Utilisation of wastes for low-cost synthesis of chitosan composites with nanosized sodium aluminium silicate hydrate and geopolymer/zeolite A for the removal of Hg(II) and Pb(II) ions from aqueous media

In this work, nanosized sodium aluminium silicate hydrate and geopolymer/zeolite A samples were obtained using hydrothermal and precipitation methods, respectively. In these methods, aqueous solutions of sodium hydroxide were utilised for the extraction of aluminium and silicon from waste aluminium cans and rice husk ash, respectively. Also, chitosan composites with the aforementioned samples were fabricated. The properties of the obtained nanosized samples and their chitosan composites were identifiedutilizingFT-IR, XRD, HR-TEM, and FE-SEM tools. The average crystallite size of the sodium aluminium silicate hydrate and geopolymer/zeolite A samples is 39.72 and 22.56 nm, respectively. Moreover, the obtained nanosized samples and their chitosan composites were utilised as adsorbents for the effective uptake of Pb(II) and Hg(II) ions from aqueous media. The maximum capacities of sodium aluminium silicate hydrate, geopolymer/zeolite A, sodium aluminium silicate hydrate/chitosan, and geopolymer/zeolite A/chitosan adsorbents towards Hg(II) ions are 88.65, 125.94, 168.35, and 211.86 mg/g, respectively. The maximum capacities of the previous adsorbents towards Pb(II) ions are 123.61, 160.51, 211.86, and 269.54 mg/g, respectively. Furthermore, the uptake processes of Pb(II) and Hg(II) ions using the obtainednanosized samples and their chitosan composites are exothermic, chemical, spontaneous, and well-matched with Langmuir equilibrium isotherm and pseudo-second-order kinetic model.