Preparation Of Carbonaceous Adsorbents From Sewage Sludge And Its Application In Adsorption Of Lead, Copper Ions

Due to the quantity and complex of sewage sludge,which is not effective treatment and dispal,it should not only cause a secondary pollution problem in the environment,but also cause the waste of available resource and energy.Therefore, how to develop a technology for the appropriate treatment of sewage sludge to achieve reducing,stabilization,unharmful, resource, which is a widespread attention to our country and the whole world.In this work,we focused on the preparation of carbonaceous adsorbents from sewage sludge and considered its application in metal wastewater treatment.This is great significance for the reuse of sewage sludge.In this paper,sewage sludge generated during municipal wastewater treatment process has been identified as precursor for carbonaceous adsorbents production,chemical activation by zinc chloride.Experimental design enables to study the effects of the preparation factors: the concentration of activating agent ZnCl2,activation temperature,dwell time,the mixing ratio of ZnCl2/sawdust, the impregnation time and granularity of raw material and so on, the influence of the additive to raw material modified the carbonaceous adsorbents,which influenced on the iodine adsorption value and methylene blue adsorption value,and compared with characteristics of the modified carbonaceous adsorbents and unmodified carbonaceous adsorbents by specific surface area, pore size distribution,scanning electron microstructure and FTIR spectrum.In this study,we discussed the mechanism of the prepared process and the application of unmodified and modified carbonaceous adsorbents to the simulated wastewater treatment including copper and lead ions.In the experimental scope,the main results of the study were summarized as follows:Carbonaceous adsorbents prepared by sludge sewage with ZnCl2 activation,through single factor experiments and orthogonal test,to determine the optimal activation conditions with the iodine value and methylene blue value as follows:Under the environment of the flowing nitrogen(400±25mL/min), the concentration of activating agent ZnCl2 3mol/L,activation temperature 550oC,dwell time 1h,the mixing ratio of ZnCl2/sawdust 2:1, the impregnation time 1h, and granularity of raw material 0.15mm.The iodine value and methylene blue value of carbonaceous adsorbents were 423.53 mg/g, 94.69mg/g respectively,the specific surface area was 227.3 m2/g.The addition of some (manganese sulfate:ferrous sulfate in a certain ratio) to these sewage sludge modified the charicteristic of carbonaceous adsorbents. The iodine adsorption value,methylene blue adsorption value and copper adsorption value of carbonaceous adsorbents were considered as evaluating index.We obtain the results as follows:under the best produced condition,when (manganese sulfate:ferrous sulfate ratio of 2:1) to 3% mass fraction of particles mixed with the sludge, the iodine value, methylene blue value and copper adsorption value of modified carbonaceous adsorbents were more than unmodified carbonaceous adsorbents, the iodine value was 493.57mg/g, the methylene blue value was 97.99 mg/g, the copper adsorption was 23.52mg/g, the specific surface area was 211.6m2/g.Carbonaceous adsorbents and modified carbonaceous adsorbents treated simulated copper or lead wastewater.The results showed the adsorption capacity of modified carbonaceous adsorbents was higher than carbonaceous adsorbents,under the same conditions;modified carbonaceous adsorbents treated metal wastewater, at the 298K,the initial concentration of 40mg/L,60mg/L,80mg/L of copper wastewater respectively,its saturated adsorption capacities were 6.65mg/g,9.98mg/g,11.37mg/g, adsorption equilibrium time of 90 min,the pH value of 5.0,the best dosage of 5g/L,respectively; At the same conditions, the best dosage of 7g/L,the initial concentration of 40mg/L,60mg/L,80mg/L of lead wastewater,its saturated adsorption capacities were 5.21mg/g,7.02mg/g,10.14mg/g.The procss of adsorption conformed with Langmuir adsorption model,its adsorption dynamics model fitted secondary dynamic model.Its adsorption is exothermio reaction.