The adsorption characteristics of methylene blue (MB) onto a low-cost adsorbent, used greentea leaf powder (GTLP), were evaluated. Parameters affecting the adsorption including MB concentration, ionic strength, pH, and temperature were considered in kinetics and equilibrium adsorption experiments. It was found that the adsorption kinetics could be expressed by pseudo-second-order equation. Increasing initial MB concentration and decreasing ionic strength resulted in increases of adsorption rate and adsorption capacity. The effect of electrical double layer thickness on the adsorption kinetics was discussed. Fitting parameters revealed that the rate of adsorption was controlled by intra-particle diffusion. Batch equilibrium results indicated that the adsorption was favorable at alkaline condition and lower temperature. Both Langmuir and Freundlich adsorption isotherms can be used to describe the equilibrium adsorption of MB onto GTLP. The adsorption capacities of MB were 4.10×10-4 mol/g, which is about one third of the commercial granular activated carbon (1.23×10-3 mol/g). Thermodynamic functions indicated that the adsorption process is spontaneous and endothermic in nature. The major functional groups involved in the adsorption were –OH, –SO3 , and –CN. Work carried out has revealed that this bio-waste could remove the dye effectively from wastewater.
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