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Seawater activated TiO2 photocatalyst for degradation of organic compounds

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... Removal or remediation of pesticides can also be mediated by NT. NPs, NCs, immobilization of enzymes on NPs are some of the approaches [69]. Chlorpyrifos (pesticide) is a broadly used pesticide and shows acute toxicity. ...
... Various NMs have been developed with unique features to reduce contaminants specially heavy metals with living organisms for the treatment of industrial effluents, domestic wastewater, groundwater, surface water, and drinking water, including dendrimers, nano-iron and its derivatives, singleenzyme NPs, polymeric, and carbon-based NMs [69]. ...
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Industrial development together with the advances in technology have been used solely to overcome nature and to utilize its resources for a long while. Even after pollution and/or its consequences started to threaten lives and biodiversity went on a decline, there was no sufficient control over the industrial and municipal operations. However, a major change in the global perspective of industrial/technological progress has become a necessity-environment can not be sacrificed for development. Although it has not been achieved either by governments or industry itself, many countries try to prevent pollution at the source with the enforcement of regulations or to recuperate the environmental pollution in the light of current scientific research. The bioremediation methodology, which is among the biotechnological improvement methods, is efficient, economical, versatile, and recognized as an environmentally friendly solution. Bioremediation-recovery of pollution created by biodegradable pollutants with the aid of environmentally safe materials and methods-is one of the current subjects of research and application due to its advantages over available
... In recent years, Titanium dioxide (TiO 2 ) has attracted great attention due to its wide range of potential applications. TiO 2 nanostructures have particular relevance to photocatalysis, photovoltaics and photoelectrochemical cells which leads to numerous applications such as water splitting [1], self-cleaning [2,3] antibacterial, antimicrobial and degradation of antibiotics in wastewater [4][5][6], degradation of organic compounds [7][8][9], metal corrosion prevention [10] and abrasion [11], in electronics [12,13], photodynamic therapy [14], optical sensors [15], as well as in biological areas such as cancer therapeutics [16] and drug delivery [17]. All these applications are related to the unique properties of TiO 2 like high transparency in the visible, low cost, inertness, nontoxicity, and chemical and photochemical stability. ...
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A soft chemistry route is described to obtain glasses in the P2O5–Na2O–ZnO–H2O. It is based on the addition of zinc salts to coacervates prepared from sodium polyphosphate. The processing of these coacervates leads to polyphosphate glasses with the same properties as those of glasses prepared in the classical way. So far, little work has been implemented in this system using ‘coacervate route’. However, it makes an attractive method for coating and joining processes on the industrial scale. As the anion associated to zinc may take part in the adhesion mechanism, coacervate formation has been studied using zinc chloride, nitrate and sulphate as starting materials. The physical properties of the glasses obtained by this method are reported and potential applications of zinc and silver coacervate are described.
Article
Silica-coated titaniananoparticles are important in sunscreens, UV filters and optical nanocomposites. The surface characteristics (extent of coverage, texture and thickness) of in situ SiO2-coated, mostly rutiletitaniananoparticles made in one step by flame spray pyrolysis (FSP) were compared to FSP-made mixed (co-oxidized) SiO2/TiO2 ones by transmission electron microscopy (TEM), Raman, FT-IR spectroscopy, electrophoretic mobility and isopropanol chemisorption followed by mass spectroscopy. Increasing the silica content shifted the isoelectric point (IEP) toward that of pure silica for externally mixed SiO2 and TiO2, co-oxidized SiO2/TiO2 and low SiO2 content (<10 wt%) silica-coated TiO2 nanoparticles. At higher SiO2 contents, SiO2-coated titania exhibited negative ζ potentials at all pH values (and thus no IEP) indicating hermetic or complete coverage of the TiO2 surface by SiO2 as was confirmed by isopropanol chemisorption. Co-oxidized particles containing segregated TiO2 and SiO2 domains exhibited Si–O–Ti and Si–O–Si bonds of higher IR intensity than hermetically-coated TiO2. The latter exhibited a peak at 1225 cm−1 attributed to Si–O–Si asymmetric vibrations in contrast to the former.
Article
The reversible photoreduction of methylene blue in acrylate media is studied here. Methylene blue can be photoreduced using a benzyl dimethyl ketal photoinitiator upon 365nm irradiation. The photoreduction is due to the interaction of methylene blue with methyl radical which is generated when benzyl dimethyl ketal is photocleaved. The photoreduced polyacrylate sample exhibits reversible photoreduction behavior due to the cyclic processes of oxidation in air and reduction in nitrogen upon UV exposure. Since methylene blue is widely used across many disciplines, our results have many potential applications in sensors, data storage, electronic devices, etc.
Article
The process of low-temperature condensation of a KH2PO4 and NH4H2PO4 mixture, as the product of conversion of potassium chloride with ammonium dihydrogen phosphate, was investigated. At the same time, the ammonium ion was replaced with sodium ion (as Na2CO3) or calcium ion (as CaCO3 or CaO). The effects of process temperature (300-450 degrees C) and the initial mixture composition on the structure and on the qualitative constitution of produced polyphosphates were determined as were their water solubilities and the fraction of ortho, pyre, tripoly, and higher condensed phosphates. The most favorable conditions to obtain all water-soluble potassium-sodium polyphosphates or potassium-calcium condensed phosphates with controlled solubility were determined. The possibility of application of such products as complexing agents of nutrient microelements or as controlled-release fertilizers was considered.
Article
Photocatalytic degradation pathway of methylene blue (MB) has been studied over TiO2, 0.5wt.% Pt/TiO2, and 3wt.% Pt/TiO2 at ambient conditions (30°C and 1atm of air) by infrared (IR) spectroscopy. The reaction was proposed to be initiated via the abstraction of H from MB molecule by hydroxyl radical (·OH), followed by –CH3 elimination and CAr–N scission. The correlation in IR intensity between the decrease in C–H bond in MB molecule and the increase in hydroxyl group (–OH) at 3672cm−1 during the reaction (i) provides an indirect evidence to support the proposed ·OH-initiating pathway, (ii) suggests that the –OH sites could be related to OH generation sites, and (iii) offers new insights into the photoinduced hydrophilicity of the TiO2 surface. Subsequent breakup of the MB central ring via accepting protons and photogenerated electrons resulted in the formation of intermediates containing CO, COO−, and N–H groups.Deposition of 0.5wt.% Pt to TiO2 enhanced (i) the scission of and C–H bonds and (ii) the formation of intermediates containing CO and COO− groups. The latter suggests that Pt provided the sites for oxygen absorption, accelerating the formation rate of oxygen-containing intermediates. The comparable IR intensity of –OH at 3632cm−1 before reaction and –OH at 3672cm−1 during the reaction on TiO2 and 0.5wt.% Pt/TiO2 indicates that OH generation sites were not blocked by low Pt loading (i.e., 0.5wt.%). The simultaneous presence of OH generation, photoelectron generation, and Pt sites could play a synergetic role in enhancing and C–H bond scission and formation of CO and COO− species. Increasing Pt loading to 3wt.% resulted in the total elimination of –OH and the significant decrease in the MB degradation rate, indicating that the low activity of 3wt.% Pt/TiO2 could be attributed to the blocking of OH generation sites by the high Pt loading.
Article
Nanocrystalline I–F-codoped TiO2 was prepared by a sol–gel-impregnation method, using tetrabutylorthotitanate in a mixed NH4I–NH4F aqueous solution. The as-prepared TiO2 was characterized with UV–vis diffuse reflectance spectra, X-ray diffraction and nitrogen adsorption. The degradation of methylene blue (MB) over as-prepared TiO2 in aqueous solution under simulated sunlight irradiation was remarkably enhanced by codoping with I and F. The effects of codoping and calcination temperature on the photocatalytic activity and microstructures were investigated. The photocatalytic activity of as-prepared I–F-codoped TiO2 was remarkably higher than that of pure, I-doped, and F-doped TiO2 when the molar ratios of I and F to Ti were kept in the value of 10. The influence of I–F-modification on the photocatalytic activity was discussed by considering the higher surface area, entire anatase phase, effective dopant content, and stronger absorbance of sunlight, corresponding to the higher quantum efficiency. In addition to a complete removal of color, the as-prepared TiO2 was simultaneously able to oxidize MB and small amounts of intermediates such as formic acid and phenol were detected. After prolonged sunlight irradiation some intermediates almost vanished, and MB appeared to be eventually mineralized to NH4+, NO3− and SO42−.
Article
The photobleaching of methylene blue MB, sensitised by TiO2, in an aqueous solution is studied in the absence and presence of oxygen. In the absence of oxygen and in the presence of a sacrificial electron acceptor (SED), MB is photoreduced to its colourless leuco form, LMB, by the TiO2 photocatalyst. This same photoreduction process is observed even if an SED is not present, indicating that MB itself can act as an SED. The oxidation of LMB by oxygen to regenerate MB is significantly slower if the aqueous solution is acidified (0.01 mol dm−3 HClO4) and, at low partial pressures, the rate of reaction depends directly upon the concentration of dissolved oxygen. The TiO2-sensitised photobleaching of MB is irreversible in an oxygen-saturated aqueous solution, as expected, since the bleaching was due to an oxidative process. However, in an acidified solution (0.01 mol dm−3 HClO4), the photobleaching process, in an oxygen-saturated solution, generates LMB initially. The latter situation arises because, under acidic conditions, LMB reacts only very slowly with oxygen to form MB. The significance of these findings with respect to the popular use of photobleaching of MB as a demonstration of semiconductor photomineralisation is discussed.
Article
Photosensitization is a simple and controllable method for the generation of singlet oxygen in solution and in cells. Methods are described for determining the yield of singlet oxygen in solution, for measurement of the rate of reaction between singlet oxygen and a substrate, and for comparing the effectiveness of singlet oxygen generated by different photosensitizers in cells. These quantitative measurements can lead to better understanding of the interaction of singlet oxygen with biomolecules.
Article
This review discusses the mechanisms of generation and potential impacts of microplastics in the ocean environment. Weathering degradation of plastics on the beaches results in their surface embrittlement and microcracking, yielding microparticles that are carried into water by wind or wave action. Unlike inorganic fines present in sea water, microplastics concentrate persistent organic pollutants (POPs) by partition. The relevant distribution coefficients for common POPs are several orders of magnitude in favour of the plastic medium. Consequently, the microparticles laden with high levels of POPs can be ingested by marine biota. Bioavailability and the efficiency of transfer of the ingested POPs across trophic levels are not known and the potential damage posed by these to the marine ecosystem has yet to be quantified and modelled. Given the increasing levels of plastic pollution of the oceans it is important to better understand the impact of microplastics in the ocean food web.
Article
Anatase and rutile crystallites were isolated from Degussa (Evonik) P25 by selective dissolution with a hydrogen peroxide-ammonia mixture and diluted hydrofluoric acid, respectively, and used as standard samples for calibration curves of X-ray diffraction analyses. The results showed that P25 contains more than 70% anatase with a minor amount of rutile and a small amount of amorphous phase. The composition anatase/rutile/amorphous could be determined by analysis of P25 mixed with an internal standard, nickel(II) oxide. However, it was also found that the composition of P25 used in this study was inhomogeneous and changed depending on the position of sampling from the same package. Comparison of activities of original P25 and reconstructed P25 with those of isolated anatase and rutile particles suggested a less probable synergetic effect of the co-presence of anatase and rutile.
Article
ATP hydrolysis is the driving force of many life processes, yet the exact nature of and contributions to the energetics of this reaction are far from being clear. In particular, it is unclear how much of the driving force of this reaction is due to the separation of the already dissociated ADP + P(i) moieties rather than to the chemical event. This fundamental issue is explored here by ab initio calculations that use different solvation models, and it is found that, while the calculations are sensitive to the theoretical approach used, it is quite likely that the dissociation of the charged fragments makes a significant contribution to the energetics of ATP hydrolysis.
Article
Polyvinyl alcohol (PVA), boric acid and tri-iodide form a characteristic blue complex. For a number of PVA samples, prescribed conditions were used to examine the precision of the formation and spectrophotometry of the complex. The precision of calibration curves was 1-2 % over the range 0-4 mg of PVA per 50 ml of final solution, over which Beer's law holds. Greater deviations can be caused by faulty preparation and aging of individual PVA solutions. The absorbance is independent of the content of residual acetate groups in the PVA for the range 0-15 %. The limit of detection is about 0.01 mg of PVA in 25 ml of sample. A pink colour in the system is due to association of iodine with acetate groups in the PVA. A blue or green colour is due to helical envelopment of iodine molecules by PVA chains stiffened by scattered cyclic groups. The mechanisms of these effects are discussed.
Article
Plastic resin pellets (small granules 0.1-0.5 centimeters in diameter) are widely distributed in the ocean all over the world. They are an industrial raw material for the plastic industry and are unintentionally released to the environment both during manufacturing and transport. They are sometimes ingested by seabirds and other marine organisms, and their adverse effects on organisms are a concern. In the present study, PCBs, DDE, and nonylphenols (NP) were detected in polypropylene (PP) resin pellets collected from four Japanese coasts. Concentrations of PCBs (4-117 ng/g), DDE (0.16-3.1 ng/g), and NP (0.13-16 microg/g) varied among the sampling sites. These concentrations were comparable to those for suspended particles and bottom sediments collected from the same area as the pellets. Field adsorption experiments using PP virgin pellets demonstrated significant and steady increase in PCBs and DDE concentrations throughout the six-day experiment, indicating that the source of PCBs and DDE is ambient seawater and that adsorption to pellet surfaces is the mechanism of enrichment. The major source of NP in the marine PP resin pellets was thought to be plastic additives and/or their degradation products. Comparison of PCBs and DDE concentrations in mari
Article
The interaction between metaphosphate chains and the metal ions Ca2+ and Eu3+ has been studied in water by Eu3+ luminescence, infrared absorption, and 31P NMR spectroscopy. Two main families of sites could be identified for the metal ions in the aqueous polyphosphate colloidal systems: (1) cagelike sites provided by the polyphosphate chain and (2) a family which arises following saturation of cagelike sites. Occupation of this second family leads to supramolecular interactions between polyphosphate chains and the consequent destabilization of the colloidal system. In the polyphosphate-Ca2+ system, this destabilization appears as a coacervation process. Equilibrium existing between colloidal species as a function of the compositions could be reasoned based on the spectroscopic measurements. The determination of coordination numbers and the correlation of the results with the observation of coacervates show that Eu3+ luminescence properties can be used to probe in a unique way the coacervation process.
Plastics -the Facts 2019-An Analysis of European Plastics Production, Demand and Waste Data (Brussels)
  • Plasticseurope
PlasticsEurope, 2019. Plastics -the Facts 2019-An Analysis of European Plastics Production, Demand and Waste Data (Brussels).
Titanium dioxide pigment coated with silica and alumina
  • A J Werner
Werner, A.J., 1968. Titanium dioxide pigment coated with silica and alumina. U. S. Jpn. Outlook 3 (437), 502.