ADSORPTIVE REMOVAL OF CATIONIC AND ANIONIC DYES FROM WATER: A CASE STUDY WITH KAOLINITE AND ACID-TREATED KAOLINITE

Abstract

One of the most common clay mineral, kaolinite was tested in this work as adsorbents for both a cationic dye, Methylene Blue and an anionic dye, Congo red. The clay mineral was further modified by treatment with 0.25 and 0.50 M H₂SO₄. The influences of pH, interaction time, clay mineral amount and dye concentration on the adsorption process were monitored and explained on the basis of physico-chemical characteristics of the clay mineral and the behavior of the dye molecules. The optimum pH for both Methylene Blue and Congo red adsorption ware 10.0 and 6.0 respectively. Adsorption was very rapid initially for ~ 30 min and then slowly attained equilibrium. The adsorption rate processes followed a second order kinetic model. The Langmuir monolayer capacity of kaolinite increased after acid treatment. The results suggest that kaolinite and its acid-treated forms would be suitable for removing both Methylene Blue and Congo red from aqueous solution through adsorption-mediated surface immobilization.