The effect of soaking process of agricultural wastes on the adsorption of methylene blue dye

Locally available agricultural wastes, barely, wheat, and oat straws, were found to be of a low cost and promising adsorbents for the removal methylene blue dye (MB). The effect of soaking process of these straws in water has been investigated for 20 days. The adsorption of MB has been studied by using batch techniques. The influences of sorbent concentration adsorption time and initial dye concentration have been considered. The equilibrium adsorption capacities of straws for MB were obtained by using linear Freundlich, Langmuir, and Tempkin isotherms. The maximum dye adsorption capacity, qmax, for the straws before soaking follows the order; barely oat wheat, with the values; 27.72, 17.54, and 8.34 mg/g, respectively. While the order of qmax for the soaked straws is; oat barely wheat, with values equals; 50.34, 22.22, and 11.11 mg/g, respectively. Thermodynamic values of ΔG corresponding to the MB uptake were evaluated from Langmuir model. The negative values of ΔG indicated that the adsorption of MB by these straws is spontaneous and favorable process.