Preparation and Adsorption Efficiency of Mango Waste-derived Biosorbents for Lead Removal in Water

Abstract

The need to mitigate heavy metals contamination in the water environment using sustainable adsorbents has gain much attention recently due to compliance to sustainable development goals (SDGs) in the global context. This study explored the potential of Philippine mango (Mangifera indica L.) waste – specifically the peel, seed, and pit – as bioadsorbents for Pb²⁺ removal from synthetic wastewater. The bioadsorbents were prepared through drying and grinding, followed by chemical modification with HNO₃ and NaOH. Characterization using Fourier-transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) revealed surface functional groups and structural changes. Adsorption capacity was quantified using atomic absorption spectroscopy (AAS), and batch experiments were conducted with UV-Vis spectrophotometry. The untreated mango seed (UMSD) exhibited the highest Pb²⁺ adsorption capacity, exceeding 42.10 mg/g. Adsorption efficacy increased with higher initial Pb²⁺ concentrations, with untreated seed outperforming modified variants. Kinetic studies indicated rapid lead uptake, reaching equilibrium within 30 min. The adsorption data were best described by the Langmuir isotherm model, suggesting monolayer adsorption, while pseudo-second-order kinetics indicated that chemical bonding was the dominant mechanism. These results underscore the potential of UMSD as a cost-effective and sustainable bioadsorbent for lead removal in wastewater treatment, particularly in the Philippines.