Sustainable alternative for removing pesticides in water: Nanomodified activated carbon produced from yeast residue biomass

The systemic insecticide thiamethoxam (TMX) has been frequently used with the need to intensify agricultural activities and food production. Given the pollution concern, biosorption emerges as an efficient and low-cost treatment. Thus, this work proposes to use the environmentally friendly activated carbon magnetic nanocomposite (YAC-NP) produced with yeast residues from the sugar-alcohol industry for the sorption of TMX in water. YAC-NP and its precursors (NP and YAC) were characterized by X-ray (XRD) and Fourier Transform Infrared (FTIR) spectroscopies to investigate their morphology and interaction with TMX. The Boehm titration informed the predominance of acidic character to YAC by the presence of carboxylic, lactone, and phenolic groups. The YAC-NP pH at the point of zero charge (pHPZC) was 6.05, and the best conditions for TMX sorption by YAC-NP occurred at the 2–7 pH range and 30 min of contact time. Sorption tests were performed using batch procedures at increasing concentrations of TMX (5–100 mg/L) and 1 g/L adsorbent dose. The experimental adsorption capacities (Qexp) for YAC, NP, and YAC-NP were 31.52 ± 1.69, 2.42 ± 0.54, and 12.50 ± 0.33 mg/g, respectively. TMX contents were determined by Ultraviolet–visible Spectroscopy (UV/Vis). The pseudo-2nd-order kinetic equation best fit the experimental data (r2 = 0.9996). Among the eight isotherm models applied to the experimental data, Hill, D-R, Temkin, Toth, and R–P were the models that best described the sorption process. YAC-NP reusability in TMX removal was assessed, and a decrease from 71.87 to 0.69% was observed after 10 adsorption cycles.