| With the development of industry, agriculture, and the rapid process of urbanization, water pollution caused by heavy metals comes to be an increasingly serious problem in our daily life, and it causes the environmental and ecological problem worsen. There is a dramatic increase in the contents of sewage and the waste sludge. The random disposal of waste sludge could be a kind of a waste of land, which might result in the pollution, for the second time, and the useful element in sewage sludge won't be fully developed.Biosorption is a newly developed water treatment method. The used raw materials are resourceful, economical and can be used with simple equipment. Biosorption is usually easy to operate with great efficiency and large absorption capacity and good selectivity. It is especially good for the disposal of water of low-concentrated heavy metal. It is also valued for restoring noble metal. Thus it receives great attention from world-wide researchers, and will definitely enjoy a promising prospect and a wide application foreground. It is a kind of prospective wastewater treatment technology that the waste sludge absorbs the wastewater containing heavy metal ion. When the metal concentration in the wastewater is lower than 100 mg/L, biosorption is more effective.The subject mainly studies on the influence of pH value, adsorption time, sludge doses, temperature, initial ions concentrations and the influence of pretreatment of the absorption of heavy metals ions by waste sludge. The nature of waste sludge was also evaluated by SEM and FT-IR analysis. In addition, the work focusing on the reducing mechanism has been evaluated. The results of this research are as follows:(1)The pH value is an important factor on its capabilities of the detoxification and adsorption, and the optimal pH value is 1.0～2.0. The adsorption process of chromium (Ⅵ) is very fast, and the optimal adsorption time is 30 min. When the sludge dose is 8 g/L, the removal ration of 50 mg/L chromium (Ⅵ) is 99.65% for 30 min at pH value 1.0 and 30℃. The adsorption capacity is independent when the temperature from 20～60℃, and it can be described by Langmuir and Freundlich isotherm equation. After biosorption, SEM (scanning electron microscopy) and EDS (energy dispersive spectrometry) analysis the microstructure of waste sludge remains intact but the major components change a lot. The FT-IR always indicated that -COOH, -OH and -NH2 groups were involved in the biosorption process.(2) It is concluded that the influence of temperature on the biosorption of heavy metal is not significant, but pH value and sludge doses affect the biosorption efficiency significantly. Also it is found that the biosorption of heavy metal is a rapid process. At the same time, The sorption isotherms of heavy metal adsorption have been calculated. It has higher biosorption efficiencies of Cr6+ than that of Cu2+ and Ni2+.(3) Effects of concentration of initial chromium (Ⅵ) concentrations and pH value at different times on ability of sludge of chromium(Ⅵ) removal were investigated in the continuous experiments. The results indicated that the greater concentration, the lower removal rate, initial pH significantly affects the residual sludge in a continuous reactor Cr (Ⅵ) of the treatment effect. Low pH value is conducive for Cr (Ⅵ) removal.(4) The concentration of Cr (Ⅵ) can be reduced by Cr (Ⅲ) redox reactions and Cr (Ⅵ) adsorption. The removal of Cr (Ⅲ) is mainly by the formation of chromium hydroxide precipitation and adsorption of ECPs, as well as to the transfer of cells. Waste sludge biosorbent for Cr(Ⅵ) produced a reduction effect, generating a large number of Cr(Ⅲ). Adsorption of chromium sludge remains after the distribution of more consistent form.
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