Biosorption Of Cu²⁺ By Cupriavidus Gilardii CR3 And Transport Of Cu²⁺ In Biofilm Of Cupriavidus Gilardii CR3-porous Media

Copper ions into the underground environment of the first natural barrier is a soil water layer containing porous media and microorganisms.In the underground environment,the biosorption of copper ions by microorganisms could affect the migration of copper ions into the underground environment.At the present study,the living cells of Cupriavidus gilardii CR3 which is a unique heavy metal resistance bacterium and copper ions were chosen as the study objects.The biosorption characteristics and mechanism of copper ions by C.gilardii CR3 had been studied.Effect of Cu²⁺ concentration on the formation of C.gilardii CR3 biofilm had been studied.At the same time,the transport of different concentration of copper ions in biofilm of C.gilardii CR3-quartz sand column had been discussed.And based on this,the influence of biofilm and EPS on the transport of copper ions in biofilm of C.gilardii CR3-quartz sand column were investigated as well.The main research conclusions are as follows:?1?The biosorption characteristics of copper ions by C.gilardii CR3.Batch experiments were carried out to remove copper ions by C.gilardii CR3 under different pH,initial copper ions concentration,and contact time.The isothermal model and kinetic model were used to fit the experimental results.The biosorption capacity of C.gilardii CR3 of copper ions increased with the elevation of pH value.The optimum pH value was 5.0 and the maximum biosorption capacity for copper ions was 18.33 mg/g.The biosorption process was well described by the Langmuir isotherm,the predicted maximum biosorption capacity for C.gilardii CR3 was 18.25 mg/g,which is very close to the experimental biosorption capacity qe value?18.33 mg/g?.The biosorption process as a function of contact time occurs in two steps?the initial rapid process and subsequent slower process?.Kinetic data were properly fitted with both the second order kinetic model and intraparticle diffusion model.The results indicated that the monolayer chemisorption and physisorption might be involved in the biosorption process simultaneously.?2?The biosorption mechanism of copper ions by C.gilardii CR3.The morphology and structure of C.gilardii CR3 were observed by Zeta potential,SEM-EDX and FTIR before and after the biosorption of copper ions.Zeta potential confirmed that electrostatic interaction involved in copper ions biosorption process.The surface topography changes of strain CR3 were observed by SEM-EDX,where images showed that biosorption takes place on bacterial cell surface.FTIR spectra provided evidence that carboxyl,hydroxyl,amino,and phosphate groups on the surface of strain CR3 could be available for characteristic coordination bonding with copper ions.In addition,reticulo-filamentous substances were obviously observed in the outer cells after copper ions loaded,which was mostly like secreted by C.gilardii CR3 in the presence of ions of copper stress.This might reflect a self-protection of the strain CR3 which has potential application value in practical application.?3?Effect of Cu²⁺ concentration on the formation of C.gilardii CR3 biofilm.The optimum conditions for the formation of C.gilardii CR3 biofilm were determined by the method of crystal violet dyeing.20 % LB was the most suitable nutritional condition at different LB concentrations.The results of crystal violet dyeing and CLSM showed that copper ions at 32 mg/L could promote C.gilardii CR3 secretion of protein and polysaccharides forming the largest biofilm area.?4?Transport of copper ions in biofilm of C.gilardii CR3-quartz sand.The formation of uniformly stable biofilm was to inject 20% LB in C.gilardii CR3-quartz sand column for 12 h which C.gilardii CR3 was in short-term hunger.BTCs of copper ions at 6.4 mg/L,32 mg/L and 64 mg/L were the irregular graphics in biofilm of C.gilardii CR3-quartz sand column.Transport ability of copper ions increased with the increase of copper ions concentration.In addition,the interception of biofilm column for copper ions was consistent with the biomass distribution.The results showed that copper ions trapped in the column was mainly due to the biosorption of copper ions by EPS.