Synthesis of Thiol Functionalised γ-Al o2 as adsorbent for Cd2+

The modification of gamma alumina (_-Al2O3) derived from used aluminium (Al) beverage cans as an adsorbent for wastewater treatment is an eco-friendly strategy that supports the Al recycling initiative in Malaysia. This research aimed to evaluate the potential of thiol functionalised _-Al2O3 as an adsorbent for Cd2+ removal. The research was conducted with three objectives: first the synthesis of _-Al2O3 from Al beverage cans (later named as _-Al2O3(S)) and thiol-functionalised _-Al2O3 (_-Al2O3-BDMT and _-Al2O3-TgA) from both commercial and synthesised _-Al2O3 (named _-Al2O3(C) and _-Al2O3(S) respectively); secondly, the characterisation of the adsorbents and finally the equilibrium adsorption studies in aqueous solution towards Cd2+, which includes adsorption isotherm profile and kinetics. From the adsorption studies, all adsorbents demonstrated an optimum Cd2+ removal at pH 6 at an initial Cd2+ concentration of 10 mg/L. However, _-Al2O3(C)-BDMT, _-Al2O3(S)-BDMT, _-Al2O3(C)-TgA and _- Al2O3(S)-TgA recorded different equilibrium times (30 min, 20 min, 30 min, and 20 min, respectively). These results indicated that each adsorbent had different performance during the adsorption studies. All the adsorbents were best fitted with the linearised Freundlich isotherm model (regression coefficient, R2 between 0.991-0.999) and the pseudo-second order adsorption kinetics regression coefficient, R2 between 0.996-0.999). From the adsorption studies, _-Al2O3(S) was on par with _-Al2O3(C) in removing Cd2+. The characterisation and adsorption studies concluded that the thiolmodified _-Al2O3 demonstrated greater surface characteristics and adsorption capacity towards Cd2+ as compared to _-Al2O3, with _-Al2O3(C)-BDMT showing the highest adsorption capacity (463.767 mg/g). These research outcomes could pave the way for the development of cost-effective adsorbents for water treatment using recycled material.