Optimization of brilliant green biosorption by native and acid-activated watermelon rind as low-cost adsorbent

The use of low-cost and eco-friendly adsorbent such as watermelon rind (WR) has been investigated as an ideal alternate for removing dyes from wastewater. This study deals with the removal of textile dye brilliant green (BG) from aqueous solutions by native WR and chemically activated watermelon rind (AWR). Chemical activation of WR was carried out using 1:1 ortho-phosphoric acid. The loading capacity of WR and AWR was found to be 92.6 and 188.6 mg g(-1), respectively. The equilibrium data were fit to Langmuir, Freundlich, and Temkin isotherms and found to have better fit to Langmuir isotherm. The sorption of BG onto WR and AWR was rapid and follows pseudo-second-order kinetic model. Thermodynamic parameters including change in free energy ( increment G degrees), enthalpy ( increment H degrees), and entropy ( increment S degrees) are derived and found to be spontaneous and exothermic in nature. These observations suggest that WR can be used as a non-hazardous agro material for removal of BG from aqueous solutions.