Treatment of pyrite cinder sludge after usage in dye degradation: Feasibility study

Abstract

Over the last couple of years greener concept in hazardous waste management is gaining increasing relevance. This term refers to the processes and activities that have little or negligible impact on the environment. The aim of this study is to systematically quantify the physical and chemical properties of the solidified/stabilized (S/S) sludge generated in dye effluent treatment, when pyrite cinder is used as catalytic iron source in the modified heterogeneous Fenton process. S/S treatment was performed by using two clay materials (kaolinite and bentonite) and lime in order to immobilize Cu, Pb and Zn present in the sludge. Microwave assisted sequential extraction procedure was employed to assess potential metal mobility and risk to the environment. In order to determine the long-term behaviour of the S/S mixtures, the semi-dynamic ANS 16.1 leaching test was performed. S/S effectiveness was evaluated by measuring the cumulative fractions of leached metals, effective diffusion coefficients - De and leachability indices - LX. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were implemented to elucidate the mechanisms responsible for immobilization of the Cu, Pb and Zn. This analysis confirmed the formation of compact matrices and pozzolanic products. Compressive strength measurement also proved the treatment efficacy. It can be concluded that the S/S technique has significant potential for solving the problem of hazardous industrial waste and its safe disposal.