Removal of Methylene Blue Dye from Wastewater of Textile Industry in Catalytic Ozonation Process by Pumice Modified by Magnesium Nitrate

Chemical dyes used in the textile wastewater besides having harmful effect on the environment, have carcinogenic and mutagenic effects. Methylene blue has harmful effect on living organisms in short period of exposure. The goal of this study was optimization of the catalytic ozonation process by pumice modified by magnesium nitrate in removal of methylene blue dye based on Taguchi statistical model.
In this experimental study ozonation process was in a batch ozonation reactor. The prepared pumice was crushed and pulverized by standard ASTM (American Society for Testing and Materials) sieves at range of 70 mesh, then modified by magnesium nitrate. Effective factors such as reaction time, initial dye concentration, adsorbent dose, and initial pH at 4 different levels were considered using an L-16 Taguchi method. Residual concentration of contaminants was read using a spectrophotometer at a wavelength of 663 nm. Analysis of data was performed using one- way variance and calculation of S/N (signal- to- noise) rate.
The results showed best conditions for removal dye were at contact time of 15 min, pH of 10, dye concentration of 50 mg/l,and adsorbent dosage of 0.7 g/L and efficiency of dye removal was 98%. Analysis of variance results indicated that the reaction time was the most important variable influencing the dye removal percentage with the contribution value of 51.8% and pH was the least important variable influencing the dye removal with the contribution value of 3.8%
The results showed that ozonation process can be a selective method to reduce the concentration of pollutants in textile wastewater effluent.