Preparation Of Sludge Biochar After Bioleaching And Its Effects On The Adsorption Of Pb(?) And Cd(?)

With the rapid development of social economy in our country,the amount of sludge in the process of urban sewage treatment has been increasing year by year,but it is difficult to transfer the sludge into resource because it is hard for sludge to dewater and it probably has heavy metals.This paper aims to investigate municipal sludge concerning the problems mentioned above.Experiment about sludge dehydration,removal of heavy metals and biochar preparation will be conducted in order to provide theoretical basis for transferring sludge into resource.Municipal sludge will be used as raw material through biological leaching method for pretreatment and activation.We use single factor experiment design;make biochar after biological leaching;analyze its characterization and do research on the Pb?II?,Cd?II?adsorption performance and discuss its adsorption mechanism.The details are as below:?1?FeSO₄ serves as substrate of biological leaching.We control the substrate concentration and biological leaching time to modify the physical and chemical properties of the biochar.When FeSO₄ substrate concentration is 6 g/L and the bioleaching is 72,sludge specific resistance of sludge decreased from 1013 to 1.92 x 0.26 x 1013.At the end of the experiment,removal rate of the Pb,zinc,Cu,Ni,Cd,Cr removal rates were 61.48%,85.36%,87.01%,90.47%,81.57%and 71.78%.Experiments show that biological leaching method can effectively increase the rate of municipal sludge dewatering and reduce the heavy metal content in the sludge.?2?we use single factor experiment to get the optimum preparation conditions:the best temperature of the sludge biological carbon calcination is 500 ^oC calcination time is 2 hours,the proportion of straw is 20%.Characterization analyzing results shows that the holes of the raw materials has increased.X-ray diffraction?XRD?analysis showed that iron exists in the form of Fe₂O₃.Infrared spectrum analysis showed that composite adsorbent contains phenol hydroxyl,carboxyl,hydroxyl,lactone and phenol.?3?During the process of dealing wastewater containing Pb?II?after biological leaching,the optimum pH value was 5;Dosing quantity was 0.1 g;when the temperature was25 ^oC,it got balanced at 20 h.The effect of the kinetics of quasi secondary fitting was better;Langmuir equation can well express the adsorption process,when the temperature was 25 ^oC,35 ^oC and 45 ^oC,the adsorption capacity were 30.68 mg/g,39.95 mg/g and 43.93 mg/g.The adsorption process is also the endothermic process.It is thermodynamic spontaneous;When biological carbon adsorbs Pb?II?,carbon functional group C=O and C=C also works in adsorption.?4?During the process of dealing wastewater containing Cd?II?after biological leaching,the optimum pH value was 6;Dosing quantity was 0.1 g;when the temperature was25 ^oC,it got balanced at 16 h.The effect of secondary dynamics was the best.Langmuir was better for the fitting effect of absorption.When the temperature was 25 ^oC,35 ^oC and 45 ^oC,the adsorption capacity were 35.93 mg/g?38.58 mg/g and 48.29 mg/g.The adsorption process is also the endothermic process.It is thermodynamic spontaneous;When biological carbon adsorbs Cd?II?,O-H?C=O and C=C also works in adsorption.