Characterization of Romanian Bentonitic Clays for the Removal of Dyes from Wastewater

ABSTRACT

Bentonites from Oraşul Nou (Satu Mare County), Petreşti (Cluj County), Valea Chioarului (Maramureş County), and Gurasada (Hunedoara County), Transylvania, Romania, were characterized and tested as adsorbents for the removal of toluidine blue, malachite green, and Congo red from aqueous solution. The clay materials were characterized using X-ray diffraction, scanning electron microscopy-energy-dispersive X-ray spectroscopy, specific surface area using the Brunauer–Emmett–Teller method, and infrared spectroscopy. Physicochemical and mineralogical analyses of the samples indicated that all included montmorillonite as their main constituent and that important modifications of their properties occurred upon treatment. Each bentonite was subjected to size-fractionation, ionic exchange with tetra-n-butylammonium bromide (organoclay), and Al-pillaring. Adsorption was conducted using batch conditions for 4 h using 0.1 g adsorbent and 40 mL of 100 mg/L dye solution at 20 ± 2°C and 25 rpm with a three-dimensional shaker. The most efficient bentonite deposits were from Oraşul Nou. The most suitable modified samples were treated by size-fractionation.

KEYWORDS:

• Adsorption
• characterization
• dye
• efficiency
• montmorillonite

Acknowledgments

A. Măicăneanu would like to thank Prof. Steven Suib and PhD students from the Suib Research Group, University of Connecticut, Chemistry Department, for their help. The authors also wish to acknowledge Bioscience Electron Microscopy Laboratory of the University of Connecticut.