Funda Sayilkan

Photocatalytic degradation of Congo Red by hydrothermally synthesized nanocrystalline TiO2 and identification of degradation products by LC-MS.

Degradation of Congo Red (CR) dye in aqueous solutions was investigated by means of photocatalysis of TiO2 which was hydrothermally synthesized at 200 degrees C in 2 h, in anatase phase with 8 nm crystallite size. Efficiency of TiO2 in photocatalytic degradation under visible irradiation was studied by investigating the effects of amount of TiO2, irradiation time, initial CR concentration and pH. It was found that complete decolorization is achieved within 30 min of irradiation. Effects of nitrate and sulphate ions and humic acid on the degradation were also tested. The results were compared with Degussa P-25 TiO2 at the same degradation conditions. Degradation products were detected using LC-MS technique. The probable pathways for the formation of degradation products were proposed.

Photocatalytic antibacterial performance of Sn4+-doped TiO2 thin films on glass substrate.

Pure anatase, nanosized and Sn(4+) ion doped titanium dioxide (TiO(2)) particulates (TiO(2)-Sn(4+)) were synthesized by hydrothermal process. TiO(2)-Sn(4+) was used to coat glass surfaces to investigate the photocatalytic antibacterial effect of Sn(4+) doping to TiO(2) against gram negative Escherichia coli (E. coli) and gram positive Staphylococcus aureus (S. aureus). Relationship between solid ratio of TiO(2)-Sn(4+) in coatings and antibacterial activity was reported. The particulates and the films were characterized using particle size analyzer, zeta potential analyzer, Brunauer-Emmett-Teller (BET), X-ray diffractometer (XRD), SEM, AAS and UV/VIS/NIR techniques. The results showed that TiO(2)-Sn(4+) is fully anatase crystalline form and easily dispersed in water. Increasing the solid ratio of TiO(2)-Sn(4+) from 10 to 50% in the coating solution increased antibacterial effect.

Hybrid sol–gel coating on Al

New coating materials providing mechanical and chemical resistance to corrosion were developed for protection of metal surfaces. An aluminum plate surface was coated with polyurethane and epoxy based resins which were previously modified with ceramic powders, such as Al2O3, SiO2, or SiC. Effects of the type and particle size of ceramic powder, organic matrix, co-reactants, the dispersant type and mixing rate on the coating material were investigated. Coated metal surface was subjected to taber-abrasion, adhesion and corrosion tests. Surface properties and thermal resistance of the coating materials were characterized by scanning electron microscopy (SEM) and thermogravimetric and differential thermal analysis (TG/DTA). Results revealed that polyurethane based coatings, whether contain ceramic powder or not, seems to be more advantageous than epoxy based one, besides surface modified ceramic powders provide excellent properties to the coatings.

Removal of Inorganic–Organic Bound Cu(II) from Different Aqueous Solutions by New Adsorbents Synthesized by Sol–Gel Process

Abstract Hydrolysis product of alcohol modified titanium(IV)‐n‐propoxide and its coated form were prepared as new and regenerable adsorbents for adsorbing and removing Cu(II) ions from its different aqueous solutions. The hydrolysis and alcoholysis products and adsorbents were characterized using GC, 1H‐NMR, FT‐IR, SEM, and TG‐DTA analysis. It was found that Cu(II) ion adsorption rather increased when hydrolysis product of alcohol modified titanium(IV)‐n‐propoxide was coated with prehydrolyzed 3‐mercaptopropyltrimethoxy silane in n‐propanol and this coated material was used as adsorbent. Depending on the results of experiments performed at optimum conditions of initial Cu(II) concentration, amount of adsorbent, contact time, and pH, maximum adsorption of Cu(II), i.e., >98% has been achieved under the non‐competitive conditions, while almost 60% is achieved under the competitive conditions of Pb(II), Zn(II), Fe(III), and alkali and earth alkali metals. It was also concluded that Cu(II) adsorption efficiency is not affected from the media containing acetate, tannic acid, or Turkish Blue dye. The adsorbent was easily regenerated with 5 N HNO3 solution and used over and over again for the adsorption of Cu(II) ions.

Natural Pyrophyllite and M(OR)x Based MxOy Powders as New Adsorbents for Heavy Metal Adsorption

Heat treated hydrolysis-condensation products of aluminiumtri-sec-butoxide (Al(OBu s )3) and alcohol modified Al(OBu s )3 were synthesised by sol-gel process. These synthetic powders, natural pyrophyllite and their 3-mercaptoprophyltrimethoxysilane coated forms were utilised as adsorbents for the removal of Cu(II) ions from aqueous solutions. The adsorption increased when natural and synthetic powders coated with SH-Si were used. It was concluded that the dried powders obtained from the hydrolysis-condensation product of Al(OBu s )3 and its alcohol modified form, and coated pyrophyllite would substitute for Amberlite IR 120 Na form resin. Introduction The disposal of heavy metals by wastewaters has been considered as one of the most important environmental problem [1]. There are numerous examples of reports on water pollution and the majority agrees to adsorb the heavy metals on adsorbents to cope with this problem [2]. Clays are low cost adsorbents for organic molecules but they can not be used to adsorb toxic heavy metals without modification. On the other hand, when the clay surface is modified with organo-functional silanes, the surface gains perfect properties to remove toxic organic and heavy metals, depending on the type of functional silane [3]. Metal oxides obtained from the metal alkoxides by sol-gel process, and their forms coated with organo-functional silanes are also novel adsorbents for adsorption of toxic contaminants from aqueous solutions. Erdemoğlu et al. and Sayılkan et al. [4,5] synthesized new adsorbents by the hydrolysis-condensation reaction of titanium-n-propoxide, zirkonium-npropoxide and titanium etoxide and they coated the synthetic ZrO2 and TiO2 powders with amino-, mercaptoand epoxy functional silanes to prepare adsorbents for removal of Cu 2+ , Pb 2+ , Fe 3+ , aniline and phenol from aqueous solutions. In this study, it was aimed to develop novel and efficient adsorbent powders by using sol-gel process techniques and to utilise these powders as adsorbents for the removal of Cu(II) ions from aqueous solutions. The results of adsorption experiments were compared with Amberlite IR 120 Na form commercial resin (IR120). Materials and Methods Materials Pyrophyllite is a hydrous aluminium silicate mineral with the chemical formula of Al2Si4O10(OH)2. The pyrophyllite sample consisting of 28% Al2O3, 66.2% SiO2 and 4.27% loss on ignition at 1000°C was obtained from Malatya-Pütürge region of Turkey. Al(OBu s )3 was used as precursor to prepare synthetic powders. 3-mercaptoprophyltrimethoxysilane was used as coupling agent. 2Butoxyethanol (2-BuOEtOH) was used as modifier for Al(OBu s )3. Methyl iso-butyl keton (MIBK) and methanol used as solvents were stored over molecular sieve (Fluka, 3ÅXL8) for a day before use. Analytical grade Cu(NO3)2 were used to prepare Cu(II) solutions. Key Engineering Materials Online: 2004-05-15 ISSN: 1662-9795, Vols. 264-268, pp 2239-2242 doi:10.4028/www.scientific.net/KEM.264-268.2239