Establishment of severe environmental roles by governments and economical consideration have caused a great attention toward removal of pollutants from industrial wastes. The wastewaters of textile industries are large in volume and have different quality. Therefore, their treatments are complicated. Removal dyes from wastewaters has been performed by coagulation and flocculation, oxidation, membrane filtration, ion exchange, electrolysis and adsorption processes. The best treatment choice among these methods depends on dye concentration in the wastewater and treatment costs. Adsorption is widely used for removal of dyes from wastewater because of its simplicity and low cost. Many natural and synthetic adsorbents are used for this method. Recently, natural adsorbents have gained importance, and the choice of these materials depends on their availability, cost and adsorption capacity. In this study, removal of dye from aqueous solutions by adsorption onto charred dolomite, and activated carbon (AC) was investigated as a function of initial dye concentration (in the range of 50-200mg/L), initial pH (in the range of 2-8), stirring speed (in the range of 50-200rpm) and adsorbent dosage (in the range of 2-8g/L) in a batch system. The optimum conditions were found by Taguchi approach. Also, sorption data of dyes are described by Langmuir, Freundlich and BET models and the equilibrium process is described well by the Freundlich isotherm model. The principle adsorption takes place at the first time of the adsorption process. In optimum conditions, the maximum removal of dye obtained from batch studies for the adsorption of Acid Red 88 on charred dolomite (initial concentration: 50mg/L, initial pH: 6, stirring speed: 200rpm and adsorbent dosage: 8g/L), for Acid Red 88 on AC (initial concentration: 200mg/L, initial pH: 2, stirring speed: 100rpm and adsorbent dosage: 4g/L), for Reactive Red 29 on charred dolomite (initial concentration: 50mg/L, initial pH: 2, stirring speed: 200rpm and adsorbent dosage: 6g/L) and for Disperse Red 151 on charred dolomite (initial concentration: 100mg/L, initial pH: 4, stirring speed: 200rpm and adsorbent dosage: 8g/L) was more than 99%. All of experimental factors was statistically significant on dye removal, while adsorbent dosage was not statistically significant for adsorption of Acid Red 88 onto AC. Overall, it can be concluded that the charred dolomite perform well for the removal of acid, reactive and disperse dyes from wastewaters as a low cost adsorbent.
