New Heavy Metal Adsorbent

Bacterial cellulose（BC）is a new kind of biologic compound material,compared with other chemical methods;the biologic method is simple,high efficiency,little consumption.BC has many advantages over foliage cellulose,such as its natural nano structure,higher purity,higher crystallinity,higher water absorption capacity,higher tensile strength and good biocompatibility.Therefore,BC has attracted intensive attention for its potential in the preparation of advanced materials.This thesis is focused on preparation of BC based materials for adsorption of heavy metals.First,we synthesized BC by culturing Gluconacetobacter xylinum and prepared carboxymethylated cellulose-bacterial cellulose（CMC-BC）and diethylenetriamine bacterial cellulose（EABC）by modifying BC; second,the basic structure of the materials was characterized and then adsorption properties for metal ions of these materials were investigated.The research work mainly includes the following parts; 1 Synthesis,characterization and adsorptive properties of BCThe fermentation condition of Gluconacetobacter xylinum was optimized by studying the pH of the initial media,inoculum’s size,the volume of fermentation container,the surface of container area and the fermentation time.The purity of BC is 95.6%,The water-holding capacity of BC is 98.0%.The polymerization degree of BC is 2380.With Fourier transform infrared（FT-IR）spectroscopy,it was determined that the structure of BC is in accord with the structure of cellulose.BC was type I cellulose as proved by X-ray diffraction（XRD）.Crystallinity index was 83.2%.SEM,AFM and Thermal stability were tested. These results showed that BC had in-twisting network structure of many fiber ribbons and decomposes at 259.6℃The adsorption capacity of BC for Cu²⁺and Pb²⁺was investigated.The parameters such as the solution pH,contact time, amount of BC and initial concentration of mental ions were analyzed.The adsorption capacities depended on the pH of solution;the optimum pH is about 5.The adsorption reached equilibrium within 60min.Pseudo second-order described the adsorption process well.The equilibrium isotherms for the adsorption were correlated by the Langmuir equation.The theoretic maximum capacity of BC is 11.17mg/g and 24.57mg/g. 2 Synthesis,characterization and adsorptive properties of CMC-BCCMC-BC was synthesized by incubation of Gluconacetobacter xylinum in mixed culture containing D-glucose and water-soluble CMC.We found that the water-holding capacity of CMC-BC increased with the amount of CMC in the culture.The degree of carboxymethylation reached a maximum（10.4%）when CMC is about 0.5%（w/v）in culture medium.With Fourier transform infrared（FT-IR）spectroscopy,it was determined that CMC-BC has carboxymethyl function;The pore like cellulose network structure of CMC-BC is better than BC observed by scanning electron microscopy;with the effect of CMC in culture medium the crystallite dimension of CMC-BC is higher than BC.The adsorption capacity of CMC-BC for Cu²⁺and Pb²⁺was investigated.The optimum pH is about 5.The adsorption reached equilibrium within 60min.It was best described the second-order kinetic equation.The equilibrium isotherms for the adsorption of Cu²⁺、Pb²⁺were correlated by the Langmuir equation.The theoretic maximum capacity of CMC-BC is 20.35mg/g and 65.53mg/g which increased by 45.1%and 62.5%compared to BC. 3 Synthesis,characterization and adsorptive properties for Cu²⁺of EABCEABC was synthesized and characterized by elemental analysis,FT-IR.The result proved the existence of amino group in the EABC,and the percentage content of N is 13.56%.The adsorption properties of EABC for Cu²⁺were investigated.The equilibrium isotherm for the adsorption of Cu was correlated by the Langmuir equation.The theoretic maximum capacity of EABC is 25.42mg/g when pH=5 which increased by 56.1% compared to BC.