Synthesis of zeolite-A from bagasse ash and removal of heavy metals from industrial effluents

Abstract

Zeolite-A was indirectly synthesised from bagasse ash from the sugar industry using a hydrothermal conversion method. Active silicon dioxide (SiO2) and aluminium oxide (Al2O3) were obtained from the bagasse ash and aluminium sulfate, respectively. The synthesis involves the dissolution of amorphous aluminosilicate releasing [SiO2(OH)2]−2 and Al(OH)−4, the formation of sodium aluminosilicate gel and the crystallisation of zeolite. Results showed that amorphous silica obtained from ash dissolved completely during the first hour of the crystallisation stage. With the increase in crystallisation time up to 4 h, a slight change in the composition of zeolite crystals was observed, due to the dissolution of zeolite-A. The synthesised zeolite showed an excellent adsorption capacity for heavy metal cations from aqueous solutions, especially for Pb++ (187.25 mg/g), followed by Cu++ (63.22 mg/g). This observation indicates that the zeolite-A synthesised from bagasse ash can be used as a low-cost and relatively effective adsorbent for the remediation of heavy metals from the effluents of chemical industries before being released to the environment.