Removal of chromium hexavalent from rinsing chromating waters electrochemical reduction in a laboratory pilot plant

In this work, experiments in a 16 L operating volume laboratory pilot plant with ring iron rotary electrodes were performed, obtaining an overall kinetic equation rate of hexavalent chromium reduction concentration and current density-dependent. Other scale-up criteria such as Reynolds' number were also evaluated to ensure a completely stirred reactor at low energy expenditure. A dimensionless N_E is a relationship between liquid properties and the electric charge supplied to the system. The number, which depends on the rotation iron ring electrode speed number and the current density, is proposed to be used as scale-up criterion. It was found that at N_Re = 42,179 (130 rpm rotation electrodes rate) and at NE = 9.8 × 105 (current density of 113 A/m²), complete mixing was reached at minimum energy spent and the process becomes more efficient. In addition, it was found that the higher the current density, the less treatment time and less energy spent on agitation. After the electrochemical treatment the CrVI concentration in the rinsing wastewater was less than 0.5 mg/L.