Common Water Contaminants Research Articles

Simultaneous Photocatalytic Tetracycline Oxidation and Cr(VI) Reduction by Z-Scheme Multiple Layer TiO2/SnIn4S8.

Wastewater pollutants are a major threat to natural resources, with antibiotics and heavy metals being common water contaminants. By harnessing clean, renewable solar energy, photocatalysis facilitates the synergistic removal of heavy metals and antibiotics. In this paper, MXene was both a template and raw material, and MXene-derived oxide (TiO2) and SnIn4S8 Z-scheme composite materials were synthesized and characterized. The synergistic mode of photocatalytic reduction and oxidation leads to the enhanced utilization of e-/h+ pairs. The TiO2/SnIn4S8 exhibited a higher photocatalytic capacity for the simultaneous removal of tetracycline (TC) (20 mg·L-1) and Cr(VI) (15 mg·L-1). The main active substances of TC degradation and Cr(VI) reduction were identified via free radical scavengers and electron paramagnetic resonance (EPR). Additionally, the potential photocatalytic degradation route of TC was thoroughly elucidated through liquid chromatography-mass spectrometry (LC-MS).

Removal of rhodamine B and methylene blue using residual Onecarpus bacaba Mart fibers as biosorbent: kinetic and thermodynamic parameters

Among the most common water contaminants, dyes are responsible for polluting rivers and other water bodies as well as contributing to other environmental problems, thus posing serious health hazards to humans and animals. In order to minimize these environmental impacts, this study proposes the use of Onecarpus bacaba Mart fiber residues, in natura (OBMi) and NaOH-modified (OBMm), to bioadsorb rhodamine b (RhB) and methylene blue (MB) dyes. The biosorbents OBMi and OBMm were characterized by means of infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, Boehm titration, PZC, and scanning electron microscopy. This study also analyzed the influence of pH, contact time, absorbent mass, temperature, and contaminant concentrations by means of batch equilibrium assays. It was observed that the OBMi absorbent showed a low dye removal capacity. Maximum OBMm adsorption capacity for RhB and MB at 25 °C was 26.60 mg g−1 and 407.98 mg g−1, respectively. In both systems, OBMm:RhB and OBMm:MB, adsorption kinetics followed a pseudo-second-order model, and the Langmuir and Freundlich models constituted the best fit for isothermal curves. Lastly, thermodynamic parameters indicated that adsorption of both RhB and MB onto OBMm is spontaneous.

Enhanced Electrocatalytic Conversion of Nitrates to Ammonia: Fuel from Waste.

Ammonia (NH3) is globally one of the most produced chemicals. Despite being known for its use as a fuel and as a precursor of multiple chemicals, during its production, it is responsible for more than 1.2 % of the total global CO2 emission and consumes a large amount of energy. In this work, we studied a flow-through membrane-free electrocatalytic device (CMED) to produce continuous stream of NH3 from a common water contaminant, nitrate (NO3 -). Indium-palladium (In-Pd) nanoparticles were impregnated in activated carbon cloth (ACC) and used as a cathode in the electrochemical device. It is found that in the counter electrode, adding oxygen evolution reaction (OER) active catalysts like platinum (Pt) for the regeneration of hydrogen ions enhances the rate of ammonia conversion to 7.28 μmol min-1 cm-2, eliminate the production of toxic nitrite by-products, as well as provide a platform for a stable energy consumption over long periods of time. This method for the conversion of NO3 - into NH3 promises a way forward for sustainable resource utilization while generating fuel from waste and contributing to future circular economies, and managing the nitrogen cycle in water that is a major challenge of the 21st century society.

Exposure to volatile organic compounds induces cardiovascular toxicity that may involve DNA methylation

Volatile organic compounds (VOCs) are common air pollutants and water contaminants. We previously found maternal exposure to VOCs was associated with offspring congenital heart disease (CHD). However, little information is available about the effects of VOCs on cardiovascular development at embryonic stage and the underlying mechanism remains unclear. In this study, we aimed to investigate the effects of a mixture of six VOCs on cardiovascular development in zebrafish embryos. Embryos were exposed to different concentrations of VOCs mixture (32 mg/L, 64 mg/L and 128 mg/L) for 96 h, cardiovascular abnormalities including elongated heart shape, increased distance between sinus venosus and bulbus arteriosus, slowed circulation and altered heart rate were observed in a dose- and time-dependent manner. Meanwhile, VOCs exposure increased global DNA methylation levels in embryos. Analysis identified hundreds of differentially methylated sites and the enrichment of differentially methylated sites on cardiovascular development. Two differentially methylated-associated genes involved in MAPK pathway, hgfa and ntrk1, were identified to be the potential genes mediating the effects of VOCs. By enzyme-linked immunosorbent assay, altered human serum hgf and ntrk1 levels were detected in abnormal pregnancies exposed to higher VOCs levels with fetal CHD. For the first time, our study revealed exposure to VOCs induced severe cardiovascular abnormalities in zebrafish embryos. The toxicity might result from alterations in DNA methylation and corresponding expression levels of genes involved in MAPK pathway. Our study provides important information for the risk of VOCs exposure on embryonic cardiovascular development.

Cyanobacterial bioreporter of nitrate bioavailability in aquatic ecosystems

The water eutrophication, resulting from the discharge of industrial and agricultural wastewater, leads to ecological degradation. However, to date, how to assess and manage the risks of water pollution, especially nitrogen pollution, remains a particularly noteworthy issue. Nitrate, the most important nitrogen compound, has become a bottleneck restricting total nitrogen management. The development of bioreporters monitoring nitrate pollution contributes to the estimation of water quality, especially the availability of nutrients. In this study, we obtained 9 bioreporters from 40 cyanobacterial derivatives which were constructed based on different hosts, copy numbers, and sensing elements and evaluated the performance of bioreporters. The results showed that single-celled Synechocystis was more sensitive to nitrate than filamentous Anabaena, that the reporter gene luxABCDE responded faster than sfgfp in most bioreporters, and that relatively medium-copy plasmid improved the performance of sensing elements. Nine bioreporters performed well in bioavailable nitrate detection, of which AD-AS-X and AR-NI-X, activated by nitrate repletion, had the shortest response time (2 h) and the widest response range (20–800 μM), respectively. Moreover, SR-GLN-SG, activated by nitrate deficiency, exhibited the best linear response (R2 = 0.998). After parameter optimization, exponential growth phase bioreporters, culture temperature of 30 °C, sample volume of 200 μL were determined as optimal monitoring conditions. We found that common water contaminants (copper, cadmium, and phosphorus) had no impact on the performance of bioreporters, indicating the stability of bioreporters. Six out of 9 bioreporters, especially the SR-NB-X, were highly effective in detecting the bioavailable nitrate in wastewater sample. This study provides valuable references for developing more cyanobacterial bioreporters and their practical application in nitrate detection.

Photo-catalytic applications of green synthesized AM-Ag/CuO/ZnO nano-composite and its synergistic effects

Toxic organic and inorganic chemical contaminants in the discharged effluents from textile and pharmaceutical industries have been directly polluting fresh and marine water bodies. The present study described significant degradation of two common water contaminants viz Methylene blue (MB) dye and Ciprofloxacin (CF) drug using green synthesized three mono-metallics AM-AgNP, AM-CuONP, AM-ZnONP (AM = Plant code, NP = Nanoparticles) and one trimetallic AM-Ag/CuO/ZnO nano-composite (TMNC). The biomolecules present in the leaf extract of A. monohpylla (AM) and microwave irradiation play a crucial role in tuning the nanomaterial’s size and shape. The spherical to rod shaped monometallic and irregular-shaped (spherical to oval) TMNC have shown polycrystalline nature with the FCC (AM-AgNP), monoclinic (AM-CuONP), wurtzite (AM-ZnONP) and mixed (AM-Ag/CuO/ZnO NC) crystal phases. Mono-metallics have shown significant degradation activity of 98.69% (50 min), 97.87% (70 min), 99.95% (50 min) and 59.48% (120 min), 64.69% (300 min), 76.13% (300) at 0.5 mg/ml of AM-AgNP, AM-CuONP, AM-ZnONP respectively against MB dye and CF drug. However, at the same concentration (0.5 mg/ml) TMNC degraded 99.5% MB dye and 97.53% CF drug within 40 min and 180 min respectively that reinforce the synergistic activity of the combined nano-materials at the specific concentration ratio. The R2 value confirmed that all the reactions followed the pseudo-zero order reaction, kinetic models.

Magnetic tubular nickel@silica-graphene nanocomposites with high preconcentration capacity for organothiophosphate pesticide removal in environmental water: Fabrication, magnetic solid-phase extraction, and trace detection

Organothiophosphate pesticides (OPPs) are the most common water contaminants, significantly endangering human health and bringing serious public safety issues. Thus, developing effective technologies for the removal or trace detection of OPPs from water is urgent. Herein, a novel graphene-based silica-coated core–shell tubular magnetic nanocomposite (Ni@SiO2-G) was fabricated for the first time and used for the efficient magnetic solid-phase extraction (MSPE) of the OPPs chlorpyrifos, diazinon, and fenitrothion from environmental water. The experimental factors affecting extraction efficiency such as adsorbent dosage, extraction time, desorption solvent, desorption mode, desorption time, and adsorbent type were evaluated. The synthesized Ni@SiO2-G nanocomposites showed a higher preconcentration capacity than the Ni nanotubes, Ni@SiO2 nanotubes, and graphene. Under the optimized conditions, 5 mg of tubular nano-adsorbent displayed good linearity within the range of 0.1–1 μg·mL–1, low limits of detection (0.04–0.25 pg·mL–1), low limits of quantification (0.132–0.834 pg·mL−1), good reusability (n = 5; relative standard deviations between 1.46% and 9.65%), low dosage (5 mg), and low real detection concentration (< 3.0 ng·mL−1). Moreover, the possible interaction mechanism was investigated by density functional theory calculation. Results showed that Ni@SiO2-G was a potential magnetic material for the preconcentration and extraction of formed OPPs at ultra-trace levels from environmental water.

Rational design enabling aptamer‐based sensors for surface‐enhanced Raman detection of small molecules

AbstractHomogeneous surface‐enhanced Raman scattering (SERS) sensors could have a significant impact in environmental analysis. The reagentless mechanism of these sensors makes them capable for in situ analysis and continuous monitoring of environmental pollutants, without having to collect environmental samples for laboratory analysis. Homogeneous SERS sensors take advantage of functional DNA strands on the surface of a SERS‐active particle. These sensors are commonly used for the detection of genomic targets. A clear path to adapt these homogeneous sensors to detect small molecules is to employ aptamer sequences. In particular, the use of duplex aptamer can make these sensors highly adaptable to different target molecules. Although there have been examples of SERS duplex aptamer sensors to detect small molecules, the design rules for this type of sensors have not been elucidated. Without design rules or a design protocol, we would not be able to fully take advantage of the adaptability of this approach to focus on new targets and applications (e.g., environmental analysis). Herein, we aim to define a protocol for the design of aptamer‐based homogeneous SERS sensors. First, we demonstrate their nonequilibrium character and the necessary length for the complementary element for the sensors to work. We demonstrate the design protocol on a well‐characterized aptamer sequence for ATP binding and then transfer the knowledge gained on an aptamer for estradiol, a common water contaminant. In this work, we establish the design protocol for a short aptamer (i.e., ATP) and analyze the issues and remedies associated with extending this protocol to longer aptamer sequences (e.g., E2).

Novel environmentally friendly approach to wastewater treatment eliminates aluminum sulfate and chlorination

Wastewater treatment uses harmful chemicals, including aluminum sulfate and chlorine. Aluminum sulfate, a common metal-based coagulant, can be toxic to both humans and aquatic life if ingested. Chlorine is used to disinfect wastewater by killing bacteria and other harmful microorganisms, and if ingested, chlorine and its byproducts can lead to respiratory irritation and cancer. The purpose of this research was to find equally efficient, environmentally safe alternatives to aluminum sulfate and chlorine water treatments. We investigated the effectiveness of zeolite, Moringa oleifera seed powder, and activated charcoal for wastewater filtration using common water contaminants and compared to the purification with aluminum sulfate. We tested lemon and orange peels as environmentally safe alternatives to chlorination by measuring the amount of bacterial growth suppression. We used inductively coupled plasma optical emission spectrometry (ICP-OES), colorimetric analysis (Lachat), bacteria colony counting, and scanning electron microscopy to analyze the effectiveness of these alternatives. For all the tested water contaminants and for analytical techniques used, our data demonstrated zeolite and charcoal were better or comparable to aluminum sulfate at removing the metals and nutrients tested. Lemon peels were very effective in suppressing bacteria growth, although further research is needed to compare chlorine to lemon peels in identical conditions to ensure that lemon peels could be a viable alternative to chlorination.

Acute and sub-lethal toxicity of a common water contaminant (copper sulfate) on edible freshwater fish: assessment of hemato-biochemical and tissue morphological biomarkers

Acute and sub-lethal toxicity of a common water contaminant (copper sulfate) on edible freshwater fish: assessment of hemato-biochemical and tissue morphological biomarkers

A process-based model for describing redox kinetics of Cr(VI) in natural sediments containing variable reactive Fe(II) species

Sediment-associated Fe(II) is a critical reductant for immobilizing groundwater contaminants, such as Cr(VI). The reduction reactivity of sediment-associated Fe(II) is dependent on its binding environment and influenced by the biogeochemical transformation of other elements (i.e., C, N and Mn), challenging the description and prediction of the reactivity of Fe(II) in natural sediments. Here, anaerobic batch experiments were conducted to study the variation in sediment-associated Fe(II) reactivity toward Cr(VI) in natural sediments collected from an intensive agricultural area located in Guangxi, China, where nitrate is a common surface water and groundwater contaminant. Then, a process-based model was developed to describe the coupled biogeochemical processes of C, N, Mn, Fe, and Cr. In the process-based model, Cr(VI) reduction by sediment-associated Fe(II) was described using a previously developed multirate model, which categorized the reactive Fe(II) into three fractions based on their extractabilities in sodium acetate and HCl solutions. The experimental results showed that Fe(II) generation was inhibited by NO3- and/or NO2−. After NO3− and NO2− were exhausted, the Fe(II) content and its reduction rate toward Cr(VI) increased rapidly. As the Fe(II) content increased, the three reactive Fe(II) fractions exhibited approximately linear correlations with aqueous Fe(II) concentrations (CFe2+), which was probably driven by sorptive equilibrium and redox equilibrium between aqueous and solid phases. The model results indicated that the reaction rate constants of the three Fe(II) fractions (kn) significantly increased with incubation time, and log(kn) correlated well withCFe2+ [log(k1)=2.84CFe2+−0.17, log(k2)=5.90CFe2+−2.49 and log(k3)=3.09CFe2+−3.37]. The numerical model developed in this study provides an applicable method to describe and predict Cr(VI) removal from groundwater under dynamic redox conditions.

Polypyrrole-based nanomaterials: A novel strategy for reducing toxic chemicals and others related to environmental sustainability applications.

Aqueous contaminants such as pharmaceuticals, dyes, personal care products, etc., are the common water contaminants that show adverse health effects. Photocatalysis is one of the well-known techniques to treat these water contaminants. Currently, most inorganic photocatalysts show a poor balance between adsorption and photocatalytic activity. In addition, heavy metal pollution and low biosafety are significant concerns in photocatalysis. Thus, environmentally friendly photocatalysts are required to avoid the secondary pollution caused by some inorganic semiconductor-photocatalysts. Organic polymer-based photocatalysts are low-cost, stable, non-toxic, and can utilize visible and NIR light for photocatalysis. In this review, we have discussed polypyrrole as a photocatalyst. Polypyrrole is a conducting organic polymer photocatalyst that is highly stable with high charge mobility and strong binding sites for photocatalytic reactions. Besides these advantages, polypyrrole has limitations, such as high charge recombination due to a small bandgap and poor dispersity. So we have explored the modifications to polypyrrole photocatalysts, such as doping and heterojunctions. Further, we have explained the applications of polypyrrole in photocatalysis as an adsorbent, sensitizer, degradation of pollutants, and energy production. Finally, the future aspects of polypyrrole photocatalysis are also explored to improve the path of future research.

Adsorptive Structure and Mobility on Carbon Nanotube Exteriors Using Benzoic Acid as a Molecular Probe of Amphiphilic Water Contaminants.

Benzoic acid is the simplest aromatic carboxylic acid that is also a common water contaminant. Its structural and amphiphilic properties are shared by many other contaminants of concern. Based on a molecular dynamics study, this work reports the competitive adsorption of benzoic acid with water on the curved exteriors of carbon nanotubes of varying oxygen content. With the help of cylindrically approximated pair correlation functions, carboxyl-carboxyl associations were found to serve as an additional mechanism providing stability to the adsorbed benzoic acid on tube exteriors. These associations are secondary to the main aromatic-aromatic interactions during the adsorption process and therefore were not sufficient to establish the energy hierarchy at the adsorbed state with increase in surface oxygen content. The same mechanism was previously ascribed to the adsorption of the structurally similar but bulkier tannic acid. Both water and benzoic acid were organized into numerous mobility groups and a correspondence was established between species residence time and the average translation time taken to escape the tube vicinity. Vigorous exchange of water molecules among the first adsorption shell, the second adsorption shell, and the immediate vicinity radially outside was estimated to take place within a short time of about 10 ps.

A critical review of advanced nanotechnology and hybrid membrane based water recycling, reuse, and wastewater treatment processes

One of the modern challenges is to provide clean and affordable drinking water. Water scarcity is caused by the growing population in the world and pollutants contaminate all remaining water sources. Innovative water treatment solutions have been provided by nanotechnology. Microorganisms, organic suspensions, and inorganic heavy metal ions, among other things, are common water contaminants. Since antiquity, a wide range of water clean-up methods have been employed to address this issue. Breakthroughs in water purification procedures have occurred during the previous four decades, with the most significant one being the use of nanomaterials and nanomembranes. Nanoparticles and nanomembranes (polymeric membranes) have recently been used in engineered materials (TiO2, ZnO, CuO, Ag, CNT's and mixed oxide nanoparticles, for example). Engineered nanomembranes, nanocomposites and nanoparticles have been used in this review article's discussion of water purification technologies. The review also discusses the risk and solutions of using nanoparticles and nanocomposites in the future.

Capture of Toxic Oxoanions from Water Using Metal-Organic Frameworks.

The effective capture of common water contaminants using metal-organic frameworks (MOFs) presents a remedy for current environmental concerns arising from the pollution of water sources. The crystalline porous nature of MOFs, their high internal surface area, and exceptional tunability make them suitable candidates for sequestration and removal of pollutants. However, the efficiency of capture depends largely on the nature of the interactions between the anions and the MOF. In this work, to elucidate the host-guest interactions involved in the capture of such pollutants, we explore three characteristically different MOFs: ZIF-8, iMOF-2c, and MOF-74. We demonstrate by ab initio electronic structure calculations the importance of exploiting qualitatively different binding modes for strong host-guest interactions available in the selected MOFs. Our simulations reveal the relative performance of neutral and cationic adsorbents while underscoring the importance of employing MOFs containing open metal sites for the efficient uptake of anions.

Synergetic effects of biochars and denitrifier on nitrate removal

Nitrate is one of the most common water contaminants and has caused severe environmental problems. This work aimed to investigate the effects of integration of denitrifier with biochars on nitrate removal and understand the underlying mechanisms. The results showed that physiochemical properties of biochars varied according to different feedstocks, which influenced bacteria attachment and nitrate removal through adsorption. However, bacteria could colonize on biochars no matter biochars surface were favorable for bacteria attachment or not. Immobilization of denitrifier on biochars significantly improved nitrate removal efficiencies and reduced lag time. Underlying mechanisms investigation showed that the integration of denitrifier with biochars had synergetic effects on promoting nitrate removal, which improved not only the expression and activity of nitrate reductase, but also the electron transport system activity.

Zeolite as a natural adsorbent for nitrogenous compounds being removed from water

Water is vital to the survival of humans and all other life forms, yet many sources of freshwater are being contaminated due to pollution, significantly limiting freshwater availability, and threatening human existence. Nitrates and ammonium are common water contaminants whose concentrations in water have increased significantly due to the excessive use of fertilisers. High concentrations of such contaminants in water can lead to multiple health issues, and thus controlling the concentration levels of these pollutants in water grows into the main task for environmental scientists. A natural zeolite filter was employed in this study to minimise traces of contaminants in water. Samples of synthetic polluted water were prepared that contained 50 mg/L of each contaminant for the laboratory tests. Testing natural zeolite doses ranging from 1 to 5 g/L at various pH levels (between 3 and 10) showed that a zeolite filter significantly improved the water quality from the initial concentrations of each pollutant by between 10 and 50 mg/l. In particular, more than 93% of both contaminants (nitrate and ammonium) were removed by using a 5 g/L dose of zeolite in a neutral pH level range for 120 minutes.

STUDY ON THE ANTIMICROBIAL EFFICACY OF HAND SANITIZERS DEVELOPED BY THE PHARMACEUTICAL CORPORATION (I.M) KERALA LTD (OUSHADHI)

Hand sanitizers are used to ensure hygiene in the absence of hand washing facilities or where frequent sanitizing is required especially in the wake of the Covid-19 pandemic. Handsanitizers using different combinations were prepared at Oushadhi using WHO recommendations and also to promote Kerala Government’s initiative of break the chain campaign. The campaign was launched on 15th March 2020 and it aims to cut down the progress of disease transmission. The efficacy of the batches of sanitizers prepared was tested against Escherichia coli and Staphylococcus aureus. They were also tested against common air and water contaminants found in the premises which would be of more significance to the general workforce. The susceptibility test was performed by agar well diffusion method and it revealed that the antimicrobial efficacy of the prepared hand sanitizer Batch III with Cymbopogon citratus oil was the most effective among the three combinations. A hedonic sensory evaluation was carried out for better consumer acceptability.

Polymeric nanostructures for photocatalytic dye degradation: polyaniline for photocatalysis

The motivation for the work presented in this paper comes from the need to explore novel and efficient photocatalysts for the degradation of contaminants from waste water. In this regard and in addition to the existing class of semiconductor photocatalysts, polymeric structures such as polyaniline, have emerged with the potential to degrade common water contaminants through photocatalysis. This paper elucidates the preparation of polyaniline (PANI) nanofibers and its implementation as a photocatalyst for the degradation of organic dyes such as Methylene Blue (MB) and Methyl Orange (MO). PANI was obtained using oxidative polymerisation and was examined for morphological and structural properties using XRD, SEM, TEM and FTIR which confirmed the formation of fibrous PANI sample. The chemical composition and the bonding states were studied using XPS. Subsequently, photo induced degradation of MB was performed in the presence of PANI as photocatalyst which indicated 42% degradation while MO was degraded by 97% in less than 3 h. Kinetic analysis by pseudo first order, second order and intra particle diffusion model, showed well-fit results for first order kinetic model with a rate constant of 0.0505 (g mg−1 min−1). The photocatalytic efficiency of PANI was assigned to the π–π* transition wherein the excited state electrons were transferred from the π to the π* orbital. Therefore, polyaniline was observed to be a promising photocatalyst for the degradation of environmental pollutants.

Mutualistic Outcomes Across Plant Populations, Microbes, and Environments in the Duckweed Lemna minor.

The picture emerging from the rapidly growing literature on host-associated microbiota is that host traits and fitness often depend on interactive effects of host genotype, microbiota, and abiotic environment. However, testing interactive effects typically requires large, multi-factorial experiments and thus remains challenging in many systems. Furthermore, most studies of plant microbiomes focus on terrestrial hosts and microbes. Aquatic habitats may confer unique properties to microbiomes. We grew different populations of duckweed (Lemna minor), a floating aquatic plant, in three microbial treatments (adding no, "home", or "away" microbes) at two levels of zinc, a common water contaminant in urban areas, and measured both plant and microbial performance. Thus, we simultaneously manipulated plant source population, microbial community, and abiotic environment. We found strong effects of plant source, microbial treatment, and zinc on duckweed and microbial growth, with significant variation among duckweed genotypes and microbial communities. However, we found little evidence of interactive effects: zinc did not alter effects of host genotype or microbial community, and host genotype did not alter effects of microbial communities. Despite strong positive correlations between duckweed and microbe growth, zinc consistently decreased plant growth, but increased microbial growth. Furthermore, as in recent studies of terrestrial plants, microbial interactions altered a duckweed phenotype (frond aggregation). Our results suggest that duckweed source population, associated microbiome, and contaminant environment should all be considered for duckweed applications, such as phytoremediation. Lastly, we propose that duckweed microbes offer a robust experimental system for study of host-microbiota interactions under a range of environmental stresses.