Natural Clay Modified with ZnO/TiO2 to Enhance Pollutant Removal from Water

Raw clays, extracted from Bana, west Cameroon, were modified with semiconductors (TiO2 and ZnO) in order to improve their depollution properties with the addition of photocatalytic properties. Cu2+ ions were also added to the clay by ionic exchange to increase the specific surface area. This insertion of Cu was confirmed by ICP-AES. The presence of TiO2 and ZnO was confirmed by the detection of anatase and wurzite, respectively, using X-ray diffraction. The composite clays showed increased specific surface areas. The adsorption property of the raw clays was evaluated on two pollutants, i.e., fluorescein (FL) and p-nitrophenol (PNP). The experiments showed that the raw clays can adsorb FL but are not efficient for PNP. To demonstrate the photocatalytic property given by the added semiconductors, photocatalytic experiments were performed under UVA light on PNP. These experiments showed degradation up to 90% after 8 h of exposure with the best ZnO-modified clay. The proposed treatment of raw clays seems promising to treat pollutants, especially in developing countries

Silane modified clay for enhanced dye pollution adsorption in water

peer reviewedA 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

Hybrid clay-based materials for organic dyes and pesticides elimination in water

peer reviewedNatural clay, extracted from Cameroon, was modified by ion exchange to produce 4 different clays. These latter were modified with photocatalytic semiconductor like ZnO to produce efficient hybrid materials for pollutant removal in water. ZnO was synthesized by the soft sol-gel chemistry method. The results showed that the clay belonged to the smectite family and was composed of different crystalline phases. When the hybrid materials were produced, mix crystalline patterns were obtained with both smectite and ZnO wurtzite phases. The ICP-AES analysis showed that similar ratio between ZnO and clay were obtained for the 4 hybrid materials (30 wt% of ZnO and 70 wt% of clay). The SEM observation of the samples had shown that the hybrid materials had the clay structure as skeletal structure (sheet like structure) with the ZnO spherical materials grafted at the surface, giving a good exposure to light to maintain photocatalytic property. Then, the pollutant removal property of the samples was evaluated on three different model pollutants: p-nitrophenol (PNP), Malachite green (MG) and Diamant brilliant violet (DBV). On PNP, no adsorption was observed, and photocatalytic property was necessary to eliminate this molecule. With the best hybrid material (Clay/Cu 2+ /ZnO), 80% of PNP degradation was observed after 6 h of illumination. On MG and DBV, similar behavior was observed. Indeed, the clays and three out of four hybrid materials adsorbed completely both pollutant after 2 h of contact. Only pure ZnO and Clay/ZnO needed illumination to degrade completely both molecules. This study showed the possibility to obtain very efficient hybrid materials for pollutant removal in water with the use of inexpensive natural clay modified with a low amount of photocatalytic material (ZnO around 30 wt.%)

Silane modified clay for enhanced dye pollution adsorption in water

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