Ion Chromatography Measurements Research Articles

Influence of LiNO3 on the Lithium Metal Deposition Behavior in Carbonate-Based Liquid Electrolytes and on the Electrochemical Performance in Zero-Excess Lithium Metal Batteries.

Continuous lithium (Li) depletion shadows the increase in energy density and safety properties promised by zero-excess lithium metal batteries (ZELMBs). Guiding the Li deposits toward more homogeneous and denser lithium morphology results in improved electrochemical performance. Herein, a lithium nitrate (LiNO3 ) enriched separator that improves the morphology of the Li deposits and facilitates the formation of an inorganic-rich solid-electrolyte interphase (SEI) resulting in an extended cycle life in Li||Li-cells as well as an increase of the Coulombic efficiency in Cu||Li-cells is reported. Using a LiNi0.6 Co0.2 Mn0.2 O2 positive electrode in NCM622||Cu-cells, a carbonate-based electrolyte, and a LiNO3 enriched separator, an extension of the cycle life by more than 50 cycles with a moderate capacity fading compared to the unmodified separator is obtained. The relative constant level of LiNO3 in the electrolyte, maintained by the LiNO3 enriched separator throughout the cycling process stems at the origin of the improved performance. Ion chromatography measurements carried out at different cycles support the proposed mechanism of a slow and constant release of LiNO3 from the separator. The results indicate that the strategy of using a LiNO3 enriched separator instead of LiNO3 as a sacrificial electrolyte additive can improve the performance of ZELMBs further by maintaining a compact and thus stable SEI layer on Li deposits.

Characterization of Particle Size Distributions and Water-Soluble Ions in Particulate Matter Measured at a Broiler Farm

The chemical composition and size distribution of particulate matter produced at broiler poultry houses is not well understood, so this is a novel study to understand the particulate size distributions at a poultry house as well as the ionic composition of the particulate matter using real-time methods. Two optical particle counters provided particle size distributions inside and outside the house. An ambient ion monitor and a particle-in-liquid sampler analyzed the ionic chemical composition of the particulate matter in the house while a scanning mobility particle sizer provided size information in the nanoparticle range. Ammonia concentrations in the house were measured using a chemical sensor. Ammonia concentrations in the house were consistently in the lower part of the per million range 2–20 ppm. The optical particle counter and ion chromatography measurements both showed a strong diurnal variation of particulate matter concentration in the house throughout the study, associated with the lights being on and animal activity. Particulate mass concentration inside the house was dominated by coarse mode particles as opposed to the outdoor sampler which showed much smaller sizes. A few new particle formation and growth events were observed in the house. Ionic constituents detected by chromatography made up a small fraction of the overall mass concentration. The composition of the ionic constituents was similar for most of the study with typical ions being ammonium, sodium, potassium, chloride, sulfate, nitrate, nitrite, phosphate, and several carboxylates (formate, acetate, propionate, and butyrate.) At the end of the study, bromide was also detected during the last several days. Overall, we determined that the ionic components of the particulate matter formed through secondary particle formation was small, but also that some ionic constituents can be associated with management practices.

Development of Analytical Methods for the Determination of N-Bromosuccinimide in Different Active Pharmaceutical Ingredients by High-Performance Ion Chromatography with Suppressed Conductivity Detection

Product safety is important for medicines. For drugs on the market, it must be demonstrated that the levels of toxic contaminants are below the permitted limits. These impurities are used as reagents or are generated during synthesis. N-bromosuccinimide is used as a brominating agent in the synthesis of some active pharmaceutical ingredients. The determination of N-bromosuccinimide is difficult due to its high reactivity. In this work, a high-performance ion chromatographic method was developed for the determination of N-bromosuccinimide. The ion chromatographic measurement can be performed in two ways, one involves the assay of the resulting bromide ion and the other is via the assay of the 3-carbamoyl propanoic acid ion produced from the succinimide. Both acid ions were analyzed on an anion exchange column by gradient elution with potassium hydroxide eluent and detection was performed by a suppressed conductivity detector. During the method development, the results showed that the measurement of bromide ion was more selective than the measurement of 3-carbamoyl propanoic acid ion. Two different types of active pharmaceutical ingredients (API), i.e., prasugrel and favipiravir, were chosen to test the developed method and sample preparation. For both APIs, sample preparation was performed in a vial and consists of liquid–liquid extraction with an alkaline reagent. Finally, the anion exchange ion chromatography method was validated at the limit value level, and harmonized with the guidelines. For prasugrel, the quantification limits and the accuracy at the limit level are 7.2 ppm and 96.4%, while for favipiravir these are 7.5 ppm and 114.7%, respectively.

Comprehensive investigation on physical and chemical properties of γ‐irradiated multilayer PE/EVOH/PE film: A multiscale approach

AbstractThe study evaluates findings on the impact of γ‐irradiation on the single‐use, multilayer plastic film that is manufactured for the biotechnological and biopharmaceutical environments. It is comprised of a multilayer film that offers durability and gas (O2, CO2 and H2O) shielding properties. Polyethylene (PE) and ethylene vinyl alcohol (EVOH) are the parts within this film, which as a whole, is PE/EVOH/PE. The impact of γ‐irradiation on the nonirradiated and γ‐irradiated (from 30 kGy up to 270 kGy) PE multilayer film is investigated by colorimetry measurement, Fourier transform infrared and Raman spectroscopies, pH measurement, ion chromatography and conductivity measurement, tensile tests, X‐ray photoelectron spectroscopy, differential scanning, and oxygen and water vapor transmission rate. AComDim and Principal Components Analysis are two chemometric tools that are utilized to understand both physical and chemical changes, along with the main factors contributing to polymer degradation in the PE multilayer film while under γ‐irradiation.

Oxidative and pyrolytic decomposition of an evaporated stream of 2,4,6-tribromophenol over hematite: A prevailing scenario during thermal recycling of e-waste

Brominated flame retardants (BFRs) constitute a major load in the polymeric fraction of e-waste. Degradation of BFRs-laden plastics over transition metal oxides is currently deployed as a mainstream strategy in the disposal and treatment of the non-metallic segment of e-waste. However, interaction of pyrolysis’s products of BFRs with transition metal oxides is well-known to facilitate the formation of notorious pollutants. Despite recent progress to comprehend the germane chemistry of this interaction, several important pertinent aspects remain to be addressed. To fill in this gap, an integrated experimental and simulation account of the pyrolytic and oxidative decomposition of a gaseous stream of 2,4,6-tribromophenol (TBP) over hematite (Fe2O3) has been reported herein. TBP is utilized as a model compounds of BFRs as their most common formulations include brominated phenolic rings. Overall, hematite entails a rather low cracking capacity under pyrolytic conditions. Analysis of condensate products indicates that oxidative degradation of a gaseous stream of TBP results mainly in the formation of brominated alkanes such as bromoethane and bromo-pentane. Likewise, Ion chromatography (IC) measurements disclosed a noticeable reduction in the concentrations of escaped HBr. Transformation of iron oxides into iron bromides (possibly in the form of FeBr2) during pyrolysis and combustion operations is evident through XRD measurements. Density functional theory (DFT) calculations map out important reactions pathways that operate in the initial degradation of the TBP molecule. From a broader perspective, outlined results shall be instrumental to precisely assess the effectiveness of using iron oxides in thermal catalytic recycling of e-waste and the likely emission of brominated toxicants.

Iron-Modified Titanate Nanorods for Oxidation of Aqueous Ammonia Using Combined Treatment with Ozone and Solar Light Irradiation

Sodium titanate nanorods were synthesized by a hydrothermal method and subsequently modified with an iron precursor. For comparison, Fe2O3 nanocubes were also obtained through a similar hydrothermal treatment. Pristine, Fe-modified nanorods and Fe2O3 nanocubes were suspended in diluted ammonia solutions (20 ppm) and exposed to ozone and simulated light irradiation. Ammonia abatement, together with the resulting nitrogen-containing products (NO3−), was monitored by ion chromatography measurements. The generation of reactive oxygen species (·OH and O2−) in the investigated materials and their photoelectrochemical behaviour were also investigated. Morphological and structural characterizations (SEM, XRD, XRF, UV–Vis, H2-TPR, NH3-TPD, PL, PZC) of the studied catalysts were correlated with their activity for ammonia degradation with ozone- and photo-assisted oxidation. An increase in ammonia conversion and a decreasing amount of NO3− were achieved by combining the above-mentioned processes.

Hygroscopicity and Ice Nucleation Properties of Dust/Salt Mixtures Originating from the Source of East Asian Dust Storms

Dust storms are common meteorological events that occur frequently in the late spring and early summer in arid and semi-arid areas. The resulting lofted dust and salt mixtures can impact atmospheric chemistry and climate systems through the many pathways represented by aerosol-cloud-climate interactions. In this study, dust/salt samples were collected from important sources of the East Asian dust storm, including the Badain Jaran Desert, the Tengger Desert and the Ulan Buh Desert in northwestern China. Ion chromatography (IC) measurements were performed to determine the concentrations of cations and anions. The ionic concentrations, pH and dissolvable fractions of sand samples show a positive correlation, indicating that the dissolved content is rich in alkaline ions. A positive matrix factorization (PMF) receptor model was employed to analyze the IC results, and from the PMF solutions non-obvious connections to local geography emerge. The results of hygroscopic experiments of sand samples which were measured by a vapor sorption analyzer indicate that the hygroscopicity may be related to the soluble content of samples, and the observed hygroscopic behavior can be well described by a thermodynamic model. The morphology of individual particles was chemically mapped by the synchrotron-based scanning transmission X-ray microscopy, and needle-shaped CaCO3 particles were observed to adhere to more irregular high K-containing particles. Moreover, a continuous flow diffusion chamber was used to investigate the ice nucleation abilities of typical salts, with both homogeneous freezing and deposition nucleation being observed. The results indicate that the salts primarily act as cloud condensation nuclei but can also act as ice nucleating particles at low temperatures.

Fluorescence Recognition of Anions Using a Heteroditopic Receptor: Homogenous and Two-Phase Sensing.

In contrast to monotopic receptor 3, the anthracene functionalized squaramide dual-host receptor 1 is capable of selectively extracting sulfate salts, as was evidenced unambiguously by DOSY, mass spectrometry, fluorescent and ion chromatography measurements. The receptors were investigated in terms of anion and ion pair binding using the UV–vis and 1H NMR titrations method in acetonitrile. The reference anion receptor 3, lacking a crown ether unit, was found to lose the enhancement in anion binding induced by the presence of cations. Besides the ability to bind anions in an enhanced manner exhibited by ion pair receptors 2 and 4, changing the 1-aminoanthracene substituent resulted in their exhibiting a lower anion affinity than receptor 1. By using receptor 1 and adjusting the water content in organic phase it was possible to selectively detect sulfates both by “turn-off” and “turn-on” fluorescence, and to do so homogenously and under interfacial conditions. Such properties of receptor 1 have allowed the development of a new type of sensor capable of recognizing and extracting potassium sulfate from the aqueous medium across a phase boundary, resulting in an appropriate fluorescent response in the organic solution.

Novel reusable sulfate-type zirconium alginate ion-exchanger for fluoride removal

It is still a challenge to eliminate efficiently fluoride ion from groundwater, especially to design and synthesis an adsorbent possessing high adsorption capacity, recyclability and wide pH application conditions. Herein we present millimeter-sized sulfate-type zirconium alginate hydrogel beads with 3D network structure (AHB@Zr-SO42−) that exhibited a maximum adsorption capacity of 101.3 mg/g with wide pH applicability (pH 3−9). This material have ~2.5 times higher adsorption capacity than that of pure zirconium alginate hydrogel beads (AHB@Zr) and it was ascribed to ion exchange between SO42− and F− on the surface of AHB@Zr-SO42−, which was verified via ion chromatography measurement coupled with X-ray photoelectron spectroscopy (XPS) and Fourier Transform Infrared Spectrometer (FTIR Spectrometer) analysis. Density functional theory (DFT) calculations indicated that the ion exchange process between SO42− and F− in AHB@Zr-SO42− was energetically favorable than OH− and F− in AHB@Zr. In addition, 310 bed volumes (BV) of effluent was realized via column adsorption of groundwater containing fluoride on AHB@Zr-SO42− and indicated that it is a promising candidate for mitigating the problem of fluoride-containing groundwater.

Development of microwave assisted-UV digestion using diluted reagents for the determination of total nitrogen in cereals by ion chromatography

The objective of this work is to develop a microwave assisted-ultraviolet (MW-UV) digestion in the presence of dilute HCl and H2O2 followed by ion chromatography (IC) measurements for the determination of total nitrogen in cereals. This approach (MW-UV-IC) requires lesser time and does not need environmentally hazardous materials as used in Kjeldhal method. Further, the developed method requires only microliter quantities of dilute HCl and few milliliters of H2O2 for the matrix digestion and simultaneous conversion of nitrogen to its ionic species for the subsequent analysis by IC. At the optimized acid concentrations (200 ​μL of 0.1 ​mol ​L−1 HCl) and microwave power, the nitrogen in the cereals flours is converted to nitrate (NO3−), nitrite (NO2−) and ammonium (NH4+) ions. The nitrogen species were separated using IonPac AS-20 and IonPac CS-17 columns and then quantified using suppressed conductivity detection. The method was applied to estimate the total nitrogen in flours of various cereals like; wheat (Triticum aestivum), rice (Oryza sativa), finger millet (Eleusine coracana), jowar (Sorghum) and pearl millet (Pennisetum glaucum). The results obtained using proposed method, were in good agreement with that of Kjeldhal method. Further, the precision of the values obtained by developed method was on par with the Kjeldhal method for all the tested flours as verified by F-test (n ​= ​5 and 95% confidence limit). Additionally, greenness assessment tools like analytical Eco-scale and green analytical procedure index (GAPI) suggested the proposed MW-UV-IC method, for the determination of total nitrogen in cereal flours, to be excellently green and safe.

Accountancy for intrinsic colloids on thorium solubility: The fractionation of soluble species and the characterization of solubility limiting phase

The extensive hydrolysis of tetravalent actinides leads to polynuclear formations through oxygen bridging facilitating the formation of colloids as end products. The pH, ionic strength has phenomenal effects on Thorium colloids formation. The quantitative estimation of colloids facilitates the fraction of soluble fraction into ionic, polymeric and colloidal forms of thorium. The colloids accountability and precipitate characterization explains the discrepancies in estimated solubility limits. The supernatants of long equilibrated (∼3 years) saturated thorium solution under various pH (5- 11) and ionic strengths (0–3 M NaClO4) were analysed by Inductively Coupled Plasma Mass Spectrometer (ICP-MS) and Ion Chromatography (IC) to determine total and ionic thorium respectively. Laser Induced Breakdown Detection (LIBD) was employed to determine the colloid size and concentrations. The precipitates were characterized by calorimetry and XRD to determine the solubility limiting phase. The results of pH, IC, ICP-MS, and LIBD measurements on the aged thorium samples are discussed with regard to the mechanism of the formation of thorium colloids. The results revealed the formation of colloids having particle size (10–40 nm) at concentrations (109-1011 particles/mL). The colloids accountancy resulted in estimated solubility products to 2–4 orders lower than their inclusion as soluble thorium. The soluble thorium was fractionated quantitatively into ionic, polymeric and colloidal forms of thorium. The precipitates formed are found to be semi amorphous.

Combining Ion Chromatography and Total Reflection X-ray Fluorescence for Detection of Major, Minor and Trace Elements in Quartz-Hosted Fluid Inclusions

The crush-leach technique is a frequently used method to determine the bulk composition of fluid inclusions trapped in a range of geological samples. We present a modified crush-leach technique combining ion chromatography (IC) and total reflection X-ray fluorescence spectroscopy (TXRF) which allows to determine a range of major, minor and trace elements out of one leachate. To date, trace element detection by means of TXRF is barely used in geosciences, although it combines the advantages of low to very low detection limits (µg/L to ng/L range), small sample amount needed (µL-range) and a fast and inexpensive analytical procedure. Previously described problems of adsorption of polyvalent cations at sample surfaces have been overcome by using acidified water as a leachate. Instead, it has been demonstrated that, for example, the syringe filter type used for IC measurements influences contamination and/or adsorption for a number of elements. The proposed method combination was evaluated for accuracy, reproducibility and system blanks and subsequently applied to quartz samples from hydrothermal vein deposits of the Schwarzwald ore district, SW Germany.

Experimental investigation of CO2–rock–brine interaction for injection of CO2 in an Iranian oil reservoir as an EOR method

In this study, possibility of geological storage of CO2 into an Iranian hydrocarbon reservoir is investigated as a method of enhanced oil recovery (EOR). For this purpose, a stainless steel sand packed model, containing rock and brine, was used to simulate the reservoir condition and CO2 injection. Subsequently, CO2–rock–brine interactions (dissolution and deposition of minerals) due to CO2 injection, under reservoir pressure and temperature condition (136 bar and 80 °C), was studied with ion chromatography and pH measurement at time intervals of 7, 14 and 30 days. In addition, the rock structure was identified by X-ray diffraction analysis. Results showed that up to 14 days, pH and the concentration of cations (sodium, calcium, magnesium, and potassium) and anions (chloride and sulfate) were progressively increased. However, in 30 days, assays, both pH and concentration, were decreased compared to those of 14 days of test results. Consequently, the dissolution process was observed to be the dominant phenomenon in the early days; then, the deposition of secondary minerals became the main process during the performed test. Finally, in the case of selecting the right place for CO2 injection, to avoid the porosity and permeability decrease near the well, this method can be used as a safe technique for CO2 geological storage at specific time intervals in the studied oil reservoir.

Application of TXRF in monitoring trace metals in particulate matter and cloud water

Abstract. Trace metals in ambient particulate matter and cloud are considered key elements of atmospheric processes as they affect air quality, environmental ecosystems, and cloud formation. However, they are often available at trace concentrations in these media such that their analysis requires high-precision and sensitive techniques. In this study, different analytical methods were applied to quantify trace metals in particulate matter (PM) samples collected on quartz and polycarbonate filters as well as cloud water, using the Total reflection X-Ray Fluorescence (TXRF) technique. These methods considered the measurement of filter samples directly without and with chemical pretreatment. Direct measurements involved the analysis of PM samples collected on polycarbonate filters and cloud water samples after they are brought onto TXRF carrier substrates. The chemical treatment method involved the assessment of different acid digestion procedures on PM sampled on quartz filters. The solutions applied were reverse aqua regia, nitric acid, and a combination of nitric acid and hydrogen peroxide. The effect of cold-plasma treatment of samples on polycarbonate filters before TXRF measurements was also investigated. Digestion with the reverse aqua regia solution provided lower blanks and higher recovery in comparison to other tested procedures. The detection limits of the elements ranged from 0.3 to 44 ng cm−2. Ca, K, Zn, and Fe showed the highest detection limits of 44, 35, 6, and 1 ng cm−2, while As and Se had the lowest of 0.3 and 0.8 ng cm−2, respectively. The method showed higher recovery for most trace metals when applied to commercially available reference materials and field samples. TXRF measurements showed good agreement with results obtained from ion chromatography measurements for elements such as Ca and K. Cold-plasma treatment did not significantly lead to an increase in the detected concentration, and the results were element specific. Baking of the quartz filters prior to sampling showed a reduction of more than 20 % of the filter blanks for elements such as V, Sr, Mn, Zn, and Sb. The methods were applied successfully on ambient particulate matter and cloud water samples collected from the Atlas Mohammed V station in Morocco and the Cape Verde Atmospheric Observatory. The obtained concentrations were within the range reported using different techniques from similar remote and background regions elsewhere, especially for elements of anthropogenic origins such as V, Pb, and Zn with concentrations of up to 10, 19, and 28 ng m−3, respectively. Enrichment factor analysis indicated that crustal matter dominated the abundance of most of the elements, while anthropogenic activities also contributed to the abundance of elements such as Sb, Se, and Pb. The results confirm that TXRF is a useful complementary sensitive technique for trace metal analysis of particulate matter in the microgram range as well as in cloud water droplets.

Chemical characteristics of particulate matters and their emission sources over Varanasi during winter season

The chemical composition of particulate matter impacts both human health and climate. In this study, the chemical characteristics of particulate matter was measured for four months (November 2016–February 2017) at Varanasi, which is located in the middle of the Indo-Gangetic Basin (IGB). The daily observed mean values of PM10 and PM2.5 are 134 ± 48 and 213 ± 80 μg/m3, respectively, which exceeds both national and international standards. The average value of PM2.5/PM10 ratio is 0.64 ± 0.16 which indicates a relatively higher fraction of fine particles that are attributed to anthropogenic emission sources (biomass/post-harvest burning) as corroborated by MODIS fire counts and back trajectory analysis. Ion chromatographic measurements showed that SO42−, Cl−, K+, NO3−, Na+, Ca2+, Mg2+ are the major ionic species present in the aerosol. Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM–EDX) analysis shows the prevalence of carbon-rich particles at Varanasi which is likely due to biomass burning and other anthropogenic sources.

Characteristics of Films on the Surface of Sea Sand and Effects on the Dissolution of Chloride

In this study, the effects of the specimen preparation method, temperature, and duration of the extraction step for the determination of the water-soluble chloride content of sea sand were investigated. The results demonstrated that increasing the heating temperature and duration promoted the dissolution of chloride, where the maximum value was obtained at 80°C and 60 min. Hot water extraction (80°C/60 min) could eliminate the effects of different specimen preparation methods on the final test results. Therefore, a new method was developed with drying at a temperature of 110 ± 5°C and hot water extraction at a temperature of 80°C for 60 min. The suitability of the new method for determining the water-soluble chloride content of sea sand was verified by testing the extracted specimens again. The results indicated that the chloride in sea sand dissolved fully with the new method, and thus it is suitable for testing the water-soluble chloride content of sea sand. Finally, the organic and inorganic compositions of the film adsorbed on the surface of sea sand were studied based on thermogravimetric analysis, inductively coupled plasma atomic emission spectrometry, ion chromatography, and total organic carbon measurements. The results indicated that a layer of substance (a multi-substance film) was adsorbed onto the surface of sea sand. This layer comprised inorganic salts (such as Cl–, Na+, Mg2+, SO42–, and Ca2+) and organic compounds, which were related to the composition of sea water. The multi-substance film greatly affected the dissolution and diffusion of chloride in the sea sand. Hot water extraction accelerated the dissolution of the film and increased the test results in terms of the water-soluble chloride contents.

Dialkyl imidazolium acetate ionosilica as efficient and recyclable organocatalyst for cyanosilylation reactions of ketones

We report new heterogeneous organocatalyst based on silica hybrid supported N-heterocyclic carbene (NHC-) species. The organocatalyst is formed from an imidazolium iodide based ionosilica material, followed by iodide/acetate anion exchange. The imidazolium acetate generates the organocatalytic carbene via partial deprotonation of the imidazolium ring in situ. As monitored via EDX, solid state NMR and ion chromatography measurements, the iodide/acetate exchange involving the imidazolium ionosilica material took place only in small extent. Despite the fact that the exchanged material contains only a very small amount of acetate, we observed good catalytic activity and recyclability in cyanosilylation reactions of ketones with trimethylsilyl cyanide. The versatility of the catalyst was highlighted via reaction with several substrates, yielding the corresponding cyanohydrins in good yields. In recycling experiments, the material showed decreasing catalytic activity starting from the third reaction cycle, but high catalytic activity can be regenerated via another acetate treatment. Our work is important as it highlights the possibility to combine carbene chemistry and silica, which are antagonistic at a first glance. We show that imidazolium acetate based ionosilicas are therefore heterogeneous ‘proto-carbenes’, and that there is no need to form strongly basic silica supported NHCs to obtain heterogeneous NHC-organocatalysts. This work therefore opens the route towards heterogeneous and re-usable NHC-organocatalysts from supported ionic liquid imidazolium acetates.

Degradation Phenomena of Wooden Pillars in the Main Hall of the Fengguo Monastery, Yixian, Liaoning, China - Scientific Investigation with XRD, IC, and FTIR Analysis -

The Main Hall of the Fengguo monastery in Yixian county, Liaoning province, China, is the best preserved and largest wooden Buddhist structure, typical of the Liao dynasty style, in China. However, some degradation to the timber frame of the Main Hall has been noted, and this is causing concern in terms of the long-term preservation of the structure. In this study, wooden pillars showing the degradation phenomena of whitening, for areas in contact with the stone floor, and extensive surface damage at higher locations(mostly above 1 m) have been examined. Samples taken from wooden pillar surfaces were analyzed using X-ray powder diffraction, Fourier-transform infrared spectroscopy(FTIR), ion chromatography, and pH measurements. With respect to the whitening phenomenon, we found inorganic calcium precipitates and oxalate ions, along with higher pH values. These symptoms indicated that chemical changes were taking place in response to alkaline conditions, suggesting that alkaline mixtures with calcium content in the foundations may be responsible. Regarding the upper surface-damaged areas, no valid evidence for chemical degradation was found using FTIR analysis, while damaged areas exhibited the presence of more bat guano-related materials than which were apparent in undamaged areas. The occurrence of this surface-damaged phenomenon has therefore been attributed to physical damage caused by bat activity over long periods of time.

Advanced oxidation process based on water radiolysis to degrade and mineralize diclofenac in aqueous solutions

Residual pharmaceutical compounds (PCs) are among the emerging organic contaminants detected in our water cycle. Diclofenac (Dic) is one of the commonly detected pharmaceutical contaminant in aquatic systems. This study was designed to investigate the degradation and mineralization of Dic in aqueous solutions by ionizing radiation emitted from radioactive Co60 under several conditions. Ultra-performance liquid chromatography, ion chromatography and TOC measurements confirmed the radiolytic degradation of Dic. The absorbed doses needed to degrade 99% Dic at 25, 50, 100, 190, 280, and 480 μM were 0.560, 0.950, 1.950, 4.000, 5.400, and 7.400 kGy, respectively. This process follows pseudo-first-order kinetics. The γ-ray/N2O system decreased the dose required to degrade 99% to 1.47 kGy. The presence of bromide anions inhibits degradation. Remarkably, adding H2O2, S2O82−, or N2O promotes mineralization. Conversely, the absence of dissolved oxygen hinders mineralization. This study provides a viable finding that ionizing radiation are useful tolls to remedy water containing pharmaceutical organic compounds.

Monitoring of the total carbon and nitrogen balance during the mineralization of nitrogen containing compounds by heat activated persulfate

Peroxydisulfate (S2O82−) is widely applied in environmental remediation and water treatment as an agent for the unselective oxidation of organic contaminants. S2O82− itself is a strong oxidation agent but activation by heat, UV radiation, or metal catalysts forms sulfate radicals (SO4−), which offer a higher oxidation potential and faster reaction kinetics. The mechanism of degradation for many organic contaminants by sulfate radicals is well studied, but the final mineralization products are not commonly evaluated. Nitrogen containing compounds are known to produce different mineralization products depending on their structure and the reaction conditions. For the identification of the main mineralization products, two approaches for the determination of nitrogen mass balances were evaluated. The first approach was based on a combination of total organic carbon (TOC), and total nitrogen bound (TNb). The second approach used a combination of TOC and ion chromatography (IC). The evaluation based on the TOC and TNb by high temperature combustion was found to be significantly biased as measured ammonium concentrations were underestimated by the TNb measurements in the presence of peroxydisulfate. With the TOC/TNb method, 83.2 ± 1.1% of the initial nitrogen could be recovered after the oxidation. The TOC/IC based approach led to an overall recovery of 91.1 ± 1.4%, where NO3− and NH4+ were identified as the main products. Based on the fraction of ammonium provided by the IC measurements, the TOC/TNb based results could be corrected for the underestimation of ammonium which led to a recovery of 95.9 ± 3.1%. The presented methods are applicable for the determination of nitrogen mass balances in lab-scale studies, as well as for the monitoring of mineralization products in field applications.