Research On The Impact In The Chalcopyrite Slag Bio-leaching Process Of The Interactionbetween Rhizobium, Rhodotorula And Acidithiobacillus Ferrooxidans

Bioleaching has become a widely used method in the extraction of heavy metals inslag and low-grade mine, but the low reaction speed limited its use. It is documentedthat laterality and mutual-benefit could raise the number and ability of single population,but the reports of improving leaching rate by using synergy were relatively few. In thispaper, we add some microorganisms in the leaching solution to try to improve the livingenvironment of Acidithiobacillus ferrooxidans(Referred to as A.f)and the leaching rate byusing the interaction between A.f and adding microorganism to, then provide atheoretical basis to solve the environmental safety issues of heavy metal tailings. Thedetailed content and conclusions of this paper are as follows:The tailing was sampled in a copper mine in Yunnan province, the results ofcharacterization analysis of sample, the isolation of Rhizobium from the nodule ofkidney bean, the determination of the growth curve of A.f, the leaching experiments ofA.f respectively with Rhizobium and Rhodotorula and the fitting of microbial growthmodel in bioleaching process indicated that:①The average particle size of the tailingsample was18.30μm. The contents of main elements are: Si=250.35mg/g,Fe=141.9mg/g, Al=82.2mg/g, Ca=71.7mg/g, S=66.7mg/g, Cu=3.5mg/g, Mn=2.4mg/g,As=1.2mg/g and Cd=0.064mg/g. Main existing form of heavy metals was residual state.②The Rhizobium strains FJ-5could endure pH=2and the copper concentration of100mg/L, also could use most organics except ethanol and secret organic acids.③TheA.f strain AFCQU-01grew best when pH=2and30℃, the final concentration of A.f was3.8×108cells/mL. It could endure the concentration of copper more than1g/L. Theoxidation rate of Fe2+decreased more than55%when the concentration of Cd was1mg/L. The maximum specific growth rate of A.f, μmax=0.131/h-1when Fe2+was theonly growth medium, and saturation constant, Ks=1.21g/L. Rhodotorula could reducethe negative impact of Cd to A.f.④When the ratio of A.f: Rhizobium was5:1at5%pulp density, the leaching efficiency was the best, the leaching rates of Total Fe, Cu, Asand Cd respectively were10.0%、19.5%、16.9%and13.1%, higher than the experimentof only A.f and sterile at5%pulp density.⑤The leaching rates of Total Fe, Cu, As andCd in the leaching experiment with Rhodotorula respectively were7.2%、8.1%、4.1%and5.1%，also higher than the experiment of only A.f and sterile at15%pulp density.⑥The mutual coefficients, α=0.25and β=1.12, and the estimation number of A.f and Rhizobium were respectively6.46×109cells/mL and2.61×109cells/mL in their jointgrowth. The partial interest coefficient, α=0.25, and the estimation number of A.f andRhodotorula were respectively1.94×109cells/mL and4.84×108cells/mL in the jointgrowth of A.f and Rhodotorula.According to the results of above tests, it can be concluded that:①The contains ofFe and S were high in tailing sample, it was appropriate for bio-leaching.②TheRhizobium isolated from kidney bean could grow in the leaching environment of strongacids and high concentrations of heavy metals.③Cadmium could inhibit the metabolismof bacteria A.f. Rhizobium could use the organic metabolites to reduce their negativeimpact to A.f, to promote the growth of the two microorganism.④Rhizobium couldimprove the activity and the number of A.f and the leaching efficiency.⑤Rhodotorulacould absorb heavy metal ions in the solution and reduce their negative impact to A.f,then improve the activity and the number of A.f and the leaching efficiency. Theadsorption of Cd by Rhodotorula fits Langmuir model best, it indicated that monolayeradsorption was the main effect. Lagergren equation of pseudo-second-order modeldescribed the adsorption process best.⑥According to the interaction models betweentwo species, the interaction models between two microorganism in the leaching processwas established, the fitting results was good.Acidithiobacillus ferrooxidans could effectively leach metals from tailing, but theleaching rate is low due to the restriction by many factors. Rhizobium and Rhodotorulacould improve the leaching efficiency of most element. The paper clarified themechanism of laterality and mutual-benefit in the leaching process of Acidithiobacillusferrooxidans, and provides the technical support of reducing the harm of heavy metals.