Humus Of U (â…¥) Adsorption And Humus/corruption Shiva's Bacteria Reduction Of U (â…¥) Experimental Study

The primary process to explore Uranium ore is leaching mining in our country,resulted in massive tailings and wastewater which contains radioactive nuclides （e.g,U, Pu, et al） metal elements （e.g, Cr, Mn, Fe, et al）, organic compounds （e.g,substituted benzene, chlorinated hydrocarbon, et al），as well as microorganism such asbacteria.Uranium exists in the environment primarily in the form of the uranyl cationUO2²⁺for uranium mobility. The mobility of residual microorganism, uranium andorganic compounds can be realized by solubility or transformation, resulting in apotential permanent radioactive and heavy metal pollution threat on theenvironment.Currently, the chemical release theory of uranium is clear due to thedevelopment of leaching mining theory. However, The correlation betweenmicroorganisms and uranium remains unclear.The adsorption of U（Ⅵ） by the humic acid（HA） were studied in the experimentsThe results indicated that the adsortion equilbriumis achieved in60min, and U（Ⅵ）removal rate increased with the decrease of the dosage of adsorbent HA.It wasobserved that pH had a strongly impact on the adsorption of U（Ⅵ）, and the bestadsorption was obtained at pH5.The results of the effects of avionics on U（Ⅵ）adsorption implied that citrate ions had strongly negtive impacts on the adsorption ofU（Ⅵ）. Meanwhile, strongly positive effects ofHCO3-, H2PO4-on the adsorption ofU（Ⅵ） were observed. A positive correlation of the effects of these anionics on U（Ⅵ）reduction with their concentrations was discovered. The significant effects of F-, NO3-, SO42-on the adsorption of U（Ⅵ） were not observed. Theadsorption of U（Ⅵ） wasaffected by traces of Cr（Ⅵ）/Mn²⁺negatively, and the effects on U（Ⅵ） reduction had apositive correlation with their concentrations. The process of U（Ⅵ）adopted by HAcould be described by equations of pseudo^-1st-order mode and pseudo-2nd-ordermode, and the relation coefficients were0.9825/0.9951,respectively. At25℃, theprocess of adsorption fitted better to Langmuir isotherm （R2=0.9955） than Freundlichisotherms （R2=0.84695） and Dubinin-Raduskevich isotherms （R2=0.80697）, thesaturated adsorption capacity Qmaxobserved was up to170.94mg/g. SEMmicrographs of HA show the surface form of HA was changed.IR micrograph of HAindicated that the HA would be mainly composed of Hydroxyl, carboxylic,-NH2, C-N, aromatic and Carbohydrate;IR micrograph of after HA adsorpting uraniumindicated that-OH、-C=O、-C-N、-NH2would be the main functional groups;and theiondexchange or surface complexing would be the main way of adsorption ofuranium.The reduction of U（VI） by Shewanella. putrefaciens was examined under theanaerobic environment，anthraquinone-2-sulfonate（AQS） present，The impacts on thereduction of U（VI） of different concentrations of AQS, heavy metal ions(Cr（Ⅵ）, Cu²⁺,et al) and toxic organic compounds were studied. Experimental results suggested S.putrefaciens is capable of utilizing various organic acids as electron donors and AQSas a electron shuttle vector under anaerobic condition to reduce U（VI） efficiently.Theresults indicated that at low concentration（<2mmol/L） AQS was a effectiveaccelerator for bioreduction of U（Ⅵ）. However, when the concentration of AQS wasmore than2mmol/L,the effect of acceleration was gradually decreased with theconcentration of AQS increasing （2mmol/L to10mmol/L）. These results indicatedthat the humic substances were not only as a electron shuttle vector during thereduction process, but also as the competitor for electron from respirationchain.Meanwhile, the observed experimental results implied that Cu²⁺has a stronglynegtive effect on the bioreduction of U（VI）, as a typical inhibitors of respirationchain. A strong inhibition of bioreduction of U（VI） by Ca²⁺was also observed.Thereduction of U（VI） was only weakly affected by Cr6+, Mn²⁺, and in60h, thesignificant change of the concentration of Cr（Ⅵ）.in the solution is not observed.Theeffect of metal ions on U（VI） reduction has a positive correlation with theirconcentrations.Some toxic organic compounds（e.g.,toluene.etc） are capable to beutilized as electron donors to reduce U（VI） efficiently by S. putrefaciens.Meanwhile,the toxic organic compounds were degraded. The result of FT-IR analysessuggest that the process of U（Ⅵ） remediation is a closely coupled, biotic-abiotic,two-step reaction pathway.