Study On Remediation Of Groundwater Polluted By Chrome And Fluorine By Nano-ZrO₂-SRB Particles

Some pollutants in groundwater in a certain area of metallurgy exceed the standard,such as F^-?Cr????Cr????SO₄^2-.Based on microbial immobilization technology,a kind of hybrid material of nano-ZrO₂-polyacrylamide was made in laboratory and used as entrapment agent.It was used to immobilize the cultured and purified sulfate-reducing bacteria?SRB?to form nano-ZrO₂-SRB particles.Through single factor experiments and regression rotation experiments,the optimum reaction conditions of nanometer ZrO₂-SRB particles to mixed water samples containing F^-?Cr????Cr????SO₄^2-were optimized.A series of kinetic experiments and microscopic characterization of the particles were carried out to explore the mechanism of the removal of pollutants by this kind of particles.Finally,nano-ZrO₂-SRB particles were used to treat groundwater.The experimental results are as follows:?1?The optimum preparation conditions were obtained by studying the preparation method of hybrid materials.In zirconia sol of 200 mL,adding 0.6 g acrylamide,adding sodium bisulfite and potassium persulfate as initiator,adding dosage of 0.05 g,reaction temperature of25?and polymerization of 30 min,the viscosity of the organic-inorganic hybrid material was the best.Using nano-ZrO₂-polyacrylamide hybrid material to treat water samples containing Cr????Cr????SO₄^2-and F^-in 100 mL,the results of single factor experiments showed that:The emoval rates of Cr????Cr????F^-and SO₄^2-were 87.2%?95.4%?92.4%?30.2%,respectively,when the dosage of the hybrid material was 4.15 g,the initial solution pH=4⁷,the control reaction temperature was 20⁴0?,and the reaction was 20 min.The co-existing ions in the solution have different effects on the removal rate of the polluted components.It was found that the organic-inorganic hybrid materials were difficult to be separated from water.The optimum composition distribution ratio was determined as follows:2 g ZrOCl₂ dissolved in 200mL ethanol,the dosage of acrylamide in NaOH/Zr=7.5,the dosage of acrylamide was 0.65 g,and the dosage of initiator was 0.05 g.The instrumental structure of the hybrid material and the treated water shows that the hybrid material and the treated water material are characterized by the instrument structure.The main results are as follows:after the adsorption reaction,the absorption peaks of S?Cr?F were observed between nano-ZrO₂ and polyacrylamide by covalent bond.?2?Through purification,culture,domestication and gram staining,methyl red test,spore staining,TEM analysis,gene sequencing and other methods,the strain belongs to facultative anaerobes and is a lemon acid bacilli.The sulfate reducing bacteria obtained after the cultivation and domestication are used for treating the water containing Cr????Cr????SO₄^2-?and F^-composite polluted water.The results showed that when the mixed water samples containing 5 mg/L of F^-?10 mg/L of Cr????10 mg/L of Cr????and 500 mg/L of SO₄^2-were treated,the dosage of SRB was 3%,the initial pH=7,reaction temperature was 35?,and the reaction time was 24 hours,the removal rates of Cr????Cr????SO₄^2-were 95.2%?67.4%and 70.3%,respectively.?3?The nano-ZrO₂-SRB particles were prepared by embedding and immobilization of SRB using self-made nano-ZrO₂-polyacrylamide hybrid materials.Single factor experiments were carried out with SRB dosage,hybrid material dosage,reaction temperature and reaction time as factors.The results show that the dosage of SRB is 35%,the dosage of the hybrid material is 300 mL,and when the reaction temperature is 35?,F^-?Cr????Cr????SO₄^2- are 92.4%?99.8%?99.7%?70.4%,and pH can be raised to 6.8.The dosage of SRB,the amount of hybrid material and the reaction temperature were used as three factors,and the orthogonal rotation test of three factors was used.The results showed that these conditions are the best.When the bacteria particles were characterized by instrument,the absorption peaks of S?Cr?F were obvious.The reduction of Cr???and SO₄^2-by nano-ZrO₂-SRB particles was in accordance with the first-order reduction kinetics,and the adsorption process of Cr????Cr????F^-and SO₄^2-obeyed the second order reaction kinetics.The correlation coefficient of fitting is more than 0.99.The adsorption process is in accordance with the Freundlich isotherm model.?4?Through the study of different types of reaction layer,different influent velocity and different influent concentration in dynamic test,it is shown that:The dynamic device of the nano-ZrO₂-SRB particle as the reaction layer has the advantages of higher removal rate of Cr????Cr????F^-?SO₄^2-.And the water inlet flow rate is more suitable when the water inlet flow rate is controlled at 2.935 m³/?m²·d?.Increasing the concentration of Cr???and F^-has little effect on the change of effluent concentration.Through the effluent effect at the beginning of the reaction,it can be seen that the selectivity of nano-ZrO₂ to each pollutant is different,and the adsorption selectivity of F^-is better than that of Cr???and SO₄^2-.the adsorption selectivity of F^-is better than that of Cr???and SO₄^2-.