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Dyes are being extensively used in textile, dyeing and leather industries and usually have a synthetic origin and complex chemical structure that may be mutagenic and carcinogenic. Among various processes of dye removal from wastewater, adsorption is considered to be the most efficient process. Activated carbon is the most widely used adsorbent with great success because of its high adsorption capacity, but its use is limited due to its high-cost, has led to a search for cheaper substitutes. Optimization methods, such as the Taguchi method has been generally adopted to optimize the design parameters, because this systematic approach can significantly minimize the overall testing and the experimental costs. In this study; the optimum condition of Reactive Blue 19(RB19) removal by activated carbon based on pomegranate residual is determined using Taguchi method. For this purpose, 4 main factors such as pH, adsorbent dose, initial dye concentration and contact time were considered in 5 levels. Therefore, an L25 orthogonal array was chosen, and the experimental conditions were obtained. In addition, after design of experiments, an analysis of the signal-to-noise (S/N) ratio was needed to evaluate the experimental results. The analysis of mean (ANOM) statistical approach was adopted herein to construct the optimal conditions. In addition to ANOM, the analysis of variance (ANOVA) statistical method was also used to analyze the influence of each controllable factor on the dye removal efficiency. To prepare the To prepare the activated carbon (AC), pomegranate residual was collected. Collected sample has been dried in an oven for 2 h at 100 0C. It was then ground in a ball mill and the material passed through the No.30 mesh was collected and tested. They were soaked for 24 h in a 1:1 wt. ratio with 50 wt. % phosphoric acid as the carbonized at room temperature. The sample is then decanted and dried in a muffle furnace for 1 h at 500 0C. They were then washed sequentially several times with hot distilled water, until pH of the washing solution became neutral. AC was finally powdered and sieved by the No. 100 mesh. The experiments were done 3 times according to the tests conditions determined by the Taguchi method and the dye removal efficiency was measured. Due to the results of S/N and ANOM, it can be inferred that the optimum mixture proportions to obtain the highest RB19 removal efficiency are as follows. (1) Initial dye concentration of 100 mg/L; (2) pH of 11; (3) adsorbent dose of 1.75 gr/L; and (4) contact time of 7 minutes. The experiment with aforementioned condition was done and result was shown the highest efficiency (98.94%). According to the result of ANOVA, the rank order of the contribution percentage of each factor on RB19 removal efficiency is as follows: (1) initial dye concentration (52.67%), (2) adsorbent dose (33.32%), (3) pH (13.61%), and (4) contact time (2.72%).

Keywords: Adsorption, Taguchi, Reactive Blue 19, pomegranate residual, Analysis of Variance

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