Study On Biosorption Of Heavy Metal By Mycelium Of Streptomyces Avermitilis

Our work is to study the biosorption of heavy metal by waste mycelium of avermectin (Streptomyces avermitilis) .The amount of the avermectins production is great in our country,but the utgrowths of the products- mycelium are always disposed as offal. In this paper,the characteristics of biosorption, biosorption mechanism, the effects of pretreatment on biomass, the reuse effects of the biomass and adsorption effects with several kinds of metal coexistence were studied to discuss the feasibility of the waste mycelium exploitation as a new adsorption material and learn some mechnism of this material.As the first step,the adsorption properities of mycelium were investigared using the batch method as a function of biosorbent amount to the solution,the initial concentration of heavy metal ion, pH,temperature and contact time. It was shown that the biomass amount to solution,the initial concentration of heavy metal ion, pH and contact time are the main factor influencing the absorption. The initial pH in 3.5 to 5.5 are optimal, and at this range, the removal efficiency of waste mycelium of avermectins reached the maximum level. And it can reach absorption saturation just in 1hour at relatively high concentrations. At the same metal ion concentration, the efficiency of removing metal ions in the solution was increased with the increasing of biomass concentration. However, when it reached the equilibrium condition, the quantities of adsorbance were gradually decreased with the increasing of biomass concentration. When the metal concentration was increased, the efficiency of removing metal ions is decreased and the equilibrium absorbance increased with the metal concentration increasing.On the research of biosorption mechnisam, the biosorption of Cu, Zn, Mn, Cd can be better described by Langmuir modle than Freundlich modle ,the theoretie maximum adsorption capability was between 9.3721 mg/g and 42.7350 mg/g in pH4-5,and the regulation of the capability was Cd>Cu>Zn>Mn .The experimental results show that the process of biosorption can devided into two phase :rapid sorption phase and relatively slow sorption phase. The biosorption kinetics can be well described by the second-order equation, the relative coefficient of the equation (R²) was above 0.99. Compared FIR scanning spectra of initial biomasss with ion-exposed cells, it can be known that the biomass contains hydroxyl group, amido group, acyl group and methylene group,and these group changed when the biomass adsorpt metal ions. In order to enhance the adsorption capability ,the effect of pretreatment were studied. To treat the biomass with EDTA, NaOH, HCl, CaCl₂,the effect of NaOH was better than others and the removal of the Cu was 85.83%. FIR scanning spectra show that the hydroxyl changed a lot when the biomass was treated with NaOH , it enhanced the biosorption.In the research of the biomass reuse, treat the Cu-absorbed biomass with EDTA,NaOH,HCl,CaCl₂, the effect of HCl was the best. And carries on the modelling to application equipment, the packing column used to be good, can continuously adsorption-desorption for about 5 times.Finally, based on the results of the characteristices gained from single metal existed solution,study the characteristices of four metal coexisted solution. It was not shown that the kinds of the metal influence the contact time to absorption saturation. The theoretie maximum adsorption capability of each metal changed a lot in admixture,but the totle adsorption capability was increased .