Biosorption of cesium and strontium from aqueous solution by Aspergillus flavus biomass
Sahar M. Mousa, Mohamed M. E. Breky, M. F. Attallah
Abstract
Abstract This study investigates the potential biosorption of Aspergillus flavus biomass for the removal of Cs⁺ and Sr²⁺ ions from aqueous solutions. The biosorbent was characterized using FTIR, SEM-EDS, BET surface area analysis, and thermal stability tests, revealing key functional groups (–OH, –COOH, –NH₂) and a surface area of 9.65 m²/g. Batch adsorption experiments demonstrated that pH significantly influenced uptake, with optimal removal at pH 5 for Sr²⁺ (~ 90%) and pH 8 for Cs⁺ (~ 27%). Kinetic studies followed the pseudo-second-order model (R² > 0.97), indicating chemisorption dominance. Equilibrium data fitted the Freundlich isotherm, suggesting multilayer adsorption, with maximum capacities (qₘₐₓ) of 211.1 mg⋅g −1 (Sr²⁺) and 26.7 mg⋅g −1 (Cs⁺). Thermodynamic analysis revealed endothermic (ΔH > 0), spontaneous (ΔG < 0), and entropy-driven (ΔS > 0) adsorption. Competitive ion studies showed Ca²⁺ strongly inhibited Sr²⁺ uptake, while Na⁺ reduced Cs⁺ adsorption. The biosorbent exhibited excellent reusability (3 cycles) with 0.1 M HNO 3 as the best eluent (81.2% Sr²⁺, 71.5% Cs⁺ recovery). The proposed mechanisms include ion exchange, surface complexation, and electrostatic interactions. These findings highlight A. flavus as a promising, low-cost biosorbent for nuclear wastewater treatment.