Study On Preparation Of Activated Carbon From Sewage Sludge By Microwave Radiation And Its Performance

With the development of wastewater treatment, sewage sludge was produced in an ever increasing amount. Without proper treatment and disposal, Sewage sludge would be cause a secondary pollution problem, because it was rich in not only organic materials and dangerous substance but also pathogenic germs. Making full use of available component in sludge and converting waste into valuable substance was the final disposal way in the future. Sewage sludge was carbonaceous in nature and rich in organic materials, hence it had the potential to be change to activated carbon. It was proposed that sewage sludge was converted into activated carbon through microwave radiation in existence of H₃PO₄. Compared with traditional electrical heating, microwave heating had outstanding excellence, that is, high efficiency and quickly reaction speed. The time of disposing sample was shortened largely.In the experiment of making activated carbon from sewage sludge, these conclusions could be obtained that the largest influence factor to iodine value was microwave power, the secondary was radiation time, and the smallest influence factor was concentration of H₃PO₄. The largest influence factor to yield was radiation time, the secondary factor was microwave power, and concentration of H₃PO₄ was the last one. The optimum condition was microwave power 120W, radiation time 260S, and concentration of H₃PO₄ 30%⁴0% for activated carbonmade from mixed sludge. The better condition of activated carbon made from surplus sewage sludge was microwave power 480W, radiation time 315S, the concentration of H3PO4 40%⁴5%.Characteristic of sewage sludge-based activated carbons made under the best operation were tested. The sewage sludge-based activated carbons were mainly mesoporous. The surface area of ACSS-1, which made from mixed sludge was 192 m2/g, and the pore volume was 0.30ml/g, and the average pore diameter was 6.25nm. The surface area of ACSS-2, which made from surplus sludge was 168 m2/g, and the pore volume was 0.37ml/g, and the average pore diameter was 8.8nm.The sewage sludge-based activated carbons from were used to adsorb dye dilute aqueous solution, the dilute aqueous from TNT red water and the discharged water from wastewater plant. The effect of pH value, contacted time, activated carbon's amount on the adsorption efficiency were studied. The adsorption isotherm was also discussed. It could be get the following conclusions that the optimum pH of ACSS-1 was 11, the optimum pH of ACSS-2 was 12, equilibrium of ACSS-1 was reached with 60 min, the adsorption equilibrium time of ACSS-2 was 40min, the adsorption isotherm was more fit Freundlich model than Langmuir model for the dye dilute aqueous solution. For the dilute aqueous from TNT red water, the optimum pH of ACSS-1 was 3 and 9, the optimum pH of ACSS-2 was 4 and 9, equilibrium of ACSS-1 was reached with 80 min, the adsorption equilibrium time of ACSS-2 was 60min, the adsorption isotherm was well fit Langmuir model. For the discharged water from wastewater plant, when the amount of ASCC-1 and ACSS-2 reached 8g/L, the removal rate of CODcr was 56% and 87%, and the adsorption isotherm was fit Langmuir model.Sewage sludge was treated by microwave in existence of phosphorous acid, which proposed a new way for utilization of sewage sludge, and built foundation for further development of microwave sewage sludge-based activated carbon.