Removal Of Glyphosate From Water By Microbe-biochar Composite

The widespread use of glyphosate in the world has caused it to be frequently detected in surface water and soil,which can cause certain damage to the environment and humans.It is necessary to remediate the glyphosate in the environment.Biodegradation is the main method to remove glyphosate,but the functional microorganisms screened in the laboratory are easily disturbed by the environment.And the immobilization technology can protect the microorganisms and improve their environmental adaptability.Therefore,in this paper,a glyphosate-degrading bacterium was selected from the soil polluted by glyphosate for a long time,using rice straw biochar as a carrier,and using immobilized microbe technology to prepare a microbial-biochar composite material.Research the removal effect and removal mechanism of single biochar,single microorganism and biochar-microbe composite material on glyphosate through removal kinetics and removal thermodynamic experiments.Constructing a simple glyphosate wastewater treatment device is to study the removal effect of composite materials on glyphosate wastewater and basic treatment parameters.The main research results are as follows:(1)Screening and identification of glyphosate degrading bacteria and research on the removal effect and removal mechanism of glyphosate.A strain Z-1 that efficiently degrades glyphosate was obtained from the soil in the glyphosate wastewater treatment area of a pesticide factory in Suzhou,Jiangsu Province.We use glyphosate as the only carbon source to acclimate and isolate it,and it was identified as a sewage bacteria by molecular biology Genus(Aquamicrobium sp.).Experiments on the removal effect of glyphosate at different temperatures,different p Hs,and different inoculation amounts show that the best conditions for the degradation effect of strain Z-1 on glyphosate are the cultivation temperature of 30?,the inoculation amount of 2%,and p H=7.0.The initial concentration of glyphosate has a greater impact on Z-1's removal of glyphosate and its growth.When the glyphosate concentration is 200mg/L and 400 mg/L,Z-1 grows well and can completely degrade glyphosate;when the concentration is increased to 600mg/L,the removal effect of Z-1 drops to 63%.Through Z-1 analysis of the degradation products of glyphosate,the degradation pathway is:the C-N of the glyphosate molecule is first broken under the action of oxidoreductase to degrade glyphosate into aminomethylphosphonic acid(AMPA)and glyphosate It is further metabolized by Z-1 into methylamine and phosphoric acid,and then participates in the circulatory metabolism of microorganism,and finally degrades into water and CO₂.(2)The removal effect and removal mechanism of biochar,free microorganism and the biochar-microbial composite material on glyphosate show that the adsorption of glyphosate by rice straw biochar is more in line with the quasi-second-order kinetic equation,which is a physical-chemical composite adsorption process.In this study,the microbial-biochar composite material was prepared by the immersion adsorption method,and the Langmuir and Freundlich equations were used to establish an adsorption isotherm model.The process of biochar adsorption of glyphosate is more consistent with the Langmuir model,which is a single-layer adsorption;the adsorption process of the composite material is consistent with The Freundlich model is a multilayer adsorption.The maximum adsorption capacity of biochar is 8.77 mg/g,and the composite material is 633.42 mg/g,which is nearly 70times higher than that of biochar.The composite material can strengthen the effect of Z-1to remove glyphosate.The 600 mg/L glyphosate can be completely removed within 96hours,while the degradation efficiency of Z-1 at this time is 55%.The composite material has a 100%degradation efficiency for 1200mg/L glyphosate,so it can be used in high-concentration glyphosate polluted environments.The composite material can adapt to acidic conditions,indicating that biochar can protect microorganisms from environmental persecution,thereby improving the removal efficiency.Through the characterization of biochar and composite materials,the removal mechanism of glyphosate by composite materials is analyzed,including biochar functional groups,persistent free radicals,electrostatic adsorption,and microbial degradation and adsorption.By calculating the contribution mechanism of adsorption and degradation in the process of removing glyphosate by microbe-biochar composites,it is found that the degradation is dominant,and the degradation is mainly achieved by microorganisms.Biochar,free microorganisms and composite materials were used to repair glyphosate contaminated soil.The effect was measured 7 days later,and it was found that composite materials>microbes>biochar,and with the increase of material dosage,the repair effect became stronger.(3)Construct a simple glyphosate wastewater treatment device.First,biochar was used as a filler.The experiment was carried out by changing the addition amount of biochar and the flow rate of influent water.The results of the breakthrough curve showed that as the dosage increased from 2g to 4g,the grass The detection time of glyphosate was shortened by 2 times;the flow rate had a greater influence on the removal effect,and the increase of the influent flow rate shortened the detection time of glyphosate by 10 times.Therefore,the effect is best when the amount of biochar added is 4g and the flow rate is 0.18m L/min.Using this optimal parameter to fill and remove glyphosate wastewater experiments found that the composite material has high degradation activity in the water treatment device,the removal effect is much greater than that of biochar,and when the glyphosate concentration is increased to 100mg/L,it is within 500min.No glyphosate was detected in the effluent.