Selection of better cationic surfactant for zeolite modification using surface studies and its application in the removal of anionic and cationic dyes

In this work, the surfactant-modified natural zeolite (SMZ) as a low-cost and eco-friendly adsorbent have been used for the removal of Eosin Y or Acid Red 87 (AR87) and Basic Red 46 (BR46) dyes from aqueous solutions. In order to modify the surface of zeolite, a new approach was proposed based on the surface properties of the surfactants. Two cationic surfactants with the same head group structure and different alkyl chain length (dodecylpyridinium chloride, DPC and tetradecylpyridinium chloride, TPC) were investigated using surface tension measurements and then surfactant TPC was selected as the better option for the preparation of modified zeolite. Natural and modified zeolite are characterized with Fourier transform infrared spectroscopy (FT-IR), BET surface area analysis, thermogravimetric analysis (TGA), pore volume measurement, XRD, the scanning electron microscopy (SEM) images and Zeta potential techniques. To identify the performance of the surfactant modified zeolite (SMZ) in the removal of ionic compounds were selected two different types of dyes with oppositely charged head groups (AR87: anionic and BR46: cationic). The adsorption equilibrium and kinetic data were analyzed using different models (ten isotherms and eight kinetic models in nonlinear forms). The rate of removal of dyes by SMZ shows two different ranges, very fast for AR87 (less than 5 min) and slow for BR46 (45 min.). The maximum adsorption capacity (qm) are 21.02 and 8.62 mg/g for removal of AR87 and BR46, respectively. The results indicate that SMZ can be used as efficient adsorbent for the removal of the anionic dyes such as AR87 form aqueous solutions.