Utilization of peanut shell: investigating the adsorption mechanism and optimization of red 195 and reactive black-5

In this study, peanut shells (PS) called waste were utilized in powdered form for the removal of Red 195 (R-195) and Reactive Black-5 (RB-5) from synthetic wastewater solutions. Various operational parameters such as PS dosage (0.1–5.0 g), pH (2–12), contact time (5–150 min.), and temperature (20–40 °C) were investigated to optimize the batch adsorption process. FTIR, TGA, pHZPC, and SEM analyses were conducted to investigate the structural features and surface chemistry of PS. FTIR analyses revealed the existence of specific functional groups on the PS surface capable of successfully adsorbing R-195 and RB-5. TGA results demonstrated thermal stability for all prepared samples. SEM highlighted the porous structure of PS, which is advantageous for dye adsorption. The process, characterized by physical adsorption predominance and single-layer adsorption, was well-fitted to Langmuir and PFO for both dyes. Maximum removal efficiencies of 95.30% for RB-5 at pH 2.0 and 94.00% for R-195 at pH 2.5 were determined. Thermodynamic factors suggested that the adsorption of R-195 and RB-5 onto PS occurred spontaneously and exhibited an endothermic nature. Due to the interaction with a higher number of functional groups, PS exhibited a higher maximum adsorption capacity for R-195 (27.027 mg/g) compared to RB-5 (10.989 mg/g). The results support the idea that PS can act as an efficient and eco-friendly adsorbent, capable of removing both R-195 and RB-5.