Reduction of hexavalent chromium using L-ascorbic acid in rotating reactors

Batch results on reduction of hexavalent chromium by L-ascorbic acid have been widely reported due to manifold advantages of the reductant. In this study, continuous flow experiments were performed in three novel rotating reactors (rotating packed bed, rotating zigzag bed, and rotating spiral bed reactor) wherein centrifugal force is known to enhance micro-mixing for intensifying the reduction rate of chromium vis-a-vis traditional reactors. A multi-regression model was used to relate the percentage reduction to the parameters studied (rotational speed, flow rate, concentration of the reactants, and pH). A mathematical model was also developed to estimate the reaction rate constant. Maximum percentage reduction was achieved in the rotating spiral reactor. Experimental results suggested that the volume of conventional reactors (continuous stirred tank reactor and fixed bed) could be significantly reduced by rotating ones.