Chromate removal by river sand

Hexavalent chromium can cause skin disease, respiratory tract infection, and cancer. Treatment methods, using river sand (ordinary and microorganism activated river sand, for short ORS and MARS) as adsorbent and reductant, were tested as cost-effective means for removal of Cr(VI) from wastewaters of electroplating facilities. Batch experiments were conducted to examine the effects of contact time, pH and temperature on the removal efficiency of Cr (VI). Results showed that MARS was more effective than ORS for the removal of Cr(VI). It had a greater sorption capacity than ORS and required longer contact time to reach equilibrium. Increases in pH and temperature had adverse effects on the removal efficiency of Cr (VI). Subsequently, two column tests were performed. One column received sewage and electroplating wastewater alternately and the other received sewage and electroplating wastewater in combination. The experimental results showed that the latter was more effective than the former and the removal of Cr(VI) was due to the combination of surface adsorption, reduction, complexation and chelation.