UV Photodegradation Research Articles

Removal Of Phenol From Wastewater By Using Low-Cost Catalyst From Metal Production

Abstract Utilization of AOPs (Advanced oxidation processes) as an emerging technology for removing of pollutants from wastewater is developed. In this paper, UV photodegradation was used for removing of phenol from wastewater. As a source of UV radiation medium pressure mercury lamp with output 400W was used. The influence of low-cost catalysts on this process was also monitored. Wastes from metal production, red mud and black nickel mud, were used as catalysts.

Study of the effects of incorporation of UV-absorbing compound in parylene C films

Novel thin films of UV-absorber-doped parylene C were produced by a deposition technique consisting in a coarse vacuum co-evaporation of parylene C dimer and 2-hydroxy-4-(octyloxy)benzophenone (UVabs). Co-deposited samples were obtained by evaporating UVabs compound at temperatures ranging from 100 °C to 120 °C. The films were characterized by Fourier transform infrared (FT-IR) analysis, Rutherford backscattering spectrometry (RBS), x-ray diffraction (XRD), atomic force microscopy (AFM), optical absorption and emission spectroscopy. RBS and XRD analyses show that the UVabs evaporation strongly affects the deposition and growth of parylene film, giving rise to a significant increase in the film thickness and to a change in the microstructure. UV photodegradation tests of the co-deposited samples were carried out in air and showed that the photodegradation of co-deposited samples was slower than that of parylene alone, but the change in the film microstructure as induced by absorber incorporation gave rise to a faster deterioration of the C–Cl groups.

UV and simulated solar photodegradation of 17α-ethynylestradiol in secondary-treated wastewater by hydrogen peroxide or iron addition

The extensive use of estrogens and their release, through various pathways, into the environment, constitutes an emerging environmental problem that poses serious threats onto public health. In this work the efficiency of UVC/H2O2 and solar/Fe2+ treatment to degrade 17α-ethynylestradiol (EE2) in environmentally relevant concentrations of 100μg/L in secondary-treated wastewater matrices was investigated. Also, photolytic treatment was performed under different irradiation sources, namely UVC, UVA and simulated solar light. The effect of H2O2 (0–20mg/L) and Fe2+ (0–15mg/L) concentration was investigated and, at optimal operating parameters, EE2 removal was 100% after 15min of UVC/H2O2 treatment, while EE2 removal reached 86% after 60min of solar/Fe2+ treatment. In addition, the effect of water matrix and pH was studied. Total organic carbon (TOC) and yeast estrogen screening (YES) measurements showed the formation of stable intermediate products during EE2 treatment and an attempt to elucidate the reaction pathways and mechanisms through the identification of transformation products (TPs) by means of UPLC–MS/MS was made. Several TPs, including quinone methide and 1,2-quinone derivatives, were identified and competing pathways were suggested, in which hydroxylation, alkylation, dealkylation, demethylation and dehydroxylation, amongst others were described as major transformation mechanisms.

Aquatic photolysis of florfenicol and thiamphenicol under direct UV irradiation, UV/H2O2 and UV/Fe(II) processes

Abstract The destruction of antibiotic pharmaceuticals, florfenicol (FF) and thiamphenicol (TAP), by direct UV alone, UV/H2O2 and UV/Fe(II) processes was investigated. For direct UV photodegradation, the removal efficiency increased with the decreasing of initial FF and TAP concentrations. Radical scavengers’ experiments showed that singlet oxygen was the most important in UV photodegradation of FF and TAP, and accounted for 67.1% and 69.1% of their total photodegradation, respectively. In UV/H2O2 process, degradation rate increased comparing to UV irradiation alone. An increase in H2O2 concentration up to the optimum concentration of 5.0 mM led to the highest destruction; however, the effect of hydroxyl radical quenching by H2O2 became significant for high H2O2 concentrations. Both the presence of anions and increasing of solution pH contributed to a decrease in the destruction rate of FF and TAP. The presence of Fe(II) at pH 3, compared to that without Fe(II), revealed a higher rate of photodegradation due to the formation of reactive hydroxyl radicals. The optimum condition was found for an initial Fe(II) concentration of 0.1 mM. Additionally, O2 accelerated the degradation rate of FF and TAP in UV/Fe(II) process. Major degradation products of FF and TAP by UV irradiation, including degradation intermediates, organic acids and some inorganic ions were detected by LC/MS/MS and ion chromatography (IC) and the main photolysis products of FF and TAP were identified. The possible photodegradation pathways of FF and TAP were proposed. The toxicity of the photolysis compounds was evaluated using luminescent bacteria, and the results revealed that the toxicity of the final products was lower than that of FF and TAP.

Hazard Analysis in Phenol Removal from Natural Water Sources

AOP processes (Advanced Oxidation processes) are presently used as an alternative to traditional methods for removing of persistent pollutants from wastewater. Article is focused on removal of phenol from wastewater by using UV photodegradation. As a source of UV light medium pressure mercury lamp with output 400W is used. The aim of article is to perform hazard analysis in work with UV photoreactor by HAZOP method, eliminate risks in working with this equipment and propose corrective measures to improve quality of health and safety during work.

Preparation, characterization, and photocatalytic activity of three-dimensionally ordered macroporous hybrid monosubstituted polyoxometalate K5[Co(H2O)PW11O39] amine functionalized titanium catalysts

A novel and efficient, amine-functionalized three-dimensionally ordered macroporous (3DOM) titanium (Ti) catalyst modified using transition metal-monosubstituted polyoxometalate (3DOM K5[Co(H2O)PW11O39]–(EtO)3SiCH2CH2CH2NH2–TiO2 or 3DOM PW11Co–APS–TiO2) was fabricated by self-assembly method. First, methanol bath was used to soak polystyrene spheres to obtain large size 3DOM TiO2, which was further functionalized using 3-aminopropyltriethoxysilane (APS). Amine-functionalized 3DOM TiO2 materials impregnated with monosubstituted polyoxometalate (POM, K5[Co(H2O)PW11O39]) were prepared by coordination of cobalt (Co) present in the units of POM, with the amine groups present on the surface of 3DOM TiO2. The materials so obtained were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, Inductively coupled plasma atomic emission spectrometry, Ultraviolet–visible (UV–vis) diffuse reflectance spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, Scanning electron microscopy, Transmission electron microscopy, and nitrogen adsorption–desorption tests. The results showed that the primary Keggin structures of the composites remained intact, simultaneously, 3DOM PW11Co–APS–TiO2 had anatase crystalline structure, and PW11Co was successfully bonded to 3DOM TiO2 by CoN bond with APS as the coupling agent. Broadening of absorption band was observed for the product compared to the monomers, 3DOM TiO2 and PW11Co. However, the 3DOM structure was retained in the product; therefore, the accessibility of the diffusing species was significantly improved because of the permeability offered by the macroporous structure. The UV photocatalytic degradation of organic pollutants revealed better activities of 3DOM PW11Co–APS–TiO2 compared to PW11Co, 3DOM TiO2, and PW11Co–APS–TiO2. Moreover, 3DOM PW11Co–APS–TiO2 exhibited superior photocatalytic degradation of Rhodamine B (RB), Salicylic acid (SA), Congo red (CR), and Malachite green oxalate (MG) under microwave-assisted irradiation. Leakage of PW11Co from the hybrid photocatalyst was barely observed during the photocatalytic tests, attributed to strong coordination interactions between the Keggin units and the amine-functionalized Ti surface. The capture experimental results of photocatalysis revealed that the dominant active species were OH• and O2−•. Moreover, in this study, the procedure and possible mechanism of the UV photodegradation of organic pollutants in the aqueous system was proposed and discussed.

Enhanced ferroelectric and UV photocatalytic properties in a Bi4Ti3O12@ZnO core–shelled nanostructure

Composited Bi4Ti3O12@ZnO nanoparticles with a core of Bi4Ti3O12 (BIT) and a shell of ZnO have been synthesized by liquid chemical reaction method. Compared with pure BIT nanoparticles, the ferroelectricity in BIT@ZnO core–shell nanostructure was greatly enhanced. Moreover, the dielectric loss of BIT@ZnO is lower than that of BIT nanoparticles in a low frequency range. The band gap energy of BIT@ZnO core@shell nanostructure is larger than that of BIT, which formed as a type-II band alignment. Furthermore, the BIT@ZnO core–shell nanoparticles exhibit better UV photodegradation activity for organic contaminant. Such a BIT@ZnO core@shell nanostructure may have potential applications in microelectronics, photoelectronic, and photocatalytic of contamination.

Hybrid sol–gel layers containing CeO2 nanoparticles as UV-protection of plastic lenses for concentrated photovoltaics

Fresnel lenses made of polymethylmethacrylate (PMMA) represent a cost-effective approach for concentrated photovoltaic (CPV) panels. The lens must sustain suitable working performance during the whole lifetime of the photovoltaic plant, as UV photodegradation is the main issue to be avoided. In this work, PMMA sheets were covered with a hybrid organic–inorganic sol–gel coating consisting of a matrix of an organically modified silicate (ORMOSIL) in which CeO2 nanoparticles 10–20nm in size were dispersed, acting as the UV-absorbing agent. Ceria contents up to 40% w/w were studied and blended with the precursor ORMOSIL solution before deposition and in-situ polymerization at 80°C. The UV–visible spectra were analyzed between 200 and 800nm. Furthermore, the effect of the aging on outdoor weathering was investigated for the coated PMMA sheets and compared to the unprotected sample. The results show that a load of 30% w/w of ceria nanoparticles provides a reasonable compromise in terms of UV protection and absorption in the visible range. The weathering test also demonstrates enhanced protection against UV degradation for the coated PMMA sheet compared to the bare substrate, although the adherence should be further improved for optimum performance.

Synthetic zinc layered hydroxide salts intercalated with anionic azo dyes as fillers into high-density polyethylene composites: first insights

Using a co-precipitation process, we intercalated zinc layered hydroxide salts (zinc LHS) with anionic orange azo dyes (methyl orange—MO or orange II—OII), co-intercalated with chloride anions; for comparison purposes, we also intercalated zinc LHS with chloride anions only, which furnished ZHC. After XRD characterization, we filled high-density polyethylene (HDPE) with the intercalated materials and submitted them to melt compounding and injection molding. We also obtained control batches of HDPE filled with ZHC, the MO sodium salt, or the OII sodium salt. XRD, thermal (simultaneous TGA/DTA), DSC, SEM, and UV-radiation photostability analyses confirmed that homogeneous composites were obtained. HDPE filled with zinc LHS intercalated with MO (a probable more hydrophobic anionic azo dye) displayed improved mechanical properties, good interface bonding, and stability to UV photodegradation; the other fillers afforded materials with poorer mechanical properties.

Reusable PdO/Al2O3–Nd2O3 photocatalysts in the UV photodegradation of phenol

The UV photodegradation of phenol in aqueous medium using PdO supported on binary Al2O3–Nd2O3 oxides as photocatalysts was studied. The PdO/Al2O3–Nd2O3 photocatalysts were prepared by the sol–gel method and characterized by N2 physisorption, XRD, Raman spectroscopy and UV–vis diffuse reflectance spectroscopy. Bare PdO/γ-Al2O3 was found active for the photodegradation of phenol in aqueous medium. However, the addition of Nd2O3 to the γ-Al2O3 improves the photocatalytic activity of PdO photocatalysts as well as the decrease of dissolved organic carbon in aqueous milieu. Highest photocatalytic activity of PdO photocatalysts was observed for 10wt% of Nd2O3 added to the γ-Al2O3 increasing the activity by a factor of two with respect to that of PdO/γ-Al2O3 after six hours of irradiation. The photocatalytic activity in the degradation of phenol by using the recovered PdO/Al–Nd photocatalysts is preserved after reaction.

Ozone-assisted UV254 nm photodegradation of gaseous ethylbenzene and chlorobenzene: Effects of process parameters, degradation pathways, and kinetic analysis

Ultraviolet photodegradation can destroy a wide range of organic compounds and has gained considerable interest for use in reducing environmental pollution. In the present study, ozone-assisted UV photodegradation was developed for the decomposition of gaseous ethylbenzene (EB) and chlorobenzene (CB). The effects of various experimental parameters were investigated, namely initial concentration, initial ozone addition, relative humidity, and reaction time. The results showed that an ozone/EB ratio of 2.5 and an ozone/CB ratio of 1.5 increased the conversion efficiencies 13.0 and 6.3 times, respectively, compared with photolysis alone. The relative humidities of the reaction media affected the target conversions, and also the dominant oxidizer in the conversion process (O3 for EB and hydroxyl radicals for CB). Possible pathways and mechanisms were suggested on the basis of the intermediates identified, some of which were more soluble and biodegradable than the target compounds. Two kinetic models, based on initial concentration and ozone addition, were developed to describe the EB and CB conversion behaviors. The preliminary results indicated that ozone-assisted photodegradation enhanced gaseous EB and CB decomposition, and that this could be a promising technology for the conversion of recalcitrant and insoluble volatile organic compounds.

Determination of Sucralose by Controlled UV Photodegradation Followed by UV Spectrophotometry

Abstract A simple and time-efficient UV spectrophotometric method was developed for the determination of sucralose in artificial sweeteners. The procedure is based on the UV spectrophotometric determination of the photodegraded product at 270 nm in alkaline medium (pH 12). LOD for this method was 0.02 g/L, and the calibration curve was found to obey Beer's law in the concentration range of 0.1 to 1.2 g/L, with a correlation coefficient (R2) value of 0.9977. The proposed method was studied for accuracy and precision.

Combining Top-Down and Bottom-Up Routes for Fabrication of Mesoporous Titania Films Containing Ceria Nanoparticles for Free Radical Scavenging

Nanocomposite thin films formed by mesoporous titania layers loaded with ceria nanoparticles have been obtained by combining bottom-up self-assembly synthesis of a titania matrix with top-down hard X-ray lithography of nanocrystalline cerium oxide. At first the titania mesopores have been impregnated with the ceria precursor solution and then exposed to hard X-rays, which triggered the formation of crystalline cerium oxides within the pores inducing the in situ growth of nanoparticles with average size of 4 nm. It has been observed that the type of coordinating agent in the solution plays a primary role in the formation of nanoparticles. Different patterns have been also produced through deep X-ray lithography by spatially controlling the nanoparticle growth on the micrometer scale. The radical scavenging role of the nanocomposite films has been tested using as a benchmark the UV photodegradation of rhodamine 6G. After impregnation with a rhodamine 6G solution, samples with and without ceria have shown a remarkably different response upon exposure to UV light. The dye photodegradation on the surface of nanocomposite films appears strongly slowed down because of the antioxidation effect of ceria nanoparticles.

UV and visible light photodegradation effect on Fe–CNT/TiO2 composite catalysts

Using multi-walled carbon nanotube (CNT) as an one-dimensional support, we have succeeded in uniformly anchoring of TiO2 and Fe nanoparticles at its surface. The as-prepared Fe–CNT/TiO2 composite photocatalysts have been investigated by degrading methylene blue (MB) under UV and differently intensified visible light irradiation. The ability of CNT to store and shuttle electrons, and Fe nanoparticles demonstrate its capability to serve as a yield and transfer electrons on demand to separate h + /e − pairs. Moreover, the MB photodegradation increase with an increase of visible light intensity can be ascribed to the enhancement MB cationic radical. In addition, chemical oxygen demand (COD) of piggery waste and reduction efficiency of Cr (IV) was done at regular intervals, which gave a good idea about mineralization of wastewater.

Photodegradation of three benzotriazoles induced by four FeIII–carboxylate complexes in water under ultraviolet irradiation

Environmental context Benzotriazoles are chemicals widely used to inhibit corrosion in various industrial processes and in household products. They persist in aquatic environments, even under UV irradiation, and thus there is a need to improve their photolytic degradation to minimise the environmental exposure risks. We investigated the effects of four iron–carboxylate complexes on the UV photodegradation of three benzotriazoles in aqueous solutions and show that they significantly increase the degradation rates of benzotriazoles. Abstract The effects of FeIII–carboxylate complexes on the photodegradation of three benzotriazoles (BTs), i.e. benzotriazole (BT), 5-methylbenzotriazole (5-TTri) and 5-chlorobenzotriazole (CBT) in aqueous solutions were investigated under exposure to UV irradiation at 254nm in the presence of FeIII and four carboxylate ions (oxalate, tartrate, succinate and citrate). The results showed that the presence of FeIII–carboxylate complexes significantly enhanced the photodegradation rates of all three selected BTs. The photodegradation of BT, 5-TTri and CBT followed first-order reaction kinetics with half-lives ranging from 0.57 to 3.98h for BT, 6.08 to 8.25h for 5-TTri and 2.63 to 5.50h for CBT in the four systems of the FeIII–carboxylate complexes. In comparison, the half-lives ranged between 3.40 and 4.81h for BT, 6.42 and 11.55h for 5-TTri and 4.13 and 6.79h for CBT in pure aqueous solution and in the presence of FeIII or carboxylate. The degradation rates of these BTs were dependent on the pH values, type of carboxylate and FeIII/carboxylate ratios. Both BT and CBT showed the highest photodegradation rates with the shortest respective half-lives of 0.57 and 2.63h at the initial FeIII/oxalate ratio of 10/200µmolL–1 in aqueous solutions at pH 3, whereas 5-TTri had the highest photodegradation rate with the shortest half life of 6.08h at the initial FeIII/succinate ratio of 10/10µmolL–1.

Synthesis, characterization of cesium and cobalt substituted wells–Dawson heteropolyoxotungstates salts and their photocatalytic applications

Heteropoly compounds in the solid state are ionic crystals (sometimes amorphous) consisting of large polyanions, cations, water of crystallization, and other molecules. Heteropolyacids (HPAs) have several advantages as catalysts. On the one hand, they have a very strong Bronsted acidity, especially the cobalt and cesium salts; on the other hand they are exhibiting fast reversible multielectron redox transformations under mild conditions. The cobalt and cesium salts of wells- Dawson HPAs were synthesized and characterized using elemental analysis and spectroscopic techniques ( 31 P-NMR, FT-IR). The wells-Dawson anions possess the ability to accept or release electrons through an external potential or upon exposure to UV radiation (photochemical reactions). The catalytic tests of these salts were investigated on phenol degradation where the UV photodegradation of acidified aqueous solutions (pH = 2) were studied in a batch photoreactor under ambient temperature and continuous circulation of phenol solution. The results reveal high catalytic activity for two HPAs, the best catalyst is the salt of cesium; where the presence of cesium improves significantly both the photcatalytic activity and the selectivity to oxalic acid.

Spectroscopic study of the effect of a new metal chelate on the stability of PVC

This work deals with the preparation of a new tetradentate ligand [ H2L] of the N2O2 type, N{2[3(1-carboxyiminoethyl)-1-phenyl]butilydene-2-amino propionic acid}, and its metal complexes with Cr(III), Fe(III), Cu(II) and Zn(II) and fully characterized by H1 NMR, C13 NMR, FT-IR, UV–Vis, CHN elemental analysis, magnetic moment and molar conductance in DMF solutions. Based on the experimental results obtained, octahedral geometries of Cr(III) and Fe(III) have been suggested, while Cu(II) and Zn(II) had square planar and tetrahedral symmetries, respectively.The effect of this new metal complex on the photo degradation of poly(vinyl chloride) PVC films blended with a concentration range of 2–2.5% by weight of this new complex was investigated. The changes in the average molecular weight of PVC with irradiation time were tracked to determine the order of activities of each metal complex toward the photodegradation of PVC, andthe photodegradation of PVC films was determined by measuring carbonyl, hydroxyl and polyene indices. The results showed that Cr(III) and Fe(III) complexes increase the rate of C–C cleavage and behave as UV photo degradation substances, while the Zn(II) complex behaves as a UV stabilizer.

Hydrogen peroxide-assisted low pressure UV photodegradation of atrazine in aqueous solution

Aqueous solutions of atrazine (ATZ, 2-chloro-4-ethylamino-6-isopropylamino-1, 3, 5-triazine) were photolysed (λ = 254 nm) by low pressure UV/H2O2 process (LP/UV/H2O2) under a variety of parameters including hydrogen peroxide, the initial concentration of ATZ, pH, and humic acid. The results show that the most favourable reaction condition appears to be a moderate concentration of H2O2 from 100 mg/L to 120 mg/L. The presence of humic acid in the solution has a negative impact on the LP/UV/H2O2 treatment because of scavenging effects. Ninety percent of ATZ is destroyed in one hour under the optimum conditions. In this study, LP/UV/ H2O2 treatment of ATZ yielded several organic by products which are identified, including DIA, DEA, OHDIA, OHDEA, DAA and OAAT. They are quantified over the range of treatment tested and the ATZ degradation scheme is proposed combined with by products information.

Comparison of the nanoparticles performance in the photocatalytic degradation of a styrene–butadiene rubber nanocomposite

AbstractMuch has been talking about the advantages of polymeric nanocomposites, but little is known about the influence of nanoparticles on the stability of these materials. In this sense, we studied the influence of both oxides of zirconium and titanium, known to have photocatalytic properties, as well as the influence of synthetic clay Laponite on the photodegradation of styrene–butadiene rubber (SBR). SBR nanocomposites were prepared by the colloidal route by mixing commercial polymer lattices and nanometric anatase TiO2, monoclinic ZrO2 or exfoliated Laponite clays colloidal suspensions. To better understand the degradation mechanisms that occur in these nanocomposites, the efficiency of different photocatalysts under ultraviolet radiation was monitored by FT‐IR and UV–vis spectroscopies and by differential scanning calorimetric. It was observed that TiO2 and ZrO2 nanoparticles undoubtedly acted as catalysts during the photodegradation process with different efficiencies and rates. However, when compared to pure SBR samples, the polymer degradation mechanism was unaffected. Unlike studies with nanocomposites montmorillonite, exfoliated laponite clay effectively acts as a photostabilizer of polymer UV photodegradation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Mass transfer and degradation dynamics analysis of biofiltration enhanced by ultraviolet photodegradation for the removal of hydrophobic alpha-pinene

Ultraviolet photodegradation (UV) was utilized as a pretreatment to enhance the biofiltration process (BF and BTF) for the removal of hydrophobic α-pinene. Based on the experimental data, the mass transfer behavior and microbial activity were analyzed by the theoretical models. The gas phase saturated constant K m of α-pinene was 1.0 g m -3 in the UV-BTF, 20 times than that in the sole BTF; while this value in the sole BF was slightly higher than that in the UV-BF. Fitted by the Ottengraf-van den Oever model, the critical inlet concentration in the UV-BTF was 555.22 mg m -3 , which was much higher than that in other systems. Through the analysis of microbial activity and specific oxygen utilization rate, the biofilm in the UV-BTF was much more active, and the maximum specific oxygen utilization rates for α-pinene and its photodegradation intermediates were respectively 1.16, 0.34, 0.41and 0.25 mgO 2 mg -1 DW h -1 , slightly higher than 150%–200% of the values in other systems. Such results illustrated that UV photodegradation could reduce the mass transfer inhibition for α-pinene and simulate the growths of microorganisms in the subsequent BTF, thus enhancing the overall removal capabilities. But the UV technology was not a suitable pretreatment for the subsequent BF owing to BF’s own characteristics and cumulative toxic effects of ozone.