Optimization and application of <i>Musa paradisiaca</i>-derived mesoporous hydrogel beads for selective adsorption of potentially toxic elements from aqueous environments

Hydrogel beads were constructed using sodium alginate (SA) and banana pith powder (BPP). The ability of beads to adsorb Copper (Cu²⁺), Lead (Pb²⁺) and Nickel (Ni²⁺) was examined using SA-BPP ratios (1:1, 1:2, 1:3, 1:4, 1:5, 1:0 and 0:1). BET, FTIR, SEM-EDS, TGA and ZP were used to analyse the composite structural characteristics. BET surface area of SA-BPP (1:5) is found to be 28.308 m²/g. The impacts of adsorbent blend ratio, dosage, adsorption contact time, pH, and temperature were evaluated. The efficiency was attained at SA-BPP (1:5), 0.3 g, 180 min, pH 6 and 35°C, with adsorption rates of 83.38% for Cu²⁺, 77% for Pb²⁺ and 94.7% for Ni²⁺. The pseudo-first-order equation displayed good adsorption mechanism using (<i>R</i>² = 0.993, 0.998 and 0.994) for Cu²⁺, Pb²⁺ and Ni²⁺. The Freundlich adsorption isotherm fits perfectly for the adsorption process of SA-BPP (1:5) (<i>R</i>² = 0.967) for Pb²⁺ and Langmuir (<i>R</i>² = 0.979 and 0.983) for Cu²⁺ and Ni²⁺. The thermodynamic analysis shows that the adsorption process is endothermic. The removal efficiency was determined by optimizing the theoretical adsorption experiments through the Box–Behnken Design (BBD). Cumulatively, the Cu²⁺, Pb²⁺ and Ni²⁺ ions have an electrostatic nature that facilitates their easier acceptance of the SA-BPP (1:5) adsorbent electrons. After five cycles, a maximal removal effectiveness of 75% is achieved, which concludes a long-lasting adsorbent for industrial wastewater.