Reduction of Water Color in a Spinning Disc Reactor

Abstract

In this study, spinning disc (SD) technology was successfully applied to a synthetic water to remove its color. The preliminary data performed in a regular mixing system using a potential adsorptive material, i.e., double-layered hydroxide of a ZnAlLDH type, did not provide a significant decrease (no more than 10–15%) in the water color content. Thus, ZnAlLDH (2 g/L) was added to the synthetic water containing 50 mg/L Rosso Remazol RB dye that was subsequently fed onto the spinning disc. The SD efficiency was investigated at four different water-supplying flow rates (5.76, 6.00, 7.44 and 8.16 L/h) and four different disc rotational speeds (100, 250, 500 and 800 rpm). The best color removals of 44.39%, 41.14% and 42.70% were obtained at 6 L/h and 250 rpm, 6 L/h and 500 rpm and 5.76 L/min and 800 rpm, respectively, in only a 50 min working time period. In addition, for a relatively low color concentration in water (~30 mg/L dye) and at the lowest electric power consumption, Fenton oxidation was performed in the SD setup for a more advanced color removal of 62.54% within a 50 min time period. Furthermore, two other materials, titanium and aluminium oxides, underwent similar investigations in the SDR setup, and the obtained results were comparatively discussed. The FTIR spectra of each solid material before and after the SD technology application were used to appreciate the dye-retention performance of each material used. The obtained results indicated that the spinning disc technology correlated with the tested materials could significantly improve the water color (over 40% color reduction), this level of color reduction being higher than that obtained following a coagulation–flocculation test (20–28% color reduction), an ion exchange (25–30% color removal) or a sand filtration step (15–20%) applied to the same dye-based water sample. A further increase in color removal could be achieved by using an additional oxidative step (more than 65% color reduction).