Optimization Based on Response Surface Methodology of Anionic Dye Desorption From Two Agricultural Solid Wastes

The Congo red (CR) desorption, from two dye-loaded agricultural solid wastes such as Argan nutshell (ArS) and Almond shell (AmS), was evaluated in this study. The adsorbents were characterized by FTIR and SEM analyzes. Process optimization was conducted using Response Surface Methodology (RSM) feature central composite design (CCD). At optimum conditions (CR-adsorbent dose =16 g L-1, pH =4, contact time= 50 min, NaOH concentration = 0.1M, temperature = 23 +/- 1 degrees C), the CR adsorption values were found to be 98.15% and 98.43%, respectively, for CR-ArS and CR-AmS. Further, a good agreement was found between the experimental results and those predicted by the pseudo-second-order kinetic model. CR desorption efficiencies of 98.45% for CR-ArS, and 98.86% for CR-AmS, were obtained from the CCD-RSM study. Such efficiency values of the CR desorption were reached under optimized conditions of CR-adsorbent dose, contact time, and NaOH concentration: 13 g L-1, 35 min, and 0.07M for CR-ArS and 12.4 g L-1, 32 min, and 0.06M for CR-AmS. Furthermore, the ArS and AmS adsorbents showed good regeneration and reusability. The overall data indicate that agricultural solid wastes such as Argan nutshell and Almond shell are suitable adsorbents for wastewater treatment. [GRAPHICS] .