Research On The Removal Characteristics Of Soil Pollutants By Bio-electric Coupling Technology

Residues of contaminants in agricultural soils can enter the food chain,ultimately posing a potential threat to human health,and in turn can act as a secondary pollutants to air and water pollution.In view of the serious status of agricultural soil pollution in China,herbicide Atrazine was selected as the target pollutant,and constructed soil microbial fuel cell(soil MFC)in this study which coupling biological with electrochemical action.Sequential batch method was used to remove Atrazine.The effects of soil MFC on removal of Atrazine and synchronous electricity production was investigated from following four aspects:co-substrates,buffer solution concentration,soil medium and cathode performance.The main research contents and results were as follows:The differences of the soil electricity production and Atrazine degradation were compared by adding different co-substrates,selecting sodium acetate,glucose,citric acid and sodium citrate.The results showed that the electricity production efficiency of sodium acetate was the highest in soil MFC,and the maximum voltage was 94 mV,the internal resistance of soil MFC was 539?.At the same time,the higher current density produced by the system promoted the removel of Atrazine.The addition of sodium acetate was conducive to the anodic microorganisms secreted organic degradation enzymes,and improved the removal of Atrazine in soil MFC.Therefore,sodium acetate was suitable as a co-substrate for the construction of soil MFC.Soil MFC was constructed using PBS buffers with concentrations of 0,0.05,0.1,and 0.3M,respectively,while set up the circuit control group of the 0.3 M group.The effect of buffer concentration on the performance of soil MFC and the effect of current on Atrazine removal were studied.The experimental results showed that when the buffer concentration was increased within range of 0~0.1 M can improve the mass transfer in the soil MFC,improve the polarization in the battery,and generate the higher voltage.In this study,the soil MFC added PBS buffer concentration of 0.1 M batteries obtained the maximum voltage was 144mV,the maximum power density was 89.35 mW/m~2,the 0.3 M was inhibited instead.The Atrazine removal rate increased with the increase of the current intensity,the removal rate in the open circuit device was 1.56 times that of the control group,and the degradation rate was 90.41%in the soil MFC with the concentration of 0.1 M.At the same time,the degradation rate of Atrazine in different positions in the soil MFC was quite different,which satisfied the law:upper level>lower layer>middle layer.And the removal rate of the lower layer soil in each group increased as the buffer concentration increased in a certain range.Soil MFC was constructed by adding different media,and studied the effects of media changes on the electrical performance of soil MFC and Atrazine removal.The results showed that the addition of conductor medium can promote the transfer of protons and ions in soil,thus reducing the ohm internal resistance and increasing the battery's electrical performance.The degradation rate of Atrazine was relatively high in the device of adding conductor medium,and obtained the shortest half-life 62.34 days.The cathode water layer reduced the cathode oxygen concentration and lowered the conductivity of the soil solution.Confirmed that the cathode oxygen concentration was the limiting factor of the output voltage.Set up different cathode and studied the effects of cathode on the electrical performance of soil MFC and Atrazine removal.The results showed that for the air cathode MFC,added Atrazine to the cathode under aerobic conditions can produce a higher voltage and increase the electrochemical performance of soil MFC,but the oxygen deficiency can still lead to deterioration of the cathode performance.Therefore,the oxygen content was still the key to improve the overall performance of the soil MFC.Atrazine can be degraded in the cathode,and the cathode aerobic was conducive to increase the Atrazine removal rate.At the same time,the Atrazine in the soil near the cathode can also be removed,but the removal effect was not as good as that of the cathode.