Baobab (Adansonia digitata) Pulp and Mango Seeds as New Adsorbents for the Removal of Pb (II) Ions from Aqueous Solutions

Abstract

Baobab pulp (Adansonia digitata) and mango seeds were employed in the synthesis of activated carbon, serving as a cost-efficient adsorbent for the elimination of Pb (II) ions from aqueous solutions. The carbonization of baobab pulp and mango seeds was executed within a muffle furnace at 500°C for 2 hours and 30 minutes, followed by activation using orthophosphoric acid. Batch adsorption experiments encompassed assessments of initial metal ion concentration, adsorbent dosage, contact time, pH, and temperature, aimed at optimizing conditions to achieve maximal adsorption. The maximum monolayer adsorption capacities for Pb(II) were determined as 18.69 mg/g for Baobab activated carbon (BAC) and 16.02 mg/g for Mango seed activated carbon (MAC) at a concentration of 500 mg/l. Adsorption data were subjected to analysis using Langmuir, Freundlich, and Temkin isotherm models. Among these models, Langmuir exhibited superior fit, as indicated by a correlation coefficient (R²) exceeding 0.99. Kinetic evaluation encompassed Pseudo-first-order, Pseudo-second-order, and Intra-particle diffusion models, with the Pseudo-second-order model emerging as the most appropriate. This finding suggests that the adsorption process is primarily governed by chemisorption, potentially serving as the rate-limiting step. Thermodynamic investigations revealed the spontaneity, endothermic nature, and heightened randomness at the solid-solution interface of the adsorption process. Further assessment involved desorption experiments to ascertain the reusability and lifespan of the adsorbents. The outcomes underscore the potential of activated carbon derived from baobab pulp and mango seeds as economical and efficient adsorbents for Pb (II) ion removal.