Comparison of Basic Dye Crystal Violet Removal from Aqueous Solution by Low-Cost Biosorbents

The removal of basic dye crystal violet by low-cost biosorbents was investigated in this study using a batch experimental system. The adsorption of crystal violet onto various adsorbents was solution pH-dependent and the maximum removal occurred at basic pH 10.0. The kinetic experimental data were analyzed using pseudo-first-order and pseudo-second-order equations to examine the adsorption mechanism and the intraparticle diffusion model to identify the potential rate controlling step. These results suggested that the adsorption of crystal violet onto various adsorbents was best represented by the pseudo-second-order equation. The suitability of the Langmuir and Freundich adsorption isotherms to the equilibrium data was also investigated at various temperatures for all four sorbents and the adsorption isotherms exhibited Freundlich behavior. The Freundlich constant K-f was 1.55 for alligator weed, 2.33 for Laminaria japonica, 9.59 for rice bran and 5.38(mg/g)/(mg/L)(1/n) for wheat bran, respectively at adsorbent concentration 5g/L, pH 10.0 and 20 degrees C. The thermodynamic parameters (Delta H, Delta G, and Delta S) were calculated and the results showed that the adsorption process for various adsorbents was spontaneous, endothermic, with an increased randomness, respectively. The particle size and the reaction temperature exhibited an insignificant impact on the adsorption equilibrium of crystal violet. The adsorbents investigated could serve as low-cost adsorbents for removing the crystal violet from aqueous solution.