Investigation on the copper ion removal potential of a facile-fabricated foamed geopolymer sphere for wastewater remediation

[Display omitted] •Direct moulding method is feasible to produce foamed geopolymer sphere.•Foaming enhances the Cu(II) removal efficiency of geopolymer sphere by about 45%.•Foaming improves the Cu(II) removal capacity of geopolymer sphere by six times.•The maximum Cu(II) removal capacity of foamed geopolymer sphere is 37.9 mg/g. Heavy metal contamination is regarded as one of the most serious hazards to the environment and living organism. The scenario is exacerbating especially due to the continuous development. Therefore, the goal of this study is to examine the copper ion removal potential of a facile-fabricated foamed geopolymer sphere. The foamed geopolymer sphere is synthesized via direct moulding method, using locally available materials of fly ash and calcined kaolin as the starting materials. The foamed geopolymer sphere is beneficial in terms of the ease of use where it can be used in packed bed system directly and the retrieval process upon exhausted is much simpler. Due to the plentiful binding sites created by foaming of the geopolymer sphere, the copper ion removal efficiency increases from 47.5% to 92.8% and the removal capacity improves by six times. pH 5 is identified to be the best pH for copper ion removal utilizing the foamed geopolymer sphere. The maximum copper ion removal capacity found experimentally is 37.9 mg/g, which is satisfactory compared to the foamed geopolymer spheres prepared via suspension and solidification. Meanwhile, increasing the dosage of the foamed geopolymer sphere can increase the foamed geopolymer sphere’s removal ability when concerning high copper ion concentration. Pseudo second-order kinetic and Langmuir isotherm models are found to describe well the adsorption process.