Potential solidification/stabilization of clay-waste using green geopolymer remediation technologies

Solidification and stabilization is a remediation technique for hazardous wastes that promotes resource recycling and reduces the environmental burdens of waste management. To accomplish this successfully, different types of wastes or hazardous materials are treated with different binders and techniques. This study proposed a green remediation approach to treat and recycle clay-waste by using solidification/stabilisation which is enhanced by the injection of two chemical solutions, sodium hydroxide (NaOH) and sodium silicate (Na2SiO3) and partial addition of low-calcium class F fly ash. The unconfined and compressive strength tests were conducted to investigate the mechanical properties of the developed geopolymer pastes at different time conditions. The change in the microstructures was characterized by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Microanalysis (EDX). The effects of Si/Al ratio on the compressive strength and the microstructure of the solidified geopolymer product are also summarized in this paper. In addition, the normalized weight variations after 28 days curing in deionized water (pH = 7.0) was highlighted and the leaching behavior of heavy metals in the clay-waste based geopolymer specimens after soaking up to 14 days was examined with atomic absorption spectroscopy. Experimental results demonstrate the potential treatment, solidification and stabilization of the clay-waste by employing geopolymer remediation technologies and the optimum compressive strength can be obtained with a ratio of 30% fly ash. The collected clay-waste has strength of up to 5-20 MPa at 28 days curing which meet suitable mechanical properties and compact microstructure characterization. (C) 2018 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.