Adsorptive removal of Methyl Orange and Reactive Red 198 dyes by <i>Moringa peregrina</i> ash

Abstract

In the present study, a low-cost adsorbent derived from <i>Moringa peregrina</i> plant has been used for its ability to remove two common textile dyes, namely Methyl Orange (MO) and Reactive Red 198 (RR-198) from aqueous solutions. The effect of various operating parameters such as initial concentration of dye (10-150 mg L^-1), contact time (10-150 min), adsorbent dosage (1-13 g L^-1) and <i>p</i>H (2-11) is investigated. At an optimum <i>p</i>H of 2, approximately 96% removal of dye (50 mg L^-1) is obtained for an adsorbent dose of 7.0 g L^-1 after a 70 min contact time. The equilibrium assessment reveals that the Langmuir model is better than Freundlich model for the experimental data. The thermodynamic properties (ΔGº, ΔHº and ΔSº) show that the adsorption of RR-198 and MO dyes onto <i>Moringa peregrina</i> tree shell ash (MPTA) is spontaneous, endothermic and feasible in the temperature range of 293-313 K. Also, the magnitude of enthalpy change indicates that the adsorption is physical in nature. Finally it can be concluded that the MPTA can be used as a low-cost adsorbent for the removal of different concentrations of anionic dyes from aqueous solutions.