Medium Pressure Mercury Lamp Research Articles

Assessment of Biological and Persistent Organic Compounds in Hospital Wastewater After Advanced Oxidation Process UV/H2O2/O3

This work studies the reduction of biological and organic compounds in hospital wastewaters (HWW) by advanced oxidation process (AOP). The HWW samples were previously treated with an extended aeration process and, thereafter, a post-treatment with AOP based on UV/H2O2/O3 system with a medium pressure mercury lamp was applied. After using the AOP system, the water samples were characterized using chemical oxygen demand (COD), turbidity, color test, coliforms and E. coli test, gas chromatography coupled to mass spectrometry (GC-MS), and UV-Visible absorption spectra. The results showed that 73% of organic compounds were removed in 20 min and the HWW sample was sterilized; nevertheless, 10 persistent organic compounds and 8 by-products formed after AOP UV/H2O2/O3 were observed, some of them are toxic compounds. In this sense, current HWW treatment plants cannot eliminate all contaminants in HWW; therefore, it is necessary to improve current processes by techniques as AOP and create standards to control biological and organic compounds in HWW in Mexico

Investigating the photo-Fenton process for treating soil washing wastewater.

Petroleum hydrocarbons have created numerous problems for water resources. The main objective of this study was focused on the application of advanced oxidation processes (AOPs) in treatment of effluent of petroleum contaminated soil washing operation. The AOP process in the present study was run with Fe2+/H2O2 (Fenton's reagent), Fe2+/H2O2/UV (photo-Fenton's reagent) and UV lamp (medium pressure mercury lamp, 400W) in the batch-mode reactor at laboratory-scale. Various parameters and optimized values which could maximize the removal efficiency of COD were: Fe2+ = 0.1g/L, H2O2 = 1g/L, pH = 3 and irradiation time of 120min. Under the optimal conditions, the removal efficiency of COD and TOC were achieved 86.3% and 68% respectively. The results showed that the reaction of the oxidation of diesel fuel by Fenton and photo-Fenton systems followed second-order kinetic model with reaction rate constants (k) of 7 × 10-6 and 3 × 10-6l/mgmin-1 respectively. The photo-Fenton process can be used as an effective and environmental friendly method in the degradation of petroleum organic compounds.

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene.

Photolysis is one of the main transformation pathways for 2,4,6-trinitrotoluene (TNT) released into the environment. Upon exposure to sunlight, TNT is known to undergo both oxidation and reduction reactions with release of nitrite, nitrate, and ammonium ions, followed by condensation reactions of the oxidation and reduction products. In this study, compound classes of transformation products from the aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene (TNT) have been identified by liquid and solid state 13C and 15N NMR. Aqueous phase experiments were performed on saturated solutions of T15NT in deionized water, natural pond water (pH = 8.3, DOC = 3.0 mg/L), pH 8.0 buffer solution, and in the presence of Suwannee River Natural Organic Matter (SRNOM; pH = 3.7), using a Pyrex-filtered medium pressure mercury lamp. Natural sunlight irradiations were performed on TNT in the solid phase and dissolved in the pond water. In deionized water, carboxylic acid, aldehyde, aromatic amine, primary amide, azoxy, nitrosophenol, and azo compounds were formed. 15N NMR spectra exhibited major peaks centered at 128 to 138 ppm, which are in the range of phenylhydroxylamine and secondary amide nitrogens. The secondary amides are proposed to represent benzanilides, which would arise from photochemical rearrangement of nitrones formed from the condensation of benzaldehyde and phenylhydroxylamine derivatives of TNT. The same compound classes were formed from sunlight irradiation of TNT in the solid phase. Whereas carboxylic acids, aldehydes, aromatic amines, phenylhydroxylamines, and amides were also formed from irradiation of TNT in pond water and in pH 8 buffer solution, azoxy and azo compound formation was inhibited. Solid state 15N NMR spectra of photolysates from the lamp irradiation of unlabeled 2,6-dinitrotoluene in deionized water also demonstrated the formation of aromatic amine, phenylhydroxylamine/ 2° amide, azoxy, and azo nitrogens.

Comparison of UV/Persulfate and UV/H2O2 for the removal of naphthenic acids and acute toxicity towards Vibrio fischeri from petroleum production process water

The ultraviolet light-activated persulfate process (UV/Persulfate) has received much attention in recent years as a novel advanced oxidation method for the treatment of municipal and industrial wastewater. This work investigated the UV/Persulfate and UV/H2O2 processes for the treatment of real oil sands process water (OSPW) at ambient pH condition using a medium pressure mercury lamp (emission between 200 and 530 nm). The degradation performances towards fluorophore organic compounds and naphthenic acids (NAs) in OSPW were evaluated using synchronous fluorescence spectrometry and ultra performance liquid chromatography time-of-flight mass spectrometry, respectively. Compared to the UV/H2O2 process, the UV/Persulfate process exhibited higher efficiency to remove both NAs and fluorophore organic compounds. Under 40 min of UV exposure and incident irradiance of 3.50 mW cm−2, fluorophore organic compounds were greatly degraded by UV/Persulfate (2 mM) and two- and three-ring fused organics were completely removed. 59.4%, 83.8% and 92.2% of O2-NAs in OSPW were removed with persulfate dosages of 0.5, 2, and 4 mM, respectively. The removal efficiency decreased along with the number of oxygen atoms in NAs (83.8%, 49.3%, and 46.8% for O2-, O3-, and O4-NAs, respectively) with 2 mM of persulfate, because of the formation of oxidized NAs in the same process. The structure-reactivity of O2-NA compounds fitted pseudo-first order kinetics in UV/Persulfate process with the rate constants ranging from 0.0156 min−1 to 0.1511 min−1. NAs with higher carbon numbers and double bond equivalence were more reactive in the UV/Persulfate oxidation process. The acute toxicity of OSPW to Vibrio fischeri was significantly reduced after the UV/Persulfate and UV/H2O2 treatments. Overall results demonstrated that the UV/Persulfate oxidation can be an effective alternative for future reclamation of OSPW.

Principles and mechanisms of ultraviolet light emitting diode technology for food industry applications

Abstract The application of ultraviolet (UV) light to water, food contact surfaces and medical equipment for microbial inactivation is widely employed. To date, UV disinfection sources employed are primarily low-pressure and medium-pressure mercury lamps; emitting monochromatic and polychromatic light, respectively. Despite the widespread use of mercury lamps, there are multiple drawbacks associated with their use including; high energy consumption, large size which limits reactor design, high heat emission and the presence of mercury. Light emitting diodes (LEDs) have potential for use as a highly efficient UV decontamination technology. Recent advances in semiconductor development have resulted in UV-LEDs becoming more widely available. UV-LEDs emit monochromatic light, which enables customised UV-LED disinfection systems at specific wavelengths to be developed. The application of UV-LEDs for disinfection purposes has been studied in recent years, particularly with respect to water disinfections systems. In this review, studies relating to UV-LED food applications are discussed. Furthermore, the chemical changes induced in foods, as a result of UV treatment, together with advantages and limitations of the technology are outlined.

Bisphenol A photocatalytic degradation by magnetic nano-Fe304

Bisphenol A (BPA) is a typical environmental endocrine disrupting chemicals. Photodegradation of BPA was catalyzed by magnetic nano-Fe3O4 under irradiation of medium pressure mercury lamp (500W, λ ≥ 290nm). Effects of pH value, initial concentration of BPA and magnetic Fe3O4 dosage were discussed respectively. The research results show that the photodegradation of BPA can be enhanced by Fe3O4. The removal rate decreased with the increase of initial concentration of BPA, and the reaction was in accordance with the first-order reaction kinetics. The removal rate is over 98% under acidic (pH ≤ 3) and alkaline (pH ≥ 9) conditions. The removal rate of BPA increased with the increase of magnetic nano-Fe3O4 dosage at the beginning of the reaction, and when the removal rate of BPA was more than 95% after 60min irradiation, the effects of dosage were small.

N-Nitrosodimethylamine (NDMA) Degradation by the Ultraviolet/Peroxodisulfate Process

This study investigates the photodegradation kinetics of N-nitrosodimethylamine (NDMA) by the ultraviolet (UV)/S2O82– process initiated by a medium-pressure mercury lamp in a collimated beam setup....

Synthesis of Novel Fused Regioisomeric Oxetane Bicycles via Paternò-Büchi Reaction of L-Ascorbic Acid and Evaluation as Antiproliferative Agents

Aim and Objective: To develop efficient method for the synthesis of unusual oxetanes bicycle and diversely functionalized oxetane motifs bearing medicinally relevant functional group in new chemical space and evaluation as cytotoxic agents. Materials and Methods: General procedure for the synthesis of 2, 3, 9 and 11: A mixture of L-ascorbic acid derivative 1 or 8 or 10 (10 mmol) and benzophenone (12 mmol) in dry benzene (125 mL) was purged with dry nitrogen for 5 min. The solution was then irradiated for 20-24 h with UV light (125 W, medium-pressure mercury lamp) in an immersion-well photoreactor at ambient temperature under nitrogen. After completion of the reaction, the solution was washed with aqueous NaHCO3 (10%), dried (Na2SO4), and concentrated under reduced pressure to give crude product which was purified by column chromatography using ethyl acetate: n-hexane (5-20%) as eluent to yield pure product as white solid. Results: 3-O and 2-O methyl derivatives of 5,6-O-isopropylidene-L-ascorbic acid 8 and 10 were irradiated with Benzophenone to give single regioisomer 9 and 11 in 78 % and 69 % yield respectively, while in case of 5,6-O-isopropylidene-2,3-di-O-methyl-L-ascorbic acid, it gave both regioisomer 2 and 3. The presence of only oxetanes moiety improved the cytotoxic activity compared to oxetanes bicycle moiety. It was scrutinized that all the compounds in series of 2 and 4 displayed more MCF-7 cell proliferation than their regioisomers 3 and 6. Conclusion: We have developed a versatile strategy to prepare diversely functionalized fused oxetane bicycles involving alkoxy, hydroxy methyl, alkyl, and aryl substituents. A wide variety of functional groups have been introduced on the oxetane ring, accessing new chemical space. These compounds were tested for growth inhibition against MCF-7 breast cancer cell line, compounds 2d, 4b, 4d and 6d showed comparable cytotoxic activity with L-ascorbic acid. These oxetane motifs will provide interesting new structural elements for medicinal chemistry programs as well as synthesis.

Castor oil-based waterborne hyperbranched polyurethane acrylate emulsion for UV-curable coatings with excellent chemical resistance and high hardness

Synthesis, characterization, and coating performance of castor oil (CO)-based waterborne hyperbranched polyurethane acrylate (WHPUA) emulsions are highlighted in this work. Herein, a second-generation CO-based hyperbranched polyester (C20) was synthesized by introducing the renewable CO as a B3 core and dimethylolpropionic acid as an AB2 monomer via a pseudo-one-pot condensation procedure. Three types of CO-based WHPUA emulsions were prepared through the addition of the hyperbranched C20 with maleic anhydride (MA) and the isocyanate-bearing semiadduct (IPDI-HEA) at different MA/IPDI-IH molar ratios without the addition of any emulsifiers. The prepared emulsions were further formulated into UV-curable coating formulations and exposed to a medium-pressure mercury lamp. Consequently, the obtained UV-cured coatings exhibited outstanding adhesion performance, excellent transparency, and an acceptable degree of final double bond conversion. Owing to a relatively low concentration of hydrophilic units and a large number of acrylate functionalities in the waterborne oligomer, the obtained films were endowed with high crosslinking density and low hydrophilic nature, thus producing enhanced tensile strength, pencil hardness, water resistance, and chemical resistance. Due to their combination of renewable materials, a waterborne system and a UV-curing technique, these CO-based WHPUA emulsions offer promising opportunities to be used as environmentally friendly coatings.

Nonnegligible Generation of Hydroxyl Radicals from UVC Photolysis of Aqueous Nitrous Oxide.

Nitrous oxide (N2O) is widely used in radiation-chemistry and photochemistry as a scavenger to convert a hydrated electron ( eaq-) into a hydroxyl radical (·OH). However, few investigations pay attention to the photochemistry of dissolved N2O itself. The effects of purged N2O on photochemical processes are unclear and neglected. In the present work, the effects of N2O on the hydroxylation of terephthalic acid (TPA) were investigated with both medium-pressure and low-pressure mercury lamps as the light sources. Under short-wavelength UV (200-300 nm) irradiation, N2O accelerated the decay of TPA and the formation of 2-hydroxylterephthalic acid (hTPA). The effective quantum yield of ·OH from the photolysis of dissolved N2O at 254 nm was determined as 1.15-1.63, which was far larger than those of NO3- (0.09) and NO2- (0.046). On the basis of the kinetic analysis in N2 and N2O purged solutions, isotope fractionation with heavy oxygen water, and ·OH scavenging experiments with tert-butyl alcohol, the contribution of the ·OH radicals generated from the photolysis of N2O to the formation of hTPA (61.7%) was determined to be 1 order of magnitude higher than that from the converted eaq- (6.5%). These results demonstrate that using N2O and ·OH probes to quantify photogenerated eaq- in UVC irradiation might lead to false results. The work here is helpful for the proper design of scavenging and probing experiments by the combination of N2O and ·OH probes.

Synthesis, Characterization and Photocrosslinkable Studies of Certain Thermotropic Liquid Crystalline Poly(ester-amides)

Five thermotropic liquid crystalline poly(ester-amides) were synthesized by polycondensation method using varying dicarboxylic acids with a common diamine namely 4,4-diaminodiphenyl and a common diol namely 2,6-bis(4-hydroxy-3-methoxybenzylidene)cyclohexanone (CHBV). The solubility data and viscosity measurements of these synthesized poly(ester-amides) were used for qualitative characterization. The spectroscopic techniques such as FT-IR, ¹H NMR, ¹³C NMR were performed for investigating micro structural features. By differential scanning calorimetry (DSC), the thermal phase transition behavior of these poly(ester-amides) was studied. Scanning electron microscopy (SEM) technique was used to investigate the morphology of these poly(ester-amides). By using UV-visible spectroscopic technique, the photocrosslinkability of these poly(ester-amides) were studied by irradiating these poly(ester-amides) under a 160 W medium pressure mercury lamp. SEM analysis of these UV irradiated poly(ester-amides) showed the changes in morphology. Thus, the poly(ester-amides) containing arylidene keto moiety in the main chain exhibited nematic mesophase and were photocrosslinked upon UV irradiation. X-ray diffraction (XRD) patterns of these poly(ester-amides) were taken to assess the degree of crystallinity.<div><br></div>

Removal of 2-phenylbenzimidazole-5-sulfonic acid using heterogeneous photocatalysis

UV filters are classified as environmental pollutants (emerging pollutants). One of the most frequently detected UV filters in real samples is 2-phenylbenzimidazole-5-sulfonic acid (PBSA). It has been shown that conventional technologies applied in sewage treatment plants are not adapted for complete removal of sunscreen agents. Therefore, there is a trend to undertake activities leading to improvement of water quality by enhancing treatment methods. This is important due to the fact that in an aqueous environment, in the presence of UV radiation or sunlight irradation, PBSA generates reactive oxygen species that can damage the DNA of living organisms. The aim of study was to investigate an effect of pH and TiO2 on PBSA stability in the presence of UV radiation. It was found that the rate of PBSA degradation depends on the catalyst dose and pH of solution. The photocatalysis reaction was carried out in a Heraeus laboratory exposure set equipped with a 150 W mediumpressure mercury lamp. The course of PBSA degradation process as a function of time was monitored using UV/VIS spectrophotometer and liquid chromatograph equipped with UV-Vis detector.

Photolysis of parabens using medium-pressure mercury lamps: Toxicity effects in MCF7, Balb/c 3T3 cells and Ceriodaphnia dubia

Degradation studies of the propylparaben (PrP), butylparaben (BuP) and of the propylparaben-butylparaben mixture (PrP-BuP) in deionized water and surface river water was investigated as a function of pH and initial concentration of the reactants using a medium-pressure mercury lamp. The photolysis of parabens (concentration ranging from 5 to 30 mg L−1) followed apparent pseudo-first-order kinetics, with rate constants (k) in deionized water and surface river water changed from 1.80 × 10−1 to 3.68 × 10−2 min−1 and 1.43 × 10−1 to 1.45 × 10−2 min−1, respectively. Degradation reaction was faster at pH 5 in comparison with pH 7 or 11. The photolysis of parabens was greater than 91%, with low mineralization (26.15%) observed in acidic medium after 95 min. Analysis by chromatography coupled to mass spectrometry (LC-MS/MS) showed that only one product was generated during the degradation reaction and has UV bands similar to 3,4-dihydroxybenzoic acid. Estrogenic activity tests showed that non-degraded parabens stimulated the growth of breast adenocarcinoma (MCF-7) cells and this effect was evaluated after the photolysis. Cytotoxicity assays using fibroblasts cells (Balb/C 3T3 clone A31) indicated that the parental compounds and degradation products were not cytotoxic. On the contrary, non-degraded parabens were toxic to Ceriodaphnia dubia, but the product of photolysis was not. Overall, the photolytic method presented was able to degrade these parabens providing safe and non-estrogenic reaction product.

Manipulating [2 + 2] photodimerization of 1,4-dihydropyridines within γ-cyclodextrin

Irradiation of 1,4-dihydropyridines (DHPs) in the presence of γ-cyclodextrin (γ-CD) performs an efficient formation of the cage-dimer under a medium-pressure mercury lamp. The cage-dimer yields for DHPs complexed within γ-CD may achieve approximately 80%, far higher than those in the non-complexed state. It is postulated that the available cavity volume in γ-CD is responsible for the observed selectivity. The formation of 1:2 host-guest inclusion complex plays an important role in this reaction, and manipulates DHPs to perform [2 + 2] photodimerization as expected. In order to investigate the inclusion process, the spectral characteristics were investigated and the theoretical study was performed using density functional theory (DFT).

Photocatalytic activity of Lu3+/TiO2 prepared by ball milling method

Ball milling method was applied to prepare Lu3+/TiO2 photocatalysts. The catalysts were characterized with X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–visible diffuse reflectance spectra (UV–vis DRS), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and Brunauer–Emmett–Teller (BET) method. The photocatalytic activities were determined by the degradation of methylene blue (MB) equipped with a 300 W medium pressure mercury lamp. Results show that the first order reaction rate constants of Lu3+/TiO2 and pure TiO2 are 0.0565 and 0.0263 min−1, respectively, which both were evaluated under the condition of catalysts loading of 0.2 g/L, initial concentration of 25 mg/L for MB, mole ratio of Lu3+/TiO2 of 1.5% and milling time of 4 h. The average crystal sizes of 1.5 mol% Lu3+/TiO2 and pure TiO2 are 18.7 and 19.3 nm, respectively.

Photocatalytic degradation and mineralization of perfluorooctanoic acid (PFOA) using a composite TiO2 −rGO catalyst

The inherent resistance of perfluoroalkyl substances (PFASs) to biological degradation makes necessary to develop advanced technologies for the abatement of this group of hazardous substances. The present work investigated the photocatalytic decomposition of perfluorooctanoic acid (PFOA) using a composite catalyst based on TiO2 and reduced graphene oxide (95% TiO2/5% rGO) that was synthesized using a facile hydrothermal method. The efficient photoactivity of the TiO2-rGO (0.1gL−1) composite was confirmed for PFOA (0.24mmolL−1) degradation that reached 93±7% after 12h of UV–vis irradiation using a medium pressure mercury lamp, a great improvement compared to the TiO2 photocatalysis (24±11% PFOA removal) and direct photolysis (58±9%). These findings indicate that rGO provided the suited properties of TiO2-rGO, possibly as a result of acting as electron acceptor and avoiding the high recombination electron/hole pairs. The release of fluoride and the formation of shorter-chain perfluorocarboxilyc acids, that were progressively eliminated in a good match with the analysed reduction of total organic carbon, is consistent with a step-by-step PFOA decomposition via photogenerated hydroxyl radicals. Finally, the apparent first order rate constants of the TiO2-rGO UV–vis PFOA decompositions, and the intermediate perfluorcarboxylic acids were found to increase as the length of the carbon chain was shorter.

Titania Gold Composite: Effect of Illumination on Size of Gold Nanoparticles with Consequent Implication on Photocatalytic Water Splitting

This work deals with the study of photodeposition (PD) of gold nanoparticles (AuNPs) on TiO2 by using different illumination sources, Medium pressure Mercury lamp (ML), Solar Simulator equipped with AM 1.5 (SL) and Tungsten lamp (WL). Different particle size of AuNPs on TiO2 were obtained by photodeposition method under different illumination sources, which clearly proves the influence of light source on the synthesis of Au–TiO2. The plasmonic activity of Au–TiO2 photocatalyst for water splitting reaction was observed to be strongly influenced by the particle size of Au as well as illumination source. Amongst the three different illumination sources used, smallest particle size for AuNP–TiO2 were observed under ML followed by SL and WL, as revealed by TEM analysis. Different illumination sources were also investigated to evaluate the activity of Au–TiO2 samples thus prepared under different illumination conditions. The order of hydrogen evolution rate (HER) observed for Au–TiO2 with different source of illuminations is ML > SL > WL. The highest HER of 1709 μmol/h was observed for Au–TiO2, which was synthesized and evaluated under ML irradiation. This may be explained on the basis of reduced catalytic activity and photothermal effect of Au nanoparticles with increasing particle size.

Photocatalytic degradation of paracetamol over magnetic flower-like TiO 2 /Fe 2 O 3 core-shell nanostructures

Abstract The presence of pharmaceutical residues and their metabolites in water, even in low concentrations, is of significant concern due to their effects on aquatic environment. The application of new recyclable photocatalysts with high photocatalytic activity and stability for water treatment has received increasing attention in recent times. In this work, photocatalytic degradation of paracetamol (PA) has been investigated in aqueous solution over magnetically separable flower-like TiO 2 /Fe 2 O 3 core-shell photocatalysts using 450 W medium pressure mercury lamp. SEM, TEM, N 2 sorption (BET method), XRD, FTIR, Raman spectroscopy and VSM were used to characterize the prepared photocatalysts. Results showed that photodegradation and photomineralization of paracetamol was increased with increasing TiO 2 content in the TiO 2 /Fe 2 O 3 core-shell. GC and GC/MS were used to identify the intermediate products formed during the degradation of paracetamol. 4-Acetamidoresorcinol, 4-acetamidocatechol, hydroquinone, 1,2,4-benzenetriol in addition to aliphatic acids were identified in the photolysate mixture. The 33%TiO 2 /Fe 2 O 3 core-shell photocatalyst showed high photoctalaytic efficiency for the degradation of paracetamol after four repeated cycles which demonstrates the high stability of the prepared photocatalyst. A pseudo first order rate was demonstrated for the photocatalytic degradation process of paracetamol.

Influence of cationic photoinitiator type on properties of coating materials based on cycloaliphatic and glycidyl epoxy resins

Abstract Epoxy binder based on 3,4-epoxycyclohexylmethyl-3′,4′-epoxycyclohexanecarboxylate (EEC) and polytetrahydrofurane diglycidyl ether (PTHDE) was cured using four types of commercial cationic UV-photoinitiators (two iodonium salts and two sulfonium salts) and a medium-pressure mercury lamp. Influence of a type of photoinitiator on thermal, optical, mechanical and barrier features of the varnish coatings was investigated. Moreover, conversion of cycloaliphatic epoxy (CC) and glycidyl (GC) groups was analyzed. Generally, systems containing iodonium or sulfonium hexafluorophosphates exhibited higher GC, gel content, gloss and water-vapor transmission rate as well as lower yellowness and hardness than samples based on SbF6−-type salts. Photoinitiator type did not significantly affect CC parameter, however, application of the iodonium salts mixtures influenced on CC as well as GC, thermal features and gloss of epoxy varnishes and coatings.

Applicability of light sources and the inner filter effect in UV/acetylacetone and UV/H2O2 processes

Light source is a crucial factor in the application of a photochemical process, which determines the energy efficiency. The performances of acetylacetone (AA) in conversion of aqueous contaminants under irradiation with a low-pressure mercury lamp, a medium-pressure mercury lamp, a xenon lamp, and natural sunlight were investigated and compared with those of H2O2 as reference. In all cases, AA was superior to H2O2 in the degradation of Acid Orange 7. Using combinations of the different light sources with various cut-off and band-pass filters, the spectra responses of the absorbed photons in the UV/AA and UV/H2O2 processes were determined for two colored and two colorless compounds. The photonic efficiency (φ) of the two photochemical processes was found to be target-dependent. A calculation approach for the inner filter effect was developed by taking the obtained φ into account, which provides a more accurate indication of the reaction mechanisms.