Investigation of fly ash for sorption of copper ions in multiple contaminant system: An implication on re-use of waste material under concept of sponge city

Many previous studies of soil contaminant treatment have primarily analysed heavy metal contaminant ion retention in fly ash (FA) in a single isolated medium whereas, factoring out the competitive systems. This study seeks to determine the interaction of the heavy metal copper ion (Cu⁺²) with fly ash under single and competitive systems and also to expound its impact on fate prediction. Freundlich and Langmuir non-linear isotherms were adopted to quantify the sorption results. The retardation factor attained from Freundlich isotherm predicts more than Langmuir. The Langmuir isotherm break-through-curves (BTC) was slightly earlier in break through, with a sharp front and prolonged tailing, whereas the Freundlich isotherm appears considerably after the production of a spreading pollutant front. Freundlich retardation factors established in this study was employed to one-dimensional (1-D) solute transport model, which successfully stimulated good prediction for sorption by fly ash. Conversely, significant inconsistencies were identified from the Langmuir isotherm for evaluating the fate of Cu⁺² at high concentration range. This study recommends Freundlich isotherm for modelling transport of copper ions in a competitive environment in fly ash.