Adsorption of Reactive Brilliant Blue Dye from Aqueous Solution Using Modified Walnut Shell: Kinetics, Equilibrium, and Thermodynamics

A new modified walnut shell (TWNS) was synthesized through sequentially reacting the walnut shell (WNS) with thionyl chloride and triethylamine, and it was applied to adsorb Reactive Brilliant Blue (RB-19) from dye wastewater. In the range of 288 to 308 K, the isotherms, thermodynamics, and kinetics of RB-19 adsorption onto TWNS were investigated. The isothermal experimental data have a good correlation with the Langmuir isotherm model, and the theoretical maximum monolayer adsorption capacity of TWNS was 258.59 mg/g at 288 K. The kinetic data of RB-19 adsorption onto TWNS accorded with the pseudo-second-order model. The diffusion mechanism of RB-19 adsorption onto TWNS was studied by Weber and Morris intraparticle diffusion equation and Boyd and Reichenberg model, and the results showed the adsorption is primarily controlled by membrane diffusion. The thermodynamic calculation results demonstrated that the adsorption process of RB-19 onto TWNS is a spontaneous, exothermic, and favorable process. Moreover, the recycled TWNS retains high adsorption capacity after four cycles.

Automated summary

A new modified walnut shell (TWNS) was synthesized and successfully applied to adsorb Reactive Brilliant Blue (RB-19) from dye wastewater. The adsorption process is primarily controlled by membrane diffusion and is spontaneous, exothermic, and favorable.