Effects Of Phosphorus-rich Sawdust Biochar Immobilization On Heavy Metals In Electroplating Sludge

Biochar,as a environment-friendly material,has a strong adsorption properties for organic pollutants and heavy metal elements in soil and water pollution.The aim is to improve the adsorption capacity of biochar,and investigate the adsorption/fixed effects of modified biochar on heavy metals in electroplating sludge.This paper mainly researches the effect of biochar the adsorption efficiency of main heavy metals in electroplating sludge.In this study,the preparation of biochar with sawdust as raw materials,calcium super phosphate as modifier,utilizing limited oxygen pyrolysis under 300? and 600?.Through the single factor experiment to analysis the influence of different factors on adsorption efficacy of Cu?TCr?Zn?Cd?Pb,which control the initial p H value,biochar dosing quantity and adsorption time respectively.The morphology of heavy metals in electroplating sludge was analyzed according to the improved BCR continuous extraction method.The second-order kinetics and Langmuir model were used to simulate the adsorption of heavy metals in biochar.The effect of Na+,Ca2+,SO42-and CO32-ion on heavy metals was investigated under the different ion strength and p H value.Results shown that phosphorus-rich biochar have the best adsorption performance.When initial p H value is 6.0,adsorption time is 3h,tempretrue is 25±2?,and dosage of biochar is 3g,BCP600 has best removal rate on Zn2+?Pb2+?TCr?Cu2+?Cd2+,which is 98.44%,98.83%,87.75%,98.89% and 77.82% respectively.Second-order dynamics and Langmuir model can accurate describe the phosphorus-rich biochar for heavy metal adsorption process.The speciation of Cu?TCr?Zn?Cd?Pb were determined before and after the adsorption experiment.As shown,the heavy metal speciation is still dominated by the stable residue state(above 50%),indicating that the heavy metal mobility is reduced after adsorption.This is due to the ions Cu?Pb?Zn?Cd?TCr combined with the surface functional groups of biochar,led to the sediment state of Cu?Pb?Zn?Cd?TCr increased.It is shown that biochar has the effect of adsorbing heavy metals in fixed electroplating sludge.The results of coexisting ion experiments has shown that the greater the ion intensity,the greater the interference effect on heavy metal adsorption.Among them,the adsorption capacity of Pb and TCr via Ca2+ ion has decreased by 90.8mg/g and 56mg/g respectively,indicating that the presence of Ca2+ had a competitive effect on biochar.