Utilization of municipal sludge in adsorption of cadmium and phenol in Saudi Arabia

Activated carbon (AC) was produced from municipal sewage sludge collected from Al-Khobar wastewater treatment plant in the Eastern Province of Saudi Arabia. The best produced AC sample that was obtained from ZnCl2 activation at an impregnation ratio of 1:1 and activation temperature and time of 700 degrees C and 60 min, respectively, was tested for its capability in the removal of Cd2+ and phenol from a synthetic wastewater. Adsorption experiments were conducted in single solute systems for both contaminants, where effects of operational parameters such as pH, initial concentration, adsorbent dosage, and contact time were investigated. The experimental results revealed that removal efficiencies of 28 and 56% were achieved for Cd2+ and phenol, respectively, at optimum conditions of pH value of 5.5, AC dosage of 0.15 g per 50 ml and contact time of 120 and 720 min for Cd2+ and phenol, respectively. Isotherm modelling of the experimental data showed that Cd2+ adsorption can be well described by the Freundlich isotherm, while phenol adsorption was well described by the Langmuir isotherm. The mechanism of adsorption of both contaminants was ascribed to chemisorption, which was based on the adsorption data that fitted well to the pseudo-second order model.