Strategic utilization of chicken bones immobilized by Aspergillus terreus for sustainable bioremediation of cobalt: statistical modeling, kinetics and thermodynamic studies

To address the environmental and health risks of cobalt, agricultural byproducts (peanut shells and luffa sponge), spent chicken bones, and sea sand were recruited as immobilization matrices for Aspergillus terreus. Their adsorptive performance toward cobalt (250 mg L−1 at pH 7 and 30 °C for 1 h) was evaluated. The fungi-immobilized chicken bones (At-I-CB) showcased superior adsorptive performance (45.42±0.66%) among other examined bio-carriers. To maximize biosorption efficacy, Box–Behnken design inferred that 8.7 g L−1 of At-I-CB could adsorb 103.04 mg L−1 of cobalt by 96.8% at pH 6.76 within 101.4 min. Characterization via EDX, FTIR and SEM confirmed the presence of signals and functional groups of the hybrid constituents with higher distribution of cobalt particles on the surface of fungal conidia/hyphae and hydroxyapatite, which implied the structural heterogeneity/porosity of bio-carrier. Such design furnished a potent stabilization and enhanced the adsorption performance. Meanwhile, kinetic analysis declared that cobalt biosorption onto At-I-CB followed chemisorption mechanisms via electrostatic interactions, ion exchange, and complexation. The most fitting model was Intra-Particle Diffusion (R2 = 0.99), followed by Fractional Power and Elovich (R2 = 0.96), reflecting multi-stage dynamics of adsorption including external surface interaction, internal pore diffusion, and boundary layer diffusion. Thermodynamic studies revealed maximum adsorption capacity (84.60%) at 75 °C, with positive ΔG° values unveiling a non-spontaneous process with favorability at higher temperatures. Further, enthalpy change (∆H°; 49.54 kJ/mol) emphasized the endothermic chemisorption. Remarkably, no study reported such a deeply detailed bio-adsorption capacity of novel At-I-CB. Finally, this study demonstrates the feasibility of biowastes recyclability and safe utilization as natural, sustainable and eco-benevolent fungal carriers for implementing sustainability goals and circular bioeconomy.