Cadmium removal from aqueous solutions using pyrolyzed activated sludge of petroleum refining industry

The presence of heavy metals such as Cd in the environment is harmful for living organisms. In this study, the activated sludge from wastewater treatment plant of Tehran oil refinery (Iran) was used as the feed stock for production of carbonaceous sorbent using pyrolysis process. The optimum conditions of Cd removal by pyrolyzed activated sludge (PAS) were determined using Taguchi method. The highest Cd removal by PAS (up to 99%) was obtained under optimum conditions. Langmuir and pseudo-second order were the best isotherm and kinetic models for description of Cd sorption by PAS, respectively. It is concluded that the pyrolysis of activated sludge could be an approach to produce a low-cost sorbent having the potential to remove Cd from contaminated solutions. However, more researches are needed to investigate the capacity of the sorbent for removal of various heavy metals and their interactions.