Influence of Temperature and pH on the Stability and Colorimetric Measurement of Textile Dyes

Most of the textile dye removal techniques operate within temperature and pH ranges of 20-60°C and 2-12, respectively. Both the pH and temperature have been reported to have significant effects on the efficiencies of the dye removal techniques. In this study, the effects of pH and temperature on the stability and color measurement (absorbance) of the textile dye remazol brilliant at different dye concentrations were investigated. Changing the pH from 1 to 13 and /or the temperature from 15 to 55°C did not have any significant effect on the absorbance of the dye remazol brilliant blue at two concentrations (65 and 300 mg L). The results showed the stability of the remazol brilliant blue in water under wide ranges of temperature and pH. However, the neutral compound C₂₂H₁₆N₂Na₂O₁₁S₃ is transformed to an ionic form with either negative charge C₂₂H₁₅N₂Na₂O₁₁S₃]^- under alkaline condition or positive charge [C₂₂H₁₅N₂Na₂O₁₁S₃]⁺ under acidic condition. The formation of ionic form of the dye will facilitate its removal by various removal techniques. The results showed that a standard curve can be constructed at ambient conditions (a pH of 7 and a temperature of 25°C) and used to determine the concentration of the dye using the colorimetric method.