Sema Erdemoğlu

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.

Evaluation of polyphenol contents in differently processed apricots using accelerated solvent extraction followed by high-performance liquid chromatography–diode array detector

Concentrations of 17 polyphenols in ripe-fresh, sun-dried and sulfited-dried apricots either harvested from organic or pesticide-treated trees before harvest were determined using reverse-phase high-performance liquid chromatography with UV–Vis diode array detector, and the change of polyphenol profile with origin of the apricot product was established. Extraction of polyphenols was achieved using the accelerated solvent extraction technique (ASE). A mixture of methanol, water (70:30 v/v) including 0.1 g of tert-butylhydroquinone as solvent, 60 min extraction time, 60°C temperature and 1,500 psi pressure were found the most productive operating conditions for ASE. Concentrations of polyphenols in organic apricots were higher than pesticide-treated samples, and roughly the same in ripe-fresh and sun-dried apricots. Polyphenol concentrations of either organic or pesticide-treated sulfited-dried apricots were lower than the ripe-fresh apricots. Considering the organic ripe-fresh apricots, there was a decrease in some polyphenol concentration in the sulfited-dried apricots compared with the ripe-fresh apricot, and the range of decrease is between 1.4 and 53%.

Toxicological aspects of photocatalytic degradation of selected xenobiotics with nano-sized Mn-doped TiO2.

The toxic effects of two selected xenobiotics, bisphenol A (BPA) and atrazine (ATZ), were evaluated after photocatalytic degradation using nano-sized, Mn-doped TiO2. Undoped and Mn-doped TiO2 nanoparticles were synthesized. The samples were characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), UV-vis-diffuse reflectance spectra (DRS), X-ray fluorescence spectroscopy (XRF), and BET surface area. The photocatalytic efficiency of the undoped and Mn-doped TiO2 was evaluated for BPA and ATZ. The toxicity of the synthesized photocatalysts and photocatalytic by-products of BPA and ATZ was determined using frog embryos and tadpoles, zebrafish embryos, and bioluminescent bacteria. Possible toxic effects were also evaluated using selected enzyme biomarkers. The results showed that Mn-doped TiO2 nanoparticles did not cause significant lethality in Xenopus laevis embryos and tadpoles, but nonfiltered samples caused lethality in zebrafish. Furthermore, Mn-doping of TiO2 increased the photocatalytic degradation capability of nanoparticles, and it successfully degraded BPA and AZT, but degradation of AZT caused an increase of the lethal effects on both tadpoles and fish embryos. Degradation of BPA caused a significant reduction of lethal effects, especially after 2-4h of degradation. However, biochemical assays showed that both Mn-doped TiO2 and the degradation by-products caused a significant change of selected biomarkers on X. laevis tadpoles; thus, the ecological risks of Mn-doped TiO2 should be considered due to nanomaterial applications and for spilled nanoparticles in an aquatic ecosystem. Also, the risk of nanoparticles should be considered using indicator reference biochemical markers to verify the environmental health impacts.

Photocatalytic degradation of azo dye using core@shell nano-TiO2 particles to reduce toxicity

Clean and safe water is fundamental for human and environmental health. Traditional remediation of textile dye-polluted water with chemical, physical, and biological processes has many disadvantages. Due to this, nano-engineered materials are drawing more attention to this area. However, the widespread use of nano-particles for this purpose may lead to photocatalytic degradation of xenobiotics, while increasing the risk of nano-particle-induced ecotoxicity. Therefore, we comparatively evaluated the toxicity of novel synthesized core@shell TiO2 and SiO2 nano-particles to embryonic stages of Danio rerio and Xenopus laevis. The ability of photocatalytic destruction of the synthesized nano-particles was tested using toxic azo dye, disperse red 65, and the effects of reducing the toxicity were evaluated. The reflux process was used to synthesize catalysts in the study. The samples were characterized by scanning electron microscopy, X-ray fluorescence spectroscopy, X-ray diffractometry, BET surface area, and UV–vis-diffuse reflectance spectra. It was determined that the synthesized nano-particles had no significant toxic effect on D. rerio and X. laevis embryos. On the other hand, photocatalytic degradation of the dye significantly reduced lethal effects on embryonic stages of the organisms. Therefore, we suggest that specific nano-particles may be useful for water remediation to prevent human health and environmental impact. However, further risk assessment should be conducted for the ecotoxicological risks of nano-particles spilled in aquatic environments and the relationship of photocatalytic interaction with nano-particles and xenobiotics.

Fractionation and Speciation of Cu in Different Processing Apricots

An analytical procedure was proposed to study the operational fraction of Cu in ripe-fresh, sun-dried and sulphited-dried apricots harvested from either treated Bordeaux mixture or unexposed trees. Based on the methods that consists pressurized liquid extraction procedure and solid phase extraction to separate diverse Cu fractions on different sorbents such as Dowex 50Wx8-40 and Amberlite XAD-7, and then flame atomic absorption spectrometry (FAAS) and ion selective electrode were used for off-line determination of Cu concentrations in the effluents obtained.Total copper concentrations in different processing the apricot samples exposed to Bordeaux mixture were 4.58, 4.48 and 4.25 μg/g in ripe fresh, sun-dried, sulphuring-sun drying, respectively. However, Cu concentrations in the organic apricot samples were determined 2.92; 2.97 and 2.25 μg/g. While circa 40-59% of total copper are extractable with water solvent including about 67-68% cationic copper, 25-33% organically bound copper and 26- 44% labile in Kabaasi apricot samples. Besides, while about 27-48% of total copper are extractable with methanol: water solvents containing about 40-23% cationic copper, 60-78% organically bound copper and 56-71% of copper was absorbed in the stomach.It was applied to analytical procedures for Cu speciation in the apricot samples were verified and validated.

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