Evaluation of the kinetics of gold biosorption processes and consequent biogenic synthesis of AuNPs mediated by the fungus Trichoderma harzianum

Abstract Gold has several applications in electronic equipment, jewelry, catalysts, and nanoscale, emphasizing the biomedical field. Some conventional effluent treatment methods are used in gold recoveries, such as electrochemical treatments, reverse osmosis, and ion exchange resins. However, these technologies have disadvantages, such as high cost and toxicity. Biosorption appears as a low cost and environmentally friendly alternative. Studies have shown that many biosorbents also synthesize biologically metallic ions into nanoparticles from reduction, nucleation, and subsequent stabilization. This work aims to evaluate gold’s biosorption utilizing fungal biomass of Trichoderma harzianum, promoting nanoparticles’ biogenic synthesis simultaneously. The results showed that 0.4 g L−1 of fungal biomass added the gold ion solution to 400 mg L−1 is possible to perform the processes of biosorption (metal removal) and biogenic synthesis of gold nanoparticles from 30 min under agitation simultaneously. The fungus T. harzianum has a high biosorbing gold capacity, approximately 1340 mg of the metal per g of biomass in 180 min, and a removal rate above 60%. The gold biosorption mediated by T. harzianum was adjusted to the kinetic pseudo-second-order (PSO) model, with R2 of 0.99 and biosorption capacity calculated according to this model 1342.93 mg g−1. The biosynthesized nanoparticles had a nanometric size distribution below 30 nanometers and spherical shape.