Heavy metals are one of the most important pollutants in industrial wastewater. Chromium is one of the hazardous metals which is used in electroplating, leather tanning, metal finishing and chromate manufacturing industries. The commonly used procedures for removing metal ions from aqueous streams include chemical precipitation, coagulation, ion exchange, reverse osmosis and adsorption. In this study, a comparison of three widely used isotherms (the Langmuir, Freundlich, and BET) was examined in an experiment using Cr (VI) ion biosorption onto excess municipal sludge. Experiments were carried out as a function of pH, initial concentration, biosorbent dosage, contact time, and agitation speed. A removal of 96% was achieved under optimised conditions. The mechanism of metal sorption by adsorbent gave good fits for Freundlich and Langmuir models with max
value of 41.69 mg/g.
Keywords: biosorption, chromium (Cr (VI)), isotherm, Freundlich model, Langmuir model, BET model, heavy metal, excess municipal sludge