The Study Of Homemade AC Used In Electrokinetic Removal Technology On Heavy Metal Removal From The MSWI Fly Ash

The Municipal Solid Waste Incineration(MSWI)fly ash was classified as hazardous waste due to its high content of heavy metals(HMs)that needed to be processed.Electrokinetic removal technology(EKR)was greatly restricted by the long processing time and low removals rate of HMs.In order to improve the removal rate of HMs and shorten the repair time,this present paper was focused on the manufacture of activated carbon(AC)and its application in the EKR technology on r emoval of the HMs from the MSWI fly ash.AC was activated by H3PO4,the effects of the molding conditions(activation temperatures,impregnation ratios(phosphoric acid/dry precursor)and soaking time)on the adsorption capacity of AC on HMs were firstly studied through equilibrium adsorption experiments,the molding factors affecting its adsorption were analyzed;moreover,the optimal forming conditions were confirmed.Then,AC produced in the optimum conditions was added in the S3-region(near cathode)of the electrolyzer,together with synergistic effects,the removals of HMs in S1 and S2 region were greatly improved,the coupling effect was verified to be effective in the contrast experiment.Finally,the coupled parameters(voltage gradient,proportion(AC/fly ash)and processing time)of the coupled system were further optimized in the orthogonal experiment.In this paper,the application of self-made AC in fly ash EKR experiment was studied and the mechanism of coupling experiment was explored.Through the analysis of the physical and chemical properties of fly ash,The MSWI fly ash samples was relatively concentrated in particle size,which mainly distributed between 40~400um,the internal structure of MSWI fly ash samples was loose and porous,and the specific surface area was larger.Zn,Pb,Cd,Ba,Cu and Mn was the main heavy metal elements in MSWI fly ash samples,the total content was 1.60%.The total amount of Cu,Pb,Cd and Zn is 2.48,6.34,33.47 and 11.70 times of the standard value,and the leaching toxicity value was 0.31,28.44,28.42 and 1.43 times of the standard value.According to the results of the equilibrium adsorption experiments,the optimum molding conditions for activated carbon were set as the condition of 450℃ of activation temperature,10 h of soaking time and 1.5 of the impregnation ration,at this condition,the equilibrium adsorption capacity for Cu,Zn,Cd and Pb was 117.96 mg/g,73.72 mg/g,21.01 mg/g,35.97 mg/g,respectively.In the contrast experiments,the removal rate(δ)of HMs in 2# was significantly elevated in the experimental region compared with the other two groups,the addition of AC in the S3-region of the electrolyzer could effectively improve the removal efficiencies of HMs.In the orthogonal coupling experiment,the optimum voltage gradient,processing time and proportion was 2 V/cm,8 d a nd 20%,respectively.And under this condition,the removal rate of Cu,Zn,Cd,and Pb was 84.93%,69.61%,79.57%,and 78.55%,individually.