Removal of lead (II) ions from solution by adsorption using geopolymer derived from sugar bagasse ash (SBA)

Author

Chidawanyika, Xavier T

Title

Removal of lead (II) ions from solution by adsorption using geopolymer derived from sugar bagasse ash (SBA)

Abstract

The escalating global challenge of heavy metal pollution, particularly lead (Pb(II)) ions in aqueous environments, necessitates efficient, sustainable, and cost-effective remediation. This study addresses this by valorizing sugar cane bagasse ash (SBA), an abundant agricultural waste, into a novel geopolymer adsorbent for Pb(II) removal. Geopolymers were successfully synthesized from SBA via alkali activation. Characterization using Fourier Transform Infrared (FTIR) spectroscopy confirmed the aluminosilicate network (Si-O-T band around 1019 cm⁻¹) and the presence of crucial hydroxyl groups. X-ray Diffraction (XRD) patterns revealed a predominantly amorphous structure (broad hump around 2θ=20−30 degrees), indicative of successful geopolymerization and beneficial for adsorption. Adsorption experiments systematically evaluated Pb(II) removal under varying conditions. Optimal adsorption occurred at pH 4.5-5, attributed to increased negative surface charge. Kinetic studies showed the process followed the pseudo-second-order model (R2 =0.9973), suggesting chemisorption as the rate-limiting step. The calculated equilibrium adsorption capacity (qe) was 4.73 mg/g. Thermodynamic investigations indicated a positive standard enthalpy change (ΔHo =81.15 kJ/mol), signifying an endothermic process favored by higher temperatures. A positive standard entropy change (ΔSo=284.51 J/molK) suggested increased randomness at the interface. Consistently negative standard Gibbs free energy change (ΔGo), ranging from −2.31 kJ/mol at 20∘C to −13.69 kJ/mol at 60∘C, confirmed the spontaneity and thermodynamic favorability of the adsorption. In conclusion, this study successfully demonstrated that SBA-derived geopolymers are efficient and sustainable adsorbents for Pb(II) removal. This research offers a dual environmental benefit: iv sustainable agricultural waste management and improved water quality, highlighting the significant potential of these cost-effective and eco-friendly materials for heavy metal remediation.

Date

June 2024

Publisher

BUSE

Keywords

Lead (Pb(II)) ions

Sugar bagasse ash (SBA)

Geopolymer

Supervisor

Dr. Munzeiwa