No abstract

The aim of the present study was to investigate the removal of reactive dyes, Black 5 and Orange 16, through a combined coagulation/adsorption process on activated carbon. A coconutbased powdered activated carbon was used as an adsorbent and aluminum chloride was chosen as the coagulant. In order to obtain the best removal conditions for these dyes, the influence of the following parameters were investigated: coagulant dosage, aqueous solution pH, addition of sodium chloride and the application of increased temperature plus sodium chloride. Adsorption results for the reactive dyes were analyzed by Langmuir and Freundlich isotherm models and showed good correlation. The presence of sodium chloride in the mixture resulted in significant adsorption improvement. The influence of increased temperature plus sodium chloride on the dye removal from aqueous solution showed the feasibility of adsorption and its endothermic nature. Through the reactivation experiments it was verified that the adsorbent can be reused three times, consecutively, after the first adsorption with the virgin carbon. For the final evaluation of the effluent, obtained after the coagulation and adsorption process, acute toxicity tests were carried out with Daphnia magna, and the results obtained showed that the final effluent was not toxic. The combined coagulation/adsorption process was found to be an excellent option for the removal of reactive dyes.