Encapsulation in ceramic material of the metals Cr, Ni, and Cu contained in galvanic sludge via the solidification/stabilization method

The stabilization/solidification (S/S) process at the semi-industrial level in the recovery of sludge from industrial wastewater treatment plants used in galvanic processes with a high content of the metals Cu, Cr, and Ni was evaluated. As the encapsulating agent, red clay, traditionally used in the manufacture of ceramic tiles, was used. The capacity of the retention of the metals Cu, Cr, and Ni in the ceramic material was determined for different contents of sludge: 1%, 5%, and 10% by weight of sludge compared with the ceramic material without sludge. The sintering process was carried out at two temperatures, 1120 °C and 1190 °C, in a semi-industrial roller kiln with a firing cycle of 30 min. The effectiveness of the ceramic for the retention of the metals Cu, Cr, and Ni was determined on the basis of the leaching test in order to characterize the toxicity (TCLP) according to norm EPA 1311. For the characterization of the ceramic materials, technical, mechanical, and micro-structural properties were evaluated. The results show that at 1190 °C, around 99% of the metals is retained, and at 1120 °C between 95% and 99% is retained.