Effect of sulphate and nitrate anions on heavy metal immobilisation in ferronickel slag geopolymersEffect of sulphate and nitrate anions on heavy metal immobilisation in ferronickel slag geopolymers Peer-Reviewed Journal Publication Δημοσίευση σε Περιοδικό με Κριτές 2015-11-022013enIndustrial wastes need to be valorised and new techniques need to be developed for the production of secondary materials or immobilisation of hazardous elements in order to improve sustainability of the respective industrial sector. In the present experimental study the effect of monovalent and divalent anions, such as sulphate and nitrate, on heavy metal immobilisation in ferronickel slag geopolymers was investigated. Low calcium electric arc ferronickel slag was geopolymerised using KOH and Na2SiO3 as activators, in the presence of limited quantities of sulphate and nitrate salts of Pb, Cu, Cr or Ni. Gel properties, final strength of the specimens produced and immobilisation of heavy metals were determined, in order to explore the potential of geopolymerisation in developing a hazardous waste encapsulation matrix. In addition, the Toxicity Characteristics Leaching Procedure was used to assess the potential toxicity of the produced geopolymers. The experimental results indicate that even limited quantities of sulphates and nitrates in the starting mixture affect adversely geopolymerisation of ferronickel slag. XRD (X-ray diffraction), SEM (scanning electron microscopy) and FTIR (Fourier transform infrared spectroscopy) studies were carried out to identify new phases, reactions taking place and thus elucidate the main mechanisms involved.Δημοσίευση σε επιστημονικό περιοδικό http://creativecommons.org/licenses/by/4.0/Applied Clay Science73103–109 Komnitsas Konstantinos Κομνιτσας Κωνσταντινος Zaharaki Dimitra Bartzas Georgios Elsevier Geopolymer Ferronickel slag Heavy metals Anions