Efficient Adsorption of Crystal Violet via Highly Crystalline and Non‐Modified Waste Pumpkin Shell

ABSTRACT This study aimed to adsorb crystal violet from aqueous solution on non‐modified and naturally dried pumpkin shell waste. For this purpose, after the characterization of the adsorbent with scanning electron microscopy‐energy dispersive x‐ray (SEM‐EDX), x‐ray powder diffraction (XRD), N 2 physisorption, and Fourier transform infrared (FT‐IR) spectrometer analysis, parametric studies to determine the optimum conditions of pH, adsorbent amount and size, temperature, and dye concentration to reach maximum adsorption capacity and removal efficiency were conducted. After that, kinetic, isotherm, and thermodynamic studies were carried out regarding these experimental data. The maximum removal efficiency was obtained as 93% at 20 mg/L initial dye concentration, 45°C, pH 7, and 0.4 g of adsorbent. In addition, the maximum adsorption capacity was recorded as 69 mg/g at the optimum conditions (100 mg/L initial dye concentration, 25°C, pH 7, and 0.1 g adsorbent amount). The experimental data fitted with the pseudo‐second‐order kinetic ( R 2 > 0.99) and the Freundlich isotherm ( R 2 : 0.98) models. The results of the thermodynamic study showed that the adsorption occurred spontaneously (∆ G < 0), and the reaction was endothermic (∆ H > 0). Briefly, this study presents a perspective to observe the possibility of removing hazardous textile dye without any thermal or chemical modification of agricultural waste.