Optimisation of the removal conditions for heavy metals from water: A comparison between steel furnace slag and CeO2 nanoparticles

Abstract

This work studies an innovative approach to water treatment by using recycled electric induction furnace slag for the removal of Cd, Cr and Pb-ions and comparing the results to a treatment with specifically developed CeO2 nanoparticles. The slag was characterised by X-ray Fluorescence, X-ray diffraction and SEM. The effects of initial ion concentration and adsorbent dose were investigated according to an experimental design. Adsorption tests were carried out with ion solutions present in concentrations ranging from 1 to 10 mg/L and adsorbent doses from 0.064 to 0.64 g/L. The removal mechanism for CeO2 is adsorption. For slag, literature proposes a mechanism involving chemical adsorption of Cd2+, Cr6+ and Pb2+ by silanol and aluminol groups; precipitation in the form of metal silicates formed between the cations and silicic acid leached from the slag provides an alternative explanation. The removal efficiencies with nanoparticles are higher than reported for any other adsorbent (including slag) under all test combinations for the three metals investigated. The maximum removal efficiency with slag was 74% for Cr6+, 64% for Cd2+ and 34% for Pb2+, comparable to, or higher than, other materials reported in literature. The treatment with slag has clear promises in terms of economy and scalability.