Abstract

Textile industries known as basic industry in any country are considered one of the most major polluting industries by producing colored wastewater and their entrance into the environment. Among from different dyes in the wastewater of these industries, due to the specific properties such as resistance to biodegradation, toxic, mutagenic and carcinogenic, azo dyes have more dangers than other dyes. The present study sought to evaluate the efficiency of cotton pod ash on the absorption of Direct Blue 71. This study was performed on a laboratory scale. To do the test, after preparing the cotton pod ash and stock solution of Direct Blue 71, the effect of pH of solution, adsorbent dosage, contact time, initial dye concentration and temperature on the removal of Direct Blue 71 in a closed environment within Erlenmeyer was examined and the behavior of absorption system was finally analyzed based on isotherm models. The obtained results showed that the removal efficiency decreased by increasing the pH of solution and increased by increasing the temperature. It was also found that the highest rate of removal of Direct Blue 71 was 99.6 at pH 2, adsorbent dose of 0.5 g per 100 mL, dye concentration of 60 mg/L and temperature of 50 °C. Balance data have been adapted to four Langmuir, Freundlich, Temkin and Dubinin- Radushkevich Models and it was determined that the obtained data had the highest consistent with Langmuir model (R2 = 0.9553). Pistachio pod ash had a high ability to remove the dye from aqueous solution through the removal of a high percentage of Direct Blue 71 as an agricultural waste and cheap. Copyright © EM International.