| The activated carbon was prepared from sewage sludge of municipal wastewater treatment plant by chemical activation(activation reagent is ZnCl2),meanwhile,the preparation condition and mechanism were discussed.Based on characterization of the activated carbon from sewage sludge(ACS for short),the adsorption kinetics and thermodynamics of three dyes(Acid Scarlet GR,Acid Blue 324 and Reactive red-violet X-2R) on the ACS were studied by batch adsorption tests and the changes of the groups on the surface of the pre- and post-dye absorption of the ACS were also carried out in qualitative and quantitative analysis to clarify the mechanism of absorption further.Moreover,a small absorption column with the ACS was designed and the ACS was renewed twice to make a comparison study of the Acid Red GR dye wastewater treatment by dynamics adsorption.It was found that,based on the iodine value and the methylene blue value,the best preparation condition was ascertained:the concentration of activation reagent was 40%,the ratio of activation reagent to sludge was 1.5:1,the activation temperature was 450℃and the activation time was 25 min.On this condition,the iodine value of the ACS was 633.95 mg/g,the methylene blue value of the ACS was 15.68 mg/g(the concentration of methylene blue was 150 mg/L).Surface area and pore structure analysis shows that the ACS BET surface area was up to 418.79 m2/g,total pore volume was about 0.2597 cm3/g and the ACS was with a more open pore structure and suitable for the adsorption of the dye molecular.The results of the infrared spectroscopy and Boehm acid-base titration are that the surface of ACS may contain -OH,unsaturated -C=C- or -C=O,-CH- in paraffin,-C-Cl- and so on,and the the major Oxygen groups---basic group,acid group,carboxyl and phenolic hydroxyl levels were:0.5492 mmol/g,1.8104 mmol/g,1.0161 mmol/g and 0.2709 mmol/g. TGA showed that the role of activator ZnCl2 is dehydration and condensation,so that to separate the H and O of the raw material in the form of water and remain more of C in the material.The extract of the ACS was tested and the ion concentrations of Cu, Pb,Cd,As and Ni were not detected,the ion concentrations of Fe and Cr were less than 0.002 mg/g and concentration of Zn ion was higher,that can reduced by increasing clean-up-times.The static adsorption showed that the ACS possessed high adsorption capability for three dyes by controlling the appropriate dosage,adsorption time and pH value.The order of adsorption capability of the ACS for three dyes was as follows:Acid Scarlet GR> Acid Blue 324 > Reactive red-violet X-2R and the static absorption capacities were:43.67 mg/L,33.56 mg/L and 31.35 mg/L.The adsorption of three dyes on the ACS followed the pseudo second-order kinetic model.For Acid Blue 324 and Reactive red-violet X-2R,the intra-particle diffusion is one of the rate-controlling steps.Langmuir isotherm equation showed reasonable applicability for the adsorption of three dyes on the ACS.The adsorption of three dyes on the ACS was a monolayer adsorption.Moreover,it was endothermic(enthalpy△H>0),spontaneous(free energy△G<0) and accompanied by an increase in entropy(△S>0).The phenolic hydroxyl, carboxylic acid and other acid groups on the surface of the ACS played an important part in the absorption.A small absorption column with the ACS was designed and the ACS was renewed twice to make a comparison study of the Acid Red GR dye wastewater treatment by dynamics adsorption.(room temperature,adsorption column(Φ16×165 mm,15 g sorbent) and the flow of Acid Scarlet GR wastewater was 10 ml/min).Their breakthrough points about 11 hours,9.7 hours and 8.8 hours and their dynamic absorption capacity:40.7 mg/L,37.26 mg/L and 31.24 mg/L showed that the renewable method of heating is good.The above results indicate that the ACS can be employed as an effective,safe and economically activated carbon in treatment of wastewater that contains large molecular pollutant such as dye and that provided an effective way to make the sludge as resources.
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