Solidification of Metal Finishing Slurry with Cement

Abstract

From July, 1986 to March, 1987, the author developed laboratory, tests on cementation of electroplating wastewater treatment sludges. Perfomed at the laboratories of Escola Politécnica of the University of São Paulo and of CETESB, tests were conducted with three types of cement produced in Brazil: CPC - Portland Cement, POZ pozzolanic cement and CAF - blast furnace cement. The tests had the following steps:–characterization of electroplating industry wastewater treatment sludge and study of the sludge - cement mixtures;–preparation of sludge - cement mixtures with 3 different water/cement ratios;–measurements of mixture consistency with Casagrande soil mechanics equipment;–determination of leaching quality and resistance to compression of solidified specimen at 3 ages;–analytical determination in the sludge-cement mixture;–test for solubility in water;–analytical determination of cyanide and heavy metals in the cure water of specimen. Results showed that solidification with cement is an efficient technology for the fixation of toxic metal ions such as Cd, Hg and Pb and other metals such as Cr, Ni, Cu or Zn present in large concentrations in electroplating wastewater treatment sludges. With the only exception of Al+++ the other metallic ions determined in the leachate showed concentrations below drinking water standards. As to mechanical resistance after 90 days, the sludge - cement mixtures presented a performance similar to that of structural concrete.