| Water is indispensable environmental resources to human production and living, and heavy metal wastewater treatment is related to people's life quality and environment. Adsorption is one of best ways for wastewater treatment, and thus adsorption material is the key of this method. Ceramic is a kind of adsorbent with high adsorption efficiency and low cost for wastewater treatment. In the current field of wastewater treatment technology, the bio-film treatment method is one of aerobic biological treatment methods along with activated sludge process.In this paper, on the basis of theoretical simulation, porous ceramics filter material was prepared with abundant and cheap clay as ceramics aggregate by pore-forming agent addition and particle accumulation. The adsorption capacity and mechanism of the porous ceramics toward heavy metal ions were investigated, thus providing experimental and theoretical basis for the treatment of heavy metal wastewater. In addition, by cloning the genes (metallothionein genes), which can combine heavy metal ions, from the stress-resistant jujube tree, this study constructed a gene engineering bacterium applicable to practical wastewater treatment field, and investigated adsorption behavior of heavy metal ions on porous ceramics loading metallothionein genes. The main research contents and results are as follows: 1. The performance of ceramics was closely related to ceramic microstructure, so the research of microstructure evolution in ceramic sintering process was essential. The Monte Carlo method was improved based on the classic Monte Carlo method. It took into account the influence of ceramic grain as well as of porosity phase during simulation process. On the basis of the improved Monte Carlo method, the simulation program of microstructure evolution in the ceramic sintering was developed, with which the microstructure evolution in the ceramic sintering process under different sintering temperature and sintering times was simulated.2. The clay adsorbent with good adsorption and ion exchange performance was prepared. With the addition of60～80mesh pulverized coal and graphite as pore-forming agent at15%and5%, respectively,100～120mesh vermiculite as modifying at2%, the clay-based porous ceramic filter with porosity58%and bulk density1.081g/cm3was fabricated at1250℃by pore-forming agent addition and particle accumulation methods.3. The metal ion adsorption performance of porous ceramic was influenced by pH value, the initial concentration and other factors. The change of the adsorption rate of porous ceramics for Zn2+and Cu2+with changing initial concentration and the pH value was investigated. Through the adsorption kinetic curve analysis, the adsorption process was divided into three stages:the initial fast adsorption, the subsequent slow adsorption and the final equilibrated adsorption. With Langmuir and Freundlich equations the adsorption of Cu2+on porous ceramics was described. It was found that adsorption rate was mainly controlled by chemical adsorption, and adsorption process was controlled by multiple steps.4. The adsorption of metallothionein on graphene and doping metal-doped graphene was studied by the first principle methods, and the method of doping metal atoms was put forward to improve adsorption of metallothionein graphene from theoretical perspective. 5. The biological treatment of heavy metal wastewater was a efficiently and economically feasible way. The carrier including glutathione S-transferase genes and metallothionein genes of jujube tree was constructed and introduced into E.coli BL21(DE3) to give a gene engineering bacterium which can express metallothionein. The adsorption capacity of the gene engineering bacterium for heavy metal ions was investigated, and the factors such as optimal dosage and inoculation amount were discussed, which affected the adsorption of the bacterium on Zn2+, Cu2+and Cd2+on the bacteria. This paper laid the foundation for heavy metal wastewater treatment. |
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