The Research On Stabilization Of Heavy Metals And Adsorption Of Tetracycline With Vermicompost Of Sewage Sludge

This study mainly researched the vermicomposting of sewage sludge from municipal waste water treatment plant,focused on the changes of physical and chemical properties of vermicompost and the total amount and morphological change of heavy metals during vermicomposting of sludge.The static equilibrium adsorption characteristics and kinetic adsorption characteristics of heavy metal lead,cadmium and tetracycline were investigated.Fourier transform infrared spectroscopy(FTIR),scanning electron microscopy(SEM),and BET specific surface area analyzer were applied to explained the adsorption mechanism.The heavy metal toxicity leaching test(TCLP)was carried out by combining the vermicompost with the sediment of Dongting Lake to explore the change of the leaching content of heavy metals in the sediment.The results showed that the moisture content in vermicompost is finally maintain about 50%,and the conductivity(EC)is steadily increasing.The total amount of heavy metals in the compost product was lower than that of the initial substrates.The analysis of heavy metal morphology showed that the content of heavy metal and other substances decreased significantly and the exchangeable content decreased.The single and mixed adsorption equilibrium equations of heavy metal lead(Pb),cadmium(Cd)and tetracycline(TC)can be fitted with Freundlich and Langmuir equation.The maximum adsorption capacity of the compost product can reach to 12.8 mg.g-1,85.2 mg.g-1 and 42.94 mg.g-1 for lead,cadmium,tetracycline respectively.Compared with the single adsorption system,the mixed adsorption capacity of Pb showed a slight increase of Pb and decrease of Cd and TC.The adsorption kinetic model with S10 as the object of study is suitable for pseudo-second-order model.SEM scanning electron microscopy(SEM)showed that the composting characteristics of vermicompost were changed after the adsorption process.The BET specific surface area analysis showed that the total specific surface area was decreased and the adsorption mechanism was mainly surface adsorption.The results showed that the addition of vermicompost could reduce the leaching amount of lead(Pb),manganese(Mn)and cadmium(Cd)in the sediments,and the maximum removal efficiencies were 88.2%,43.4%and 39.1%,respectively.