Modelling and Response Surface Optimisation of Methyl Violet Removal by a Mixture of Titaniferous Sand and Non-Activated Attapulgite

Abstract

In recent years, the discharge of dye-laden effluents from the textile industries into the aquatic environment has increased considerably. These industries are among the largest consumers of water. They generate huge amounts of pollutants from their huge discharge of toxic effluents and pose serious public health problems. So, this study focuses on the use of the mixture of titaniferous sand and attapulgite for the removal of methyl violet by adsorption in discontinuous mode. The different adsorbents were characterized by X-ray fluorescence spectroscopy and their different physico-chemical properties such as pH, zero charge potential, bulk and absolute density, porosity and specific surface area were determined. The response surfaces, through the Box-Behnken model, were used to model and optimize the operating conditions. The different factors studied were the ratio of titaniferous sand and attapulgite, the initial concentration of methyl violet and the pH. These vary between 1.25 and 8, 20 and 100 mg/L, 4 and 10 respectively. The results obtained after statistical analysis of the data show that the optimum mixture ratio is 2, the optimum concentration is 99.92 mg/L and the optimum pH is 9.88 corresponding to a maximum capacity of 5.52 mg/g and a maximum removal efficiency of 99.56%. The study of the effects of the different factors showed that the initial concentration of methyl violet and the pH significantly influence the adsorption capacity and the removal efficiency of the dye.