Pathak Ashish, Dastidar M G, Sreekrishnan T R
Centre for Energy Studies, Indian Institute of Technology, Hauz Khas, New Delhi, India.
J Environ Sci Health A Tox Hazard Subst Environ Eng. 2008 Mar;43(4):402-11. doi: 10.1080/10934520701795624.
The effects of sulfur concentration, initial pH of the sludge and sludge solid content on metal bioleaching were examined using anaerobically digested sewage sludge procured from a typical sewage treatment plant in Delhi, the capital city of India. Experiments on effect of sulfur concentration were carried out using 0-4 g L(-1) of elemental sulfur to optimize the concentration of elemental sulfur for efficient bioleaching. For the type of sludge (20 g L(-1) solid content) used in the present study, 2 g L(-1) of elemental sulfur was found sufficient in metal bioleaching in the following order: Zn 86%, Cu 71.5%, Mn 70%, Ni 58.3% and Cr 43.8%. Changes in pH, sulfate concentration and oxidation-reduction potential (ORP) as a function of time were experimentally monitored. A rapid change in the above parameters took place in 4-6 days followed by a slow change until the 10th day. The change in pH with time was observed to vary at different initial pH values (pH 7 to pH 3) of the sludge; however, there was not much difference in the final pH achieved and final metal solubilization which ranged from: Cu 83.6-94.2%, Ni 27.7-29.8%, Zn 89-94.8%, Mn 67.5-79% and Cr 34.1-44.1% The results of the present studies strongly indicate that using 2 g L(-1) elemental sulfur, indigenous sulfur oxidizing microorganisms can bring down pH to a value needed for significant metal solubilization. Also, bioleaching can be carried out successfully over a wide range of initial pH values of the sludge. Further, at higher sludge solid concentration than 20 g L(-1), lower metal solubilization was achieved due to the buffering capacity of the sludge.
采用从印度首都德里一家典型污水处理厂获取的厌氧消化污水污泥，研究了硫浓度、污泥初始pH值和污泥固体含量对金属生物浸出的影响。使用0 - 4 g L⁻¹的元素硫进行硫浓度影响实验，以优化元素硫浓度实现高效生物浸出。对于本研究中使用的污泥类型（固体含量20 g L⁻¹），发现2 g L⁻¹的元素硫足以实现金属生物浸出，浸出顺序如下：锌86%、铜71.5%、锰70%、镍58.3%和铬43.8%。通过实验监测了pH值、硫酸盐浓度和氧化还原电位（ORP）随时间的变化。上述参数在4 - 6天内迅速变化，随后缓慢变化直至第10天。观察到污泥在不同初始pH值（pH 7至pH 3）下，pH值随时间的变化有所不同；然而，最终达到的pH值和最终金属溶解率差异不大，范围为：铜83.6 - 94.2%、镍27.7 - 29.8%、锌89 - 94.8%、锰67.5 - 79%和铬34.1 - 44.1%。本研究结果有力地表明，使用2 g L⁻¹的元素硫，本地硫氧化微生物可将pH值降低至显著溶解金属所需的值。此外，生物浸出可在污泥初始pH值的较宽范围内成功进行。此外，在污泥固体浓度高于20 g L⁻¹时，由于污泥的缓冲能力，金属溶解率较低。
