Regeneration of argan nutshell and almond shell using HNO3 for their reusability to remove cationic dye from aqueous solution

This study reported the desorption of adsorbed crystal violet (CV) dye on the argan nutshell (ANS) and almond shell (AS) using nitric acid (HNO3) as a desorbing agent and their reusability to remove the CV in multiple consecutive adsorption-desorption cycles. The prepared adsorbents were characterized using FTIR and SEM analysis. Different desorbing agents (HCl, HNO3, H3PO4, CH3COOH, NaOH, H2O, H2O (pH = 2), and H2O (pH = 11)) were tested to determine the best eluent. The effect of experimental parameters, such as CV-adsorbent dose (4-40 g L-1), contact time (0-180 min), and HNO3 concentration (0.01-2 M) on the desorption of the CV from CV-ANS and CV-AS was studied. The HNO3 (0.1 M) solution was an excellent eluent for the CV desorption from CV-ANS (98.21%) and CV-AS (98.60%) using 16 g L-1 of CV-adsorbent dose at 23 +/- 1 degrees C for 60 min. The pseudo-second-order kinetic model well-exemplified experimental data. Excellent regeneration reusability of ANS and AS for the CV removal for six consecutive adsorption-desorption cycles. This study showed that argan nutshell and almond shell as low-cost adsorbents have tremendous potential for removing the CV in multiple consecutive adsorption-desorption cycles as an alternative eco-friendly process.