Development and utilization of raw and NaOH-modified peanut hull as potential adsorbents for crystal violet dye removal from wastewater

This study examines the effectiveness of raw peanut hull (PHR) and NaOH-modified peanut hull (PHN) adsorbents in removing crystal violet (CV) dye from wastewater. Several analytical methods, including scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDAX), Brunauer-Emmett-Teller (BET) analysis, thermogravimetric analysis (TGA), X-ray diffraction (XRD), proximate and component analyses, and point of zero charge (pHPZC), were employed to characterize the prepared adsorbents. Analyses revealed that PHN exhibited a higher cellulose and fixed carbon content than PHR. Additionally, PHN had lower levels of hemicellulose, lignin, ash, volatile matter, moisture, and extractive content. Batch experiments were conducted to investigate the effects of various parameters, viz., adsorbent dosages, contact duration, pH, starting dye concentration, and temperature. Various isotherm and kinetic models were employed to analyze and interpret the experimental data. Among these, the Langmuir isotherm and the pseudo-second-order (PSO) kinetic models were the most accurate in describing the adsorption behavior of both adsorbents. The thermodynamic analysis indicated that the adsorption of CV onto both adsorbents was spontaneous and endothermic. The process was accompanied by an increase in entropy. Both adsorbents, PHR and PHN, notably utilized for four successful adsorption-desorption cycles using hydrochloric acid (HCl) as an eluent. The present work demonstrates the fruitful utilization of waste material to treat polluted wastewater. The additional benefits of easy synthesis, low cost, and reusability of the PHN for several cycles make it novel.