Biogenic Palladium By Shewanella Oneidensis/FeSO₄ Catalytic Degradation Of Methylene Blue

Dye wastewater comes from textile printing and dyeing industry which is one of the most refractory industrial wastewater because of its high chromaticity,high COD,low BOD5.From the perspective of environmental protection,the wastewater must be preprocessed or it will pose a threat to various forms of lives.At present,methods of treating dye containing wastewater can be divided into physical/chemical methods and biological methods.Although these two kinds of methods gain good treatment effect,but there are also shortcoming in energy consumption and economy.To sum up,most of the degradation of methylene blue are only related to oxidation method,reduction method is rarely reported.some scholars has proved that some pollutants through reductive degradation can also achieve the same or even better results as oxidation degradation.There is of great significance to synthesize a new material and method to the development of wastewater treatment.The catalyst of biological palladium is confirmed by some scholars,so biological palladium is used as catalyst in the degradation of methylene blue in this paper.We used the biological palladium as catalyst which was synthesized by Shewanella Oneidensis and FeSO₄ as reducing agent in the degradation of methylene blue prepared in the laboratory.We discussed the effects of pH,the dosage of FeSO₄,the dosage of biological palladium,the initial concentration of methylene blue,We treated removal rate as the target factor to determine the optimum reaction conditions of single factor experiment,then studied on the kinetics of degradation of methylene blue under the optimum reaction conditions of single factor experiment.The orthogonal experimental was designed based on the optimal reaction conditions.The main conclusions of this paper are as follows:?1?The Pd?II??existed in the forms of Na₂PdCl₄?in the solution was reduced to Pd?0?black particles catalyzed by Shewanella Oneidensis in the presence of electron donor sodium formate.?2?The removal rate was the objective factor in the single factor experiment.The optimum reaction conditions of catalytic reduction of methylene blue: When the pH value was 7.0,the removal rate was 85.35%;When the the dosage of reducing agent FeSO₄ was 3mg/l,the removal rate was 88.71%?At this time,the ratio of FeSO₄ to methylene blue is 1.405:1?;When the the dosage of biological palladium was 400mg/l,the removal rate was 84.61%;When the the initial concentration of methylene blue is 10mg/l,the removal rate was 77.69%.?3?The kinetics of degradation of methylene blue catalyzed by biological palladium/FeSO₄ in the single factor experiment showed that ln?c0/ct?was linear with the reaction time t,so the reaction was first order reaction.When the pH is the best,the reaction rate constant is 0.0158min^-1;When the dosage in FeSO₄ is the best,the reaction rate constant is 0.0185min^-1;When the biological palladium dosageis the best,the reaction rate constant is 0.0157min^-1;When the initial concentration of methylene blue is the best,the reaction rate constant is 0.0175min^-1.?4?The removal rate was the objective factor in the orthogonal experiment,the optimum reaction conditions in the reduction of methylene blue catalyzed by biological palladium: pH value was 7.0,the dosage of reducing agent FeSO₄ was 4mg/L,the dosage of biological palladium was 400mg/L,the initial concentration of methylene blue was 20mg/L.Under the optimum conditions,the removal rate of methylene blue was 84.85%,and the reaction rate constant was 0.0156min^-1.