Adsorptive separation of Acid Red 33 by groundnut shell–based activated carbon

The adsorptive separation of Acid Red 33 (AR33) dye by groundnut shell-based adsorbent obtained using phosphoric acid as an activating agent was investigated. The adsorbent characteristics were determined by Brunauer–Emmett–Teller (BET), scanning electron micrograph (SEM), and Fourier transformed infrared spectroscopy (FTIR) analysis. Thermochemical activation yielded a significant enhancement in surface area from 1.971 to 1150.252 m²/g. The effects of pH (2–10), adsorbent loading (1–5 g/L), concentration (50–200 mg/L), temperature (288–318 K), and time (15–270 min) were investigated on the extent of adsorption. Isotherm and kinetic analysis of adsorption trials revealed best fitting of experimental data by Langmuir isotherm and pseudo-second-order models. Maximum Acid Red 33 uptake by modified adsorbent was obtained as 107.53 ± 0.91 mg/g at dose of 3.5 g/L and pH of 2 in 180 min. Thermodynamic characteristics demonstrated spontaneous and endothermic adsorption. The reusability study implied the drop in the removal efficiency from 98.26 ± 0.97% at first cycle to 79.57 ± 1.04% to the third cycle. These results demonstrated the reusability potential up to three cycles. The presented research demonstrated that physio-chemically activated groundnut shell powder is a promising sorbent for adsorptive separation of Acid Red 33.