Exploring the biosorption of nickel and lead by Fusarium sp. biomass: kinetic, isotherm, and thermodynamic assessment.

Fungal biomass is as a cost-effective and sustainable biosorbent utilized in both active and inactive forms. This study investigated the efficacy of inactivated and dried biomass of Fusarium sp. in adsorbing Ni²⁺ and Pb²⁺ from aqueous solutions. The strain underwent sequential cultivation and was recovered by filtration. Then, the biomass was dried in an oven at 80 ± 2 °C and sieved using a 0.1-cm mesh. The biosorbent was thoroughly characterized, including BET surface area analysis, morphology examination (SEM), chemical composition (XRF and FT-IR), thermal behavior (TGA), and surface charge determination (pH-PZC and zeta potential). The biosorption mechanism was elucidated by fitting equilibrium models of kinetics, isotherm, and thermodynamic to the data. The biosorbent exhibited a neutral charge, a rough surface, a relatively modest surface area, appropriate functional groups for adsorption, and thermal stability above 200 °C. Optimal biosorption was achieved at 25 ± 2 °C, using 0.05 g of adsorbent per 50 mL of metallic ion solution at initial concentrations ranging from 0.5 to 2.0 mg L^-1 and at pH 4.5 for Pb²⁺ and Ni²⁺. Biosorption equilibrium was achieved after 240 min for Ni²⁺ and 1440 min for Pb²⁺. The process was spontaneous, mainly through chemisorption, in monolayer for Ni²⁺ and multilayer for Pb²⁺, with efficiencies of over 85% for both metallic ion removal. These findings underscore the potential of inactive and dry Fusarium sp. biomass (IDFB) as a promising material for the biosorption of Ni²⁺ and Pb²⁺.