentrated emulsion system with feature of higher Fd values. The innovative methods of "ultra-concentrated emulsion polymerization in PHC"was created, it not only improve the efficient distribution of the product latex content, but also resolve the emulsion oil phase product of the shortcomings of oil separated out. On the other hand, by the use of hydrotalcite chemical modification with perfect dispersity, it can disperse to nanosize cluster and form small gel sol, therefore the"Polymerization in foam system"was created.According to this new hybrid hydrotalcite type sludge dehydration agent efficiency, it is found that the accumulation and disintegration of hydrotalcite and its chemical modifier can enhance the sludge dewatering additional function of acrylamide functional group. Based on the sludge dewatering performance experiment, the assumptions are put forward: "In the implement process, as the sludge adsorption of organic component-CONH2 and other functional groups, inorganic layers gap were pulled larger. But also it shield effect with the negative charge of sludge, both inorganic compound resulted in binding force between the plates laminated films have been significantly weakened. Mg3Al-Cl-LDH or Mg3Al-LDHEPCL in the sludge dehydrated agent can be disintegrated, and several secondary sludge dehydrated agent was formed as the carrier of secondary cluster, at the same time generate Mg(OH)2 and Al(OH)3. The secondary sludge dehydrated agents will undoubtedly increase molecules per unit volume in the sludge dewatering agent. While the precipitation of Mg(OH)2 and Al(OH)3 play a role in small inorganic molecules coagulant. The increase of sludge dewatering agent in unit volume and coagulation of Mg(OH)2 and Al(OH)3 lead to the additional sludge dewatering effect." This assumption was confirmed by the initial framework of backbone decomposition.By molecular design and innovative synthesis, the hybrid hydrotalcite-type cationic polyacrylamide emulsion and solid powder were obtained. Through laboratory evaluation and determination, the cake moisture content was 2~3% higher than the existing sludge dehydrated agent cationic polyacrylamide, which equals to 20% decrease in sludge volume. After mechanical sludge dewatering, the cake moisture content can be 75% and lower, which solved the follow-up of sludge processing enormous burdens and challenges. This new agent has relatively low price, easy to prepare before use, especially the emulsion type can be directly converted into aqueous solution. The power type has good preparation process controllability and low energy cost, it can not be degraded as CPAM through mechanical agitation. As the hydrotalcite structures can be disintegrate itself, while the reduction in amount of excess agent achieved environment friendly objectives.