Biosorption of crystal violet and methylene blue dyes using coconut shell powder

In this study, coconut shell biosorbent was synthesized through chemical processes and activated using concentrated sulfuric acid to serve as an organic adsorbent for the effective removal of dye molecules, particularly Crystal Violet (CV) and Methylene Blue (MB), from wastewater. The biosorbent's surface characteristics, including morphology and functional groups, were comprehensively analyzed using techniques such as BET, FTIR, SEM, and EDX. The experimental investigations revealed that optimal conditions, including a pH of 10.0, biosorbent dosage of 3 g/L, initial dye concentration of 20 mg/L, and a contact time of 60 minutes, led to the efficient removal of 89.74% of CV and 82.32% of MB dye molecules from synthetic solutions. Several isothermal studies were conducted to assess whether the adsorption process exhibited homogeneity or heterogeneity, aiming to gain a deeper understanding of its characteristics. Alongside the aforementioned tests, kinetic investigations were performed to ascertain whether the dye adsorption on the adsorbent was of a physical or chemical nature. Thermodynamic analyses were also undertaken to determine the outward-releasing or inward-absorbing characteristic of the dye adsorption process and to assess its spontaneity. Based on the outcomes of the desorption studies, the addition of 0.3N hydrochloric acid (HCl) resulted in the highest desorption rate. This effectively enhanced the recovery of dye molecules from the exhausted adsorbent, underscoring the effectiveness of 0.3N HCl in facilitating the desorption of adsorbed dye molecules.