| With industrial development, more and more heavy metals are widespread used. But there has been a relative lack of heavy metal resource. Accompanied by another serious problem is the pollution of water by heavy metals. The heavy metals are a class of pollutants on the ecological environment which are great harm. After entering the environment, they can not be biodegradable, most of the metal ions involved in the food chain cycle. Ultimately, bioaccumulation and the destruction of the organisms’ normal physiological activities, harm to human health. Therefore, how to effectively deal with heavy metals in waste water, recovery of precious metals has become a prominent issue in today’s field of environmental protection.The experiment compared the 3 kinds of porous materials such as volcanic, activated carbon and quartz sand adsorption effect of recombinant bacteria Pseudomonas putida YN-2S, and comparison of volcanic rocks of different aperture filter adsorption effect of recombinant bacteria. Experimental results show that volcanic filter adsorption effect of the recombinant strain is best, followed by activated carbon, quartz sand. The volcanic rock filter which aperture is 2-4 mm has maximum adsorption efficiency of recombinant bacteria. The samples of Pseudomonas putida recombinant YN-2S and Volcanic filter material fixed Pseudomonas putida YN2S using SEM observation, results show that the volcanic rock filters is a porous carrier, and has the effect of adsorption of Pseudomonas putida.Combination of adsorption and embedding methods, the preparation of Sodium Alginate volcanic immobilized, and smelly Pseudomonas putida recombinant balls. We study the influence of pH, initial metal ions concentration, temperature and rotate speeder on the biosorption capacity Cu(Ⅱ), Zn(Ⅱ), Cd(Ⅱ). Then use orthogonal experiments to search the optimum conditions. Experimental results show that the optimum uptaken of Cu(Ⅱ) ions was observed at pH5,35 ℃, agitation 180 rpm. The optimum uptaken of Zn (Ⅱ) and Cd(Ⅱ) ions were observed at pH6,35℃, agitation 180 rpm. The adsorption equilibrium was carried out with 180 min, and Pseudo second-order was applicable to all sorption data over the time course, which was found to be fitted well to both the Langmuir and the Freundlich isotherm models. In the adsorption/desorption cycles studies show that after six cycles the Ca-alginate immobilized Pseudomonas putida YN2S cells still exhibited good desorption efficiency with a desroption efficiency of 95%.Competitive test show that compared with the adsorption rate in the single metal ion systems, in competitive biosorption experiments where Cu(II) competes Cd(II), there is a selective adsorption towards Cu(II) and in competitive biosorption experiments where Cu(II) competes Zn(II), there is a selective adsorption towards Cu(II). In competitive biosorption experiments where Zn(II) competes Cd(II), there is a selective adsorption towards Cd(II). The biosorption order under multi-metal ions conditions was Cu(II)> Cd(II)> Zn(II) for all the tested biosorbents.FTIR analysis indicated that the engineered P. putida cells were mainly responsible for the biosorption of Cu(II), Zn (II) and Cd(II) ions. It is described that recombinant bacteria in the amino and carboxyl and Metallothionein likely participate in combination of heavy metal ions.The Ca-alginate gel immobilized efficiently the P. putida cells and also contributed partially to Cu(II), Zn (II) and Cd(II) sorption. Therefore, the Ca-alginate immobilized biosorbent improved both mechanical strength and performance, which could confer the potential for further large-scale or continuous operations. |
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