Extraction of hexavalent chromium from wastewater using novel rotating zigzag contactor

HIGEE (an acronym of high gravity) devices have attracted considerable attention among the researchers due to its immense process intensification capability. In order to achieve desired process efficiency this technology replaces terrestrial acceleration by centrifugal one (typically 1000g) which can be attained by rotating a specially shaped rigid bed. This study focuses on liquid-liquid extraction of hexavalent chromium [Cr(VI)] from wastewater using aliquat-336 as an extractant inside a novel rotating zigzag contactor (RZC). Extraction efficiency of RZC were observed with the variation in pH (2-10), rotational speed (300-1100rpm), aqueous phase (0.4-1.2 L-min(-1)) and organic phase (0.05-0.15 L-min(-1)) flow rate, feed (25-200 mg-L-1) and extractant (0.5-1.25 vol%) concentration. The results obtained from this study showed a significant improvement in extraction efficiency (85-99%) with the variation in rotational speed (300-1100rpm). It was observed that the efficiency increased with rotational speed, total flow rate and the organic phase flow rates but decreased with the feed concentration and pH of the aqueous solution. Comparison with some conventional contactors reveals that the extraction efficiency obtained in RZC was nearly 40-50% higher under the same operating conditions.