Adsorption of methylene blue using untreated biosorbent prepared from Geranium plant waste: Isothermal, kinetic and thermodynamic study

The potential of untreated biosorbent prepared from Geranium plant waste for the adsorption of methylene blue from aqueous solution has been investigated. The effects of various experimental parameters such as biosorbent dose, contact time, concentration of dye, pH and temperature have been studied. The maximum adsorption is found at the time of 120 min and pH 7. Sorption increases with increasing temperature. Langmuir, Freundlich, Temkin and Jovanovic adsorption isotherm have been studied. R2 value suggested better fitment of Freundlich adsorption isotherm. Adsorption of MB followed pseudo second order kinetics with R2 value 0.9932. The calculated values of ΔH°, ΔS° and ΔG° are found to be 20.75 kJ/mol, 0.078 kJ/mol/K and -0.04682 kJ/mol, respectively. Adsorption processed with physical interaction, it is spontaneous and endothermic in nature. Application to real wastewater, regeneration of biosorbent, cost analysis and disposal of biosorbent have also been discussed. It is found that the prepared GPW biosorbent is stable and may be utilized repeatedly without losing its affinity up to five cycles. GPW is tested against commercial activated carbon (CAC) and it showed adsorption efficiency of 88% compared to 93% of CAC.