Alkali-activated composites of calcium carbide and black rice husk ash for immobilizing electroplating sludge

This study investigated the use of two waste products, black rice husk ash (BHA) from biomass power plants and calcium carbide residue (CCR) from acetylene gas production as an alkali-activated binder to solidify and stabilize the heavy metal plating sludge (PS) from electroplating plants. Optimum strength of the alkali-activated product was obtained using a weight percentage ratio of CCR to BHA of 60:40. CCR-BHA compacts containing 50 wt % PS developed strength after 3 days, but the addition of 2 wt % Na2SiO3 or 4 wt % Na2CO3 developed strength in all the samples after 1 day. The CCR-BHA paste containing 50 wt % PS developed a 7-day strength >0.35 MPa in the sample containing 4 wt % Na2SiO3 and the same strength was developed after 3 days in the sample containing 4 wt % Na2CO3. The Cr concentration of leachate from all the samples was greater than the regulatory limit except for the CCR-BHA paste containing 50 wt % PS and 4 wt % Na2CO3. After contacted all samples with synthetic acid rain, less corroded surface was observed from sample containing Na2SiO3 and Na2CO3. (c) 2018 American Institute of Chemical Engineers Environ Prog, 37: 1901-1907, 2018