Assessing the Dual Use of Red and Yellow Algerian Pomegranate Husks: Natural Antiradical Agents and Low-Cost Biosorbents for Chromium (VI) Removal from Contaminated Waters

The hexavalent chromium (Cr(VI)) released in industrial wastewaters can cause adverse effects on both the environment and human health. This study aimed to investigate the efficiency of the red and yellow pomegranate husk powders (RHP and YHP) as natural quenchers for free radicals and as adsorbents towards Cr(VI) ions. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and Brunauer-Emmett-Teller (BET) surface area analyses were used for biosorbent characterization. The antiradical activity was assessed via 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays. The adsorption isotherms and kinetics were conducted by the batch method. The results showed the roughness and heterogeneity of the biosorbent surface in the presence of active functional groups. At a dose of 5 mg, both biomasses showed a radical inhibition activity (I) > 85% for DPPH, and (I) > 91% for ABTS. Finally, the isotherms modeling showed that the Langmuir model was the best fit with a maximum adsorption capacity (Qmax) of 413.22 and 403.22 mg/g at pH 2 within 60 min with a solid/liquid ratio (S/L) of 0.5 mg/mL for RHP and YHP, respectively. The kinetic data aligned better with the pseudo-second-order model. This study demonstrates the effectiveness of these biomasses as natural quenchers for free radicals and as biosorbents for Cr(VI) removal from contaminated waters.