Development of ZnO-GO-NiO membrane for removal of lead and cadmium heavy metal ions from wastewater

The presence of heavy metal (HM) ions, such as lead, cadmium, and chromium in industrial wastewater discharge are major contaminants that pose a risk to human health. These HMs should separate from the wastewater to ensure the reuse of the discharged water in the process and mitigate their environmental impacts. The distinctive mechanical properties of 2D graphene oxide (GO), and the antifouling characteristics of metal oxides (ZnO/NiO) nanoparticles combined to produce composites supporting special features for wastewater treatment. This study employed solution casting and phase inversion methods to synthesize PSF-based GO, ZnO-GO, and ZnO-GO-NiO mixed matrix membranes and the effects of variation in composition on the removal of lead (Pb2+) and cadmium (Cd2+) ion was examined. Several characterization techniques including X-ray diffraction analysis, scanning electron microscopy, energy dispersive X-ray, and Fourier transform infrared spectroscopy were applied to analyze the synthesized NPs and MMMs. The composite membranes were also analyzed in terms of their porosity, permeability, hydrophilicity, surface roughness, zeta potential, thermal stability, mechanical strength, and flux regeneration at various transmembrane pressures (2-3 kgcm-2), and pH value (5.5). The highest adsorption capacities were measured to be 308.16 mg g-1 and 354.80 mg g-1 for Pb (II) and Cd (II), respectively, for membrane (M4_A) having 0.3 wt% of ZnO-GO-NiO nanocomposite, at 200 mg L-1 of feed concentration and 1.60 mL min-1 of permeate flux. The Pb (II) and Cd (II) adsorption breakthrough curves were created, and the results of the experiment were compared with the data of the Thomas model.

Dielectrophoresis-assisted removal of Cd and Cu heavy metal ions by using Chlorella microalgae

A novel dielectrophoresis (DEP)-assisted device for the bioremediation of heavy metal ions by using Chlorella microalgae is presented in this paper. To generate the DEP forces, pairs of electrode mesh were inserted in the DEP-assisted device. By applying DC electric field via the electrodes, the inhomogeneous electric field gradient is induced and the strongest non-uniform electric field exists near the mesh cross-corner. After the adsorption of Cd and Cu heavy metal ions by Chlorella, the Chlorella chain were trapped along the vicinity of the electrode mesh. Then, the effects of Chlorella concentration on the adsorption of heavy metal ions, and the applied voltage and electrode mesh size on the removal of Chlorella are conducted. In the co-existing Cd and Cu solutions, the individual adsorption ratio of Cd and Cu reaches as high as approximately 96% and 98%, respectively, showing excellent bioremediation capability of multiple heavy metal ions in wastewater. By adjusting the applied electric voltage and the mesh size, the Chlorella adsorbed with Cd and Cu are captured by negative DC-DEP effects and the removal ratio of Chlorella reach an average of 97%, providing a method for the removal of multiple heavy metal ions in wastewater by using Chlorella microalgae.

Water-soluble inorganic ions (WSIs) in the aerosols from Central Asia via transboundary transport measured in Jimunai in 2020

Air pollution is a global issue that often transcends national borders, leading to disputes over environmental concerns and climate-mitigation responsibilities. Between March and July 2020, we collected aerosol samples in Jimunai, a town in western China neighboring Kazakhstan, to assess transboundary air pollution in the region. Our analysis focused on major water-soluble inorganic ions (WSIs), with Ca2+ and SO42- accounting for almost 60% of the total ion loading. The ratio of cations to anions was greater than one (1.33 ± 0.27), indicating alkaline aerosols during the sampling period. Our results suggest that the pollutants measured were primarily sourced from Kazakhstan, as demonstrated by local meteorological data, air-mass trajectory analysis, and pollutant emission inventories in Kazakhstan. Correlation and primary component analysis indicated that NH4+ played an important role in neutralizing NO3- and SO42-, while Cl- was significantly depleted by the probable reaction HNO3↑ + NaCl = HCl↑ + NaNO3. These findings highlight the need for continued monitoring and regulation of air pollution sources in the region to address transboundary air pollution.

Enhanced Zn(II) adsorption by chemically modified sawdust based biosorbents

Heavy metals present in industrial effluents, when discharged into water channels, not only affect humans but also negatively impact plants and aquatic organisms. Sawdust is available readily in developing countries and can be used by small-scale industries for effluent water treatment containing low concentrations of bivalent zinc ions. This study explores the potential of sawdust-derived biosorbents, after boiling (SDB), chemical modification with formaldehyde (SDF), and sulfuric acid (SDS), for sequestration of Zn(II) from simulated wastewater as well as industrial effluents. The morphological analysis of the three biosorbents indicated a suitable porous structure with a pore size of 232.928 m2/g (SDB), 291.102 m2/g (SDF), and 498.873 m2/g (SDS). The functional analysis of native and metal-laden biosorbents indicated the role of - OH, - C = O, and - NH functional groups in Zn(II) binding. The process parameters were optimized and the spontaneous adsorption of Zn(II) was found to proceed by multilayer formation by following pseudo-second-order kinetics. SDS adsorbent (0.1 g) exhibited a greater potential for removal of Zn(II) from industrial effluents as compared to SDB and SDF at pH = 6.0 with the equilibrium adsorption capacity of 45.87 mg/g. Therefore, SDS could be a promising adsorbent for the treatment of wastewater in small-scale industries.

Fog and rain water chemistry in a tea plantation of northern Taiwan

Tea plantations are expanding globally and many are in mountainous areas with frequent fog but few studies have examined fog chemistry in these areas. We examined chemical composition of fog and rain water at a tea plantation in northern Taiwan. Fog water was collected using a Kroneis passive cylindrical fog-water collector and rain water was collected using a 20-cm-diameter funnel. The most abundant ions were Cl- and Na+ in both fog and rain waters due to the proximity of the site to the coast. The order of abundance of other ions was NO3-  > Mg2+  > SO42-  > Ca2+  > NH4+  > K+  > H+ in fog water and SO42-  > K+  > NO3-  > NH4+  > Ca2+  > Mg2+  > H+ in rain water. The concentration enrichment ratio (fog to rain) ranged between 2.2 (K+) and 22 (Mg2+) lying between sites near major emission sources and sites in remote areas, possibly because the immediate surrounding landscape is covered with secondary forests although it is near large cities. Factor analysis highlights the influences of sea-salt aerosols on the variation of fog and rain water chemistry. Sea-salt corrections using Na+ as the sea salt tracer led to negative concentrations of Cl- and Mg2+ suggesting that assumptions involved in sea-salt corrections were not satisfied. Agriculture influence is identified as a unique factor for explaining variance of K+, NH4+, and dissolved organic nitrogen (DON) concentrations in fog water but not rain water. Ion concentrations in fog and rain water were generally higher in the weekly samples associated with air trajectories passing through the continental East Asia than those associated with oceanic trajectories pointing to the role of regional pollution sources in affecting local fog and rain water chemistry. Our study highlights greater effects of tea agriculture on fog than rain water chemistry.

An advanced treatment process for 3-high wastewater discharged from crude oil storage tanks

The wastewater discharged from crude oil storage tanks (WCOST) contains high concentrations of salt and metal iron ions, and high chemical oxygen demand (COD). It belongs to "3-high" wastewater, which is difficult for purification. In this study, WCOST treatments were comparatively investigated via an advanced pretreatment and the traditional coagulation-microfiltration (CMF) processes. After WCOST was purified through the conventional CMF process, fouling occurred in the microfiltration (MF) membrane, which is rather harmful to the following reverse osmosis (RO) membrane unit, and the effluent featured high COD and UV254 values. The analysis confirmed that the MF fouling was due to the oxidation of ferrous ions, and the high COD and UV254 values were mainly attributable to the organic compounds with small molecular sizes, including aromatic-like and fulvic-like compounds. After the pretreatment of the advanced process consisting of aeration, manganese sand filtration, and activated carbon adsorption in combination with CMF process, the removal efficiencies of organic matter and total iron ions reached 97.3% and 99.8%, respectively. All the water indexes of the effluent, after treatment by the advanced multi-unit process, meet well the corresponding standard. The advanced pretreatment process reported herein displayed a great potential for alleviating the MF membrane fouling and enhanced the lifetime of the RO membrane system in the 3-high WCOST treatment.

Efficiency evaluation of Falcaria vulgaris biomass in Co(II) uptake from aquatic environments: characteristics, kinetics and optimization of operational variables

In the present research, the seeds of Falcaria vulgaris were extracted from the investigated environment and used for crop cultivation. This study has focused on the efficiency evaluation of Falcaria vulgaris biomass (FVB) in cobalt ions removal from aqueous solutions. The biosorbent was characterized using FTIR, BET, EDAX-EDS, and SEM. The optimal conditions were determined by the response surface methodology (RSM) based on a Box-Behnken design (BBD) model. The BBD model had   R 2 ,   R adj 2 and   R pred 2 values of 0.9919, 0.9774, and 0.8929, respectively. The cobalt removal under different conditions of the BBD model varied from 36.14% to 82.11%. Based on the numerical optimization of the quadratic model, the maximum cobalt removal at a biosorbent-to-metal ratio of 10:1, pH = 4.88 and contact time of 70 min was calculated at 80.941%. The high accuracy of the model in predicting the optimal conditions for cobalt adsorption by FVB was confirmed using statistical analysis and validation tests. The adsorption process of FVB also follows a pseudo-second-order kinetic model, which suggests that the rate-controlling step in cobalt removal is the chemical interaction between functional groups in FVB and Co+2 ions. This study shows that FVB, a low-cost biosorbent, can be a suitable candidate for removing heavy metals such as cobalt from aqueous solutions.

A microscale soft ionic power source modulates neuronal network activity

Bio-integrated devices need power sources to operate1,2. Despite widely used technologies that can provide power to large-scale targets, such as wired energy supplies from batteries or wireless energy transduction3, a need to efficiently stimulate cells and tissues on the microscale is still pressing. The ideal miniaturized power source should be biocompatible, mechanically flexible and able to generate an ionic current for biological stimulation, instead of using electron flow as in conventional electronic devices4-6. One approach is to use soft power sources inspired by the electrical eel7,8; however, power sources that combine the required capabilities have not yet been produced, because it is challenging to obtain miniaturized units that both conserve contained energy before usage and are easily triggered to produce an energy output. Here we develop a miniaturized soft power source by depositing lipid-supported networks of nanolitre hydrogel droplets that use internal ion gradients to generate energy. Compared to the original eel-inspired design7, our approach can shrink the volume of a power unit by more than 105-fold and it can store energy for longer than 24 h, enabling operation on-demand with a 680-fold greater power density of about 1,300 W m-3. Our droplet device can serve as a biocompatible and biological ionic current source to modulate neuronal network activity in three-dimensional neural microtissues and in ex vivo mouse brain slices. Ultimately, our soft microscale ionotronic device might be integrated into living organisms.

Valorised polypropylene waste based reversible sensor for copper ion detection in blood and water

Heavy metals and plastic pollutants are the two most disastrous challenges to the environment requiring immediate actions. In this work, a techno-commercially feasible approach to address both challenges is presented, where a waste polypropylene (PP) based reversible sensor is produced to selectively detect copper ions (Cu2+) in blood and water from different sources. The waste PP-based sensor was fabricated in the form of an emulsion-templated porous scaffold decorated with benzothiazolinium spiropyran (BTS), which produced a reddish colour upon exposure to Cu2+. The presence of Cu2+ was checked by naked eye, UV-Vis spectroscopy, and DC (Direct Current) probe station by measuring the current where the sensor's performance remained unaffected while analysing blood, water from different sources, and acidic or basic environment. The sensor exhibited 1.3 ppm as the limit of detection value in agreement with the WHO recommendations. The reversible nature of the sensor was determined by cyclic exposure of the sensor towards visible light turning it from coloured to colourless within 5 min and regenerated the sensor for the subsequent analysis. The reversibility of the sensor through exchange between Cu2+- Cu+ was confirmed by XPS analysis. A resettable and multi-readout INHIBIT logic gate was proposed for the sensor using Cu2+ and visible light as the inputs and colour change, reflectance band and current as the output. The cost-effective sensor enabled rapid detection of the presence of Cu2+ in both water and complex biological samples such as blood. While the approach developed in this study provides a unique opportunity to address the environmental burden of plastic waste management, it also allows for the possible valorization of plastics for use in enormous value-added applications.

Development of ratiometric fluorescent probes based on peptides for sensing Pb2+ in aquatic environments and human serum

The detection of Pb²⁺ ions in aquatic environments and biofluid samples is crucial for assessment of human health. Herein, we synthesized two fluorescent probes (1 and 2) consisting of the peptide receptor for Pb²⁺ and a benzothiazolyl-cyanovinylene fluorophore that exhibited excimer-like emission when it aggregated. The peptide-based probes sensitively detected Pb²⁺ in purely aqueous solution (1% DMF) through ratiometric fluorescent response with a decrease in monomer emission at 520 nm and an increase in excimer emission at 570 nm. Specially, probe 2 showed remarkable detection features such as high selectivity for Pb²⁺over 15 metal ions, high binding affinity (K_d = 5.83 × 10^-7 M) for Pb²⁺, significant emission intensity changes, low detection limit (3.8 nM) of Pb²⁺, high water solubility, and visible light excitation (450 nm). Probe 2 was successfully used to quantify nanomolar concentration (0 ∼ 800 nM) of Pb²⁺ in real water samples (ground water and tap water). Specially, 2 was successfully applied for the quantification of Pb²⁺ in human serum by combination of microwave-assisted human serum digestion and filtration of digested serum by anion exchange cartridge. We clearly investigated the binding mode of 2 with Pb²⁺ using ¹H NMR, IR spectroscopy, pH titration, confocal microscopy, and size analysis. The peptide-based fluorescent probe might have great application potential for sensing Pb²⁺ in aquatic environments and biofluid samples.

Investigation of the chemical nature of precipitation and source apportionment of its constituents in Tehran metropolis, Iran

Precipitation is a key process for purifying the atmosphere of pollutants. However, precipitation chemistry is also a significant environmental catastrophe on a global scale. Tehran Metropolitan Area, Iran's capital, is one of the world's most polluted cities. Nonetheless, little effort has been paid to determining the chemical composition of precipitation in this polluted metropolis. The chemical components and likely sources of trace metals and water-soluble ions in precipitation samples collected from 2021 to 2022 at an urban location in Tehran, Iran, were investigated in this study. The pH of the rainwater samples varied from 6.330 to 7.940 (mean 7.313, volume weighted mean (VWM) 7.523). The following is the order of the VWM concentration of main ions: Ca²⁺ > HCO₃^- > Na⁺ >SO₄^2- > NH₄⁺ > Cl^- > NO₃^- > Mg²⁺> K⁺> F^-. Furthermore, we discovered that VWM concentrations for trace elements are modest, with the exception of Sr (39.104 eq L^-1). The primary neutralizing species for precipitation acidity were Ca²⁺ and NH₄⁺. Vertical feature mask (VFM) diagrams derived from cloud-aerosol lidar and infrared pathfinder satellite observation (CALIPSO) track data indicated that polluted dust was the most common pollutant in the Tehran sky that might contribute significantly to the neutralization of precipitation. A study of species concentration ratios in seawater and the earth's crust indicated that virtually all Se, Sr, Zn, Mg²⁺, NO₃^-, and SO₄^2- were anthropogenic. While Cl^- was largely obtained from sea salt, K⁺ was obtained from both the earth's crust and the sea, with the earth's crust playing a larger role in K⁺. The earth's crust, aged sea salt, industry, and combustion processes were all verified as sources of trace metals and water-soluble ions by positive matrix factorization analysis.

Fine particulate matter and its chemical constituents' levels: A troubling environmental and human health situation in Karachi, Pakistan

Like many urban centers in developing countries, the effect of air pollution in Karachi is understudied. The goal of this study was to determine the chemical characterization, temporal and seasonal variability, sources, and health impacts of fine particulate matter (PM_2.5) in Karachi, Pakistan. Daily samples of PM_2.5 were collected using a low-volume air sampler at two different sites (Makro and Karachi University) over the four seasons between October 2009 and August 2010. Samples were analyzed for black carbon (BC), trace metals, and water-soluble ions. Results showed that the annual average concentrations of PM_2.5 at Makro and Karachi University were 114 ± 115 and 71.7 ± 56.4 μg m^-3, respectively, about 22.8 and 14.3-fold higher than the World Health Organization annual guideline of 5 μg m^-3. BC concentrations were 3.39 ± 1.97 and 2.70 ± 2.06 μg m^-3, respectively. The concentrations of PM_2.5, BC, trace metals, and ions at the two sites showed clear seasonal trends, with higher concentrations in winter and lower concentrations in summer. The trace metals and ionic species with the highest concentrations were Pb, S, Zn, Ca, Si, Cl, Fe, and SO₄^2-. The air quality index in the fall and winter at both sites was about 68 %, which is "unhealthy" for the general population. Positive Matrix Factorization revealed the overall contribution to PM_2.5 at the Makro site came from three major sources - industrial emissions (13.3 %), vehicular emissions (59.1 %), and oil combustion (23.3 %). The estimates of expected number of deaths due to short-term exposure to PM_2.5 were high in the fall and winter at both sites, with an annual mean estimate of 3592 expected number of deaths at the Makro site. Attention should be paid to the reduction of inorganic pollutants from industrial facilities, vehicular traffic, and fossil fuel combustion, due to their extremely high contribution to PM_2.5 mass and health risks.

A tetraphenylethene-based Schiff base AIEgen with a large Stokes shift as probe for highly sensitive and selective detection of aqueous Cu2+ ions and its application in cell imaging

In this work, an AIE-active tetraphenylethene-based Schiff base fluorescent probe 3 with a large Stokes shift (247 nm) was designed and synthesized. It was found that the aggregated probe 3 exhibited very high selectivity and anti-interference ability for Cu²⁺ in PBS buffer (70% f_w) through a fluorescence "turn-off" strategy. Job's plot and NMR analysis indicated the two phenolic hydroxyl groups of the benzene ring and the N atom (-CH=N-) on probe 3 interacted with Cu²⁺ ions in a 1:1 stoichiometric ratio. A comprehensive analysis of the Stern-Volmer and binding constant indicated a rather strong interaction between probe 3 and Cu²⁺ ions. Probe 3 illustrated excellent sensitivity toward Cu²⁺ under ppb level (4.5 nM) and achieved more than 95% recovery in river, lake and tap water toward estimation of Cu²⁺ ions in the analytical applications. Moreover, probe 3 was able to realize bioimaging of HepG2 cells and be quenched by intracellular Cu²⁺ ions, making it promising as a sensitive Cu²⁺ sensor for organisms.

Comprehensive profiling of chemical composition of Gleditsiae spina using ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight mass spectrometry

RATIONALE

Gleditsiae spina (GS) is an important herb used in traditional and folk medicinal systems of East Asian countries for its various medicinal properties. In China, it has been traditionally used through the centuries for its anticancer, detoxication, detumescence, apocenosis, and antiparasitic effects. Although some of its ingredients have been isolated and identified, most active constituents remain unknown. Past research mostly exploited nuclear magnetic resonance for the identification of compounds, which is suitable for monomers only. Moreover, the extraction and isolation procedures for obtaining purified molecules are time consuming. Therefore, establishing an efficient approach will assist in rapid discovery of the potential active ingredients of GS. The present study aimed to identify the chemical constituents in GS by a data analysis strategy using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight tandem mass spectrometry.

METHODS

First, the theoretical formula of the candidate compound was calculated using the accurate mass of the precursor/adduct ions. Second, the compounds were classified by the diagnostic ions from the MS/MS data. Third, characteristic ion filtering was used to identify the structures. Finally, the diverse skeletons and substitutions were further identified through the neutral loss in the GS.

RESULTS

A total of 277 compounds were identified in GS, comprising 169 flavonoids, 70 lignans, and 38 other compounds. At least 43 potential new compounds were represented.

CONCLUSIONS

This experiment devised an efficient and systematic method for detecting complex compounds and provided a foundation for future research into bioactive ingredients and quality control of GS.

Elemental Composition and Sources of Fine Particulate Matter (PM2.5) in Delhi, India

In this study we have analysed the elemental composition of fine particulate matter (PM_2.5) to examine the seasonal changes and sources of the elements in Delhi, India from January, 2017 to December, 2021. During the entire sampling period, 19 elements (Al, Fe, Ti, Cu, Zn, Cr, Ni, As, Mo, Cl, P, S, K, Pb, Na, Mg, Ca, Mn, and Br) of PM_2.5 were identified by Wavelength Dispersive X-ray Fluorescence Spectrometer. The higher annual mean concentrations of S (2.29 µg m^-3), Cl (2.26 µg m^-3), K (2.05 µg m^-3), Ca (0.96 µg m^-3) and Fe (0.93 µg m^-3) were recorded during post-monsoon season followed by Zn > Pb > Al > Na > Cu > Ti > As > Cr > Mo > Br > Mg > Ni > Mn > and P. The annual mean concentrations of elemental composition of PM_2.5 accounted for 10% of PM_2.5 (pooled estimate of 5 year). Principal Component Analysis (PCA) identified the five main sources [crustal/soil/road dust, combustion (BB + FFC), vehicular emissions (VE), industrial emissions (IE) and mixed source (Ti, Cr and Mo rich-source)] of PM_2.5 in Delhi, India.

Physico-chemical properties and transboundary transport of PM2.5 in Bien Hoa City, Dong Nai Province, Southeastern Vietnam

Air pollution is one of the most concerning environmental issues, wherein PM2.5 concentration plays an important role. This study monitored and evaluated the PM2.5 concentration trends in Bien Hoa City, Dong Nai Province, Vietnam. Twenty 24-h PM2.5 samples were continuously collected during the rainy (15 Oct. to 25 Oct. 2021) and dry (19 Mar. to 29 Mar. 2022) seasons. The PM2.5 samples were analyzed by scanning electron microscopy to determine the surface pattern and size distributions were analyzed using ImageJ software. The water-soluble fractions of 15 trace metal(oid)s concentrations (Al, Cu, Ni, K, Ca, Co, Mn, Cr, As, Zn, Pb, Cd, Na, Fe, and Mg) bound to PM2.5 were analyzed by inductively coupled plasma-mass spectrometry. The results showed that the 24-h fine fraction PM2.5 concentrations were 24.1 ± 12.2 μg/m3 and 63.0 ± 18.7 μg/m3 in the rainy and dry seasons, respectively. The results indicate that the size distributions of the particles of 2.0-2.5 μm are minor, and the majority are ultrafine particles with aerodynamic diameter ≤ 1.0 μm. Overall, the mass concentration level of the water-soluble fraction of trace metal(oid)s in PM2.5 in the rainy season was higher than that in the dry season. Among these, Ca, K, and Na were the most abundant earth crustal elements in PM2.5 in the rainy and dry seasons, accounting for 85% and 41.2% of the total trace element concentrations, respectively. The major sources of PM2.5 are local and regional sources of thermal power plants, industrial parks, and waterborne transportation (domestic rivers and marine). The activities undertaken to remove Agent Orange (e.g., soil excavation, transportation, and rotary kiln incinerators) at the Bien Hoa airbase area also cause increases in the PM2.5 level in the atmosphere of Bien Hoa City.

Luminescent Pyrene-based Schiff base Receptor for Hazardous Mercury(II) Detection Demonstrated by Cell Imaging and Test Strip

Qualitative and quantitative analysis of mercury at concentration levels as low as parts per billion (ppb) is a basic and practical concern. The vast majority of research in this field has centered on the development of potent chemosensor to monitor mercuric (Hg²⁺) ions. Mercury exists in three oxidation states, + 2, + 1 and 0, all of which are highly poisonous. In this study, (N¹E,N²E)-N¹,N²-bis(pyrene-1-ylmethylene)benzene-1,2-diamine (PAPM), a novel photoluminescent sensor based on pyrene platform was synthesized. Over the tested metal ions (Cd²⁺, Co²⁺, Cu²⁺, Mg²⁺, Mn²⁺, Ni²⁺, K⁺, Na⁺, Zn²⁺, Sr²⁺, Pb²⁺, Al³⁺, Cr³⁺ and Fe³⁺) the sensor responds only to Hg²⁺ by showing high selectivity and sensitivity. After treatment with mercuric ions at room temperature, the luminescence intensity of probe was quenched at 456 nm. The quenching of fluorescence intensity of probe upon addition of mercury is due to the effect of "turn-off" chelation enhanced quenching (CHEQ) by the formation of 1:1 complex. The ESI-MS spectrum and the Job's experimental results confirm the formation of 1:1 complex between PAPM and Hg²⁺. The detection limit and association constant of sensor for mercury is computed using fluorescence titration data and were found to be 9.0 × 10^-8 M and 1.29 × 10⁵ M^-1 respectively. The practical application of sensor towards recognition of mercury(II) ions was explored through economically viable test strips and also using cell imaging studies.

Quantitative and qualitative analyses of metal ions in food and water by using a multicolor sensor array and chemometrics

Rapid and accurate detection of toxic metal ions is the key to combating food contamination and environmental pollution. In sensor arrays, gold nanoparticles play a crucial role in monitoring metal ions based on surface plasmon resonance. However, identifying metal ions with unknown concentrations in a complex system through this assay is difficult because of its monotonous color change and weak anti-interference ability. To overcome these limitations, a sensitive, flexible, low-cost, and multicolor sensor array was designed herein. The applicability of the sensor array for the qualitative and quantitative analyses of metal ions in food and water was also verified. The developed sensor array could classify 14 metal ions (Cu²⁺, Fe²⁺, Fe³⁺, Mn²⁺, Ni²⁺, Zn²⁺, Cd²⁺, Cr³⁺, Co²⁺, Ba²⁺, K⁺, Tl⁺, Pb²⁺, and Hg²⁺) of unknown concentration with an accuracy of 100%. In addition, partial least squares models were established to quantify Tl⁺, Pb²⁺, and Hg²⁺ in water and rice samples, with square correlation coefficients (R²) of 0.9991, 0.9742, and 0.9731, respectively. This method can be used for accurate quantitative and qualitative analyses of heavy metal ions in water and food.

A noise-robust deep clustering of biomolecular ions improves interpretability of mass spectrometric images

MOTIVATION

Mass Spectrometry Imaging (MSI) analyzes complex biological samples such as tissues. It simultaneously characterizes the ions present in the tissue in the form of mass spectra, and the spatial distribution of the ions across the tissue in the form of ion images. Unsupervised clustering of ion images facilitates the interpretation in the spectral domain, by identifying groups of ions with similar spatial distributions. Unfortunately, many current methods for clustering ion images ignore the spatial features of the images, and are therefore unable to learn these features for clustering purposes. Alternative methods extract spatial features using deep neural networks pre-trained on natural image tasks; however, this is often inadequate since ion images are substantially noisier than natural images.

RESULTS

We contribute a deep clustering approach for ion images that accounts for both spatial contextual features and noise. In evaluations on a simulated dataset and on four experimental datasets of different tissue types, the proposed method grouped ions from the same source into a same cluster more frequently than existing methods. We further demonstrated that using ion image clustering as a pre-processing step facilitated the interpretation of a subsequent spatial segmentation as compared to using either all the ions or one ion at a time. As a result, the proposed approach facilitated the interpretability of MSI data in both the spectral domain and the spatial domain.

AVAILABILITYAND IMPLEMENTATION

The data and code are available at https://github.com/DanGuo1223/mzClustering.

SUPPLEMENTARY INFORMATION

Supplementary data are available at Bioinformatics online.

Seasonal variations, source apportionment and dry deposition of chemical species of total suspended particulate in Pengjia Yu Island, East China Sea

Total of 172 total suspended particulate (TSP) samples and its chemical compositions were collected and analyzed from January to December 2010 in Pengjia Yu Island, an open region in East China Sea (ECS). Despite the predominance of sea-salt major ions (Na⁺, Cl^-), the presence of non-sea-salt SO₄^2- (nss-SO₄^2-) and NO₃^- as well as combustion-derived trace metals clearly establishes the impact of anthropogenic sources over ECS. The annual contributions of coal, heavy-fuel oil and traffic to the measured chemical species were 21.0 %, 15.0 % and 15.5 %, respectively. Especially in spring, the contributions of crustal minerals to measured chemical species during dust period (33.6 %) were higher than that (13.2 %) during non-dust period. The calculated annual average dry deposition fluxes for trace metals and total inorganic nitrogen were 246.1 ± 345.8 μg/m²/d and 2950.4 ± 2245.0 μg/m²/d, suggesting that atmospheric deposition is an important source of nutrient elements for the south of ECS.

Chemistry and buffering capacity of fog water collected in and around New Delhi, India

In this study, fog water samples collected from New Delhi and its satellite township Sonipat for 2 years 2015-16 and 2016-17 are characterized by soluble ions and internal buffering capacity. The pH of fog water is close to 5.6 due to the limited contributions of Ca²⁺ and Mg²⁺ ions by virtue of low wind speed during winters. NH₄⁺ and Ca²⁺ were dominant cations in fog at both sites during both sampling years. NH₄⁺ and Ca²⁺ contributions were similar in New Delhi during 2015-16, but Ca²⁺ increased during 2016-17 on account of construction activities. Emissions from agriculture fields through fertilizer applications and animal breeding lead to an increase of NH₄⁺ compared to Ca²⁺ at Sonipat. SO₄^2- was comparable with Cl^-, followed by NO₃^- ions. Plastic burning in this region during wintertime was a possible source of Cl^- ions. Acid neutralization decreases as NH₄⁺  > Ca²⁺ and Mg²⁺ for all samples in Sonipat and as Ca²⁺  > NH₄⁺ and Mg²⁺ in New Delhi. Higher NO₃^- in New Delhi was due to vehicular emissions. Vehicular emissions in New Delhi and agriculture fields in Sonipat were dominant sources of organic acids. Observed internal buffering capacity was different than theoretical values over a pH range from 4 to 7 in New Delhi, whereas both buffering capacities were close to each other in Sonipat samples. Lead in fog water at both sites was higher than prescribed safe limits for drinking water. Pollution sources were responsible for higher concentrations of metals, organic acids, and soluble ions in fog in New Delhi compared to that in Sonipat.

A feasibility study on production, characterisation and application of empty fruit bunch oil palm biochar for Mn2+ removal from aqueous solution

Empty fruit bunch oil palm (EFBOP) is one of the byproducts after oil palm fruitlet is removed in oil palm processing and is considered as waste. In this study, EFBOP was converted to biochar (BC-EFBOP) at 350-700 °C, with an overarching aim of determining the feasibility of adsorptive removal of manganese (a second dominant element in acid mine drainage) from water. Results showed that with increasing temperature, the BC-EFBOP yield decreased from 44.34% to 26.74%, along with the H/C (0.89%-0.29%) and O/C ratios (0.38%-0.23%), and the carbon content increased (62.7%-73.93%). As evidenced by Fourier Transform InfraRed spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS), abundant oxygen-containing surface functional groups such as hydroxyl (-OH), carboxyl (-COOH), and ether (C-O-C) were retained, and aromatic CC groups were largely generated in the biochar. Pyrolysed biochar at 350 °C (BC350), with the least surface area (0.5 m² g^-1), exhibited the highest Mn²⁺ adsorption capacity (8.2 mg g^-1), whereas for BC700, with the largest surface area (2.19 m² g^-1), had the lowest capacity for Mn²⁺ (1.2 mg g^-1). Regardless of the temperature, solution pH of 5 was found to be optimal for Mn²⁺ removal from water. The Langmuir isotherm model best described the equilibrium adsorption data with a maximum adsorption capacity of 1.2-8.2 mg g^-1 for initial concentrations of 5-250 mg L^-1, whereas the adsorption kinetics followed the pseudo-second-order model. There was nearly four-fold increase in Mn²⁺ ions removal with increased biochar dosage (0.05-0.5 g), at initial Mn²⁺ concentration of 100 mg L^-1. The study showed that a low-cost, environmentally friendly BC-EFBOP with optimal surface chemistry could potentially remediate Mn²⁺ ions from aqueous media. However, a proper cost-benefit and techno-economic analysis is needed prior to potential pilot scale studies.

Portable ratiometric fluorescence analytical device for copper ions based on smartphone in environment and living organisms

The concentration of copper ions (Cu²⁺) in the environment is closely related to water quality, food, and biological health. As an indispensable metal element for the human body, its content is closely related to many diseases. However, the current detection methods for Cu²⁺ have some limitations, such as complicated operations and unfavorable on-site analysis. Therefore, this work constructs a novel ratiometric fluorescent probe (QLP), which has the advantages of rapid response, good anti-interference ability and high sensitivity. It has been successfully used for the detection of Cu²⁺ in water samples, soil, and food. In addition, low cytotoxicity and strong tissue penetration make it suitable for the detection of Cu²⁺ in living cells and zebrafish, offering a chemical tool for exploring the physiological and pathological processes related to Cu²⁺. It is important to use probe QLP and portable UV lamp to create an easy-to-operate Cu²⁺ detection platform, which can quickly detect Cu²⁺ on-site by combining with a smartphone. This work not only provides a detection tool for on-site analysis of Cu²⁺, but also provides a reference strategy for the development of on-site detection methods for other environmental pollutants.

Simultaneous removal of Cu (II) and Cr (VI) ions from petroleum refinery wastewater using ZnO/Fe3O4 nanocomposite

The presence and removal of heavy metals such as Cu(II) as well as Cr(VI) in petroleum refinery wastewater calls for concerted efforts due to their mobility, toxicity, bioaccumulation, and non-biodegradability in the environment. In this present work, zinc oxide (ZnO), iron oxide (Fe₃O₄) nanoparticles and ZnO/Fe₃O₄ nanocomposites were synthesized via simple sol-gel and chemical reduction methods; characterized using different analytical tools and then applied as nanoadsorbent to sequester Cu(II) and Cr(VI) ions from Petroleum Refinery wastewater via batch adsorption process. Cu(II) and Cr(VI) adsorption processes were examined with respect to contact time (kinetic effect), nanoadsorbent dosage, isotherm equilibrium, and thermodynamic parameters. ZnO/Fe₃O₄ nanocomposites with higher surface area (39.450 m²/g) have a mixture of rod-like and spherical shapes as compared to ZnO and Fe₃O₄ nanoparticles with spherical shape only and surface areas of 8.62 m²/g and 7.86 m²/g) according to the high-resolution scanning electron microscopy (HRSEM) and Brunauer-Emmett-Teller (BET) analysis. The X-ray diffractometer (XRD) results revealed the formation of hexagonal wurtzite structure of ZnO and the face-centered cubic structure phase of Fe₃O₄ nanoparticles, after the formation of the ZnO/Fe₃O₄ nanocomposites the phases of the nanoparticles were not affected but the diffraction peaks shifted to higher 2θ degree. The average crystallite size of ZnO and Fe₃O₄ nanoparticles and ZnO/Fe₃O₄ nanocomposites were 20.12, 26.36 and 14.50 nm respectively. The maximum removal efficiency of Cu (II) (92.99%) and Cr (VI) (77.60%) by ZnO/Fe₃O₄ nanocomposites was higher than 85.83%; 65.19% for Cu (II) and 80.57%; 62.53 for Cr (VI) using ZnO and Fe₃O₄ nanoadsorbents individually under the following conditions: contact time (15), dosage (0.08 g) and temperature (30 °C). The experimental data for Cu (II) and Cr (VI) ion removal fitted well to the pseudo-second-order kinetic and Langmuir isotherm models. The thermodynamic study suggested that the removal of the two metal ions from petroleum wastewater was endothermic. The reusability study after the fourth adsorption-desorption cycle indicated the stability of ZnO/Fe₃O₄ nanocomposites with 85.51% and 69.42% removal efficiency of Cu (II) and Cr (VI). The results showed that ZnO/Fe₃O₄ nanocomposite achieves higher performance than ZnO and Fe₃O₄ alone in the removal of Cu (II) and Cr (VI) ions from the petroleum refinery wastewater.

Extraction of extracellular polymeric substances (EPS) from indigenous bacteria of rare earth tailings and application to removal of thorium ions (Th4+)

Thorium, as an important radioactive element, is widely present in nature, and its accompanying environmental pollution is also serious. Extracellular polymeric substances (EPS) are commonly found on the surface of microbial bodies and have strong adsorption capacity for metal ions. In this study, four methods were used to extract EPS from indigenous bacteria of rare earth tailings and to determine the best extraction method. The extracted EPS was applied to treat Th⁴⁺, and the changes in functional groups and composition of EPS were investigated. The results showed that the ultrasonic method was more efficient than other methods. The best removal efficiency was observed at pH 3.5, Th⁴⁺ concentration of 20 mg/L, and EPS dosage of 30 mL at 25 °C. After 9 h, the adsorption process reached equilibrium with a maximum removal efficiency of 75.93% and a maximum theoretical adsorption capacity of 25.96 mg/g. The Th⁴⁺ removal process was consistent with the Langmuir and Freundlich adsorption isotherms and the kinetic data were consistent with the pseudo-second-order kinetic model, which is mainly based on chemisorption. Amide I and amide II of proteins, C-H from aliphatic, as well as O-H and C = O from carboxylic acid play important roles in the adsorption process.