Cadmium Biosorption in a Batch Reactor Using Excess Municipal Sludge Powder

This study was conducted to investighate the adsorption of Cadmium from aqueous solutions by using the powder of excess sludge (biosolid) from municipal wastewater, at 24 to 26°C, a pH value of 2 to 6, over a contact time of 5-420 minutes, and at 50 to 300 rpm stirring rate in a batch reactor on the laboratory scale. The pretreatment of biosolids consisted of dewatering, grinding, and grainsizing with sieves (mesh dimensions between 50 and 120). According to the results, the best conditions for biosolids to adsorb Cadmium was pH=4, 120 minutes of contact time, and a stirring rate of 200 rpm. Cadmium adsorption kinetics followed the pseudo second order model. Maximum equilibrium adsorption was observed after two hours. The adsorption isotherm was in accordance with the Langmuir model. Maximum Cadmium adsorption capacity of biosolids (qmax) was estimated at 0.38 m-mol/g of dry biosolid (41.5 mg/g) and the Langmuir constant (kd) was found to be 0.1044 m-mol/lit (11.37 mg/lit)