Stabilization of chloro-organics using organophilic bentonite in a cement-blast furnace slag matrix

The application of cement-based stabilisation/solidification treatment to o rganic-containing wastes is made difficult by the adverse effect of organic s on cement hydration. The use of organophilic clays as pre-solidification adsorbents of the organic compounds can reduce this problem because of the high adsorption power of these clays and their compatibility with the cemen titious matrix. This work presents an investigation of the effect on hydrat ion kinetics, physico-mechanical properties and leaching behaviour of cemen t-based solidified waste forms containing 2-chlorophenol and 1-chloronaptha lene adsorbed on organophilic bentonites. These were prepared by cation exc hange with benzyldimethyloctadecylammonium chloride and trimethyloctadecyla mmonium chloride. The binder was a 30% pozzolanic cement, 70% granulated bl ast furnace slag mixture. Several binder-to-bentonite ratios and different concentrations of the organics on the bentonite were used. Kinetics of hydr ation were studied by measurement of chemically bound water and by means of thermal and calorimetric analyses. Microstructure and other physico-mechan ical properties of the solidified forms were studied by means of mercury in trusion porosimetry, scanning electron microscopy and unconfined compressiv e strength measurement. Leaching was checked by two different leaching test s: one dynamic, on monolithic samples, and the other static, on powdered sa mples. This study indicates that the incorporation of the organic-loaded be ntonite in the binder matrix causes modifications in the hardened samples b y altering cement hydration. The effects of the two organic contaminants ar e differentiated. (C) 2001 Elsevier Science Ltd. All rights reserved.