Study On Cu²⁺ And Zn²⁺ Removal By Extracellular Polymeric Substances Extracted From Aniline Aerofloat-degradating Bacteria（Bacillus Vallismortis）

Extracellular polymeric substances is a viscous substance which is secreted by the microorganism., The components, including protein, polysaccharide, nucleic acid and lipid, contains abundant functional groups like carboxyl, amino, hydroxyl and carbonyl, which are able to coordinate and chelate with metal, such as copper, lead, zinc, etc., The present work was to investigated the characteristics of extracellular polymeric (EPS) substances that was extracted from aniline aerofloat degradation bacteria(Bacillus vallismortis) in our laboratory.Bacillus vallismortis observed by a scanning electron microscopy (sem) form, in order to guarantee is not subject to the influence of other chemicals, three kinds of physical method to extract the Bacillus vallismortis extracellular polymers, and then the single factor analysis was carried out on the adsorption of heavy metals, respectively change initial metal ion concentration and pH, temperature, time, with the Langmuir adsorption isothermal model and the Freundlich adsorption isothermal model fitting effect, combined with the pseudo first order kinetics equation and the secondary dynamic equation of dynamics analysis, adsorption process was calculated by the thermodynamics equation of gibbs free energy, enthalpy and entropy change, which before and after the adsorption of infrared spectrum analysis, studies the coexistence of extracellular polymer substances adsorption of metal ions, the influence of the main results are as follows:(1) After 72h activation of the initial concentration of 100 mg·L-1 aniline aerofloat concentration dropped to 20.4 mg·L-1, degradation rate reached 79.6%, Bacillus vallismortis have excellent degradability, scanning electron microscope analysis showed that Bacillus vallismortis is a short rod like morphology, average particle size about 649.7nm, length about 1.67 mm, Protein and polysaccharide concentration and characterization of extracellular polymeric substances content, accurate determination of extraction of extracellular polymeric substances protein and polysaccharide concentrations that and hot extraction than the centrifugal method and ultrasonic method efficiency is higher, the concentration of EPS extracted for 71.659 mg·L-1, and centrifugal method and ultrasonic method for extracting EPS concentration distribution only 5.675 mg·L-1 and 41.303 mg·L-1.(2) The single factor study, selected the pH, temperature, metal ion concentration and adsorption time is variable, the Cu2+ and Zn2+ adsorption, pH range 3-9, at pH less than 7. along with the increase of pH, the removal rate gradually increased from the original 35%, 20.3% increased to 95% and 52.5%, the adsorption capacity from 0.236 mg-mg"1 and 39 mg·mg-1 increased to 0.633 mg·mg-1 and 0.35 mg·mg-1. because the surface of EPS deprotonated and is electronegative, provide more binding sites, when pH continue to rise, the solution was alkaline, Cu2+ and Zn2+ and OH- generated by combination of precipitation, the effect of extracellular polymeric substances adsorption performance analysis. The temperature of extracellular polymer substances adsorption of Cu2+ and Zn2+ had little effect, when the temperature from 20℃ increased to 60℃ degrees removal rate and adsorption capacity of only small changes, Cu2+ removal rate remained at about 89%, Zn2+removal rate maintained at 45% that temperature of aniline aerofloat degradation bacteria extracellular polymeric substances adsorption of heavy metals have little effect.(3) When the extracellular polymeric substances adsorbed in metal ion to about 8 minutes removal rate reached the highest, Cu2+ removal rate of 90.7% and Zn2+ removal rate was 52.3% and removal rate and adsorption capacity began to change,30 minutes can be reached the adsorption equilibrium, adsorption process probably induction into three stages, fast adsorption, slow adsorption, adsorption equilibrium, the pseudo first order kinetic equation and pseudo second order kinetics equation fitting to the adsorption process. correlation coefficient R2 of Cu2+ and Zn2+. The results show that the proposed second order kinetic model can better fit the kinetic data.(4) Of the initial concentration of metal ions was set as 5、10、15、20、25、30、40 mg·L-1. the higher the concentration, and the probability of contact adsorbent increases,adsorption material of Cu2+, the amount of Zn2+ also increased, the adsorption amount increased, the adsorption amount of Cu2+ from the initial 0.3263 mg·mg-1 to 1.907 mg·mg-1, the adsorption amount of Zn2+from 0.281 mg·mg-1 to 0.504 mg·mg-1, according to the relationship between the adsorption quantity and concentration of metal ions can be drawn using the adsorption isotherm, the commonly used Langmuir isotherm and Freundlich isotherm fitting results show that the better fitting effect of Freundlich equation in the process of Cu2+. Good Langmuir equation fitting effect of adsorption process of Zn2+, through the Langmuir Cu2+ and Zn2+ equation is obtained, the maximum adsorption capacity was 2.155 mg·mg-1 and 0.508 mg·mg-1,20、30、40℃ measuring adsorption amount of adsorption thermodynamics parameters calculation, Gibbs can become (AG)、enthalpy (ΔH) and entropy (AS), results show that the reaction of aniline aerofloat degrading bacteria EPS adsorption of Cu2+ and Zn2+is a spontaneous process, and belongs to the endothermic reaction.(5) The adsorption of metal ions and extracellular polymeric substances of infrared spectrum analysis, adsorption of metal ions, and some functional groups of peak shift or disappear, similar to the mechanisms of adsorption of Cu2+ and Zn2+ EPS, mainly from functional groups is hydroxy, amino, amide group, carboxy group and C-O-C groups, Coexisting ions experimental results show that coexisting ions the presence of EPS of target metal ions adsorption effect to a certain extent, Zn2+ and Cu2+ removal rate is alone fell 0.979%-5.08%, and when coexist with Cu2+ and Zn2+ removal rate is alone fell 17.6%-26.98%.