Role of oxygen in the degradation of atrazine by UV/Fe(III) process

In this study, the role of oxygen in the regeneration of Fe(III) during the degradation of atrazine in UV/Fe(III) process was studied. The degradations of atrazine in UV/Fe(III) and UV-photolysis processes in the presence and absence of oxygen were compared. The results showed that the degradations of atrazine in these processes followed the pseudo-first-order kinetics well. The process exhibiting the highest rate constant (k) was UV/Fe(III)/air process, because k-value for UV/Fe(III)/air process was about 1.47, 2.23 and 2.56 times of those for UV/Fe(III)/N₂, UV/air and UV/N₂ processes, respectively. The degradation of atrazine was enhanced by oxygen in UV/Fe(III) process and the enhancement was more remarkable at higher initial concentrations of Fe(III). The investigation into the changes of Fe(III) concentrations demonstrated that the presence of oxygen led to the regeneration of Fe(III), which resulted in the enhancement of atrazine degradation. With air bubbling, the ferric ions were 25% more than those with N₂ bubbling. The experimental data showed the regeneration of Fe(III) required the excited organic molecules and oxygen and on the basis of these results, the regeneration mechanism of Fe(III) was proposed. It was also found that due to the oxidation of Fe(II), the degradation of atrazine in UV/Fe(II)/air process was effective at a low Fe(II) concentration of 7 mg/L, similar to that in UV/Fe(III)/air process. This study makes clear the role of oxygen in the regeneration of Fe(III), and thus it provides a guide to reduce the input of Fe(III) and is helpful to the application of UV/Fe(III) process in practice.     

The excited states of bipyridyl and phenanthroline complexes of Fe(III), Ru(II) and Ru(III): A molecular orbital study

The semiempirical zero-differential-overlap molecular orbital model which was shown in earlier papers in this series to give a good account of the charge transfer and -* spectra of Fe(II) complexes with conjugated ligands such as 2,2-bipyridyl and 1,10-phenanthroline is extended to complexes having openshell ground states, such as those of Fe(III), and to complexes of Ru(II) and Ru(III). The results are used to assign the observed charge transfer and intra-ligand absorption bands to specific orbital transitions. Observed and calculated intensities are in good agreement: reasons are advanced for the much lower intensity of the charge transfer bands in Ru(III) compared to Ru(II) complexes.     

Reversed phase extraction chromatographic separation of ruthenium(III)

A new an innovative separation method has been developed using N-n-octylaniline (liquid anion exchanger) coated on silica gel. Ruthenium(III) has been extracted quantitatively from 0.05 M hydrochloric acid, striped with aqueous solution of various acids and then determined by spectrophotometric method. Mutual separation scheme for ruthenium(III), iridium(III) and osmium(VIII) has been developed. Ruthenium(III) has been separated from commonly associated elements. Different parameter are studied viz effect of acid concentration, reagent concentration, striping agent, flow rate, foreign ion and synthetic mixture corresponding to alloys. Validity of method has been verified by separation of ruthenium(III) from fissium alloy.     

On-line solid-phase extraction and multisyringe flow injection analysis of Al(III) and Fe(III) in drinking water

A new analytical method was developed for on-line monitoring of residual coagulants (aluminium and iron salts) in potable water. The determination was based on a sequential procedure coupling an extraction/enrichment step of the analytes onto a modified resin and a spectrophotometric measurement of a surfactant-sensitized binary complex formed between eluted analytes and Chrome Azurol S. The optimization of the solid phase extraction was performed using factorial design and a Doehlert matrix considering six variables: sample percolation rate, sample metal concentration, flow-through sample volume (all three directly linked to the extraction step), elution flow rate, concentration and volume of eluent (all three directly linked to the elution step). A specific reagent was elaborated for sensitive and specific spectrophotometric determination of Al(III) and Fe(III), by optimizing surfactant and ligand concentrations and buffer composition. The whole procedure was automated by a multisyringe flow injection analysis (MSFIA) system. Detection limits of 4.9 and 5.6 μg L⁻¹ were obtained for Al(III) and Fe(III) determination , respectively, and the linear calibration graph up to 300 μg L⁻¹ (both for Al(III) and Fe(III)) was well adapted to the monitoring of drinking water quality. The system was successfully applied to the on-site determination of Al(III) and Fe(III) at the outlet of two water treatment units during two periods of the year (winter and summer conditions).     

Selective extraction, separation and speciation of iron in different samples using 4-acetyl-5-methyl-1-phenyl-1H-pyrazole-3-carboxylic acid

A method for speciation, preconcentration and separation of Fe(II) and Fe(III) in different matrices was developed using solvent extraction and flame atomic absorption spectrometry. 4-Acetyl-5-methyl-1-phenyl-1H-pyrazole-3-carboxylic acid (AMPC) was used as a new complexing reagent for Fe(III). The Fe(III)-AMPC complex was extracted into methyl isobutyl ketone (MIBK) phase in the pH range 1.0-2.5, and Fe(II) ion remained in aqueous phase at all pH. The chemical composition of the Fe(III)-AMPC complex was determined by the Job's method. The optimum conditions for quantitative recovery of Fe(III) were determined as pH 1.5, shaking time of 2 min, 1.64 × 10⁻⁴ mol L⁻¹ AMPC reagent and 10 mL of MIBK. Furthermore, the influences of diverse metal ions were investigated. The level of Fe(II) was calculated by difference of total iron and Fe(III) concentrations. The detection limit based on the 3σ criterion was found to be 0.24 μg L⁻¹ for Fe(III). The recoveries were higher than 95% and relative standard deviation was less than 2.1% (N = 8). The validation of the procedure was performed by the analysis of two certified standard reference materials. The presented method was applied to the determination of Fe(II) and Fe(III) in tap water, lake water, river water, sea water, fruit juice, cola, and molasses samples with satisfactory results.     

The extraction of actinides by diphenyl(dibutylcarbamoylmethyl)phosphine oxide in the absence of a solvent

The possibility of changing the aggregate state of several solid mono- and bidentate neutral organophosphorus compounds in contact with various mineral acids was demonstrated. The formation of the liquid phase immiscible with water was observed. The, phase exhibits a high extraction capability with respect to actinides in various oxidation states. The diphenyl(dibutylcarbamoylmethyl)phosphine oxide-NHO₃ extraction system was studied in detail. The composition of the liquid phase was shown to the Ph₂P(O)CH₂C(O)NBu₂·HNO₃·nH₂O (n=2 or 3). The kinetics of formation of this phase and extraction of Amⁱⁱⁱ from solutions of nitric acid and its salts was studied. The organic phase exhibits redox properties, due to which some actinides change the oxidation state during extraction. The “aryl strengthening effect” was suggested to exist for extraction of Am^III in the absence of a solvent. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1739–1745, September, 1998.     

Mechanistic aspects of uncatalyzed and ruthenium(III) catalyzed oxidation of dl-ornithine by copper(III) periodate complex in aqueous alkaline medium: A comparative kinetic study

The oxidation of dl-ornithine monohydrochloride (OMH) by diperiodatocuprate(III) (DPC) has been investigated both in the absence and presence of ruthenium(III) catalyst in aqueous alkaline medium at a constant ionic strength of 0.20 mol dm⁻³ spectrophotometrically. The stiochiometry was same in both the cases, i.e., [OMH]/[DPC] = 1:4. In both the catalyzed and uncatalyzed reactions, the order of the reaction with respect to [DPC] was unity while the order with respect to [OMH] was < 1 over the concentration range studied. The rate increased with an increase in [OH⁻] and decreased with an increase in [IO₄⁻] in both cases. The order with respect to [Ru(III)] was unity. The reaction rates revealed that Ru(III) catalyzed reaction was about eight-fold faster than the uncatalyzed reaction. The oxidation products were identified by spectral analysis. Suitable mechanisms were proposed. The reaction constants involved in the different steps of the reaction mechanisms were calculated for both cases. The catalytic constant (K_C) was also calculated for catalyzed reaction at different temperatures. The activation parameters with respect to slow step of the mechanism and also the thermodynamic quantities were determined. Kinetic experiments suggest that [Cu(H₂IO₆)(H₂O)₂] is the reactive copper(III) species and [Ru(H₂O)₅OH]²⁺ is the reactive Ru(III) species.     

Catalytic properties of Cu/Co/Zn/Zr oxides prepared by various methods

The new Cu-Co based （Cu/Co/Zn/Zr） catalysts for higher-alcohol synthesis were prepared using coprecipitation method, plasma enhanced method and reverse coprecipitation method under ultrasound irradiation. The catalysts were investigated by the means of BET, SEM, XRD, H2-TPR and XPS. Catalytic properties of the catalysts prepared by various methods were examined using CO hydrogenation reaction. It was found that plasma enhanced method and reverse coprecipitation method under ultrasound irradiation were both effective in enhancing the catalytic properties of Cu/Co/Zn/Zr mixed oxides. The small particle size, high dispersion of active components, the improvement of specific surface area and surface contents of active phases could account for the excellent performance of the experimental Cu/Co/Zn/Zr catalysts.     

Degradation of carbofuran in aqueous solution by Fe(III) aquacomplexes as effective photocatalysts

The photodegradation of carbofuran by excitation of iron(III) aquacomplexes was investigated under UV irradiation. The degradation rate was strongly influenced by the pH, and initial concentration of Fe(III). The degradation efficiency of carbofuran at the difference pH was in good agreement with the initial concentration of Fe(OH)²⁺ in the solution. An initial carbofuran concentration of 10 mg L⁻¹ was completely degraded within 50 min at pH 2.8 with original Fe(III) concentration of 8 × 10⁻⁴ mol L⁻¹. This degradation reaction was found to follow the first order kinetics law and the rate constant of 1.60 × 10⁻³ s⁻¹ was observed. The decrease of TOC content was observed during the photocatalytic process and the removal percentage obtained was about 70% after 25 h. Furthermore, ammonium ion as an end-product was detected in the solution. Therefore, this process based on the catalytic reaction of Fe(II, III) is responsible for the continuous production of hydroxyl radicals in such system. A gas chromatography-mass spectrometry analysis showed the formation of four photoproducts, such as 2,2-dimethyl-2,3-dihydro-benzofuran-7-ol, etc., revealing that the carbamate branch, C-3 and C-2 positions in furan ring were attack targets of hydroxyl radicals. Based on these results, the photocatalytic system could be useful technology for the treatment and the mineralization of compounds like carbofuran.     

Removal of As(III) and As(V) by natural and synthetic metal oxides

The removal properties of As(III) and As(V) by the several metal oxides having different mineral type and content of metals were investigated in batch and column reactors. The used metal oxides were Fe-oxide loaded sand (ILS), Mn-oxide loaded sand (MLS), activated alumina (AA), sericite (SC) and iron sand (IS). From the pH-edge adsorption experiments with AA and ILS, maximum As(III) adsorption was observed around neutral pH while As(V) adsorption was followed an anionic-type behavior. Among five metal oxides, AA showed the greatest removal capacity for both As(III) and As(V) through adsoption process but it has little oxidation capacity for As(III). Eventhough IS had much greater content of Fe-oxides than ILS, it showed a relatively lower removal capacity for both As(III) and As(V). This result suggests that adsorption of arsenic onto metal oxides is controlled by not only the contents of Fe-oxides but also mineral type of Fe-oxides. Column tests were performed at different combinations of metal oxides in a column reactor to find the best column system, which effectively treat both As(III) and As(V) at the same time. Among several combinations, the column reactors packed with MLS-AA and MLS-ILS showed a near complete oxidation of As(III) by MLS for a long time and the greatest adsorption of total arsenic compared to the column reactor packed with MLS-IS.     

Ru(III), Cr(III), Fe(III) complexes of Schiff base ligands bearing phenoxy Groups: Application as catalysts in the synthesis of vitamin K3

Two polydentade Schiff base ligands and their Ru(III), Cr(III) and Fe(III) complexes were synthesized and characterized by elemental analysis (C, H, N), UV/Vis, FT IR, ¹H and ¹³C NMR, LC–MS/MS, molar conductivity and magnetic susceptibility techniques. The absorption bands in the electronic spectra and magnetic moment measurements verified an octahedral environment around the metal ions in the complexes. The thermal stabilities were investigated using TGA. The synthesized complexes were used in the catalytic oxidation of 2-methyl naphthalene (2MN) to 2-methyl-1,4-naphthoquinone; vitamin K₃, menadione, 2MNQ; using hydrogen peroxide, acetic acid and sulfuric acid. L₁-Fe(III) complex showed very efficient catalytic activity with 58.54% selectivity in the conversions of 79.11%.     

对乙酰氨基酚在Fe（Ⅲ）／草酸盐体系中的光降解

药品和个人护理用品(Pharmaceuticals and Personal Care Products,简称PPCPs)作为潜在环境污染物,在近几年成为新的环境热点问题[1,2].对乙酰氨基酚(APAP)作为一种典型的药品和个人护理用品被用作阿司匹林的替代物,主要起到减轻疼痛的作用.     

Spectrophotometric Determination of Piroxicam via Chelation with Fe(III) in Commercial Dosage Forms

The objective of this work is to develop and validate spectrophotometric method for the determination of piroxicam in commercial dosage forms. The method is based on the chelation of the drug with Fe(III) to form pink coloured metal chelate at room temperature which absorbs maximally at 504 nm. Beer's law is obeyed over the concentration range of 8–160 μg mL^?1 (A = 1.07 × 10^?3 + 7.75 × 10^?3 C). Under the optimized experimental conditions, proposed method is validated as per the International Conference on Harmonisation guidelines. The limits of detection and quantitation for the proposed method are 0.775 and 2.348 μg mL^?1, respectively. The proposed method has been successfully applied to the determination of piroxicam in commercial dosage forms. The results are compared with the reference El‐Ries et al. spectrophotometric method.     

Solid-phase extraction of iron(III) with an ion-imprinted functionalized silica gel sorbent prepared by a surface imprinting technique

A new Fe(III)-imprinted amino-functionalized silica gel sorbent was prepared by a surface imprinting technique for selective solid-phase extraction (SPE) of Fe(III) prior to its determination by inductively coupled plasma atomic emission spectrometry (ICP-AES). Compared with non-imprinted polymer particles, the ion-imprinted polymers (IIPs) had higher selectivity and adsorption capacity for Fe(III). The maximum static adsorption capacity of the ion-imprinted and non-imprinted sorbent for Fe(III) was 25.21 and 5.10 mg g⁻¹, respectively. The largest selectivity coefficient of the Fe(III)-imprinted sorbent for Fe(III) in the presence of Cr(III) was over 450. The relatively selective factor (α_r) values of Fe(III)/Cr(III) were 49.9 and 42.4, which were greater than 1. The distribution ratio (D) values of Fe(III)-imprinted polymers for Fe(III) were greatly larger than that for Cr(III). The detection limit (3σ) was 0.34 μg L⁻¹. The relative standard deviation of the method was 1.50% for eight replicate determinations. The method was validated by analyzing two certified reference materials (GBW 08301 and GBW 08303), the results obtained is in good agreement with standard values. The developed method was also successfully applied to the determination of trace iron in plants and water samples with satisfactory results.     

Selective extraction and determination of Au(III) by first-derivative spectrophotometry

The selective extraction of Au(III) in the presence of Zn(II) by salting-out of 2-propanol was investigated. The salting-out effect increased partitioning between water and 2-propanol in the presence of sodium chloride in aqueous–organic mixtures. This is observed through the distribution coefficient, which increases with salt addition. First-derivative spectrophotometry, which eliminates interference from overlapping spectral bands, was used for the determination of trace Au(III) in the presence of Zn(II). Absorption spectra were recorded and the first-derivative spectra were obtained using Δλ?=?10?nm. The calibration graph was linear for 0.857–5.142?µg?mL^?1 and the detection limit was 0.038–8?µg?mL^?1. The proposed method has been successfully applied to the determination of trace Au(III) in synthetic mixtures and Algerian low gold ore solutions. The results agree with those obtained by atomic absorption spectroscopy and the recoveries were >98%. The relative standard deviations were in all instances less than 3%.     

Calcium Sulfite Solids Activated by Iron for Enhancing As(III) Oxidation in Water

Desulfurized gypsum (DG) as a soil modifier imparts it with bulk solid sulfite. The Fe(III)–sulfite process in the liquid phase has shown great potential for the rapid removal of As(III), but the performance and mechanism of this process using DG as a sulfite source in aqueous solution remains unclear. In this work, employing solid CaSO₃ as a source of SO₃²⁻, we have studied the effects of different conditions (e.g., pH, Fe dosage, sulfite dosage) on As(III) oxidation in the Fe(III)–CaSO₃ system. The results show that 72.1% of As(III) was removed from solution by centrifugal treatment for 60 min at near-neutral pH. Quenching experiments have indicated that oxidation efficiencies of As(III) are due at 67.5% to HO^•, 17.5% to SO₅^•− and 15% to SO₄^•−. This finding may have promising implications in developing a new cost-effective technology for the treatment of arsenic-containing water using DG.     

Study of pepsin phosphorylation using immobilized metal affinity chromatography

The interactions of pepsin with immobilized trivalent metal ions and the participation of the enzyme phosphate group in this process were investigated using high performance immobilized metal affinity chromatography. Two different sorbents were used: the newly prepared one, consisting of Ga(3+ )chelate of (6-amino-1-hydroxyhexane-1,1-diyl) bis(phosphonic acid) covalently bound to a methacrylate support (BP-Ga(3+)), and the commercial one, containing immobilized Fe(3+ )ions (POROS MC20-Fe(3+)). The comparison of the behavior of porcine pepsin A and its partially dephosphorylated form on both sorbents showed that both forms of pepsin were adsorbed under the same conditions. To eliminate the participation of free carboxyl groups in pepsin adsorption, both enzyme forms were modified by amidation or esterification. Native enzyme and its partially dephosphorylated form both with modified carboxyl groups differed in their interaction with immobilized Ga(3+ )and Fe(3+). Phosphorylated pepsin molecules with esterified carboxyl groups were adsorbed on both sorbents while nonphosphorylated ones with esterified carboxyl groups were not adsorbed.     

Influence of the chain and layer structure of Fe(III) and In(III) aqua-pentachloro-complexes on the bending vibrations of water molecules

Studies of IR and Raman spectra of monohydrates M^I₂[M^IIICl₅(H₂O)] (where M^I=K⁺, Rb⁺, Cs⁺ and M^III=Fe³⁺, In³⁺) at 1400-1900 cm⁻¹ have been carried out. The medium intensity band, detected in the region 1580-1595 cm⁻¹ was assigned to bending vibrations of water molecules (δHOH). The shift of the δHOH band towards low wavenumbers (1580-1595 cm⁻¹) is a main sign of the water molecule interactions in the chain hydrates. Additionally in the IR and Raman spectra of these salts, the appearance of the low intensity band between 1750 and 1810 cm⁻¹ (ν_x(H₂O)) was observed. In the presented paper we also discuss the influence of M^I and M^III cations on the position and splitting of these bands.