| Dye wastewater is of great quantity,complicated composition,high colority and severe pollution.The majority of disposal methods of methylene blue is adsorption method and Photocatalytic degradation method at present.In this paper,the reduction method is used to treat methylene blue,a new method for the treatment of methylene blue that Bio-Pd,which was prepared by Shewanella oneidensis bacteria,and Fe reducing agent combined catalytic degradation of methylene blue was explored.It has a certain guiding significance of the theory and practice to the treatment of methylene blue.In this paper,Shewanella oneidensis bacterial was used to synthesis Bio-Pd.Bio-Pd and Fe reducing agent common catalytic degradation of methylene blue was studied.the influence of different Fe(0)dosing amount,different pH,different Bio-Pd dosing quantity and initial concentration of the methylene blue on the removal rate of methylene blue was studied.Through orthogonal experiment design,the best reaction condition was obtained.Through reaction kinetics experiment,the influence of different factors on the reaction rate constant was concluded.the following conclusions were reached:1)The results of of the degradation experiments showed that under different conditions,when Fe(0)powder dosage was changed from 5 mg/L to 50 mg/L,the degradation rate of methylene blue increased quickly from 49.36% to 89.83%,Fe(0)powder dosage continued to increase to 100 mg/L,the removal rate of methylene blue was changeless;When pH increased from 2.2 to 4,Bio-Pd catalytic degradation efficiency of methylene blue increased from 42.05% to 89.83%,pH increased from 4 to 8,methylene blue degradation rate reduced from 89.83% to 60.18%;Bio-Pd dosage was respectively 50 mg/L,100 mg/L,200 mg/L,300 mg/L,400 mg/L,the degradation rate of methylene blue was 65.82%,73.17%,89.83%,75.84%,67.19%,when Bio-Pd dosage was changed from 50 mg/L increase to 200 mg/L,the reduction rate of methylene blue increased from 65.82% to 89.83%,when Bio-Pd dosage was changed from 200 mg/L increase to 400 mg/L,the reduction rate of methylene blue decreased from 89.83% to 67.19%;when the initial concentration of methylene blue was 5mg/L,7.5mg/L,10mg/L,15mg/L,20mg/L,the degradation rate of methylene blue was 91.25%,91.06%,89.83%,85.06%,79.87%.The degradation rate of methylene blue Remains unchanged at first and then decreased with the increase of initial concentration of methylene blue.When the initial concentration of methylene blue changed from 5 mg/L increase to 7.5 mg/L,the removal rate of methylene blue was changeless,maintained at a higher level.When the initial concentration of methylene blue was in the range of 7.5 mg/L ~ 20 mg/L,with the increase of initial concentration of methylene blue,the degradation rate of methylene blue declined.When Fe(0)dosing quantity was 100 mg/L,pH=4,Bio-Pd dosing quantity was 200 mg/L,the initial concentration of methylene blue was 10 mg/L,the largest degradation rate of methylene blue was 89.83%,compared with the blank test 1(Fe(0)dosing quantity was 0 mg/L)and the blank test 2(Bio-Pd dosing quantity was 0 mg/L),which was 89.27% higher than the blank test 1 and 77.53% higher than the blank test 2.When Fe(0)dosing quantity was 100 mg/L,pH=4,Bio-Pd dosing quantity was 200 mg/L,the initial concentration of methylene blue was 5 mg/L,the largest degradation rate of methylene blue was 91.25% in the experiment,the molar ratio of Fe(0)and methylene blue was 114:1.2)Through orthogonal experiment,the optimal conditions was that the initial concentration of Methylene blue was 7.5 mg/L,the dosing quantity of Bio-Pd was 200 mg/L,the initial pH was 4,the dosing quantity of Fe(0)was 50 mg/L.Through the analysis,the order of the influence of various factors on the degradation rate of methylene blue was: Fe(0)> pH > biological palladium> methylene blue.Under the optimum reaction conditions,the removal rate of methylene blue after 2 h reached 90.8%,very close to the biggest removal rate of 91.25% in the single factor experiment,while the mole ratio of Fe(0)and methylene blue was 38:1 in the orthogonal experiment,the mole ratio of Fe(0)and methylene blue was 114:1 in the single factor experiment.Through the orthogonal experiment,not only the removal effect can be reached,but also the reducing agent Fe(0)dosing quantity can be greatly reduced and cost can be saved at the same time.3)By reaction kinetics study,the concentration of Fe(0)changed from 5 mg/L up to 50 mg/L,the reaction rate constant k increased slowly,Fe(0)dosing quantity from 50 mg/L to 100 mg/L,the reaction rate constant k was stable;pH rose from 2.2 to 4,the reaction rate constant k increased slowly,pH from 4 to 8,the reaction rate constant k dropped slowly;Bio-Pd dosing quantity rose from 50 mg/L to 200 mg/L,the reaction rate constant k increased slowly,Bio-Pd dosing quantity from 200 mg/L to 400 mg/L,the reaction rate constant k dropped slowly. |
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