Mercury(II) and lead(II) ions removal using a novel thiol-rich hydrogel adsorbent; PHPAm/Fe3O4@SiO2-SH polymer nanocomposite

The abundant release of toxic heavy metals into wastewater has been a serious threat to human health, aquatic environments, plants, and animals; thus, it is critical to purify wastewater of these pollutants through a proper treatment process. A novel hydrogel compound was synthesized using partially hydrolyzed polyacrylamide (PHPAm) and functionalized Fe₃O₄-coated magnetic nanoparticles (PHPAm/Fe₃O₄@SiO₂-SH) that is efficient in removal of mercury and lead from wastewater. This new magnetic nanoadsorbent is characterized using scanning electron microscope, Fourier-transform infrared, thermogravimetric analysis, vibrating sample magnetometer, and energy-dispersive X-ray analysis. The central composite design under response surface methodology (CCD-RSM) was applied in designing the experiments to optimize the main parameters affecting the adsorption capacity: initial concentration (77.50 mg L^-1), pH (6.11 and 6.48), adsorbent dosage (25 mg), and contact time (115 and 106 min) for both Hg²⁺ and Pb²⁺ adsorption, respectively. Quadratic models were used for variable predictions and analysis of variance was applied to evaluate the statistical parameters and investigate the interactions of the variables. The high determination coefficient (R² 0.99) for both metals indicates a good correlation between actual and predicted response values. Additionally, thermodynamic modeling showed an endothermic and exothermic for Hg²⁺ and Pb²⁺, respectively, and also the spontaneous nature of both metals' adsorption process within the temperature range of 288-318 K. Mercury and lead kinetic studies were in agreement with pseudo-second-order modeling, and the equilibrium results revealed that the Langmuir isotherm best fit the experimental data with maximum adsorption capacities of 256.41 and 227.27 (mg g^-1) for Hg²⁺ and Pb²⁺, respectively. Overall, PHPAm/Fe₃O₄@SiO₂-SH is thought to have highly promising potential for investigating heavy metals in wastewater treatment, and will make important contributions to similar studies that may be conducted in the future.

Chemical composition characteristics and source analysis of PM2.5 in Jiaxing, China: insights into the effect of COVID-19 outbreak

Jiaxing is a medium-sized city in the Yangtze River Delta (YRD), which showed complex local and surrounding pollution sources. To study the COVID-19 impact on the ambient PM_2.5 in Jiaxing, we collected the PM_2.5 samples from 2 January to 25 April 2020 and analysed their chemical compositions (including carbon components, water-soluble ions (WSIs), and inorganic elements). The concentration of PM_2.5 was 83.13 ± 30.93 μg/m³ before COVID-19 pandemic and then remarkably decreased with COVID-19 outbreak due to the suspension of mobility and industrial activities. Meanwhile, the concentrations of main chemical species (carbon components, water-soluble ions and inorganic elements) of PM_2.5 all decreased from period A (2-20 January 2020) to period B (23 January to 10 February 2020). Moreover, Trajectory clustering analysis showed that close-range transport was one of the dominant factors throughout all the periods, except for period D (1-25 April 2020). In addition, the PSCF model indicated that the COVID-19 outbreak resulted in a significant decrease of WPSCF value. This study highlighted the differences in chemical compositions and sources of PM_2.5 since COVID-19 pandemic was reported and provided a better understanding of its outbreak on PM_2.5.

Policy-driven variations in oxidation potential and source apportionment of PM2.5 in Wuhan, central China

China has implemented several control measures to mitigate PM_2.5 pollution and improve air quality, such as the Action Plan for the Prevention and Control of Air Pollution (APPCAP). To comprehensively assess the changes in ambient PM_2.5 concentrations and the corresponding health risk with the implementation of APPCAP, this study examined PM_2.5 samples collected in Wuhan in 2012/2013 and 2018 for water-soluble ions, carbonaceous fractions, and elements, respectively. Dithiothreitol (DTT) assay was used to determine the oxidation potential (OP) of PM_2.5. The positive matrix factorization (PMF) model and the multiple linear regression (MLR) model were used to analyze PM_2.5 sources and the contribution of each source to the OP of PM_2.5. The results showed that PM_2.5 concentrations in Wuhan decreased significantly, however, there was little change in the health risk and a significant increase in intrinsic toxicity. DTT_v (the volume-normalized dithiothreitol) showed high correlations (r > 0.5, p < 0.01) with water-soluble organic carbon (WSOC), organic carbon (OC), secondary ions (NO₃^-, SO₄^2-, and NH₄⁺), and elements. Compared to 2012/2013, the contribution of vehicle emissions and secondary aerosol sources to PM_2.5 increased significantly in 2018. Biomass burning sources significantly contribute to DTT_v in the summer and autumn, and secondary aerosol sources significantly contribute to DTT_v in winter. The human health impacts from coal combustion sources remained high, while vehicle emission sources increased. In the context of decreasing PM_2.5 concentrations, the role of vehicle emissions health impacts is increasingly significant due to the large increment in vehicle ownership and high inherent OP. Therefore, targeting vehicle emissions for control is of great importance for human health and needs to be given great attention in future policymaking.

Composition and size of retained aerosol particles on urban plants: Insights into related factors and potential impacts

The role of plants in alleviating aerosol pollution has drawn extensive attention. Most studies focus on compositions of aerosol particles on urban plants, while the leaf traits related to particle retention have not yet been intensively studied. This study selected five typical urban plants (Loropetalum chinense, Rhododendron simsii, Euonymus japonicus, Photinia × fraseri, Osmanthus fragrans), and employed scanning electron microscope (SEM) and ion chromatography, aiming to investigate the accumulation features of aerosol particles and the relationships between leaf traits and particle retention. Results show that aerosol particles were mainly retained on the adaxial leaf surface, the fine particles (Φ ≤ 2.5 μm) were the predominant components (77.8 % by number) on the leaves, and the dominant water-soluble ions of particles were Ca²⁺, SO₄^2-, and NO₃^-. By comparison, E. japonicus and P. fraseri were efficient in the retention of fine and coarse particles (2.5 <Φ ≤ 10 μm), but L. chinense was capable to retain more large particles (Φ > 10 μm). The correlation analysis indicates that leaf traits are closely related to the accumulation of aerosol particles. The result shows that plant leaves with larger stomatal area, lower stomatal density, smaller specific leaf area and higher in epicuticular wax content can retain more aerosol particles. This result indicates that the leaves are capable of retaining aerosol particles via the synergy of multiple leaf traits, such as higher wax content and the fewer but larger stomata on their leaf surfaces. This study is helpful to understand the interactions between leaf traits and particle retention, and it further contributes to the selection of potential dust-retaining plants, which is of great significance for the alleviation of urban air pollution.

Inter-comparison of chemical fingerprint and source apportionment of marine fine particles at two islands through the west and east passages of the Taiwan Island

In this study, the concentrations of marine fine particles (PM_2.5) and their chemical fingerprints were inter-compared at two islands located aside from the west and east waters of Taiwan Island and the variability of west and east passages (i.e., Routes A1 and A2) were explored. Marine PM_2.5 was simultaneously sampled at the Green and Dongsha Islands and five chemical components (i.e., water-soluble ions, metallic elements, carbonaceous content, anhydrosugars, and organic acids) were further analyzed in PM_2.5 to characterize their chemical fingerprints. The highest concentrations of chemical composition and PM_2.5 were commonly observed during the Asian Northeastern Monsoons (ANMs) via long-range transport (LRT). Water-soluble ions (WSIs) were dominated by secondary inorganic aerosols (SIAs), and followed by oceanic spray. The major metallic content of PM_2.5 was crustal elements, while trace metals originated from anthropogenic sources with an enrichment factor (EF) > 10. In terms of carbonaceous content in PM_2.5, organic carbon (OC) was superior to elemental carbon (EC). High levoglucosan concentrations were also observed during the periods of ANMs. Secondary organic aerosols (SOAs) were formed by atmospheric chemical reactions during the LRT procedure. The PM_2.5 concentration of Route A1 was 37.51 % higher than that of Route A2, and trace metals (V, Mn, Ni, Pb, Cr, and Cu) increased significantly by 96.16-325.83 %. Positive matrix factorization (PMF) results revealed that the dominant factor of PM_2.5 for Route A1 was shipping emissions and vehicular exhausts (41.2 %), while that for Route A2 was oceanic spray (30.2 %). Route A1 was mainly attributed to highly industrialized regions, densely populated urbanized areas, and ship-intensive traffics in East Asia.

Amino-coumarin-based colorimetric and fluorescent chemosensors capable of discriminating Co2+, Ni2+, and Cu2+ ions in solution and potential utilization as a paper-based device

New chemosensors, L1-L3, based on the coumarin Schiff base scaffold with substituent modifications, have been designed and synthesized. The chemosensors L1-L3 exhibited the absorbance and fluorescence spectral changes that can discriminate Co²⁺, Ni²⁺, and Cu²⁺ ions. Sensor L1 demonstrated the ability to respond to Co²⁺, Ni²⁺, and Cu²⁺ ions. Remarkably, the slight modification of substituent on L2 has been observed to cause selective binding to Ni²⁺ and Cu²⁺ ions while L3 can specifically detect Cu²⁺ ions. The in-situ formation of metal and ligand complexes was determined by Job's plot analysis. The limit of detection and the sensing ability of all probes are estimated to be within the range of safe drinking water. Incorporation of the sensing compounds into a paper-based detection system using a laminated paper-based analytical device (LPAD) was demonstrated and found to be consistent to those obtained from the batchwise solution measurements.

Associations of forest negative air ions exposure with cardiac autonomic nervous function and the related metabolic linkages: A repeated-measure panel study

Forest environment has many health benefits, and negative air ions (NAI) is one of the major forest environmental factors. Many studies have explored the effect of forest environment on cardiac autonomic nervous function, while forest NAI in the among function and the underlying mechanism still remain unclear. To explore the associations and molecular linkages between short-term exposure to forest NAI and heart rate variability (HRV), a repeated-measure panel study was conducted among 31 healthy adults. Participants were randomly selected to stay in a forest park for 3 days and 2 nights. Individual exposures including NAI were monitored simultaneously and HRV indices were measured repeatedly at the follow-up period. Urine samples were collected for non-targeted metabolomics analysis. Mixed-effect models were adopted to evaluate associations among NAI, HRV indices and metabolites. The median of NAI concentration was 68.11 (138.20) cm^-3 during the study period. Short-term exposure to forest NAI was associated with the ameliorative HRV indices, especially the excitatory parasympathetic nerve. For instance, per interquartile range increase of 5-min moving average of NAI was associated with 9.99 % (95%CI: 8.95 %, 11.03 %) increase of power in high frequency. Eight metabolites were associated with NAI exposure. The down-regulated tyrosine metabolism was firstly observed, followed by other amino acid metabolic alterations. The NAI-related metabolic changes reflect the reduction of inflammation and oxidative stress. HRV indices were associated with 25 metabolites, mainly including arginine, proline and histidine metabolism. Short-term exposure to forest NAI is beneficial to HRV, especially to the parasympathetic nerve activity, by successively disturbing different metabolic pathways which mainly reflect the increased anti-inflammation and the reduced inflammation. The results will provide epidemiological evidences for developing forest therapy and improving cardiac autonomic nervous function.

Nano-modified feather keratin derived green and sustainable biosorbents for the remediation of heavy metals from synthetic wastewater

In this study, we employed a facile method to synthesize feather keratin derived biosorbents using water dispersed graphene oxide. The successful cross-linking of feather keratin with graphene oxide was investigated through X-ray photoelectrons spectroscopy (XPS), scanning and transmission electron microscopy, and Brunauer-Emmett-Teller (BET) analysis. The modifications resulted in increased surface area of the keratin proteins with substantial morphological changes including the development of cracked and rough patches on the surface. The chicken feather keratin/graphene oxide based biosorbents exhibited excellent performance for the simultaneous removal of metal oxyanions including arsenic (As), selenium (Se), chromium (Cr) and cations including nickel (Ni), cobalt (Co), lead (Pb), cadmium (Cd) and zinc (Zn) up to 99%, from polluted synthetic water containing 600 μgL^-1 of each metal concentration in 24 h. The insights into the biosorption mechanism revealed that the electrostatic interaction, chelation and complexation primarily contributed to the removal of multiple heavy metal ions in a single treatment. This study has demonstrated that modification of chicken feather keratin with graphene oxide is an effective way to improve its sorption capacity for removing multiple trace metal ions from contaminated water.

A fast gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode screening method for short-chain and medium-chain chlorinated paraffins

RATIONALE

Chlorinated paraffins (CPs) are a group of anthropogenic pollutants that consist of complex mixtures of polychlorinated n-alkanes of different chain lengths (~C₁₀ to C₃₀ ). Persistence, bioaccumulation, toxicity, and long-range transport of short-chain chlorinated paraffins (SCCPs, C₁₀ - to C₁₃ -CPs) have prompted their classification as persistent organic pollutants (POPs) by the Stockholm Convention in 2017. Due to the varying chain lengths and chlorination degrees, quantification of SCCPs and medium-chain chlorinated paraffins (MCCPs, C₁₄ - to C₁₇ ) using gas chromatography coupled with electron capture negative ion mass spectrometry in selected ion monitoring mode (GC/ECNI-MS-SIM) is not only challenging but also very time consuming. In particular, up to eight GC runs per sample are required for the comprehensive GC/ECNI-MS-SIM quantification of SCCPs and MCCPs. These efforts are high especially if the samples do not contain CPs above the limit of detection (LOD), subsequently.

METHODS

We developed a semi-quantitative and sensitive method for the examination of SCCPs and MCCPs in one GC run. This GC/ECNI-MS-SIM screening method was based on the recording of Cl^- (m/z 35 and 37), Cl₂ ^- (m/z 70 and 72), and HCl₂ ^- (m/z 71 and 73) isotope ions and evaluation of the ratios between them.

RESULTS

Correctness of the results of the screening method was verified by analysis of edible oils with and without CPs, CP standards, as well as a technical CP mixture. Polychlorinated biphenyls (PCBs) and other polyhalogenated aromatic compounds, as well as brominated flame retardants, do not form all of the fragment ions analyzed by the screening method.

CONCLUSIONS

After the screening, only CP-positive samples may need to be measured in detail. Measurement time will already be gained in the case of ~10% samples without CPs.

Nickel hydroxide nanoflower-based dispersive solid-phase extraction of copper from water matrix

In this work, a dispersive solid-phase extraction method based on Ni(OH)₂ nanoflowers (Ni(OH)₂-NFs-DSPE) was developed to separate and preconcentrate copper ions from tap water samples for determination by flame atomic absorption spectrometry (FAAS). Ni(OH)₂-NFs was synthesized using a homogeneous precipitation technique and used as sorbent for copper preconcentration. X-ray diffraction, scanning electron microscopy, and Fourier-transform infrared spectroscopy were used to characterize the synthesized sorbent. All experimental variables were carefully optimized to achieve a high enhancement factor of 107.5-folds with respect to the detection sensitivity of the conventional FAAS. The proposed method's analytical parameters including LOD, LOQ, and linear range were determined as 1.33 μg/L, 4.42 μg/L, and 3.0-40 μg/L, respectively. To assess the applicability and reliability of the developed method, optimal conditions were applied to tap water samples and satisfactory percent recoveries (94-103%) were obtained for the samples spiked at 20 and 30 μg/L. This validated the accuracy and feasibility of the developed method to real samples. The developed method can be described as a simple, efficient, and rapid analytical approach for the accurate determination of trace copper ions in water samples.

[Characterization and Formation Mechanism of Water-soluble Inorganic Ions in PM2.5 and PM10 in Summer in the Urban Agglomeration of the Ili River Valley]

The simultaneous observation and analysis of atmospheric particles on a regional scale is an important approach to developing control strategies for air pollution. To study the spatial distribution characteristics of particulate matter and water-soluble inorganic ions in the Ili Valley Urban agglomeration, PM_2.5 and PM₁₀ samples were synchronously collected from July 19 to July 29, 2021 in Yining City and the surrounding three counties, and then nine types of water-soluble inorganic ions (WSIIs) were analyzed. The spatial distribution characteristics, existence form of WSIIs, and influencing factors were discussed in depth. The results showed that the average ρ(PM_2.5) and ρ(PM₁₀) in the Ili River Valley urban agglomeration in summer were 23 μg·m^-3 and 59 μg·m^-3, respectively. The emission of local industrial and mobile sources in Yining City was higher than that of the surrounding three counties, resulting in the highest ρ(PM_2.5) in the region (25 μg·m^-3). Due to the influence of dust sources and topography, the ρ(PM₁₀) in Yining county was the highest in the region (63 μg·m^-3). Huocheng county is located upwind of the region, and these favorable diffusion conditions resulted in the lowest ρ(PM_2.5) and ρ(PM₁₀) (20 μg·m^-3 and 49 μg·m^-3, respectively). The concentrations of WSIIs in PM_2.5 and PM₁₀ ranged from 28.2%-29.9% and 16.0%-20.2%, respectively. The four main ions (SO₄^2-, NO₃^-, NH₄⁺, and Ca²⁺) accounted for approximately 90% of WSIIs mass concentrations. The concentration order of the four main ions in PM_2.5 was SO₄^2->Ca²⁺>NH₄⁺>NO₃^- and SO₄^2->Ca²⁺>NO₃^->NH₄⁺ in PM₁₀. The results of correlation analysis showed that the similar SO₄^2- concentrations in the four cities were mainly caused by regional transport. Ca²⁺ was the highest-concentration ion in PM₁₀ of Yining City and Qapqal Xibe Autonomous county, and the proportion of Ca²⁺ was significantly higher than that in most cities in China, which reflected that the cities in the core area of the Ili Valley were greatly affected by the dust sources. The ratios of n(NO₃^-)/n(SO₄^2-) in PM_2.5 and PM₁₀ were 0.78 and 0.76, respectively, indicating that the influence of stationary sources was greater than that of mobile sources. The ratio of n(NO₃^-)/n(SO₄^2-) in Yining City>Huocheng county>Yining county>Qapqal Xibe Autonomous county, which was consistent with the motor vehicle populations of the four cities, reflecting that Yining City was affected by motor vehicle sources more than the surrounding three counties. The secondary components mainly existed in the form of (NH₄)₂SO₄, NH₄HSO₄, and NH₄NO₃. There was excess ammonia after the reaction between NH₄⁺ and SO₄^2- in each city. NH₄NO₃ mainly existed in Yining City, which was mainly related to high NO₂ in Yining City. The NOR of the four cities were 0.03-0.10 and 0.03-0.16 in PM_2.5 and PM₁₀, respectively, and the secondary transformation of NO₃^- was weak due to the influence of high temperatures in summer. The SOR were 0.21-0.41 and 0.23-0.44, respectively. The SOR of Qapqal Xibe Autonomous county was the highest due to the relatively high humidity, whereas the SOR of Huocheng county was higher than that of the three sites in Yining City due to the influence of regional transportation. The formation mechanisms showed that SO₄^2- in Qapqal Xibe Autonomous county and Yining City were mainly produced by the heterogeneous reaction, and in Yining county it was mainly formed via the homogeneous reaction. However, the formation mechanism in Huocheng county was complex and was affected by both homogeneous and heterogeneous reactions.

Orange-fluorescence carbon dots employed for the quantitative analysis of silver ions and glyphosine through the off-on mode

Here we successfully developed a kind of carbon dot (CD), which emitted obvious orange-fluorescence, based on the hydrothermal method while polyacrylic acid was employed as the carbon source. The developed CDs have been equipped with multiple functional groups such as CO, -OH and -COOH, facilitating the possibility of interacting with potential targets. Meaningfully, the introduction of silver ions induced the fluorescence quenching of the as-prepared CDs. Meanwhile, the proposed CDs achieved detection of Ag⁺ with a linear range of 2.0 × 10^-6 to 1.0 × 10^-3 M at a detection limit of 1.8 × 10^-6 M. Moreover, the further addition of glyphosine gradually recovered the fluorescence accompanied by the concentration of glyphosine varying from 7 × 10^-6 to 10^-2 M with a detection limit of 6.2 × 10^-6 M. Thereby, the CDs prepared here show potential for broadening the avenues for detecting Ag⁺ and glyphosine.

Thermodynamic valorisation of lignocellulosic biomass green sorbents for toxic pollutants removal

Various toxic heavy metals have become hazardous to human health as well as the environment. This research has been focused on a biosorption/bioremoval process of chromium (III), copper (II) and lead (II) ions from an aqueous solution by utilizing lignocellulosic biomass of Citrus limon peel (CLP) powder. CLP powder biomass was selected based on dietary fibre components having greater potential to remove target heavy metal ions in order to purify wastewater by following the eco-friendly biosorption method. At optimum conditions, the observed maximum removal efficiency of 97.47, 87.13 and 95.71% for Cr, Cu and Pb ions, respectively, was observed. An investigation has been made as a work of pH, CLP amount and temperature. The presented bio-removal processes by prepared CLP biosorbent manifested as a temperature-independent. Langmuir isotherm model was found an excellent fit of the isotherm data for tested systems with the calculated biosorption capacities of 111.11 (Cr), 76.92 (Cu) and 100 (Pb) mg/g. The positive ΔH values for selected target heavy metal ions, except lead ions, confirmed that the reaction was spontaneous and endothermic. A cooperative mechanism of second-order and intraparticle diffusion models during the adsorption processes of all three target ions was established with a higher coefficient of determination and more closely anticipated take-up (adsorption capacity). Furthermore, the interaction of -OH and -COOH functional groups of CLP that have a major role in the removal of Cr, Cu and Pb ions from single-ion aqueous solution and/or a surface biosorption was confirmed based on the results presented by SEM-EDS and FTIR analysis. Analysis from XRD revealed peak corresponding to amorphous cellulose type I as observed by FT-IR analysis.

Estimation of sorption-desorption characteristics of biosorbent of Lantana camara leaves for removal of Pb (II) ions from wastewater

This study points out the method regarding the removal of Pb (II) ions from water by treatment with Lantana camara leaves' biosorbent (LCLB). The sorption process was investigated by varying different parameters pH, contact time, adsorbent dose, initial metal ion concentration, and temperature. For a 5.00 g sorbent dose and a 45 min of the contact period, a Pb (II) ion solution with an initial metal ion concentration of 10 mg/L resulted in 90.7% maximum elimination at an optimum pH 6 and temperature 298 ± 1.5 K with LCLB. The adsorption process was spontaneous and exothermic. The maximum monolayer adsorption was 3.5 mg/g for Pb (II) sorption using LCLB. Adsorption of Pb (II) ions using LCLB (R² > 0.999) followed the pseudo-second-order kinetics. The spectroscopic characterization was done by fourier transform infrared (FT-IR) analysis, while scanning electron microscope (SEM) images were captured for the morphological characterization. Desorption experiments revealed that hydrochloric acid has a strong potential as an eluent for Pb (II) ion desorption. The findings proposed that LCLB can be used as an effectual and cost-effective biosorbent for the expulsion of Pb (II) ions.

Adsorption of Heavy Metal Ions Copper, Cadmium and Nickel by Microcystis aeruginosa

To investigate the treatment effect of algae biosorbent on heavy metal wastewater, in this paper, the adsorption effect of M. aeruginosa powder on heavy metal ions copper, cadmium and nickel was investigated using the uniform experimental method, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and TG-DSC comprehensive thermal analysis. The experimental results showed that the initial concentration of copper ion solution was 25 mg/L, the temperature was 30 °C, the pH value was 8 and the adsorption time was 5 h, which was the best condition for the removal of copper ions by algae powder adsorption, and the removal rate was 83.24%. The initial concentration of cadmium ion solution was 5 mg/L, the temperature was 35 °C, the pH value was 8 and the adsorption time was 4 h, which was the best condition for the adsorption of cadmium ion by algae powder, and the removal rate was 92.00%. The initial nickel ion solution concentration of 15 mg/L, temperature of 35 °C, pH value of 7 and adsorption time of 1 h were the best conditions for the adsorption of nickel ions by algae powder, and the removal rate was 88.67%. The spatial structure of algae powder changed obviously before and after adsorbing heavy metals. The functional groups such as amino and phosphate groups on the cell wall of M. aeruginosa enhanced the adsorption effect of heavy metal ions copper, cadmium and nickel. Additionally, M. aeruginosa adsorption of heavy metal ions copper, cadmium, nickel is an exothermic process. The above experiments show that M. aeruginosa can be used as a biological adsorbent to remove heavy metals, which lays a theoretical foundation for the subsequent treatment of heavy metal pollution by algae.

Green synthesis, characterization, and application of metal oxide nanoparticles for mercury removal from aqueous solution

In this work, a novel surface-modified, green-based wheat straw-supported magnetite nanoparticles (Fe₃O₄-NPs) were synthesized via the green synthesis method, and the adsorption of mercury (Hg(II)) ion from aqueous solutions was methodically investigated. The synthesized wheat straw-supported magnetite (Fe₃O₄-WSS) NPs were characterized using X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), and scanning electron microscopic (SEM) methods. FT-IR and TGA confirmed that the surface of Fe₃O₄-NPs was functionalized well. The XRD analysis revealed the existence of magnetite in the synthesized wheat straw-supported Fe₃O₄-NPs of 19.83 nm average crystalline size. SEM analysis showed Fe₃O₄-NPs were almost spherical, with an average particle size of 22.48 nm. Adsorption studies were carried out to investigate the adsorption of Hg(II) ions onto Fe₃O₄-WSS NPs and the effect of various adsorption parameters such as pH, time, adsorbent dosage, and Hg(II) ion concentration. The optimum adsorption conditions were obtained: pH of 6, contact time of 45 min, adsorbate of 40 mg/L, and adsorbent of 1 g. A maximum of 98.04% Hg(II) ion removal efficiency was obtained at these optimum conditions. FT-IR analysis also indicated that surface functional groups such as C = C,-OH, and C-C of the newly produced Fe₃O₄-NPs led to the more efficient removal of Hg(II) from aqueous solution. The synthesized nano-adsorbent showed an excellent adsorption capability of 101.01 mg/g. Hg(II) ions adsorption onto Fe₃O₄-WSS NPs fitted well with the Langmuir adsorption isotherm model. Therefore, these reasonable findings reveal that Fe₃O₄-WSS NPs are an efficient and promising adsorbent for Hg(II) removal from aqueous water environments.

[Chemical Component of Particulate Matters and VOCs Characteristics During Vehicle Brake Processes]

Six sets of brake systems were tested using a brake dynamometer, and the brake wear particles (BWPs) and volatile organic compounds (VOCs) were collected during the braking process. In total, 39 elements, 12 water-soluble ions, 7 carbon components, and 18 polycyclic aromatic hydrocarbons (PAHs) in BWPs were extracted and detected, and 74 VOCs in gas samples were analyzed. The average mass fractions of 12 inorganic elements (i.e., Sb, Mg, Cu, Zn, Ti, Ca, Si, Zr, K, Ba, Al, and Fe) with higher contents in PM_2.5 and PM₁₀ were 43.4% and 40.3%, respectively, and the average mass fraction of Fe was the highest, accounting for 16.6% and 13.1% of PM_2.5 and PM₁₀, respectively. The average mass fractions of the 12 water-soluble ions in PM_2.5 and PM₁₀ were 16.5% and 12.6%, respectively, and NO₃^-, SO₄^2-, and Ca²⁺ were the ions with high contents. The average mass fraction of total carbon (TC) in PM_2.5 and PM₁₀ were 21.9% and 18.1%, respectively, and the average mass fraction of organic carbon (OC) was approximately five times that of elemental carbon (EC). There were six types of PAHs with a detection rate greater than 50%, among which naphthalene (Nap) was the most abundant. The average mass concentration of 74 VOCs was 316.04 μg·m^-3, of which the aromatic hydrocarbon had the highest mass concentration. The compositions of BWPs and VOCs emitted by the six sets of brake systems were quite different, which was mainly determined by the brand and raw materials of the brake pads.

Chemical characterization of water-soluble ions in highly time-resolved atmospheric fine particles in Istanbul megacity

The diurnal and seasonal variations of water-soluble ions (WSIs) in fine particles were investigated in an area predominantly affected by traffic emissions in Beşiktaş, Istanbul between 2017 and 2018. PM_2.5 samples were collected at high time resolutions of 2 h during the daytime and 12 h during the nighttime for six sampling campaigns over all seasons. Five inorganic water-soluble ions (SO₄^2-, NH₄⁺, NO₃^-, PO₄^-3, and NO₂^-) were determined using ion chromatography. Source analysis was investigated with principal component analysis (PCA) and bivariate polar plots. In descending order, WSIs concentrations were SO₄^2->NH₄⁺> NO₃^-> PO₄^-3>NO₂^- during the different seasons. The high time-resolved concentrations ranged as follows: sulfate 1.2-1118.1, ammonium 0.3-289.9, phosphate 2.9-107.6, nitrate 4.6-179.7, and nitrite 0.8-9.0 ng/m³, with yearly averages of 226.5, 59.0, 58.4, 37.9, and 3.3 ng/m³, respectively. Except for phosphate, all WSIs had strong seasonal variations with high concentrations during the winter and low concentrations during the summer. Molar ratios revealed that the formation of ammonium sulfate was less likely than ammonium nitrate. Principal component analysis resolved secondary aerosols (43.9%), residential heating (34.6%), shipping emissions (8.7%), and vehicle emissions (6.7%) as the major sources of WSIs, OC, EC, and PM_2.5 in Beşiktaş, Istanbul. Sulfate aerosol originated mainly from two nearby areas, SW and NE, of the sampling site tentatively due to residential heating and shipping emissions, respectively.

Hydrogeochemical characteristics of groundwater uses for agricultural and drinking and groundwater quality of pollution index in the western part of Telangana, South India

A total of fifty groundwater samples were collected in the western part of Nizamabad district, Telangana State, India. The results obtained were compared with the IS 10500 standard, which shows more than 80% of the samples are unfit for drinking purposes. The results were also analyzed to know the irrigation suitability, where about 80% of the samples are fit for agricultural use. For the major ions in groundwater quality for irrigation and drinking, contradictory locations exist which are majorly caused by geogenic (silicate weathering minerals) and anthropogenic (fertilizers, manure, and industrial effluents) sources. The hydrochemical facies of CaCl and mixed CaMgCl and NaCl water types were dominant in pre- and post-monsoon seasons. The spatial distribution diagrams of the major ions were high concentration in northern areas followed by western and south-western portions. As per the groundwater quality of pollution index (GQPI), most of the study region (62%) comes under the low contamination zone and the rest (38%) under the moderate to unacceptable zone. Factor analysis reveals that the study region is predominant of weathering, ion exchange, and anthropogenic inputs of major contamination of groundwater quality.

Chemical characterization, source apportionment, and health risk assessment of PM2.5 in a typical industrial region in North China

To clarify the chemical characteristics, source contributions, and health risks of pollution events associated with high PM_2.5 in typical industrial areas of North China, manual sampling and analysis of PM_2.5 were conducted in the spring, summer, autumn, and winter of 2019 in Pingyin County, Jinan City, Shandong Province. The results showed that the total concentration of 29 components in PM_2.5 was 53.4 ± 43.9 μg·m^-3, including OC/EC, water-soluble ions, inorganic elements, and metal elements. The largest contribution was from the NO₃^- ion, at 14.6 ± 14.2 μg·m^-3, followed by organic carbon (OC), SO₄^2-, and NH₄⁺, with concentrations of 9.3 ± 5.5, 9.1 ± 6.4, and 8.1 ± 6.8 μg·m^-3, respectively. The concentrations of OC, NO₃^-, and SO₄^2- were highest in winter and lowest in summer, whereas the NH₄⁺ concentration was highest in winter and lowest in spring. Typical heavy metals had higher concentrations in autumn and winter, and lower concentrations in spring and summer. The annual average sulfur oxidation rate (SOR) and nitrogen oxidation rate (NOR) were 0.30 ± 0.14 and 0.21 ± 0.12, respectively, with the highest SO₂ emission and conversion rates in winter, resulting in the SO₄^2- concentration being highest in winter. The average concentration of secondary organic carbon in 2019 was 2.8 ± 1.9 μg·m^-3, and it comprised approximately 30% of total OC. The concentrations of 18 elements including Na, Mg, and Al were between 2.3 ± 1.6 and 888.1 ± 415.2 ng·m^-3, with Ni having the lowest concentration and K the highest. The health risk assessment for typical heavy metals showed that Pb poses a potential carcinogenic risk for adults, whereas As may pose a carcinogenic risk for adults, children, and adolescents. The non-carcinogenic risk coefficients for all heavy metals were lower than 1.0, indicating that the non-carcinogenic risk was negligible. Positive matrix factorization analysis indicated that coal-burning emissions contributed the largest fraction of PM_2.5, accounting for 35.9% of the total. The contribution of automotive emissions is similar to that of coal, at 32.1%. The third-largest contributor was industrial sources, which accounted for 17.2%. The contributions of dust and other emissions sources to PM_2.5 were 8.4% and 6.4%, respectively. This study provides reference data for policymakers to improve the air quality in the NCP.

Stable and reusable acrylic ion-exchangers. From HMIs highly polluted tailing pond to safe and clean water

The application of several ion-exchange resins (IExR) with amino and amphoteric functionalities in batch retention of heavy metal ions (HMIs) (Cu(II), Fe(II), Mn(II), Zn(II)) from mono- and multicomponent simulated waters and from real polluted water collected from tailings pond of Tarnita (Suceava, Romania) sterile dump is deeply herein explored. The tested resins exhibited high sorption capacities, as evaluated by atomic absorption spectrometry, results supported by infrared spectroscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. The effect of pH on the IExR sorption capacity in competitive condition evidenced the optimum pH where IExR sorption efficiency is maximum. Reutilization of IExR in six consecutive sorption/desorption/regeneration cycles showed their renewable sorption properties. Wheat germination tests demonstrated that the Tarnita collected water had a high toxic effect whereas the resulted supernatant after batch sorption was nontoxic. The study shows that HMIs content after IExR sorption is under the admitted maximum level for surface water, and represents an important step on the efforts to solve the environmental problem in Tarnita area, by removing the main contaminants found in the local river water.

Environmental monitoring of trace metal pollutants using cellulosic-paper incorporating color change of azo-chromophore

An essential requirement for colorimetric paper-sensor is to allow the target analytes (heavy metal ions) to access the chromophore while maintaining strong chromophore immobilization on the porous substrate surface. This work evaluates the selection of sensitive chromophores (dithizone, 1-(2-pyridylazo) 2-naphthol and 4-(2-pyridylazo)-resorcinol) and their immobilization strategies on paper sensors. Dithizone (DTz) are capable of producing a significant color transition at unadjusted pH, observed by UV-Vis absorption spectroscopy and visible recognition. After immobilizing DTz on a paper substrate (cellulose acetate/chitosan substrate), the DTz-paper sensor showed a distinctive color change from blue-green to peach-pink upon reaction with Pb²⁺ ions, and the color intensity was proportional to the metal concentration. Quantitative analysis using RGB (R:Red; G:Green; B:Blue) plots showed that increasing DTz concentration on the CA/CS paper sensor increases the difference in total color intensity (∆I_T) and the difference in red code intensity (∆I_R). This is due to the formation of more DTz-Pb²⁺ complexes on the CA/CS paper substrate. The CA/CS paper strips immobilized with 100 ppm DTz showed practical potential for rapid detection of heavy metal ions. The DTz-CA/CS paper sensor showed significant color change when detecting spiked heavy metals ions (0.1 ppm Pb²⁺, 2.0 ppm Zn²⁺, and 0.2 ppm Cu²⁺) in river water samples that prepared at the maximum permissible limit for industrial effluent in Malaysia.

Fluorescent carbon dots from water hyacinth as detection sensors for ferric ions: the preparation and optimisation using response surface methodology

The search for alternatives to chemicals from natural products as precursors for the preparation of highly doped carbon dots (CDs) remains challenging. Novel CDs (W-CDs) were synthesised using a one-step pyrolysis method with wastewater hyacinth as the sole carbon and nitrogen source at a mild temperature without using any surface-activating reagents or salt. The obtained W-CDs emitted strong blue fluorescence under 365 nm UV light excitation, with a quantum yield of 15.12%. The Box-Behnken design of the response surface methodology was applied to optimize the W-CD preparation conditions, including the reaction temperature, reaction time and weight of water hyacinths. The temperature was found to be the most important factor affecting the fluorescence intensity of the W-CDs. Additionally, the fluorescence sensor based on W-CDs demonstrated excellent selectivity towards ferric (Fe) ions, with a limit of detection of 2.35 μM. The fluorescent sensor was successfully applied for detecting Fe³⁺ in real water samples with a recovery of 97.80-103.10%. Hence, the pyrolysis of water hyacinth is proven to be a rapid, effective and green approach for CDs and provides a novel method for recycling water hyacinth.

Dual-emission carbon dots for sensitive fluorescence detection of metal ions and ethanol in water

Carbon dots (CDs) have been widely used in biomedical fields because of their superior optical properties, high sensitivity and high selectivity to specific substances. However, there are few studies on trace detection of the ethanol content in aqueous solution using CDs. Herein, novel red fluorescent CDs with dual emission are synthesized and show good dispersibility in various solvents and excitation independence of photoluminescence (PL). After investigating the structure and properties of the red CDs, a multifunctional fluorescent nanoprobe based on the red CDs with high-sensitivity detection for dual-ion trace detection of Fe³⁺ and Cu²⁺ can be successfully constructed. The limit of detection of Fe³⁺ and Cu²⁺ can be up to 0.024 μM and 0.036 μM, respectively, which is superior to that in previous reports. Meanwhile, in view of the specific solvent effect on their PL, the red CDs are able to be applied for trace detection of the ethanol content in aqueous solution. The methods of colorimetry and fluorescence spectrometry are utilized to perform the threshold test and high-sensitivity quantitative analysis of the ethanol content in aqueous solution. Based on this, a multifunctional fluorescent nanoprobe based on the dual-emission red CDs can be obtained, which provides a promising way for their applications in detection and sensing fields.

Removal of lead from aqueous solution using electrospun nanofibers: preparation, characterization, adsorption isotherm, and kinetic study

Lead is one of the most hazardous toxic heavy metal ions in industrial wastewater. The removal of Pb(II) from aqueous environment is an extremely essential topic due to acquiring clean water resources and its significant impact on human health. Adsorption is an effective and the most widely used method for heavy metal removal from an aqueous medium. Nanofibers have potential advantages in the adsorption of heavy metal ions from wastewater. In this study, nanofibers based on polyvinyl alcohol (PVA) were fabricated for the removal of lead ions from aqueous samples. Nanofibers produced by electrospinning were characterized by scanning electron microscopy (SEM/EDX) and Fourier transform infrared (FT-IR) techniques. A batch system was used for the adsorption of Pb(II) ions onto cross-linked PVA (%10) and PVA (%10):MSs (%2) (Malva Sylestris L. seed biomaterial) nanofibers. The effectiveness of cross-linking was determined by the water absorbency test. The pH, adsorbent amount, adsorption kinetics, isotherms, and thermodynamic values were thoroughly investigated in the adsorption tests. Pb(II) adsorption on the polymer was confirmed by EDX analysis. The optimum values found were a pH of 6, an adsorbent dose of 5.0 mg, and a contact time of 120 min. Lead ion concentrations were determined by flame atomic absorption spectrometry (FAAS). The Freundlich models could explain the results from the adsorption data. Similar results were obtained from adsorption isotherm models, and the results were found to support each other. The adsorption capacity for PVA (10%) and PVA (10%):MSs (2%) nanofibers were found to be 444.2 mg g^-1 and 588.2 mg g^-1, respectively. The adsorption capacity increases with the addition of MSs (2%) biomaterial. As a result, nanofibers can be used as effective adsorbents in the removal of Pb(II) ions. The developed methods are environmentally friendly and promising for the separation of toxic Pb(II) ions from aqueous systems, which is a major problem for environmental pollution.