Chemical Water Research Articles

КАТАСТРОФА SEAMARK B ЦЕМЕССКОЙ БУХТЕ

As part of the monitoring of environmental objects, studies of the environmental consequences were carried out immediately after the catastrophic shipwreck of the cargo ship Seamark in Tsemes Bay. In addition to human casualties and material losses, each wreck causes damage to the ecology of the seas. Human pollution of the marine environment leads to its degradation and the accumulation of toxic substances in water and living organisms. Sampling of sea water within two months from the moment of the disaster made it possible to assess the dynamics of the content of impurities in sea water. The general parameters of sea water were determined using standard methods (total mineralization, pH, anionic surfactants), as well as the content of petroleum products. It has been established that even at a considerable distance from the site of the disaster, the content of petroleum products in sea water exceeds the norm by almost two orders of magnitude. The real and future consequences of seawater pollution with petroleum products for the ecology of the sea are described.

Flawless polyaniline coating for preservation and corrosion protection of ancient steel spearheads: an archaeological study from military museum, Al-Qala, Egypt

The purpose of this research was to examine the viability of applying a flawless polyaniline coating on steel spearheads to preserve them and protect them from corrosion. The spearpoints, thought to be archaeologically significant, were acquired from the Military Museum in Al-Qala, Egypt. X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy were used to characterize the spearheads chemical composition and microstructure (EDX). The spearheads were determined to be constructed of steel and to have a coating of ferric oxide and other corrosion products on their exteriors. After that, a flawless polyaniline coating was electrochemically deposited onto the spearpoints in a way that was both quick and cheap. Many types of corrosion tests, such as electrochemical impedance spectroscopy and potentiodynamic polarization (PDP) readings, were used to determine the coating’s effectiveness. The steel spearheads’ findings revealed a significant improvement in their resistance to corrosion after being coated with flawless polyaniline. The coating served as a barrier, blocking out water and other corrosive substances and slowing the buildup of corrosion byproducts on the spearpoints. In conclusion, our research shows that a flawless polyaniline coating may be an effective anti-corrosion treatment for ancient steel artifacts. The approach is straightforward, cheap, and readily scalable for massive conservation efforts.

Ecological river health assessments, based on fish ordination analysis of ecological indicator entities and the biological integrity metrics, responding to the chemical water pollution

Evaluation of the ecological health of rivers requires a focused examination of how biological indicators respond to chemical stressors to offer key insights for effective conservation strategies. We examined the influence of stressors on aquatic ecosystems by analyzing various ecological entities and biotic integrity metrics of fish communities. A nonmetric multidimensional scaling (NMDS) approach was applied to determine scores based on 19 fish ecological entities (FEs) and a fish-based multi-metric index of biotic integrity (mIBI-F). The composition of fish communities in reference clusters differed from the disturbed clusters due to instream chemical stressors. These chemical stressors, including high levels of nutrients, organic matter, and ionic/suspended solids, were linked to variation in the key indicator FEs, whose guild identities were closely associated with instream chemical degradation. The scores of FEs (abundance weighted) and mIBI-F metrics in the first NMDS axis (NMDS1) were significantly linked with chemical health indicators (p < 0.001), such as total phosphorus (R2 = 0.67 and 0.47), electrical conductivity (R2 = 0.59 and 0.49), and chlorophyll-a (R2 = 0.48 and 0.25). These NMDS1 scores showed better accuracy than the conventional mIBI-F score in capturing river ecological health linked with chemical health status as determined by a multi-metric index of water pollution. Our study suggests that based on the ordination approach, the biological integrity of these systems reflected the chemical health.

Lipopeptide biosurfactant as a potential root canal irrigation agent: Antimicrobial and anti-biofilm evaluation

ObjectivesLipopeptide Biosurfactant (LB) is a bacteria derived compound able to reduce surface tension between water and hydrophobic substances and exhibit antimicrobial and anti-biofilm properties. This study aimed to investigate the antimicrobial and anti-biofilm effect of a Lipopeptide Biosurfactant (LB) on Enterococcus faecalis, and its potential use in root canal treatment, either as a standalone irrigation solution or in conjunction with sodium hypochlorite (NaOCl). MethodsLB was extracted from Bacillus clausii isolate and the dry extract was diluted in deionized water. The antimicrobial effect of LB against planktonic E. faecalis was evaluated by determining the Minimal Inhibitory Concentration (MIC50). The anti-biofilm effect was evaluated by Minimal Biofilm Inhibitory Concentration (MBIC50) and Minimal Biofilm Eradication Concentration (MBEC50) assays on biofilm grown on dentin specimen surface. To evaluate the effectiveness of LB as a single irrigation solution and as a pre-irrigation prior to NaOCl, live and dead bacterial cells were quantified using Confocal Laser Scanning Microscopy (CLSM), and cell biomass was assessed. ResultsLB exhibited an MIC50 and MBIC50 of 100 ppm, with an MBEC50 of 1000 ppm, resulting in 52.94 % biofilm inhibition and 60.95 % biofilm eradication on dentin specimens. The effectiveness was concentration-dependent, at 500 ppm, LB demonstrated comparable antimicrobial efficacy to 2.5 % NaOCl. Pre-irrigation with LB resulted in lower biofilm biomass compared to NaOCl alone. ConclusionPre-irrigation with LB enhanced the antimicrobial effect when followed by NaOCl irrigation. Consequently, LB shows promise as both a standalone root canal irrigation solution and as an adjunct to NaOCl in root canal treatment. Clinical significanceThe study highlights the potential of Lipopeptide Biosurfactant (LB) as an environmentally friendly irrigation solution for root canal treatment, demonstrating potent antimicrobial and anti-biofilm properties against Enterococcus faecalis. LB exhibits concentration-dependent efficacy comparable to 2.5 % NaOCl and can be used as a standalone irrigation solution or in conjunction with NaOCl.

Biogenic potassium: sources, method of recovery, and sustainability assessment

Abstract Nutrient management methods based on ecosystems are crucial for providing agricultural nutrient needs while reducing the environmental impact of fertilizer usage. With increasing agricultural production, the global demand for potassium is increasing, with India importing potassium from countries like Canada, USA, Israel, and Russia. Biomass-fired industries generate biomass ash as a residue so management of the resultant ash is important. Agricultural residue ashes contain abundant potassium so could potentially be used for fertilizer application. This review describes different potassium sources and recovery processes, including chemical precipitation, water extraction, solvent extraction, membrane separation, and ionic exchange. Extraction time, temperature, and solid to solvent ratio affect the recovery of potassium from biomass ash. Water extraction is the most commonly used method for potassium recovery from biomass ash. The environmental impact of potassium fertilizer recovered from biomass ash is less than that of mining source of potash. This paper discusses topics not covered in previous reviews, such as different biosources of potassium, latest recovery methods, and life cycle assessment of these methods. The gaps identified in the reports are addressed, and future research opportunities are presented.

Prospects for fisheries use of lake Sobache (Pionerskoe) in the Republic of Khakassia

We assess Sobache (Pionerskoe) lake located in The Republic of Khakassia for aquaculture using. The lake is drainless, the water-surface area is about 1.5 km2. The prevailing depths range from 2 to 4 m. We provide data on the hydrological regime of the lake (temperature, dissolved oxygen level, chemical water composition). 3 species of rotifers, 10 species of cladoceran and 3 species of copepods were found in the zooplankton. The dominant complex consists of the rotifer Asplanhna priodonta, Bosmina longirostris and Ceriodaphnia quadrangula. The zoobenthos community includes 13 groups of organisms, where chironomids predominate in abundance, and gastropods and bivalves predominate in biomass. The ichthyofauna of the lake consists of perch and pike, perch predominates in abundance. Four species of parasites were found, including trematodes and myxporidia. The infection of fish with trematode metacercariae indicates the presence of intermediate hosts in the zoobenthos community of the lake. The detected species of parasites do not pose a danger to human health. The natural fish productivity is estimated at 48.2 kg/ha. We recommended to use the lake for commercial cultivation of fish in polyculture way. We proposed two schemes of fishery exploitation of the lake on the principle of pasturable fish culture: annual cultivation of fish in polyculture (carp, trout, herbivorous fish species) and joint cultivation of fish in polyculture (carp and white amur) by continuous intensive technology (three-year turnover) with carp feeding. The expected yield of fish products varies from 460.0 to 400.0 kg/ha, depending on the chosen technology. These recommendations can contribute to the effective use of the fisheries potential of Sobache (Pionerskoe) lake to provide the region with fresh fish products and create jobs for the local population.

Per- and Polyfluoroalkyl Substances in Water (2008-2022) and Fish (2015-2022) in The Netherlands: Spatiotemporal Trends, Fingerprints, Mass Discharges, Sources, and Bioaccumulation Factors.

Per- and polyfluoroalkyl substances (PFAS) are persistent, bioaccumulative, and toxic synthetic chemicals of concern, which have been detected in nearly all environmental compartments. The present study provides a data analysis on PFAS concentrations in the Dutch inland and coastal national waters and fish sampled from 2008 to 2022 and 2015 to 2022, respectively. Although the fish database is relatively small, the water database is unique because of its temporal dimension. It appears that PFAS are omnipresent in Dutch water and fish, with relatively small spatial differences in absolute and relative concentrations (fingerprints) and few obvious temporal trends. Only perfluorooctanoic acid and perfluorooctanesulfonic acid (PFOS) aqueous concentrations in the rivers Rhine and Scheldt have substantially decreased since 2012. Still, PFOS concentrations exceed the European water quality standards at all and fish standards at many locations. Masses of PFAS entering the country and the North Sea are roughly 3.5 tonnes/year. Generally, the data suggest that most PFAS enter the Dutch aquatic environment predominantly through diffuse sources, yet several major point sources of specific PFAS were identified using fingerprints and monthly concentration profiles as identification tools. Finally, combining concentrations in fish and water, 265 bioaccumulation factors were derived, showing no statistically significant differences between freshwater and marine fish. Overall, the analysis provides new insights into PFAS bioaccumulation and spatiotemporal trends, mass discharges, and sources in The Netherlands. Environ Toxicol Chem 2024;43:965-975. © 2024 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Preliminary insights on the development of a continuous-flow solar system for the photocatalytic degradation of contaminants of emerging concern in water.

The ubiquity and impact of pharmaceuticals and pesticides, as well as their residues in environmental compartments, particularly in water, have raised human and environmental health concerns. This emphasizes the need of developing sustainable methods for their removal. Solar-driven photocatalytic degradation has emerged as a promising approach for the chemical decontamination of water, sparking intensive scientific research in this field. Advancements in photocatalytic materials have driven the need for solar reactors that efficiently integrate photocatalysts for real-world water treatment. This study reports preliminary results from the development and evaluation of a solar system for TiO2-based photocatalytic degradation of intermittently flowing water contaminated with doxycycline (DXC), sulfamethoxazole (SMX), dexamethasone (DXM), and carbendazim (CBZ). The system consisted of a Fresnel-type UV solar concentrator that focused on the opening and focal point of a parabolic trough concentrator, within which tubular quartz glass reactors were fixed. Concentric springs coated with TiO2, arranged one inside the other, were fixed inside the quartz reactors. The reactors are connected to a raw water tank at the inlet and a check valve at the outlet. Rotating wheels at the collector base enable solar tracking in two axes. The substances (SMX, DXC, and CBZ) were dissolved in dechlorinated tap water at a concentration of 1.0mg/L, except DXM (0.8mg/L). The water underwent sequential batch (~ 3 L each, without recirculation) processing with retention times of 15, 30, 60, 90, and 120min. After 15min, the degradation rates were as follows: DXC 87%, SMX 35.5%, DXM 32%, and CBZ 31.8%. The system processed 101 L of water daily, simultaneously removing 870, 355, 256, and 318µg/L of DXC, SMX, DXM, and CBZ, respectively, showcasing its potential for real-world chemical water decontamination application. Further enhancements that enable continuous-flow operation and integrate highly effective adsorbents and photocatalytic materials can significantly enhance system performance.

Intestinal alterations and mild glucose homeostasis impairments in the offspring born to overweight rats

The gut plays a crucial role in metabolism by regulating the passage of nutrients, water and microbial-derived substances to the portal circulation. Additionally, it produces incretins, such as glucose-insulinotropic releasing peptide (GIP) and glucagon-like derived peptide 1 (GLP1, encoded by gcg gene) in response to nutrient uptake. We aimed to investigate whether offspring from overweight rats develop anomalies in the barrier function and incretin transcription. We observed pro-inflammatory related changes along with a reduction in Claudin-3 levels resulting in increased gut-permeability in fetuses and offspring from overweight rats. Importantly, we found decreased gip mRNA levels in both fetuses and offspring from overweight rats. Differently, gcg mRNA levels were upregulated in fetuses, downregulated in female offspring and unchanged in male offspring from overweight rats. When cultured with high glucose, intestinal explants showed an increase in gip and gcg mRNA levels in control offspring. In contrast, offspring from overweight rats did not exhibit any response in gip mRNA levels. Additionally, while females showed no response, male offspring from overweight rats did exhibit an upregulation in gcg mRNA levels. Furthermore, female and male offspring from overweight rats showed sex-dependent anomalies when orally challenged with a glucose overload, returning to baseline glucose levels after 120 min.These results open new research questions about the role of the adverse maternal metabolic condition in the programming of impairments in glucose homeostasis, enteroendocrine function and gut barrier function in the offspring from overweight mothers and highlight the importance of a perinatal maternal healthy metabolism.

High chemical stability poly(oxindole biphenylene)/ZrO2 porous separator for alkaline water electrolysis

Porous separators are essential for alkaline electrochemical energy technologies, such as alkaline water electrolyzers (AWEs). These separators are promising alternatives to dense membranes because they offer the potential for low cost and high ionic conductivity. However, two significant challenges in developing efficient and durable alkaline energy systems are the suppression of hydroxide ions-induced degradation and the reduction of gas permeation in porous separators. Compared to hydrophobic polysulfone (PSF), KOH-doped poly (oxindole biphenylene) (POBP) is a highly stable ion-solvating polymer that can conduct both potassium and hydroxide ions. Building upon this, a series of porous separators based on POBP polymer with different zirconia loads were designed using NIPS to investigate the chemical stability and water electrolysis performance where the Z60 separator exhibits remarkable characteristics, including low area resistance (0.227 Ω cm2), high bubble point pressure (0.813 MPa), low H2 permeability (0.5 L min−1·cm−2) and exceptional 5040 h of ex-situ durability in 6 M KOH at 80 °C. Furthermore, the Z60 diaphragm showed a higher breaking time and lower weight loss after 261 h at 80 °C in the Fenton reagent, with the remaining mass being Z60 was 38 %. Notably, the Z60 diaphragm, when equipped with Ni–Al catalysts, achieved a current density of 0.5 A/cm2 at 1.7 V, which surpasses that of Zirfon (0.5 A/cm2 at 1.8 V). More importantly, when using Ni foam catalysts, the Z60 diaphragm demonstrated stable operation under 0.125 and 0.5 A/cm2 current densities at 80 °C for more than 900 h and 1200 h, significantly improving the durability of the porous separators. The results of this study showed that the blending of POBP can lead to the development of highly chemically stable porous diaphragms, thereby opening up a new avenue for advanced AWEs.

Application of electron beam technology to decompose per- and polyfluoroalkyl substances in water

The widespread detection of per- and polyfluoroalkyl substances (PFAS) in environmental compartments across the globe has raised several health concerns. Destructive technologies that aim to transform these recalcitrant PFAS into less toxic, more manageable products, are gaining impetus to address this problem. In this study, a 9 MeV electron beam accelerator was utilized to treat a suite of PFAS (perfluoroalkyl carboxylates: PFCAs, perfluoroalkyl sulfonates, and 6:2 fluorotelomer sulfonate: FTS) at environmentally relevant levels in water under different operating and water quality conditions. Although perfluorooctanoic acid and perfluorooctane sulfonic acid showed >90% degradation at <500 kGy dose at optimized conditions, a fluoride mass balance revealed that complete defluorination occurred only at/or near 1000 kGy. Non-target and suspect screening revealed additional degradation pathways differing from previously reported mechanisms. Treatment of PFAS mixtures in deionized water and groundwater matrices showed that FTS was preferentially degraded (∼90%), followed by partial degradation of long-chain PFAS (∼15–60%) and a simultaneous increase of short-chain PFAS (up to 20%) with increasing doses. The increase was much higher (up to 3.5X) in groundwaters compared to deionized water due to the presence of PFAS precursors as confirmed by total oxidizable precursor (TOP) assay. TOP assay of e-beam treated samples did not show any increase in PFCAs, confirming that e-beam was effective in also degrading precursors. This study provides an improved understanding of the mechanism of PFAS degradation and revealed that short-chain PFAS are more resistant to defluorination and their levels and regulation in the environment will determine the operating conditions of e-beam and other PFAS treatment technologies.

Unraveling a Concerted Proton-Coupled Electron Transfer Pathway in Atomically Precise Gold Nanoclusters.

Metal nanoclusters (MNCs) represent a promising class of materials for catalytic carbon dioxide and proton reduction as well as dihydrogen oxidation. In such reactions, multiple proton-coupled electron transfer (PCET) processes are typically involved, and the current understanding of PCET mechanisms in MNCs has primarily focused on the sequential transfer mode. However, a concerted transfer pathway, i.e., concerted electron-proton transfer (CEPT), despite its potential for a higher catalytic rate and lower reaction barrier, still lacks comprehensive elucidation. Herein, we introduce an experimental paradigm to test the feasibility of the CEPT process in MNCs, by employing Au18(SR)14 (SR denotes thiolate ligand), Au22(SR)18, and Au25(SR)18- as model clusters. Detailed investigations indicate that the photoinduced PCET reactions in the designed system proceed via an CEPT pathway. Furthermore, the rate constants of gold nanoclusters (AuNCs) have been found to be correlated with both the size of the cluster and the flexibility of the Au-S framework. This newly identified PCET behavior in AuNCs is prominently different from that observed in semiconductor quantum dots and plasmonic metal nanoparticles. Our findings are of crucial importance for unveiling the catalytic mechanisms of quantum-confined metal nanomaterials and for the future rational design of more efficient catalysts.

Experimental and density functional theory investigation of surface-modified biopolymer for improved adsorption of mixtures of per- and polyfluoroalkyl substances in water

Glutaraldehyde (GTH) cross-linked chitosan (CTN) biopolymer-based and polyethyleneimine (PEI) functionalized (GTHCTNPEI) aerogels were proven promising for removing mixtures of long- and short chain per- and polyfluoroalkyl substances (PFAS) in water. In this study, to further improve the performance of the aerogel for short-chain PFAS and undecafluoro-2-methyl-3-oxahexanoic acid (GenX) removal, GTHCTNPEI aerogel chunks with an average size of 13.4 mm were turned into flakes with an average size of 9.1 mm. The GTHCTNPEI flakes achieved >99 % removal of all target PFAS, including long- and short-chain PFAS and >97 % for GenX after 10 h. In addition, the flakes can be regenerated and reused for at least four cycles. When added to tap water spiked with PFAS at initial concentrations of 30, 70, or 100 ng/L, the flakes removed almost 100 % of all tested PFAS. Mechanistic investigations using density functional theory (DFT) revealed strong stabilizing hydrophobic and electrostatic interactions between the aerogels and PFAS, with GTHCTNPEI to PFAS binding energies ranging between -24.0 – -30.1 kcal/mol for PFOA; -41.3 – -48.5 kcal/mol for PFOS; and -40.5 – -47.3 kcal/mol for PFBS. These results demonstrate the great potential of the flakes for removing PFAS from drinking water, surface water, and groundwater.

Plasma Treatment Modifies Element Distribution in Seed Coating and Affects Further Germination and Plant Growth through Interaction with Soil Microbiome.

This study investigates the impact of plasma-seed interaction on germination and early plant development, focusing on Arabidopsis thaliana and Brassica napus. The investigation delves into changes in chemical composition, water absorption, and surface morphology induced by plasma filaments generated in synthetic air. These analyses were conducted using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Although plasma treatment enhanced water absorption and modified surface chemistry, its impact on germination demonstrated species- and context-dependent variations. Notably, the accelerated germination and morphogenesis of seedlings in microbiome-enriched (MB+) soil could be achieved also in microbiome-deprived (MB-) soil by short-term plasma treatment of seeds. Remarkably, the positive effects of plasma treatment on early developmental events (germination, morphogenesis) and later events (formation of inflorescences) were more pronounced in the context of MB- soil but were accompanied by a slight decrease in disease resistance, which was not detected in MB+ soil. The results underscore the intricate dynamics of plasma-plant interactions and stress the significance of accounting for the soil microbiome while designing experiments with potential field application.

A harmonized Danube basin-wide multi-compartment concentration database to support inventories of micropollutant emissions to surface waters

BackgroundThe European Water Framework Directive foresees the establishment of emission inventories for micropollutants (MP) to facilitate an evidence-based development of mitigation measures. Regionalized pathway analysis constitutes a moderately data-intensive approach to quantify the contribution of different pathways to the total pollution of surface waters. So far, only few European member states have created an inventory that includes diffuse pathways. The fundamental basis to enable it is an accessible, well-structured and harmonized database with data on the concentration of MPs in multiple compartments, such as soils, groundwater, atmospheric deposition and urban systems. Combined with the water and suspended substance balance in river basins, such data enables the estimation of emission loads via specific pathways. In the Danube River Basin, but in general in Europe, a public data management platform with such scope and criteria is still lacking.ResultsWe collected and harmonized MP measurements across multiple compartments and countries together with key metadata, harmonized and combined them into a new database. The resulting tool, available for download, facilitates the assessment of current data availability, in terms of quantity and quality. For example, while the majority of available data stems from groundwater and surface water, other highly relevant compartments are scarcely represented. By examining differences in MP concentration level across compartments, the database can lead to understand the relevance of specific emission pathways and thus to prioritize data-retrieval and calculation efforts in modelling applications. Selected examples show how to exploit the metadata associated to the measurements to extrapolate the results to regions not covered by specific monitoring programmes. For example, PFAS concentrations in treated wastewater show significant dependence on the design capacity of the treatment plant.ConclusionsThis study showcases how such database can support the setup of emission inventories, guide data providers and national authorities in prioritizing the allocation of resources for new surveys and in optimizing their national data collection and management systems. The process tested showed a great need for enhanced data literacy across countries and institutions to increase data availability and quality to secure the exploitation of the full information potential generated via monitoring programmes.

A Comprehensive Review of Novel Adsorbents for Per- and Polyfluoroalkyl Substances in Water

A Comprehensive Review of Novel Adsorbents for Per- and Polyfluoroalkyl Substances in Water

Degradation of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in water by use of a nonthermal plasma-ozonation cascade reactor: Role of different processes and reactive species

The widespread use of perfluoroalkyl and polyfluoroalkyl substances (PFAS) in the last century has caused serious pollution of water bodies around the world, threatening the health of humans and other organisms. In this work, a novel cascade reactor configuration, comprised of a dielectric barrier discharge (DBD) plasma chamber connected with an ozonation chamber was used to treat municipal secondary effluent loaded with several PFAS. The electrical energy per order (EE/O) for degradation of perfluorooctanoic acid (PFOA) and perfluorodecanoic acid (PFDA) amounts 180 and 100 kWh/m3, respectively. While the short-chain PFAS (perfluorobutanoic acid (PFBA), perfluorohexanoic acid (PFHxA)) were difficult to be degraded, i.e. degradation percentage < 32 % after 60 min, 80–90 % of the longer PFAS (PFOA and PFDA) were degraded within 60 min. The degradation of PFAS mainly occurred in the plasma chamber rather than in ozonation chamber. This is because that reductive species produced in plasma chamber, such as hydrated electrons (eaq−) and Ar+, played a direct role in defluorination, while oxidative species, including OH, O, O2−, 1O2, O3, and H2O2, has a very limited contribution for defluorination. Enhancing the utilization of reductive species is crucial to degrade PFAS. Perfluoroalkyl carboxylic acids (PFCA) generated during the plasma reactions may have a potential risk for environment. As such, further optimization should focus on full mineralization. This study provides an approach to solve the problem of PFAS-contaminated wastewater, which is of the importance to promote the application of nonthermal plasma technique in water treatment.

Purification, characterization and study of blue fluorescent substance in caffeine

AbstractBackgroundCaffeine, a xanthine alkaloid compound, is a stimulant of the central nervous system and is mainly used in the pharmaceutical and food industries. Because caffeine is directly absorbed into the body, Chinese pharmacopeia has high requirements on the quality of caffeine products, and fluorescence has always been an important indicator to measure the quality of caffeine. In this study, a major fluorescent impurity affecting the appearance and purity of caffeine products was isolated for the first time, and the solubility, thermodynamic properties and dissociation constants of this impurity were studied.Results(i) The fluorescent impurity affecting the appearance and purity of the product was successfully isolated from crude caffeine and theophylline sodium salt, and named as a blue fluorescent substance. The mass purity of the substance was 96.27%, and its structure was determined based on a comprehensive analysis of high‐resolution mass spectrometry and nuclear magnetic resonance (NMR) spectroscopy [hydrogen 1 (1H) NMR, carbon‐13 (13C) NMR, COSY, NOESY, HSQC, HMBC]. (ii) The solubility of blue fluorescent substance in four pure solvents was determined and the thermodynamic properties were calculated. (iii) The dissociation constants of the blue fluorescent substance in water at 298.15 K were determined by UV spectrophotometry.ConclusionThe results provide a theoretical basis for the crystallization separation of the blue fluorescent substance during the industrial production of caffeine, as well as basic data for the green synthesis process of caffeine. © 2024 Society of Chemical Industry (SCI).

A variational optimization algorithm for Secchi disk depth based on Multi-satellite data

A Secchi depth is a basic parameter to describe the optical properties of water, which is related to the composition and content of chlorophyll, suspended solids and yellow substances in water, and is also closely related to solar radiation on the surface of water, physical and chemical properties of water and meteorological conditions. The most direct way to obtain the spatiotemporal distribution of water Secchi depth is to use ships to regularly measure the Secchi depth of the base-stations, but this method can only obtain the Secchi depth of the measurement station state, and it is impossible to obtain the Secchi depth characteristics of seawater with large spatiotemporal distribution. As a brand-new observation method, remote sensing technology can obtain the distribution characteristics of ocean parameters in large time and space. In recent years, with the rapid development of remote sensing technology, especially the development of water-colored remote sensors and the improvement of the accuracy of inversion algorithms, many remote sensing products for water Secchi depth have been provided. However, due to the difference in orbit operation and observation parameters of different remote sensing loads, water Secchi depth products are affected by clouds and meteorological climate environment, and there is no same standard for verification and evaluation, which limit the promotion and application of water Secchi depth products. At the same time, data integrated technology has been widely recognized by many disciplines and has been greatly developed in recent years, and pixel-level, feature-level, decision-level integrated technology and development are also popular research directions in the world. Therefore, based on an improved variational optimization algorithm, this article integrates SDD retrieval products on multiple satellite data t such as SNPP, MODIS, and MERIS, and verifies them with ship survey data. The correlation is better than 0.9, proving that this method can improve the accuracy of SDD inversion products.

Hydrogel membrane composite reduces fouling and retains ammonium efficiently

The recovery of pure water and valuable substances from wastewater is a major challenge in the context of the circular economy, requiring advanced separation methods. However, actual membrane separation techniques such as forward osmosis are limited by membrane fouling and selectivity. Here, we synthesized composite membranes by crosslinking polyvinyl alcohol hydrogel, using both glutaraldehyde and borax as crosslinking agents, on top of cellulose ester membranes. We tested these composite membranes on model and real wastewater. Results show that the composite membranes retain ammonium effectively, maintain surface electroneutrality, and exhibit remarkable resistance to fouling by organic and biological contaminants. This is explained by the high hydrophilicity of the membrane surface after application of a hydrogel layer.