Photodegradation Intermediates Research Articles

Enhanced Photocatalytic Performance of Porphyrin/Phthalocyanine and Bis(4‐pyridyl)pyrrolidinofullerene modified Titania

AbstractZinc(II), copper(II) and cobalt(II) metallated porphyrins/phthalocyanines and bis(4‐pyridyl) pyrrolidinofullerene (9) were used in a supramolecular approach for the sensitization of titania. Spectral properties of the chromophores were examined in the solid state showing strong absorptions at 700 and 800 nm for porphyrins and phthalocyanines, respectively. The interaction between the chromophores and a dual ligand was investigated spectroscopically. Titania‐based composites sensitized with 9 and cobaltous porphyrin exhibited the highest photocatalytic activity against both phenol and methylene blue under solar irradiation. Photodegradation intermediates were determined based on LC‐UV‐Vis‐MS analysis. It is expected that the composites will be applied for remediation of aqueous environmental samples from transparent and colorful pollutants.

Photocatalytic degradation of Rhodamine B and Ibuprofen with upconversion luminescence in Ag-BaMoO4: Er3+/Yb3+/K+ microcrystals

Abstracts Silver dispersed BaMoO 4 octahedron microcrystals doped with Er 3+ , Yb 3+ , and K + were synthesized by microwave hydrothermal process. The photocatalytic activity of different samples toward the degradation of Rhodamine B (Rh B) dye and Ibuprofen (IBP) drug were carried in solar light and visible light irradiation, respectively. The sample, Ag-BaMoO 4 : Er 3+ /Yb 3+ , degraded the Rh B within 90 min about 99.60%, which is nearly 30 times as compared to the host material BaMoO 4. Similarly, Ag-BaMoO 4 : Er 3+ /Yb 3+ , degraded the IBP within 90 min about 41.49%, which is nearly 31 times as compared to the host in visible light. IBP photodegradation intermediates were identified by high-resolution quadrupole-time of flight-electrospray ionization-mass spectrometry (HR-QTOF ESI/MS) in negative ion mode and detailed degradation pathway mechanism was proposed. Under 980 nm excitation, two strong green emission peaks (526 nm and 555 nm) and a less intense red emission peak (661 nm) were observed, which are assigned to the 2 H 11/2 → 4 I 15/2 , 4 S 3/2 → 4 I 15/2 , and 4 F 9/2 → 4 I 15/2 transitions of the Er 3+ ions, respectively. Two photons upconversion process for green emission was observed. The upconversion luminescence intensity was increased by two-fold in magnitude by the addition of K + ion in Er 3+ /Yb 3+ doped BaMoO 4 . Moreover, silver particles were found to favor the photocatalytic activity while K + ions significantly enhanced upconversion. The photocatalytic as well as upconversion mechanism was explained. The combination of efficient photocatalytic activity and upconversion emission of the Ag-BaMoO 4 : Er 3+ /Yb 3+ /K + make the material suitable for the multifunctional application.

Study of the photodegradation of a fragrance ingredient for aquatic environmental fate assessment

Photodegradation is an important abiotic degradation process to be taken into account for more accurate assessment of the fate of chemicals in the aquatic environment, especially those that are not readily biodegradable. Although the significant role of indirect photodegradation in the environmental fate of chemicals has been revealed in recent research, because of the many confounding factors affecting its kinetics, no straightforward approaches can be used to investigate this degradation process for environmental fate assessment. The indirect photodegradation of a fragrance ingredient named Pamplewood was studied in this work for its fate assessment. Indirect photodegradation rates under various indoor and outdoor conditions were measured by using an LC-MS method. Although the half-lives varied from 4 to 13 days, they collectively indicated that Pamplewood is intrinsically photolabile and can undergo rapid photodegradation. Results from quencher experiments revealed that ⋅OH was the main reactive intermediate responsible for indirect photodegradation, with a half-life of about 18 days in sunlit surface water, based on the experimentally determined second-order rate constant (8.48 ± 0.19 × 109 M−1 s−1). Photodegradation products of Pamplewood were also studied by GC-MS, LC-MS and total organic carbon content analyses. The results indicated that intermediates of Pamplewood photodegradation continued to photodegrade into smaller and more polar species. Complete mineralization of Pamplewood was observed when it was reacted with hydroxyl radicals in an aqueous solution. This novel approach can be applied for a more realistic environmental fate assessment of other non-readily biodegradable, hydrolysis-resistant, and non-sunlight-absorbing fragrance ingredients.

In Situ ATR-FTIR Investigation of Photodegradation of 3,4-Dihydroxybenzoic Acid on TiO2

The catalytic photo-oxidation of 3,4-dihydroxybenzoic acid on TiO2 has been studied by in situ ATR-FTIR in flowing water and in flowing wet air/nitrogen gas. In flowing water it was difficult to observe photodegradation intermediates despite photocatalytic action during UV illumination. In the flowing wet air/nitrogen system carboxylic acids and carbonates were observed. It was shown that water plays an important role in the formation of oxidation active species. Oxygen shows a prominent role for carboxylic acid degradation, but the photogenerated hole plays the important role for the 3,4-dihydroxybenzoic acid ring cleavage.

Effect of TiO2–Pd and TiO2–Ag on the photocatalytic oxidation of diclofenac, isoproturon and phenol

The effects of silver and palladium metals on the photocatalytic degradation of diclofenac sodium salt (DCF), isoproturon (IP) and phenol (PHL) in water over lab-made TiO2 synthesized following a sol–gel method were investigated. Silver and palladium catalysts were prepared by photodeposition at 1wt.% of loading metal. The resulting materials were characterized through BET, XRD, TEM, SEM, XPS and DRS-UV–Vis. The photodeposition test conditions of both metals determined their final oxidation state, with reduced particles of palladium and silver as well as silver oxides found on the catalysts. The results showed that the type of metal had different effects on the photodegradation mechanism depending on the nature of the pollutants. Accordingly, the highest degradation rate for IP and DCF was obtained when using the catalyst photodeposited with palladium and for PHL the catalyst photodeposited with silver. The photodegradation intermediates of PHL, DCF and IP were also identified.

Antimicrobial, antioxidant and cytotoxic effect of Molybdenum trioxide nanoparticles and application of this for degradation of ketamine under different light illumination

A hydrothermal method was employed to synthesize Molybdenum trioxide (MoO3) nanoparticles. The synthesized samples were evaluated for photocatalytic properties and biological application. The nanoparticles characterized by scanning electron microscopy, powder X-ray diffraction, transmission electron microscopy, an energy dispersive X-ray spectrometer and UV–Vis DRS spectra. The synthesized MoO3 NPs were found to be spherical in shape with size in the range of 75nm. The synthesized MoO3 nanoparticles have good optical properties with 2.78eV of band-gap. The photocatalytic properties of the synthesized MoO3 nanoparticles were carried out by performing the degradation of ketamine under visible, UV and sunlight irradiations. A high efficiency was observed between sunlight and MoO3 nanoparticles for the photocatalysis reaction. Two compounds as intermediates of photo-degradation of ketamine under visible and UV lights were detected. The antifungal activity of the nanoscale MoO3 against Candida albicans and Aspergillus niger was assessed using the disc-diffusion susceptibility tests. All MoO3 nanoparticles concentrations showed good ABT radical scavenging activity. Then, this research has been presented to exhibit the synthesized MoO3 NPs which indicated a high antibacterial activity against Gram negative and positive bacteria and were also proved to exhibit excellent cytotoxic influence on lung and breast cancer cell lines. The results show that the high applicability of MoO3 nanoparticles biologically was great and is environmentally friendly.

Photocatalytic degradation of hazardous Food Yellow 13 in TiO2 and ZnO aqueous and river water suspensions

The photocatalytic degradation of the prevalent colourful food additive, Food Yellow 13 (FY13), was examined in TiO2 and ZnO aqueous suspensions under solar irradiation. Series of physicochemical properties of the applied photocatalysts was determined. As a benchmark of the influence of the natural conditions, photocatalytic studies were performed in the river water. Goldapa river, located in ‘The Green Lungs of Poland’, was chosen for investigations. The influence of the initial dye concentration, photocatalyst loading, pH and a buffer addition was studied. FY13 decolourization during its degradation under solar irradiation was monitored spectrophotometrically, while Raman and TGA techniques were applied to study its adsorption on the surface of TiO2 and ZnO. Photodegradation intermediates were detected and FY13 decomposition pathway was proposed on the basis of LC/ESI–MS/MS measurements. Application of the both photocatalysts led to the complete decomposition of FY13, which was accompanied by a visual decoulorization. The final degradation metabolite was identified as pyridinecarboxaldehyde. Eventually, ZnO was found to be 1.8 and 9.6 times more efficient then TiO2 in the photocatalysis process performed in aqueous and river water suspensions, respectively.

Investigation of photocatalytic activity of pure strontium hydroxyapatite and its Ti-substituted and TiO2 loaded forms

Photocatalytic activity of Strontium hydroxyapatite (SrHAP) was tested taking the degradation of p-nitrophenol (pnp) as a model reaction and its activity was compared with that of modified SrHAP (Ti4+ Substituted SrHAP and TiO2 loaded SrHAP). The compounds were synthesized by reflux method and characterized by powder XRD, FT-IR, SEM, TEM, UV–vis DRS and BET surface area analyses. Absorption edge of SrHAP (∼320nm) was found to be shifted to longer wavelength in the case of 5 mol%Ti-SrHAP and 20wt% TiO2-SrHAP. The photodegradation of p-nitrophenol studied using 365nm UV source showed the photocatalytic activity trend 20wt%TiO2-SrHAP>Ti-SrHAP>SrHAP. Photodegradation intermediates were identified by UV–vis and HRLC-MS analysis and possible degradation pathways were proposed. Photocatalytic degradation of pnp catalyzed by SrHAP and TiO2 loaded SrHAP followed hydroquinone route whereas, the process catalyzed by Ti4+ substituted SrHAP followed catechol route.

Synergistic effects of TiO2 and Cu2O in UV/TiO2/zeolite-based systems on photodegradation of bisphenol A

In this study, TiO2/zeolite (TZ)-based composite was utilized to degrade bisphenol A (BPA) under ultraviolet (UV) irradiation. The effects of the TiO2 and Cu2O doses in TZ and Cu2O/TiO2/zeolite (CTZ) on the rate of BPA removal were identified, respectively. The surface area of TZ declined as the TiO2 loading increased. The photodegradation rate (k) of BPA in the TZ and CTZ systems fitted pseudo-first-order kinetics. Under UV (365 nm) irradiation, the k values of TiO2 (20%)/zeolite (80%), TiO2 (40%)/zeolite (60%), TiO2 (60%)/zeolite (40%), and TiO2 (80%)/zeolite (20%) were 0.51, 0.55, 0.97, and 0.91 h−1, respectively. In the UV (365 nm)/TiO2 (60%)/zeolite (40%) system, the k values of CTZ with 1%, 5%, 10%, 20%, and 30% Cu2O added were 1.50, 1.04, 1.15, 1.88, and 0.47 h−1, respectively. The photocatalytic activity of TZ was enhanced by adding Cu2O. The optimal dosage of TiO2 in the TZ system was 60% and that of Cu2O in the CTZ system was 20%. p-Hydroxybenzaldehyde (p-HBA), p-hydroxyacetophenone (p-HAP), p-hydroxybenzoic acid (p-HBA acid) and hydroquinone (HQ) were intermediates of BPA photodegradation in the UV/TZ system and the rates of degradation followed the order HQ>p−HBA acid>BPA>p−HAP>p−HBA.

Dichloromethane removal and microbial variations in a combination of UV pretreatment and biotrickling filtration

Biofiltration of hydrophobic and/or recalcitrant volatile organic compounds in industry is currently limited. A laboratory-scale system integrating ultraviolet (UV) photodegradation and a biotrickling filter (BTF) was developed to treat dichloromethane (DCM), and this was compared to BTF alone. A combined UV–BTF approach permitted faster biofilm formation and greater removal than BTF. DCM distribution and its photodegradation intermediates revealed that the lower filter of the UV–BTF contributed more to CO2 production; the upper filter assisted more with DCM removal. The UV–BTF kept secretion of extracellular polymeric substances at a normal level with an evenly distributed biomass. Pyrosequencing analysis showed that the dominant population in the combined biofilter was more diverse than that in BTF alone. Our data provide a foundation for understanding the effect of UV pretreatment on BTF performance and the microbial community.

Elimination of ibuprofen and its relative photo-induced toxicity by mesoporous BiOBr under simulated solar light irradiation

3D mesoporous BiOBr microspheres via a one-step solvothermal process without templates were synthesized. The as-synthesized material was characterized by XRD, XPS, FESEM, TEM, UV-Vis and nitrogen adsorption techniques. The photodegradation behavior of the non-steroid anti-inflammatory drug (NSAID) ibuprofen (IBP) in aqueous BiOBr suspension was investigated under simulated solar light irradiation. The photocatalytic activity of the as-prepared 3D mesoporous BiOBr microspheres was excellent. IBP photodegradation intermediates were detected by GC/MS analyses, and a detailed reaction pathway was proposed. Luminous bacteria (Vibrio qinghaiensis) toxicity evaluation showed the decrease of the toxicity of the photodegradation intermediates. Based on the results, 3D BiOBr could be a promising catalyst on irradiation by visible light, and even under sunlight.

New type of [Bi6O6(OH)3](NO3)3·1.5H2O sheets photocatalyst with high photocatalytic activity on degradation of phenol

A new type of [Bi6O6(OH)3](NO3)3·1.5H2O sheets photocatalyst was synthesized via a hydrothermal route. The photocatalytic properties were characterized by SEM, TEM, XRD and UV spectroscopy. It exhibited slightly better photocatalytic activity on phenol degradation than that of classic TiO2 P25 under UV illumination. Hydroquinone, catechol, resorcinol, and benzoquinone were identified as photodegradation intermediates. It has the advantages of high effective photodegradation efficiency and easy separation properties.

Photolysis of bisphenol S in aqueous solutions and the effects of different surfactants

The photolysis of bisphenol S (BPS) in aqueous solutions was studied under a 20 W UV lamp (λ = 254 nm). The proposed intermediates and possible photolysis pathways of BPS were analyzed, and the effect of three surfactants on this photolysis was determined. UV and liquid chromatography combined with ion-trap time-of-flight mass spectrometry analyses revealed that BPS photolysis mainly occurred in two steps, and the primary photodegradation intermediates or products were p-hydroxybenzenylsulfonic acid, p-hydroxyphenol, and sulfuric acid. The results showed that BPS photolysis fitted well to a first order kinetic equation. The surfactants did not directly participate in BPS photolysis and exerted different effects depending on the structure and concentration of surfactants. The anionic surfactant sodium dodecyl sulfate (SDS) exhibited a strong inhibiting effect on BPS photolysis that increased with increased SDS concentration. At 800 mg/L SDS, the half-life of BPS photolysis was prolonged from 91.2 to 150.7 min and the inhibiting ratio of SDS was 39.5 %. By contrast, the cationic surfactant cetyl trimethyl ammonium bromide (CTAB) showed a promoting effect on BPS photolysis that increased with increased CTAB concentration. At 120 mg/L CTAB, the half-life of BPS photolysis shortened from 91.2 to 63.0 min and the promoting ratio was 44.7 %. On the other hand, the nonionic surfactant polyoxyethylene lauryl ether (PLE) had a relatively weak inhibiting effect at 140 mg/L PLE. At 240 mg/L, the promoting ratio reached 7.9 %.

Palladium phthalocyaninesulfonate functionalized mesoporous polymer: A highly efficient photocatalyst for degradation of 4-chlorophenol under visible light irradiation

A novel sulfonated palladium phthalocyanine (PdPcS) modified FDU-15 mesoporous polymer (FDU-PdPcS) has been prepared by rationally chemical modification process. The PdPcS molecules were highly dispersed inside the confined mesopores, and were further stabilized through a π–π interaction with mesopolymer, which may prevent the PdPcS molecules from agglomerating and deactivating in photodegradation reactions. The physicochemical properties of thus prepared FDU-PdPcS material were characterized by XRD, N2 adsorption-desorption, UV–vis and inductively coupled plasma techniques. FDU-PdPcS proved to be highly efficient heterogeneous photocatalyst for the degradation of 4-chlorophenol (4-CP) in the presence of H2O2 under visible light irradiation. The photodegradation of 4-CP with an initial concentration 0.6mM was completed within 5h at pH 11 using a dose of 0.2g/L of the 0.12wt% FDU-PdPcS photocatalyst. The photodegradation intermediates were identified by GC-MS. A possible mechanism involved in the photodegradation of 4-CP has also been discussed.

Photocatalytic decomposition of crotamiton over aqueous TiO2 suspensions: Determination of intermediates and the reaction pathway

The photocatalytic degradation of crotamiton in aqueous solution using TiO2 was investigated. To investigate the effect of initial pH, the photodegradation behaviors of three types of pharmaceuticals were compared (crotamiton, clofibric acid, sulfamethoxazole). The degradation rates of crotamiton in the pH range 3–9 were nearly equal, but those of clofibric acid and sulfamethoxazole were affected by pH. At pH>6.5, TiO2 particles, clofibric acid and sulfamethoxazole had negative charge, therefore, the repulsive force between TiO2 particles and anionic pharmaceuticals occurred and a low reaction rate at high pH was observed. The effect of UV intensity and TiO2 concentration on photodegradation efficiency was also investigated. Linear and logarithmical relationships between UV intensity, TiO2 concentration and the reaction rate constant were confirmed. Furthermore, the structures of photodegradation intermediates formed concomitantly with the disappearance of crotamiton were estimated. Seven intermediates were characterized by LC/MS/MS analyses, and it was assumed that the photocatalytic degradation of crotamiton was initiated by the attack of electrophilic hydroxyl radicals on aromatic rings and alkyl chains.

Photodegradation of Pb-3,4-dihydroxybenzoic acid complex under UV light illumination

The degradation of 3,4-dihydroxybenzoic acid (3,4-DHBA) in the presence and absence of Pb(2+) under UV illumination was studied. Addition of Pb(2+) caused the formation of precipitate during photoreaction when the solution pH was higher than 6. The presence of Pb(2+) remarkably inhibited the degradation of 3,4-DHBA and its photodegradation intermediates, while complexation of 3,4-DHBA and its photodegradation intermediates with Pb(2+) decreased the free Pb(2+) in aqueous solutions. Molecular oxygen played an important role in photodegradation of 3,4-DHBA in the presence of Pb(2+). UV-Vis spectroscopy was used to investigate the interaction between Pb(2+) and 3,4-DHBA at different pH conditions, and FT-IR was used to characterize the precipitate formed during photoreaction. The mineralization of 3,4-DHBA was investigate by total organic carbon analysis.

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.

Study of Photocatalytic Degradation Mechanism of Butyl Enzyl Phthalate Ester

Under ultraviolet radiation, the photocatalytic degradation mechanism of Butyl enzyl phthalate ester (BBP) was studied with TiO2as the catalyst. As a result, BBP could be degraded efficiently, and the efficiency was 85% after 6h degradation. During the degradation process, the acidity of the degradation system changed obviously. The initial pH of the solution was 6.0, and it increased to 6.23 after 15min degradation, however it decreased to 3.89 after 6h degradation. Some photodegradation intermediates in the different photocatalytic steps were examined and analyzed by means of GC-MS. For the BBP, the photocatalytic degradation firstly reacted on the benzyloxy chain, and new material occured by the recomposition of the educts in the degradation.

Photodegradation of lambda‐cyhalothrin and cypermethrin in aqueous solution as affected by humic acid and/or copper: Intermediates and degradation pathways

The influence of coexisting humic acids (HA) or Cu²⁺ on the photodegradation of pesticides lambda-cyhalothrin (λ-CHT) and cypermethrin (CPM) in aqueous solution was studied under xenon lamp irradiation. The removal efficiency of pesticides λ-CHT and CPM were enhanced in the presence of either Cu²⁺ or HA but restrained in the presence of both Cu²⁺ and HA. The photodegradation of λ-CHT and CPM followed first-order reaction kinetics. The photodegradation intermediates of λ-CHT and CPM were determined using gas chromatography/mass spectrometry. Possible photodegradation pathways included decarboxylation, ester bond cleavage, dechlorination, and phenyl group removal.

Platinum 1,10-phenanthroline: Photosensitizer for photocatalytic degradation of 4-chlorophenol

It is more economic to apply photodegradation of organic pollutants in presence of the visible light irradiation (sunlight) than applying more costfull ultraviolet lamps. Hence, platinum 1,10-phenanthroline complex has been prepared and tested as a photosensitizer for photodegrading 4-chlorophenol in water, which has been found almost completely achieved (98.5 %) after three hours of visible irradiation. Nevertheless, irradiation at 364 and 254 nm exhibits lower efficiencies. At visible irradiation, the platinum complex gives the highest activation of singlet state oxygen formation ( 1 O 2 ) compared to 364 and 254 nm irradiation as supported by electron para-magnetic resonance data. On the other hand, the behavior of formation and disappearance of photodegradation intermediates: hydroquinone, benzoquinone, hydroxybenzoquinone, using the platinum complex applying the three current irradiations are found to supports these findings. However, organic acids have accumulated as a function of irradiation time and hence considered to be rate-controlling.