Efficient removal of chromium from electroplating sludge by a novel combined process of alkaline oxidizing roasting, water leaching and on-line adsorption

Chromium-bearing electroplating sludge (ES) is a typical hazardous waste that poses significant environmental risks due to the toxic and carcinogenic nature of chromium. In this study, Cr extraction is performed by roasting with Na2CO3 and water leaching from ES, and finally recovered by an on-line adsorption process by using an eco-friendly material. Under Na2CO3 roasting and water leaching, 82.1 % of Cr was leached out, with conditions of 800 ℃, Na2CO3 dosage amount at 30 %, and a residence time of 2 h for the roasting step, and solid-liquid ratio of 1:2 for the water leaching step. The results of the column adsorption tests indicated that FH/ SCB exhibited superior adsorption performances toward Cr (VI) with a maximum adsorption capacity of 20.5 mg/g, and its adsorption isotherm was matched with the Laugmuir model. About 97.4 % of Cr was recycled from the ES under the dynamic on-line adsorption process, furthermore, the total content of Cr in the final effluent was lower than wastewater discharge standards of 0.5 mg/L. In conclusion, this combined method presents an alternative approach for the eliminating, detoxifying, and reusing of chromium-bearing ES.