Kinetics of adsorption of crystal violet from aqueous solutions using different natural materials

Adsorption studies of Crystal Violet (CV) on different natural materials were carried out by batch experiments. The parameter studied includes initial dye concentration, adsorbent dose, pH, contact time, agitation speed, particle size of adsorbent and temperature. The linear regression coefficient R² was used to elucidate the best fitting isotherm model. All isotherm models, Langmuir (R² = 0.982 to 0.999), Temkin (R² = 0.973 to 0.998) and Freundlich (R² =0.98 to 0.998 and n = 1.886 to 2.294) were found to be best fitting models. The monolayer (maximum) adsorption capacities (qm) were found to be between 142.857 to 250 mg/g for natural adsorbents under study. Lagergen pseudo -second order model best fits the kinetics of adsorption. The correlation coefficient R² for second order adsorption model has very high values of R² for all absorbents (R²::::: 0.998) and qe(the) values are in good agreement with with qe(exp) showed that adsorption of CV on these natural materials follwed second order kinetics and chemosorption playing role in rate determining step. Intra particle diffusion plot showed boundary layer effect and larger intercepts indicates greater contribution of surface sorption in rate determining step. pH was found to be an important factor in controlling the adsorption of cationic dye. Adsorption of CV on adsorbents was found to increase on increasing pH, increasing temperature and decreasing particle size. Thermodynamic analysis showed that adsorption was favourable and spontaneous, endothermic physical adsorption and increased disorder and randomness at the solid-solution interface of CV with biosorbents. Mangrove plant leaf powder was found have excellent adsorption capacity towards CV than other natural materials under study.