Equilibrium Study for Removal of Methylene Blue from Aqueous Solution by Orange peel Shiue-Chang Lee#, Wen-Ta Chiu and Yuh-Shan Ho* Taipei Medical University - Wan-Fang Hospital Introduction Color is a visible pollutant and presence of even very minute amount of coloring substance makes it undesirable due to its appearance. Most of the industries use dyes and pigments to color their products. Currently sorption process is proved to be an effective alternate for the treatment of dye wastewaters. In the present investigation, the powdered orange peel, a plant based material is used as a sorbent material for the removal of Methylene blue from its aqueous solutions. The dye Methylene blue is selected as a model compound in order to evaluate the capability orange peel to remove dye from wastewaters. Methods Batch sorption experiments were carried out at four different temperatures of 32, 40, 50, and 60C. 30 ml of dye solution of concentration ranging from 50 to 200 mg/dm3 was taken in 100 ml capped conical flasks. Accurately weighed mango seed kernel of 0.009 g of orange peel was added to the solution. Then the flasks were agitated using a water bath shaker at a constant agitation speed of 95 strokes/min. The contact was made for 24 h. After shaking, the samples were then centrifuged to separate the orange peel from the solution. The left out concentration in the supernatant dye solution was analyzed using UV spectrophotometer. Results Table 3. Isotherm parameters obtained by using non-linear method Table 1. Isotherms and their linear forms Table 2. Isotherm parameters obtained by using linear method Figure 1. Langmuir isotherms obtained by using non-linear method for the sorption of Methylene blue using orange peel at various temperatures Figure 2. Isotherms obtained by using non-linear method for the sorption of Methylene blue using orange peel at temperature 333 K Conclusion Present investigation showed that the low cost biomaterial orange peel could be used as a biosorbent for the removal of Methylene blue from its aqueous solution. Equilibrium data were obtained by both linear and non-linear method. Both the method suggests that the experimental equilibrium data was found to follow both Langmuir and Redlich-Peterson isotherm equation. Nonlinear method could be a better way to obtain equilibrium isotherm equation parameters. Langmuir is a special case of Redlich-Peterson isotherm when constant g is unity. The sorption process was found to be endothermic and spontaneous.