Silane modified clay for enhanced dye pollution adsorption in water

Abstract

A natural clay from Bakotcha in Cameroon was modified with two silanes, tetramethoxysilane (TMOS) and [3-(2-aminoethyl)aminopropyl]trimethoxysilane (EDAS) to increase its adsorption properties. The modified clay is intended to be used as an efficient adsorbent for organic pollutant removal from water. Three Clay/TMOS and two Clay/EDAS samples with different [silane]/[clay] ratios were produced and characterized by X-ray diffraction, N2 adsorption-desorption measurements, Inductively Coupled Plasma–Atomic Emission Spectroscopy and Scanning Electron Microscopy. Their adsorption properties were evaluated on three organic model pollutants (i.e. fluorescein, malachite green and brilliant violet diamond). A dilution of the montmorillonite structure of the raw clay is observed when it is modified with TMOS while its original crystalline structure is preserved with EDAS. The morphologies depended on the used silane: (i) with TMOS, highly porous materials with the formation of silica particles at the surface of the clay; (ii) with EDAS, a similar morphology as raw clay with EDAS grafted at the surface of the clay. Both morphologies give two different adsorption behaviors on the 3 pollutants. For the raw clay and the TMOS modified clays, similar adsorption properties are obtained with a better adsorption when the specific surface increases (when TMOS content increases). When clay is modified with EDAS, the adsorption properties change as the surface groups are different, these EDAS modified samples have less affinity with fluorescein and malachite green reducing the adsorption capacity for this kind of pollutants. The tuning of the raw clay with silane opens the way for the development of highly efficient adsorbent for pollutants in water from natural and inexpensive materials.

Keywords

• Silicon alkoxides
• Porous material
• Water treatment
• Pollution removal
• Hybrid compounds