Experimental Study On Removal Of Microplastics From Water By Electrocoagulation Method

With the increasing accumulation of microplastics in the water environment,it is essential to study the removal of microplastics in current water treatment processes.Electrocoagulation is an effective wastewater treatment technique with the advantages of low cost,independence of chemicals,and ease to operation.This study aims to explore the removal efficiency,influencing factors,and mechanism of microplastics from wastewater treatment by electrocoagulation.The effects of electrode material,applied voltage,initial electrolyte p H,and concentration,electrolyte concentration,microplastic concentration and type on the removal of microplastics by electrocoagulation were systematically studied.By means of response surface model（RSM）,fourier infrared spectrometer（FTIR）,scanning electron microscope-energy dispersive spectrometer（SEM-EDS）,ion chromatography,reaction kinetics model and other design and analysis methods,the optimal experimental design and reaction mechanism of electrocoagulation treatment of microplastics in simulated wastewater were further studied.The main experimental results are as follows:The single factor experiment results showed that the combination of iron anode and aluminum cathode（Fe-Al）had the best removal effect on microplastics,and the electrode combination can adapt to large initial p H changes,and had a high removal efficiency under neutral or alkaline conditions.The removal efficiency of microplastics increased with the increase of applied voltage and electrolyte concentration.Under energy consumption and cost conditions,the removal efficiency of polyamide（PA）particles and polyethylene（PE）microplastics were 96.82%and 84.60%respectively.In addition,electrocoagulation is more suitable for removal of microplastics at low concentrations.The optimization results of the response surface experiment showed that based on initial p H value,applied voltage,electrolyte concentration and electrolytic time,electrocoagulation removal microplastic model,energy consumption model and electrode loss model were constructed,so as to achieved the optimization of electrocoagulation efficiency and cost.The optimal initial p H,applied voltage,electrolyte concentration and electrolysis time were 7.80,10.00 V,0.01 mol/L and 75 min for polyamide microplastics and 7.00,13.24 V,0.02 mol/L and 60 min for polyethylene microplastics,respectively.The experimental results further prove that the response surface model can be used to optimize the removal of microplastics by electrocoagulation.The characterization analysis and mechanism exploration results showed that the SEM-EDS analysis of the flocs indicated that the Fe-Al electrode combination produced mixed Fe-Al flocs,which had both strong adsorption effects of the Al flocs and strong sedimentation performance of the Fe flocs.Moreover,the settling velocity index（SVI）of the mixed flocs was optimal.FTIR characterization indicated that new bonds were formed between the flocs and microplastics,such as Al-O bonds and Fe-O bonds.The removal mechanism of microplastics was as follows:Fe²⁺generated by electrolysis is oxidized to Fe³⁺and formed Fe（OH）₃ with and OH^-,and cathodic Al reacts with OH^-to form Al（OH）₃;Fe（OH）₃ and Al（OH）₃ groups and flocs removed microplastics from water by means of compressed double electric layer,adsorbing electro-neutralization and adsorption bridging.In addition,the flocs produced with the four electrode combinations conformed to the proposed secondary reaction kinetics,and the Fe-Al electrode combination produced the largest floc adsorption q_e.In summary,the single-factor test proved the reliability of microplastic removal by electrocoagulation;the response surface experimental model design solved the problems of removal efficiency and cost of electrocoagulation well;the mechanism characterization analysis deeply analyzed the adsorption mechanism of microplastic removal by electrocoagulation.The current study demonstrates the potential of electrocoagulation to remove microplastics from wastewater and provides engineering perspectives on the optimization of operating parameters.