Determination of Optimum Exposure Time and pH for dye Adsorption using an Adsorbent made of Sewage Sludge

In this research feasibility study of using sewage sludge as an adsorbent for the removal of Acid Blue 25 dye was carried out. Sewage sludge was first dried in an oven at 105° C for 24 hours. Then the dried sludge was washed with HCl (98%) for two hours and then with distilled water to a pH of approximately neutral. Then, it was carbonated and activated in a Nitrogen-based electric furnace at 600C° for two hours. Molecular Structure of the adsorbent was determined through XRD technique. The results of XRD revealed that the adsorbent produced for this study was mainly composed of SiO2. The experiments were carried out at pH of 3, 5, 7, 9, and 11 and for exposure times of 0, 15, 30, 60 and 120 minutes in the process of dye removal. In all steps of the experiment, dye solutions with different initial concentrations of 100, 200, and 300 mg/L and the adsorbent dosage of 10 g/L were constantly used. Finally, pH of 3 and exposure time of 30 minutes were found as the optimum condition. The maximum dye removal (97%) was achieved at 100 mg/L of dye solution. Adsorbent specifications follow Langmuir and Freunlich isotherm model.