Effect of Cement Type on Performance of Ferrous Iron–Based Degradative Solidification and Stabilization

Abstract

Abstract

Ferrous iron–based degradative solidification and stabilization is a modification of conventional solidification and stabilization in which organic compounds are destroyed while inorganic compounds are immobilized. The effect of using different sources of Portland cement (PC) (i.e., CPC, TPC, LPC, QPC) on degradation of tetrachloroethene (PCE) was examined and the solids produced in the process were examined by instrumental analyses (X-ray diffraction, scanning electron microscopy, scanning electron microscopy with energy-dispersive spectrometry). Regardless of the type of PC source, more than 90% of initial PCE were transformed within a month. Each showed different types of PCE degradation kinetics. Use of CPC and TPC resulted in pseudo-first-order kinetics for PCE degradation and the use of QPC resulted in second-order kinetics. In the case of LPC, pseudo-first-order kinetics was observed in cement slurries (cement and water mixture, 10% [w/w]) and second-order kinetics in cement extracts (acid-digested cement solution). Iron added to the cement as an additive was selectively associated with hexagonal thin plate particles, which appear to be aluminate-ferrite-mono phases. Depending on PC sources, different types of aluminate-ferrite-mono phases were associated with iron: calcium aluminum hydroxide hydrate dominated the solids produced in slurries prepared with TPC, QPC, and LPC, whereas calcium chloroaluminate (Friedel's salt) was the major phase found in solids made with CPC.