Natural Water Research Articles

Unravelling the nature differences of halide anions affecting the sorption of U(VI) by hydrous titanium dioxide supported waste polyacrylonitrile fibers in the presence of carbonates

The co-occurrence of halides and carbonates with uranium in the natural water poses a challenge to the uranium recovery for nuclear power due to the potential complexation. Hydrated titanium dioxide (HTD) contains a lot of surface hydroxyl (–OH) groups and waste polyacrylonitrile fiber (WPANF) has the advantages of both weather and chemical resistances. Herein, the nature differences of halide anions affecting the sorption of U(VI) by WPANF/HTD was investigated in the presence of carbonates. The sorption capacity (qe) decreased with the increases of initial pH, total carbonates, and halides but increased at high temperature and initial U(VI) concentration. The U(VI) sorption was a spontaneous chemisorption, which mainly involved surface sorption rather than intra-particle diffusion. The order of inhibitory ability on U(VI) sorption for the four halides was F > I ∼ Br > Cl. The aqueous F− was shown to be the most strongly inhibited with the lowest qe value of 17.2 mg·g−1, due to the formation of U(VI)–F complex anions. The characteristic peaks with weakened relative intensity after U(VI) sorption for the surface –OH groups on HTD (HTD–OH), together with the results from DFT calculations, demonstrated a key role of HTD–OH in U(VI) sorption by WPANF/HTD via the coordination with U(VI) complex anions. This work unravels the nature differences of halide anions affecting U(VI) sorption in the presence of carbonates and provides a valuable reference for the U(VI) extraction toward halogen-rich natural uranium-containing water.

Influence of Organic Carbon from Weathered Sediments on Triclocarban Distribution in Environmental Aqueous Systems

In this study, the chemical distribution of triclocarban (TCC), in natural aqueous systems, between water and sediment, with different chemical compositions of the aqueous phase and different percentages of organic carbon (OC%) in the sediments is presented. The influences of the temperature, of the composition of the aqueous matrices of natural waters and (OC%) in the sediment over the solubility of triclocarban, and its distribution coefficient Kd values were studied. log KD at 25 °C varied between 1.94 and 3.27 for a sediment with 5.50% OC and between 3.95 and 5.93% for a sediment with 6.75% OC, in the studied aqueous systems, with different concentrations of OC in the sediment.

Identifying the optimal type and locations of natural water retention measures using spatial modeling and cost-benefit analysis

Water management has shifted from solely technical and engineering approaches towards nature-based solutions (NBS), like natural water retention measures (NWRM), offering benefits beyond hydrology, such as improved well-being and biodiversity conservation. Determining the best type and location of these measures is challenging due to diverse options with varying benefits and effects depending on measure type and location characteristics. While most studies regarding the optimal allocation and implementation of NBS focus on the urban environment, this study presents a methodology for decision-makers focusing on inter-urban regions with limited data on NWRM implementation. Through hydrological modeling and cost-benefit analysis (CBA), we identify Pareto optimal NWRM sites and types, considering water quantity and quality alongside economic, environmental, and social objectives. We defined optimal locations that seek the most significant reduction of runoff, sediment, and pollutants, whilst optimal NWRM types are defined to seek the most cost-effective measures based on hydrological, ecological, and social criteria. Using the Open Non-point Source Pollution and Erosion Comparison Tool (OpenNSPECT), we simulated increased infiltration in different inter-urban areas and identified the optimal placement. The criteria for selecting suitable NWRM types for the identified areas are derived from the EU Directorate General for the Environment (DG-ENV) NWRM database. The results show different effective areas for reducing runoff, sediment, and pollutants. While one NWRM (natural bank stabilization) was identified as most beneficial for reducing sediment, several measures were selected for runoff reduction. Interestingly, measures with high potential for pollutant reduction seem to offer limited social and biodiversity benefits, suggesting conflicting objectives and highlighting the importance of accounting for multiple criteria. By employing simplified models and qualitative benefit assessments, this paper presents a practical decision-making approach to facilitate NWRM implementation in data-scarce areas.

Design, fabrication, and performance assessment for green hydrogen production unit

Creating and building an integrated system that consists of a storage tank, an electrolysis cell with many electrolyzer types, and a green hydrogen generator that produces clean, sustainable gas using solar photovoltaic (PV) energy and renewable energy sources. Three different electrolyzer modules with six, eleven, and twenty-one plates each were created locally and meant to be utilized in the production of green hydrogen. The hydrogen storage system's design was also created. It is clear that the maximum value of hydrogen production is recorded in the following ordered: KOH (5.5 L/min) > NaOH (1.2 L/min) > NaCl (0.7 L/min) > MgSO4 (0.4 L/min). Also, sea water was used as electrolyte solution with different dilution 5, 10, 15, and 20% using a natural sea water sample collected from the Mediterranean Sea. It is found that 15% sea water dilution reaches the maximum value of H2 production (3.4 L/min). Using distilled water and tap water, respectively, the volume of generated H2 gas reached its maximum value of 8 L/min and 6.5 L/min at 0.4 mols of KOH. It was observed that with increased time durations (0–90 min), enhance the rate of hydrogen production to be reaches 8.2 and 11.5 L/min when using 0.05 and 0.1 mols KOH, respectively. This approach reduces environmental effect and operational costs, providing a sustainable solution to the water and energy problems.

Visible light-improved periodate activation of natural chalcopyrite particles towards effective pollutants degradation

The aim of this paper is to build an efficient and low-cost advanced oxidation system to realize the antibiotic wastewater purification which has a realistic significance. In this study, a system of visible light-assisted activation of natural chalcopyrite to activate periodate was adopted to remove tetracycline (TC). The results demonstrated that the removal efficiency (100% within 60 min) of TC in the CuFeS2/PI/Light system was significantly improved compared to the CuFeS2/PI system or PI process alone, and the degradation rates of TC in the CuFeS2/PI/Light system were 5.9 times higher than that of the CuFeS2/PI system, which is attributed to the synergistic effect of light and PI activation. The system also effectively degraded sodium butyl xanthate (SBX), chlortetracycline hydrochloride (CTC) and Rhodamine B (RhB), while the efficiency of the degradation process was further enhanced in natural water quality. The active substance quenching experiment revealed that [Formula: see text]OH, 1O2, O2[Formula: see text], IO4[Formula: see text] and IO3[Formula: see text] were the main substances to achieve effective TC removal. In addition, the cycling of Cu[Formula: see text]/Cu[Formula: see text] and Fe[Formula: see text]/Fe[Formula: see text] present in chalcopyrite improved the activation of PI. Further, visible light is conducive to the valence cycling of Cu and Fe, as well as the production of more oxidizing free radicals, thus achieving the synergy of photocatalysis and PI activation. This study provides a low-cost and efficient advanced oxidation pathway for the removal of antibiotic wastewater.

A Novel Method to Integrate Hydropower Plants into Resource Adequacy Assessment Studies

This paper presents a novel methodology for modeling hydropower plants (HPPs) with and without pumping capability in resource adequacy assessment studies. The proposed method is based on the premise that HPPs should maximize their contribution to system adequacy within their technical constraints by using the energy reserves in their upper reservoirs without significantly deviating from their market schedule. The approach of this paper differs from the conventional operating policies for incorporating HPPs into resource adequacy assessment studies, which either adhere to a fixed market schedule or perform peak shaving, and are inelastic to real-time events or do not resort to realistic temporal correlations between natural water inflows on upper reservoirs and the water discharge needs to cover demand peaks, respectively. The modeling approach focuses on large-reservoir HPPs with natural inflows and is generic enough to deal with both stations incorporating pumping capabilities and those without. It utilizes the state-of-the-art Monte Carlo simulation technique to form the availability of system assets and determine the loss of load incidents. The market schedule and level of reservoir fulfillment for the HPPs are retrieved from a cost-optimal power system simulation algorithm executed offline before the application of the resource adequacy assessment. The effectiveness of the proposed methodology is demonstrated through its implementation in a case study of a power system experiencing different levels of adequacy, comparing the obtained results with various traditional HPP modeling methods from the literature.

Fast and efficient remediation of antimony-contaminated surface water and field soil using alumina supported Fe–Mn binary oxide

Antimony (Sb) pollution in surface water and soil has earned extensive attention. Our previous study synthesized a new class of alumina supported Fe–Mn binary oxide (Fe–Mn@Al2O3) and found that MnO2 in the composite oxidized Sb(III) to Sb(V) and FeOOH and Al2O3 played an indispensable role in adsorption of Sb(III) and Sb(V). This study further explored the removal of Sb in surface water and in situ sequestration of Sb in Sb-contaminated field soil via Fe–Mn@Al2O3. Sb removal from water was pH independent and the removal efficiencies of Sb(III) and total Sb kept constant at 95.4% and 60.5%, respectively, over a pH range of 5.0–10.0. Increasing dissolved organic matter (DOM) from 0 to 22.8 mg/L had negligible effect on Sb(III) removal whereas inhibited the total Sb removal from 60.5% to 51.2%. Dissolved oxygen cannot oxidize aqueous Sb(III), yet, enhanced the Sb(III) removal whereas decreased the total Sb removal. The composite performed well in natural surface water with high DOM and inorganic ligands. In addition, the composite effectively immobilized Sb in field soil. 5% of the composite significantly inhibited the H2SO4 and HNO3 leachable Sb by 93.6% after 30 d. The amendment transformed the Sb speciation from more easily available fractions (i.e., exchangeable, carbonate-bound, and Fe–Mn oxides-bound species) into more stable fractions (i.e., organic material bound and residual species), leading to declined Sb bioaccessibility and reduced environmental risk. The composite facilitated a long-term stability of Sb in soil. The study demonstrated an easy, fast, and effective strategy for efficient immobilization of Sb in water and soil.

Evaluation of aspartame effects at environmental concentration on early development of zebrafish: Morphology and transcriptome1

The use of aspartame as an artificial sweetener is prevalent in a wide range of everyday food products, potentially leading to health complications such as obesity, diabetes mellitus, autism spectrum disorders, and neurodegeneration. Aspartame has also been detected in natural water bodies at a concentration of 0.49 μg/L, yet research on its ecotoxicological effects on aquatic life remains scarce. This study aimed to investigate the potential negative effects of environmentally relevant concentrations of aspartame on the development of various tissues and organs in zebrafish embryos. We used a zebrafish model to treat embryos with aspartame at environmental concentration and those higher than in the environment—up to 1000 times. We observed that after exposure to aspartame body length increased, pigmentation was delayed, and neutrophil production inhibited in zebrafish. Furthermore, transcriptome analysis revealed that early exposure of zebrafish embryos to aspartame affected the transcriptomics of various systems, primarily by downregulating genes related to immune cell production, eye and optic nerve development, nervous system development, and growth hormone-related transcription. Most of the genes associated with ferroptosis were upregulated. This study provides new insights into the ecotoxicological effects of aspartame on aquatic environments.

Piezocatalytic techniques and materials for degradation of organic pollutants from aqueous solution

With the rapid development of industry, agriculture, and urbanization, various organic pollutants have accumulated in natural water, posing a potential threat to both the ecological environment and human beings, and removing organic pollutants from water is an urgent priority. Piezoelectric techniques, with the advantages of green, simple operation, and high efficiency, are highly sought after in the degradation of environmental organic pollutants. Moreover, combining piezoelectric techniques with advanced oxidation processes (AOPs), photocatalysis, or electrocatalysis can further effectively promote the efficient degradation of target pollutants. Therefore, a perspective is presented on the recent progress of piezoelectric techniques for the degradation of various organic pollutants from aqueous solutions. The classification of various piezoelectric materials, as well as modification strategies for improving piezocatalysis, are first systematically summarized. Furthermore, the latest research on piezocatalysis and its combination with other technologies, such as AOPs, photocatalysis, and electrocatalysis, in the degradation of environmental pollutants is discussed. The potential mechanisms of piezocatalysis are also analyzed in depth. Finally, the urgent challenges and future opportunities for piezoelectric techniques in the degradation of organic pollutants are provided.

Enhancing microplastic removal from natural water using coagulant aids

Microplastic (MP) pollution poses a significant environmental challenge, underscoring the need for improved water treatment methods. This study investigates the effectiveness of coagulation, flocculation, and sedimentation processes for removing microbeads, focusing on key factors that influence removal efficiency. Among the coagulants tested, polyaluminium chloride (PAC) demonstrated superior performance by enhancing the aggregation of microplastics with flocs. Optimal treatment conditions were determined to be 0.4 mmol/L PAC and 3 mg/L polyacrylamide (PAM) at pH 8 (before adding PAC), with rapid stirring at 240 rpm for 1 min, followed by slow stirring at 35 rpm for 13 min, and a sedimentation period of 25 min. Under these conditions, removal efficiencies exceeded 95 % for a range of microbeads (10–1000 μm: Polystyrene (PS), Polypropylene (PP), Polyvinyl chloride (PVC), Polyamide (PA), Polyethylene (PE), and Polyurethane (PU)) from natural water samples. Without PAM, PAC alone achieved a 97 % removal rate for PS microbeads. The addition of PAM maintained high removal efficiency, while aluminium sulphate and ferric chloride were less effective, with removal rates of 67 % and 48 % for PS microbeads, respectively. PAM enhanced MP removal across various coagulants and microbead types, with maximum efficiency observed at PAM concentrations of ≥3 mg/L. The treatment also demonstrated that organic matter in Regent's Park pond water could further improve MP removal. Size significantly impacts removal efficiency: larger microbeads (1 mm to >250 μm) were removed more effectively (95 %) compared to smaller ones (10 to <250 μm), which had a lower removal rate of 49 %. Denser microbeads like PVC (density 1.38 g/cm³) settled more efficiently than lighter microbeads such as PE (density 0.97 g/cm³). These findings suggest a need for advanced technologies to better remove lighter, smaller MPs from water.

Toxicokinetics of microplastics in Macrobrachium nipponense and their impact on the bioavailability of loaded pollutants

Microplastics (MPs) have unique toxicokinetic (TK) processes that differ from those of soluble pollutants. This study investigated the ingestion, migration, accumulation, and clearance of environmental aging MPs in the Japanese swamp shrimp (Macrobrachium nipponense). The concentrations of plastic additives and personal care products adsorbed onto MPs in natural river water were determined, and TK models for MPs and MPs-loaded pollutants were developed. Results showed that the formation of surface biofilms and alterations in the distribution of MPs in waters caused by environmental aging affect MPs bioavailability, which is mainly related to the feeding habits of shrimp. The decrease in MPs particle size caused by biological digestion and the increase in the number of oxygen-containing functional groups caused by environmental aging affect the TK process of MPs. The TK model of MPs-loaded pollutants revealed the cleaning effect of shrimp on pollutants adsorbed onto MPs during swallowing and spitting MPs. This cleaning effect significantly increases the bioavailability of MPs-associated pollutants in aquatic environments. This study provides a new perspective for understanding the interactions between environmental MPs and their associated pollutants in aquatic ecosystems.

Toxic effects of multi-walled carbon nanotubes and ZnO nanoparticle exposure on pathology and apoptosis on the liver of Cyprinus carpio

ZnO nanoparticles (ZnONPs) and carbon nanotubes (CNTs) are frequently used nanoparticles with unique features. Aquatic organisms are exposed to a combination of contaminants in natural water systems, so the combination effect of two or more nanomaterials has caused much concern. In this study, the toxicity to the liver of common carp was explored under four weeks of exposure to single ZnONPs or in combination with multi-walled CNTs (MWCNTs). The results demonstrated that ZnONPs induced pathological changes and apoptosis in the liver. In combination, decreased pathological changes were observed in the LSC-ZnONPs group (50 mg L-1 ZnONPs and 0.25 mg L-1 MWCNTs) at the microscopic level and ultrastructural level, and increased pathological changes in the HSC-ZnONPs group (50 mg L-1 ZnONPs and 2.5 mg L-1 MWCNTs). A 52% reduction in the percentage of TUNEL-positive nuclei in the LSC-ZnONPs group and a 33% increase in the HSC-ZnONPs group were observed compared to the ZnONPs group. The mRNA expression of apoptosis-related genes, including caspase3, BAX, and XBP1, were significantly up-regulated in the exposure groups, confirming the occurrence of apoptosis. Significantly decreased caspase 3 and BAX mRNA levels in the co-exposure groups were detected compared to the ZnONPs group. Nevertheless, the XBP1 mRNA level was significantly upregulated in the LSC-ZnONPs group, but downregulated in the HSC-ZnONPs group, indicating multiple signal pathways involved in the apoptosis. In conclusion, a low concentration of MWCNTs (0.25 mg L-1) decreased the toxic effect of ZnONPs on common carp, but a high concentration of MWCNTs (2.5 mg L-1) enhanced it. This study will contribute to developing future risk assessment and management strategies for nanomaterials.

Experimental detection of marine plastic litter in surface waters by 405 nm LD-based fluorescence lidar

Plastic pollution has become a global challenge, affecting water quality and health. Plastics including polystyrene (PS), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), and high-density polyethylene (HDPE), are significant contributors to environmental pollution. With the growing need for investigation and detection of plastics found in natural waters, we propose the use of a portable laser diode (LD)-based fluorescence lidar system for in-situ detection of plastic litters in surface waters based on excitation-emission fluorescence spectroscopic data. The experiments were carried out in a controlled environment using a fluorescence lidar system with 405 nm excitation wavelength to determine the fluorescence signals of several plastics at 470 nm emission wavelength. Simultaneous detection of PET plastic and Chlorella vulgaris were also observed to determine the fluorescence influence of chlorophyll in surface waters. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy was employed to study the chemical composition of the plastics used before and after being submerged in the water. Scanning electron microscopy (SEM) and high-resolution camera microscopy were used to analyze the morphology of the submerged PET samples. This study provides a basis for a new in-situ technique using a fluorescence lidar system for submerged or transparent plastics in surface waters.

Green Syngas Production from Natural Lignin, Sunlight, and Water over Pt‐Decorated InGaN Nanowires

AbstractTransformation of lignin to syngas can turn waste into treasure yet remains a tremendous challenge because of its naturally evolved stubborn structure. In this work, light‐driven reforming of natural lignin in water for green syngas production is explored using Pt‐decorated InGaN nanowires. The spectroscopic characterizations, isotope, and model compound experiments, as well as density function theory calculation, disclose that among a variety of groups including aromatic ring, −OH, −OCH3, −C3H7 with complex chemical bonds of O−H, C−H, C−C, C−O, etc., InGaN nanowires are cooperative with Pt for preferably breaking the C−O bond of the rich O−CH3 group in lignin to liberating ⋅CH3 by photogenerated holes with a minimum dissociation energy of 2.33 eV. Syngas are subsequently yielded from the continuous evolution of ⋅CH3 and ⋅OH from photocatalytic reforming of lignin in water. Together with the superior optoelectronic attributes of Pt‐decorated InGaN nanowires, the evolution rate of syngas approaches 43.4 mol ⋅ g−1 ⋅ h−1 with tunable H2/CO ratios and a remarkable turnover number (TON) of 150, 543 mol syngas per mol Pt. Notably, the architecture demonstrates a high light efficiency of 12.1 % for syngas generation under focused light without any extra thermal input. Outdoor test ascertains the viability of producing syngas with the only inputs of natural lignin, water, and sunlight, thus presenting a low‐carbon route for synthesizing transportation fuels and value‐added chemicals.

Modeling for sustainable groundwater management: Interdependence and potential complementarity of process-based, data-driven and system dynamics approaches

Groundwater systems are vast natural water reservoirs used to support human water demands and ecosystem services. Various modeling approaches have been developed to help manage these complex highly-dynamic systems. This paper discusses the strengths and limitations of three modeling approaches, namely: process-based, data-driven and system dynamics modeling. For demonstration purposes, the three modeling approaches are applied to the Konya Closed Basin, a large agricultural region with semi-dry climate located in central Turkey. Process-based modeling is grounded in the theory-based representation of the governing processes but is somewhat limited by the computational effort and the difficulty of defining the required input parameters that characterize the heterogeneous aquifer system. Process-based models are shown to be powerful tools for resource management purposes provided climatic and water demand scenarios are accurately defined. Data-driven models are efficient tools for the management of groundwater resources but are highly dependent on the availability of large training data sets encompassing the spectrum of possible system responses. The high efficiency of surrogate modeling approaches makes them ideal tools for incorporation into applications such as real-time decision support systems and digital twin platforms. System dynamics modeling examines the groundwater exploitation problem within a socio-economic context that involves multiple stakeholders and their decision making. It combines groundwater flow models with socio-economics and endogenous decision rules to conduct scenario analysis and support policy development. The analyses and model demonstrations presented in this paper underscore the interconnectedness and complementarity of these three modeling approaches and the need for more integrated use of these modeling approaches for enhanced multi-sectoral management of groundwater systems.

Hydrovoltaic Effects from Mechanical-Electric Coupling at the Water-Solid Interface.

The natural water cycle on the Earth carries an enormous amount of energy as thirty-five percent of solar energy reaching the Earth's surface goes into water. However, only a very marginal part of the contained energy, mostly kinetic energy of large volume bulk water, is harvested by hydroelectric power plants. Natural processes in the water cycle, such as rainfall, water evaporation, and moisture adsorption, are widespread but have remained underexploited in the past due to the lack of appropriate technologies. In the past decade, the emergence of hydrovoltaic technology has provided ever-increasing opportunities to extend the technical capability for energy harvesting from the water cycle. Featuring electricity generation from mechanical-electric coupling at the water-solid interface, hydrovoltaic technology embraces almost all dynamic processes associated with water, including raining, waving, flowing, evaporating, and moisture adsorbing. This versatility in dealing with various forms of water and associated energy renders hydrovoltaic technology a solution for fossil fuel-caused environmental problems. Here, we review the current progress of hydrovoltaic energy harvesting from water motion, evaporation, and ambient moisture. Device configuration, energy conversion mechanism mediated by mechanical-electric coupling at various water-solid interfaces, as well as materials selection and functionalization are discussed. Useful strategies guided by established mechanisms for device optimization are then covered. Finally, we provide an outlook on this emerging field and outline the challenges of improving output performance toward potential practical applications.

EXPERIMENTAL INVESTIGATION OF NATURAL CIRCULATING SOLAR ENERGY SYSTEM INCLUDING A PARABOLIC TROUGH SOLAR COLLECTOR

Abstract The most common natural flow water heating systems are in one-ended inclined pipes today. In this study, it is aimed to investigate the natural circulation solar energy system experimentally with parabolic trough solar collector. For this purpose, a natural circulation solar energy system including a parabolic trough solar collector that follows the sun in one dimension on the N-S axis in the outdoor environment has been established. Experiments were conducted on different dates. The radiation values coming into the opening of the moving collector were calculated. With the SolTrace program, it has been found that 56 % of this radiation can reach the vacuum tube glass pipe in the focus of the collector. In addition, the Rayleigh number was calculated for each experiment for the section of the glass tube close to the tank inlet, and it was monitored whether there was natural circulation throughout the experiment. As a result, the average Rayleigh number in the experiments conducted on 13 February, 31 March, 24 April, 23 May, 9 June, and 6 July was 1.4E+06, 7.6E+05, 7.8E+04, 2.2E+04, 3.1E+05, respectively. and calculated as 2.8E+05. In the experiments on May 23 and April 24, when the cooling system was open, it was observed that the Rayleigh number constantly dropped below the critical value. In other experiments, the situation is the opposite, and the natural flow is continuous.

Preparation and properties of multiphase composite enhanced functional organosilicon nano-coatings

BackgroundTo improve the inherent stability and environmental compatibility of traditional organosilicon coatings, nano-reinforced composite materials were innovatively designed and synthesized to improve the performance of organosilicon coatings. MethodologyThe silicon dioxide (SiO2) clusters on the surface of graphene oxide (GO) incorporated with calcium carbonate (CaCO3) and dicyclohexylamine nitrite (Dn) nanocomposites (GO@SiO2/CaCO3/Dn) were prepared successfully. Then nanocomposites were integrated into the coating matrix to comprehensively assess their effects on morphology, mechanics, corrosion resistance, and anti-fouling properties. Significant findingsScanning Electron Microscopy (SEM) observations revealed that 4.0 wt.% of the nanocomposite reinforcement led to stratification within the organosilicon coating. The mechanical properties test shows that the hardness, bonding strength, and maximum impact resistance of SiNC2.0 coating is 10.3 HV, 2.8 MPa, and 75 kg·cm, respectively. Electrochemical assessments confirmed that SiNC2.0 displayed superior corrosion resistance, with a corrosion potential (Ecorr) of 0.199 V and a corrosion current density (Icorr) of 7.308 × 10–6 A/cm2. Furthermore, the surface free energy of the nano-coatings is calculated in the range of 20–30 mN/m by contact angle measurement, indicating the anti-fouling and self-cleaning of the organosilicon nano-coatings. Long-term immersion in natural lake water further confirms the stability and durability of the SiNC2.0 coating in real environments.

The introduction of pyrochar boosts the generation of singlet oxygen in a ferrihydrite-based Fenton-like system to facilitate the Cr(III)-citrate decomplexation under Cr(VI) inhibition

Cr(III)-organic complexes are frequently detected in tanning effluent, but they are challenging to elimination. Ferrihydrite (Fh)/carbon materials (CMs) composites showed superior performance in Fenton-like oxidation process, but their effectiveness and mechanism in Cr(III)-organic complex treatment need to be deep explored. In this study, pyrochar (PC)/Fh compounds were successfully synthesized and the experimental results found that the 5%-PC/Fh/H2O2 system exhibited efficient elimination of Cr(III)-citrate complexes with 89% reduction in TOC and almost 100% elimination of total Cr. The cooperation of PC with Fh promoted the decomposition of H2O2 by accelerating the electron transfer between Fe(III)/Fe(II) pairs. In contrast to the traditional Fenton-like catalysts, 5%-PC/Fh equipped with Fe–O–C bond could boost the production of 1O2, resulting in decomplexation of Cr(III)-citrate rather than direct attack of the Cr(III) site in the Cr(III)-citrate complex. Consequently, Cr(VI) could not be produced in the 5%-PC/Fh/H2O2 system. Moreover, the developed 5%-PC/Fh/H2O2 system exhibited enhanced reusability and excellent stability when applied to natural water and real wastewater. Finally, the oxidation intermediates could even promote the growth of C. vulgaris, indicating the structure of Cr(III)-citrate was destroyed and their toxicity was decreased. All these phenomena suggested the great potential of the 5%-PC/Fh/H2O2 system for practical wastewater treatment. This study has provided theoretical guidance and technical support for the efficient treatment of Cr(III)-organic complexes in real wastewater.

Determination of Rhodamine 6G with direct immersion single-drop microextraction combined with an optical probe.

The combination of an optical probe and single-drop direct immersion microextraction (DI-SDME-OP) was used for the preconcentration and subsequent spectrophotometric determination of rhodamine 6G (Rh6G). The developed method is based on the formation of an ionic associate between Rh6G and picric acid at pH 3.0 and its extraction with amyl acetate. A microdrop of the organic phase was stably placed in the hole of an optical probe immersed in the sample solution. The absorbance of the extraction phase was monitored at 534 nm. The proposed method combines in a single step several stages of the analytical procedure, such as pre-concentration, phase separation, transfer of the extraction phase to the instrument and online measurement. The sensitivity of the proposed approach is not inferior to existing microextraction methods involving the combination of liquid-phase or solid-phase extraction with spectrophotometry or HPLC with a UV-Vis detector. The evaluation of the greenness of the developed method carried out by the AGREE method (0.58 points) showed that it outperforms other similar existing techniques using this parameter. The calibration plot for the determination of Rh6G by the DI-SDME-OP method was linear over the range of 10-500 nM with a correlation coefficient of 0.9956. The limit of detection was 3.4 nM. The accuracy and applicability of the method were evaluated by the determination of Rh6G in natural waters and lipstick.