Defatted Jojoba for the removal of methylene blue from aqueous solution: Thermodynamic and kinetic studies

The removal of the methylene blue from aqueous water by adsorption with defatted Jojoba has been studied in a batch operation mode. The percentages removal of dye increases with increasing contact time, Jojoba dosage and temperature achieving the equilibrium at 40min. The maximum removal (80% approx.) has been achieved at 50°C, 0.8g/50mL of Jojoba dosage, 200mg/L initial concentration of MB and the pH range between 6.2 and 6.8. The dynamic isotherm has been successfully modeled by the Langmuir with R2=0.98. The negative thermodynamic parameters ΔG (−14.4, −15.4, −16.8) at 25, 35, 40 and 50°C, respectively indicate spontaneous adsorption. The pseudo-second order kinetic model is much more reasonable for MB adsorption process. ► The Jojoba is good adsorbents to remove MB dye from aqueous solutions. ► MB adsorption on Jojoba increases with the increase of pH up to 6.8 and then it gradually decreases. ► The adsorption process obeys the Langmuir isotherm and a pseudo-second order kinetic model. ► The MB adsorption onto Jojoba is a spontaneous, exothermic and physical process.