Modeling four and three-way fast high-performance liquid chromatography with fluorescence detection data for quantitation of fluoroquinolones in water samples

This paper presents a study regarding the acquisition and analytical utilization of four and three-way data, acquired by following the excitation–emission fluorescence matrices at different elution times, in a fast liquid chromatographic HPLC procedure. This kind of data were implemented for first time for quantitative purposes, and applied to the determination of two fluoroquinolones in tap water samples, as a model to show the potentiality of the proposed strategy of four-way data generation. The data were modeled with three well-known algorithms: PARAFAC, U-PLS/RTL and MCR-ALS, the latter conveniently adapted to model third-order data. The second-order advantage was exploited when analyzing samples containing uncalibrated interferences. PARAFAC and MCR-ALS were the algorithms that better exploited the second-order advantage when no peak time shifts occurred among samples. On the other hand, when the quadrilinearity was lost due to the occurrence of temporal shifts, MCR-ALS furnished the better results. Relative error of prediction (REP%) obtained were 9.9% for ofloxacin and 14.0% for ciprofloxacin. In addition, a significant enhancement in the analytical figures of merit was observed when going from second- to third-order data (reduction of ca. 70% in LODs).     

Extension and application of multivariate curve resolution-alternating least squares to four-way quadrilinear data-obtained in the investigation of pollution patterns on Yamuna River,India—A case study

This study focuses on the development and extension of Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) to the analysis of four-way datasets. The proposed extension of the MCR-ALS method with non-negativity and the newly developed quadrilinear constraints can be exploited to summarize and manage huge multidimensional datasets and resolve their four way component profiles. In this study, its application is demonstrated by analyzing a four-way data set obtained in a long term environmental monitoring study (15 sampling sites × 9 variables × 12 months × 7 years) belonging to the Yamuna River, one of the most polluted rivers of India and the largest tributary of the Ganges river. MCR-ALS resolved pollution profiles described appropriately the major observed changes on pH, organic pollution, bacteriological pollution and temperature, along with their spatial and temporal distribution patterns for the studied stretch of Yamuna River. Results obtained by MCR-ALS have also been compared with those obtained by another multi-way method, PARAFAC. The methodology used in this study is completely general and it can be applied to other multi-way datasets.     

Recent advances in H2O2-based advanced oxidation processes for removal of antibiotics from wastewater

As important emerging contaminants, antibiotics have caused potential hazards to the ecological environment and human health due to their extensive production and consumption. Among various techniques for removing antibiotics from wastewater, H₂O₂-based advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rate and strong oxidation capability. Hence this review critically discusses: (i) Recent research progress of AOPs with the addition of H₂O₂ for antibiotics removal through different methods of H₂O₂ activation; (ii) recent advances in AOPs that can in-situ generate and activate H₂O₂ for antibiotics removal; (iii) H₂O₂-based AOPs as a combination with other techniques for the degradation and mineralization of antibiotics in wastewater. Future perspectives about H₂O₂-based AOPs are also presented to grasp the future research trend in the area.     

Degradation and toxicity changes in aqueous solutions of chloroacetic acids by Fenton-like treatment using zero-valent iron

Three priority pollutants, i.e. mono-, di-, and trichloroacetic acids, were degraded by the conventional Fenton AOP system (Fe²⁺ and H₂O₂). The results obtained suggest that the degradation decreased in the order: monochloroacetic, dichloroacetic, and trichloroacetic acid. The best of advanced oxidation processes (AOPs) for the degradation of trichloroacetic acid was reductive dechlorination with the use of zero-valent iron (Fe°). The results of Escherichia coli toxicity tests revealed that the reagents’ toxicity after the Fenton treatment process was decreased.     

COD reduction of waste water streams of active pharmaceutical ingredient – Atenolol manufacturing unit by advanced oxidation-Fenton process

Active pharmaceutical intermediates (API) in waste waters have adverse effects on aquatic life and environment. The API have high COD value and low BOD₃ and hence difficult to treat biologically. In this study, advanced oxidation processes (AOPs) utilizing the H₂O₂/Fe⁺², Fenton reactions were investigated in lab-scale experiments for the degradation of Atenolol containing waste water streams. The experimental results showed that the Fenton process using H₂O₂/Fe⁺² was the most effective treatment process. With Fenton processes, COD reduction of wastewater can be achieved successfully. It is suggested that Fenton processes are viable techniques for the degradation of Atenolol from the waste water stream with relatively low toxic by-products in the effluent which can be easily biodegraded in the activated sludge process. Hence, the Fenton process with H₂O₂/Fe⁺² is considered a suitable pretreatment method to degrade the active pharmaceutical molecules and to improve the biodegradability of waste water.     

Decontamination of heavy metal complexes by advanced oxidation processes: A review

Heavy metal complexes with high mobility are widely distributed in wastewater from modern industries, which are more stable and refractory than free heavy metal ions. Their removals from wastewater draw increasing attentions and various technologies have been developed, among which advanced oxidation processes (AOPs) are more effectively and promising. Progresses on five representative types of AOPs, including Fenton (like) oxidation, electrochemical oxidation, photocatalytic oxidation, ozonation and discharge plasma oxidation for heavy metal complexes degradation are summarized in this review. Their rationales, advantages, applications, challenges and prospects are introduced independently. Combinations among these AOPs, such as electrochemical Fenton oxidation and photoelectrocatalytic oxidation, are also comprehensively highlighted. Future efforts should be made to reduce acid requirement and scale up for practical applications of AOPs for heavy metal complex degradation efficiently and cost-effectively.     

A confined micro-reactor with a movable Fe3O4 core and a mesoporous TiO2 shell for a photocatalytic Fenton-like degradation of bisphenol A

Photocatalysis and Fenton process are two primary and promising advanced oxidation processes to degrade organic pollutants. However, the practical applications of single photocatalysis and Fenton process are still limited. Introducing one of them into another to form a combined photocatalytic Fenton-like system has shown great potential but still faces challenges in designing a well-tailored catalyst. Herein, a confined photocatalytic Fenton-like micro-reactor catalyst with a movable Fe₃O₄ core and a mesoporous TiO₂ shell has been constructed via a successive Stöber coating strategy, followed by an ultrasound assisted etching method. The resulting micro-reactor possesses well-defined yolk-shell structures with uniform mesopores (～4 nm), a large Brunauer-Emmett-Teller (BET) surface area (～166.7 m²/g), a high pore volume (～0.56 cm³/g) and a strong magnetization (～51 emu/g), as well as tunable reactor sizes (20?90 nm). When evaluated for degrading bisphenol A under solar light in the presence of peroxymonosulfate, the micro-reactor exhibits a superior catalytic degradation performance with a high magnetic separation efficiency and an excellent recycle ability. The outstanding performance can be attributed to its unique textual structure, which leads to a great synergistic effect from the photocatalytic and Fenton-like process. This study gives an important insight into the design and synthesis of an advanced micro-reactor for a combined advanced oxidation processes (AOPs).     

Application of advanced oxidation processes for removing salicylic acid from synthetic wastewaters

<正>In this study,advanced oxidation processes(AOPs) such as anodic oxidation(AO),UV/H_2O_2 and Fenton processes(FP) were investigated for the degradation of salicylic acid(SA) in lab-scale experiments.Boron-doped diamond(BDD) film electrodes using Ta as substrates were employed for AO of SA.In the case of FP and UV/H_2O_2,most favorable experimental conditions were determined for each process and these were used for comparing with AO process.The study showed that the FP was the most effective process under acidic conditions,leading to the highest rate of SA degradation in a very short time interval.However,the results showed that Ta/BDD films had high electrocatalytic activity for complete degradation of SA;even if it employs more time for complete elimination of the SA respect to FP.Additionally,AO led to a sixfold acceleration of the oxidation rate compared with the UV/H_2O_2 process.Finally a rough comparison of the specific energy consumption shows that AO process reduced the energy consumption by at least 90%compared with the UV/H_2O_2 process.     

Multivariate curve resolution-alternating least squares (MCR-ALS) and central composite experimental design for monitoring and optimization of simultaneous removal of some organic dyes

In this work, multivariate curve resolution-alternating least squares (MCR-ALS) has been applied to resolve and study the simultaneous degradation of three toxic organic dyes using Fenton reaction. Second-order kinetic-spectrophotometric data in the simultaneous degradation of malachite green, crystal violet and methylene blue were analyzed by MCR analysis to get their concentration profiles and calculate their degradation factors. The effect of three parameters (Fe²⁺, H₂O₂ concentration and initial pH) and their possible interaction in the simultaneous degradation of mentioned dyes were studied and optimized using experimental design and response surface method. Acquiring second-order data makes possible the analysis and study of the studied dyes in the gray systems which is termed as second-order advantage in the literatures. The prominent point of this work is the combination of second-order data and response surface methodology.     

Multiway chemometric decomposition of EEM of fluorescence of CdTe quantum dots obtained as function of pH

The effect of the pH (from 3 to 10) on the excitation emission matrices (EEMs) of fluorescence of CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were analyzed by multiway decomposition methods of parallel factor analysis (PARAFAC), a variant of the parallel factor analysis method (PARAFAC2) and multivariate curve resolution alternating least squares (MCR-ALS). Three different sized CdTe QDs with emission maximum at 555 nm (QDa), 594 nm (QDb) and 628 nm (QDc) were selected for analysis. The three-way data structures composed of sets of EEMs obtained as function of the pH (EEMs, pH) do not have a trilinear structure. A marked deviation to the trilinearity is observed in the emission wavelength order—the emission spectra suffers wavelength shift as the pH is varied. The pH-induced variation of the fluorescence properties of QDs is described with only one-component PARAFAC2 or MCR-ALS models—other components are necessary to model scattering and/or other background signals in (EEMs, pH) data structures. Bigger sized QDs are more suitable tools for analytical methodologies because they show higher Stokes shifts (resulting in simpler models) and higher pH range sensitivity. The pH dependence of the maximum wavelength of the emission spectra is particularly suitable for the development of QDs/EEMs wavelength-encoded pH sensor bioimaging or biological label methodologies when coupled to multiway chemometric decomposition.     

Multivariate curve resolution based chromatographic peak alignment combined with parallel factor analysis to exploit second-order advantage in complex chromatographic measurements

In the present contribution, a new combination of multivariate curve resolution-correlation optimized warping (MCR-COW) with trilinear parallel factor analysis (PARAFAC) is developed to exploit second-order advantage in complex chromatographic measurements. In MCR-COW, the complexity of the chromatographic data is reduced by arranging the data in a column-wise augmented matrix, analyzing using MCR bilinear model and aligning the resolved elution profiles using COW in a component-wise manner. The aligned chromatographic data is then decomposed using trilinear model of PARAFAC in order to exploit pure chromatographic and spectroscopic information. The performance of this strategy is evaluated using simulated and real high-performance liquid chromatography-diode array detection (HPLC-DAD) datasets. The obtained results showed that the MCR-COW can efficiently correct elution time shifts of target compounds that are completely overlapped by coeluted interferences in complex chromatographic data. In addition, the PARAFAC analysis of aligned chromatographic data has the advantage of unique decomposition of overlapped chromatographic peaks to identify and quantify the target compounds in the presence of interferences. Finally, to confirm the reliability of the proposed strategy, the performance of the MCR-COW-PARAFAC is compared with the frequently used methods of PARAFAC, COW-PARAFAC, multivariate curve resolution-alternating least squares (MCR-ALS), and MCR-COW-MCR. In general, in most of the cases the MCR-COW-PARAFAC showed an improvement in terms of lack of fit (LOF), relative error (RE) and spectral correlation coefficients in comparison to the PARAFAC, COW-PARAFAC, MCR-ALS and MCR-COW-MCR results.     

Can sample treatments based on advanced oxidation processes assisted by high-intensity focused ultrasound be used for toxic arsenic determination in human urine by flow-injection hydride-generation atomic absorption spectrometry?

Two advanced oxidation processes (AOPs), based on high-intensity focused ultrasound (HIFU), namely, KMnO₄/HCl/HIFU and H₂O₂/HCl/HIFU are studied and compared for the determination of toxic arsenic in human urine [As(III) + As(V) + MMA + DMA] by flow-injection hydride-generation atomic absorption spectrometry (FI-HG-AAS). The KMnO₄/HCl/HIFU procedure was found to be adequate for organic matter degradation in human urine. l-cysteine (letra minuscula) was used for As reduction to the trivalent state. The new procedure was assessed with seven urines certified in different As species. Results revealed that with KMnO₄/HCl/HIFU plus l-cysteine the toxic arsenic can be accurately measured in human urine whilst the H₂O₂/HCl/HIFU procedure underestimates toxic As. DMA and MMA degradation in urine were observed, due to the effects of the ultrasonic field. Recoveries for As(III), As(V), MMA and DMA were within the certified ranges. Arsenobetaine was not degraded by the AOPs. The new procedure adheres well to the principles of analytical minimalism: (i) low reagent consumption, (ii) low reagent concentration, (iii) low waste production and (iv) low amount of time required for sample preparation and analysis.     

Trilinearity and component interaction constraints in the multivariate curve resolution investigation of NO and O<Subscript>3</Subscript> pollution in Barcelona

Multiway and multiset data analysis extensions of the multivariate curve resolution alternating least squares (MCR-ALS) method are proposed for the investigation of the temporal distribution of the pollution by nitric oxide (NO) and ozone (O₃) in one sampling station in the urban centre of Barcelona (Catalonia, Spain), during the years 2000–2006. Different specific studies were performed considering the annual and pluriannual contamination by these two contaminants, individually or in combination using different data matrix augmentation strategies and multiway and multiset data analysis models. Daily, hourly and annual profiles were estimated describing different patterns and summarising the main contamination processes. The daily and night trends found were mainly attributed to traffic and photochemical processes favoured by light radiation. Moreover, winter–summer seasonal trends were also clearly detected and their changes over different years assessed. The extension MCR-ALS method to multiset data analysis using different constraints like non-negativity, trilinearity and interaction among components is confirmed to be a powerful method to improve the interpretability of the different contamination patterns in atmospheric contamination studies.     

Chemometric processing of second-order liquid chromatographic data with UV–vis and fluorescence detection. A comparison of multivariate curve resolution and parallel factor analysis 2

Second-order liquid chromatographic data with multivariate spectral (UV–vis or fluorescence) detection usually show changes in elution time profiles from sample to sample, causing a loss of trilinearity in the data. In order to analyze them with an appropriate model, the latter should permit a given component to have different time profiles in different samples. Two popular models in this regard are multivariate curve resolution-alternating least-squares (MCR-ALS) and parallel factor analysis 2 (PARAFAC2). The conditions to be fulfilled for successful application of the latter model are discussed on the basis of simple chromatographic concepts. An exhaustive analysis of the multivariate calibration models is carried out, employing both simulated and experimental chromatographic data sets. The latter involve the quantitation of benzimidazolic and carbamate pesticides in fruit and juice samples using liquid chromatography with diode array detection, and of polycyclic aromatic hydrocarbons in water samples, in both cases in the presence of potential interferents using liquid chromatography with fluorescence spectral detection, thereby achieving the second-order advantage. The overall results seem to favor MCR-ALS over PARAFAC2, especially in the presence of potential interferents.     

Recent advances in the application of metal organic frameworks using in advanced oxidation progresses for pollutants degradation

Metal-organic frameworks (MOFs) materials with highly ordered and porous crystalline structure, have excellent performance in advanced oxidation progresses (AOPs) for organic contaminants degradation in water treatment. This review intends to summarize the timely references and insights for the recent advances in MOFs that are used in AOPs. Starting with the preparation methodologies, including conventional hydrothermal method, electrochemical method, sol-gel method, and emerging microwave and ultrasound assisted synthesis methods. Application and mechanism for MOFs using in various AOPs of Fenton-like, photocatalysis, catalytic ozonation, persulfate catalysis and other emerging oxidation methods are emphatically discussed. We hope this review can comprehensively summarize the research and application progress of MOFs in AOPs, deepen the understanding of the catalytic mechanisms.     

A novel second-order standard addition analytical method based on data processing with multidimensional partial least-squares and residual bilinearization

In the presence of analyte-background interactions and a significant background signal, both second-order multivariate calibration and standard addition are required for successful analyte quantitation achieving the second-order advantage. This report discusses a modified second-order standard addition method, in which the test data matrix is subtracted from the standard addition matrices, and quantitation proceeds via the classical external calibration procedure. It is shown that this novel data processing method allows one to apply not only parallel factor analysis (PARAFAC) and multivariate curve resolution-alternating least-squares (MCR-ALS), but also the recently introduced and more flexible partial least-squares (PLS) models coupled to residual bilinearization (RBL). In particular, the multidimensional variant N-PLS/RBL is shown to produce the best analytical results. The comparison is carried out with the aid of a set of simulated data, as well as two experimental data sets: one aimed at the determination of salicylate in human serum in the presence of naproxen as an additional interferent, and the second one devoted to the analysis of danofloxacin in human serum in the presence of salicylate.     

A Review on the Degradation of Pollutants by Fenton-Like Systems Based on Zero-Valent Iron and Persulfate: Effects of Reduction Potentials,pH, and Anions Occurring in Waste Waters

Among the advanced oxidation processes (AOPs), the Fenton reaction has attracted much attention in recent years for the treatment of water and wastewater. This review provides insight into a particular variant of the process, where soluble Fe(II) salts are replaced by zero-valent iron (ZVI), and hydrogen peroxide (H₂O₂) is replaced by persulfate (S₂O₈²⁻). Heterogeneous Fenton with ZVI has the advantage of minimizing a major problem found with homogeneous Fenton. Indeed, the precipitation of Fe(III) at pH > 4 interferes with the recycling of Fe species and inhibits oxidation in homogeneous Fenton; in contrast, suspended ZVI as iron source is less sensitive to the increase of pH. Moreover, persulfate favors the production of sulfate radicals (SO₄^•−) that are more selective towards pollutant degradation, compared to the hydroxyl radicals (^•OH) produced in classic, H₂O₂-based Fenton. Higher selectivity means that degradation of SO₄^•−-reactive contaminants is less affected by interfering agents typically found in wastewater; however, the ability of SO₄^•− to oxidize H₂O/OH⁻ to ^•OH makes it difficult to obtain conditions where SO₄^•− is the only reactive species. Research results have shown that ZVI-Fenton with persulfate works best at acidic pH, but it is often possible to get reasonable degradation at pH values that are not too far from neutrality. Moreover, inorganic ions that are very common in water and wastewater (Cl⁻, HCO₃⁻, CO₃²⁻, NO₃⁻, NO₂⁻) can sometimes inhibit degradation by scavenging SO₄^•− and/or ^•OH, but in other cases they even enhance the process. Therefore, ZVI-Fenton with persulfate might perform unexpectedly well in some saline waters, although the possible formation of harmful by-products upon oxidation of the anions cannot be ruled out.     

CoN1O2 Single-Atom Catalyst for Efficient Peroxymonosulfate Activation and Selective Cobalt(IV)=O Generation

High-valent metal-oxo (HVMO) species are powerful non-radical reactive species that enhance advanced oxidation processes (AOPs) due to their long half-lives and high selectivity towards recalcitrant water pollutants with electron-donating groups. However, high-valent cobalt-oxo (Co^IV=O) generation is challenging in peroxymonosulfate (PMS)-based AOPs because the high 3d-orbital occupancy of cobalt would disfavor its binding with a terminal oxygen ligand. Herein, we propose a strategy to construct isolated Co sites with unique N₁O₂ coordination on the Mn₃O₄ surface. The asymmetric N₁O₂ configuration is able to accept electrons from the Co 3d-orbital, resulting in significant electronic delocalization at Co sites for promoted PMS adsorption, dissociation and subsequent generation of Co^IV=O species. CoN₁O₂/Mn₃O₄ exhibits high intrinsic activity in PMS activation and sulfamethoxazole (SMX) degradation, highly outperforming its counterpart with a CoO₃ configuration, carbon-based single-atom catalysts with CoN₄ configuration, and commercial cobalt oxides. Co^IV=O species effectively oxidize the target contaminants via oxygen atom transfer to produce low-toxicity intermediates. These findings could advance the mechanistic understanding of PMS activation at the molecular level and guide the rational design of efficient environmental catalysts.     

Designing 3D-MoS2 Sponge as Excellent Cocatalysts in Advanced Oxidation Processes for Pollutant Control

3D-MoS₂ can adsorb organic molecules and provide multidimensional electron transport pathways, implying a potential application for environment remediation. Here, we study the degradation of aromatic organics in advanced oxidation processes (AOPs) by a 3D-MoS₂ sponge loaded with MoS₂ nanospheres and graphene oxide (GO). Exposed Mo⁴⁺ active sites on 3D-MoS₂ can significantly improve the concentration and stability of Fe²⁺ in AOPs and keep the Fe³⁺/Fe²⁺ in a stable dynamic cycle, thus effectively promoting the activation of H₂O₂/peroxymonosulfate (PMS). The degradation rate of organic pollutants in the 3D-MoS₂ system is about 50 times higher than without cocatalyst. After a 140 L pilot-scale experiment, it still maintains high efficiency and stable AOPs activity. After 16 days of continuous reaction, the 3D-MoS₂ achieves a degradation rate of 120 mg L⁻¹ antibiotic wastewater up to 97.87 %. The operating cost of treating a ton of wastewater is only US$ 0.33, suggesting huge industrial applications.