Contaminants In Aqueous Solution Research Articles

Synthesis, characterization and application of xanthated Diospyros kaki (persimmon) leaves for the treatment of chemical and biological contaminants in aqueous solutions

Synthesis, characterization and application of xanthated Diospyros kaki (persimmon) leaves for the treatment of chemical and biological contaminants in aqueous solutions

The strategy of three-dimensional Covalent Organic Frameworks to exclude dye contaminants in aqueous solutions

The development of effective solid adsorbents is necessary to remove organic pollutants from wastewater in response to the global water crisis. The present study investigates the adsorption behavior of dye pollutants on a 1, 3, 6, 8-tetrakis (4formylphenyl) pyrene (TFPPy) for the self-assembly of an innovative three-dimensional (3D) covalent organic frameworks (COFs). Molecular dynamics (MD) and the well-tempered metadynamics simulation were used to evaluate the ability of COFs to adsorb seven types of dye pollutants (DPs). These include methyl orange (MO), gentian violet (GV), brilliant green (BG), tolonium chloride (TC), methylene blue (MB), anionic congo red (CR), and rhodamine B (Rh B). To examine this process, several descriptors are calculated from the simulation trajectories, including interaction energies, root-mean-square deviation, radial distribution function, solvent-accessible surface area, mean square displacement, and the number of hydrogen bonds to figure out the process. After analyzing the data, it was found that the MO/COFs system displayed exceptional stability. It was confirmed by a significant value of −448.54 KJmol−1 for total interaction energy. The density profile of dye molecules in the MO and Rh B-COFs systems exhibits the highest peaks at approximately 325.79, and 26.75 kg/m³, respectively. The free energy values for the DPs/COFs complexes at their global minima reached about, −512.127, −435.603, −381.244, −300.313, and −283.230 kJmol-1 for MO/GV/BG/TC/ and Rh B with the COFs, respectively. The nature of the design of TFFPy-COF’s unique, ultrafast kinetics, high adsorption capacity, and good reusability endow them with great potential for removing dyes in an aqueous environment.

Promoting the circular economy: Valorization of a residue from industrial char to activated carbon with potential environmental applications as adsorbents

Pyrolysis of residues enriched with carbon, such as in agroforestry or industrial activities, has been postulated as an emerging technology to promote the production of biofuels, contributing to the circular economy and minimizing waste. However, during the pyrolysis processes a solid fraction residue is generated. This work aims to study the viability of these chars to develop porous carbonaceous materials that can be used for environmental applications. Diverse chars discharged by an industrial pyrolysis factory have been activated with KOH. Concretely, the char residues came from the pyrolysis of olive stone, pine, and acacia splinters, spent residues fuel, and cellulose artificial casings. The changes in the textural, structural, and composition characteristics after the activation process were studied by N2 adsorption-desorption isotherms, scanning electron microscopy, FTIR, elemental analysis, and XPS. A great porosity was developed, SBET within 776–1186 m2 g−1 and pore volume of 0.37–0.59 cm3 g−1 with 70–90% of micropores contribution. The activated chars were used for the adsorption of CO2, leading to CO2 maximum uptakes of 90–130 mg g−1. There was a good correlation between the CO2 uptake with microporosity and oxygenated surface groups of the activated chars. Moreover, their ability to adsorption of contaminants in aqueous solution was also evaluated. Concretely, there was studied the adsorption of aqueous heavy metals, i.e., Cd, Cu, Ni, Pb, and Zn, and organic pollutants of emerging concern such as caffeine, diclofenac, and acetaminophen.

Efficient activation of peroxymonosulfate by Mn single-atom: Critical role of Mn-N4 coordination for generating singlet oxygen

Single-atom catalysts with high catalytic efficiency and simple preparation methods are critical for activation of peroxymonosulfate (PMS) to degrade emerging contaminants in aqueous solution. Herein, manganese single-atom nitrogen-doped carbon catalyst (SA-Mn-NC) was synthesized by precisely controlled catalytic carbonization using small-molecule organic compounds as precursors, and Mn was uniformly dispersed in a single-atom state and existed in the ligand structure of Mn-N4. Thus, the SA-Mn-NC had considerable catalytic activity and can realize 100% bisphenol A degradation within 3 min with kobs of 1.56 min−1, which was 4.7 and 9.2 times higher than that of NC (0.33 min−1) and Mn-NC (0.17 min−1). Moreover, SA-Mn-NC has excellent environmental adaptability, negligible metal leaching concentration, good cycling stability, and selectivity to electron-rich compounds. EPR tests, quenching experiments, electrochemical measurements, and selective degradation results together confirmed that singlet oxygen (1O2) was the main active species in the SA-Mn-NC/PMS system. The coupled N-active sites of Mn-N4 contribute to the efficient activation of PMS to generate 1O2 and achieve high catalytic turnover frequency. This work provides a simple strategy for the preparation of single-atom catalysts with considerable PMS catalytic efficiency and negligible metal leaching toxicity, which is of guiding importance for the design of single-atom catalysts for high-efficiency water treatment.

Light-Switchable Biocatalytic Covalent-Organic Framework Nanomotors for Aqueous Contaminants Removal.

Self-propelled nanomotors represent a promising class of adaptable and versatile technologies with broad applications in the realms of biomedicine and environmental remediation. Herein, we report a biocatalytic nanomotor based on a covalent-organic framework (COF) that demonstrates intelligent and switchable motion triggered by a blue-to-red light switch. Consequently, when exposed to blue light, the nanomotor significantly enhances the removal of contaminants in aqueous solutions due to its elevated mobility. Conversely, it effectively deactivates its motion and contaminant removal upon exposure to red light. This study explores the heterogeneous assembly strategy of the COF-based nanomotor and its light-controlled propulsion performance and provides a novel strategy for the regulation of movement, offering valuable insights for the design and practical applications of nanomotors.

Detection of per- and polyfluoroalkyl water contaminants with a multiplexed 4D microcavities sensor

The per- and polyfluoroalkyl substances (PFAS) are a group of organofluorine chemicals treated as the emerging pollutants that are currently of particularly acute concern. These compounds have been employed intensively as surfactants over multiple decades and are already to be found in surface and ground waters at amounts sufficient to have an effect on human health and ecosystems. Because of the carbon–fluorine bonds, the PFAS have an extreme environmental persistence and their negative impact accumulates with further production and penetration into the environment. In Germany alone, more than thousands of sites have been identified as contaminated with PFAS; thus, timely detection of PFAS residue is becoming a high priority. In this paper, we report on the high performance optical detection method based on whispering gallery mode (WGM) microcavities applied for the first time to detect PFAS contaminants in aqueous solutions. A self-sensing boosted 4D microcavity fabricated with two-photon polymerization is employed as an individual sensing unit. In an example of the multiplexed imaging sensor with multiple hundreds of simultaneously interrogated microcavities we demonstrate the possibility to detect the PFAS chemicals representatives at a level down to 1 ppb (parts per billion).

Recent advances in water falling film reactor designs for the removal of organic pollutants by advanced oxidation processes: A review

Chemical wastewater from industrial and urban activities is a major environmental concern. Advanced oxidation processes (AOPs) have emerged as efficient techniques for the removal of persistent organic pollutants from wastewater. AOPs generate highly reactive hydroxyl radicals (•OH) that effectively degrade and mineralize a wide range of organic contaminants in aqueous solutions. Research is ongoing to find simple and efficient reactor designs for AOPs. Water falling film (WFF) reactor designs have been effectively utilized for the removal of various organic pollutants from wastewater. This review provides an overview of the development and application of WFF reactor designs for organic pollutants degradation by various AOPs. This work summarizes recent studies on treating organic pollutants, highlights current challenges in applying WFF reactors for water treatment using AOPs, and proposes future research directions. The review aims to guide researchers and stimulate further investigations into practical applications of WFF reactors in wastewater treatment.

Carbon-based nanomaterials mediated adsorption and photodegradation of typical organic contaminants in aqueous fulvic acid solution.

In this work, the formation of carbon-based nanomaterials-fulvic acid (CNMs-FA) composites and their capacities for the adsorption and photodegradation of typical organic contaminants in aqueous solutions were investigated. The results suggested that the formation of CNMs-FA composites was dominated by adsorbing FA on CNMs via the physisorption process, which fit the pseudo-first-order kinetic model and the Langmuir isotherm model. The formed CNMs-FA composites were characterized by using the Brunauer-Emmett-Teller, scanning electron microscopy, and infrared spectroscopy techniques and further applied for examining their effects on the adsorption and photodegradation of selected organic contaminants in aqueous solutions. The adsorption of organic contaminants on CNMs-FA composites is mainly involved in hydrogen bonding and electrostatic interactions between organic contaminants and FA species adhering to CNMs. In addition, the CNMs-FA composites are able to promote the photosensitive degradation of organic contaminants due to the photogenerated reactive species including ROS and CNMs-3FA* under sunlight irradiation. This study provided a deeper and more comprehensive understanding of the environmental behavior of CNMs in real natural surface water and clarified the underlying mechanisms.

Effects of ball milling on biochar adsorption of contaminants in water: A meta-analysis

Reckless release of contaminants into the environment causes pollution in various aquatic systems on a global scale. Biochar is potentially an inexpensive and environmentally friendly adsorbent for removing contaminants from water. Ball milling has been used to enhance biochar's functionality; however, global analysis of the effect of ball milling on biochar's capacity to adsorb contaminants in aqueous solutions has not yet been done. Here, we conducted a meta-analysis to investigate the effects of ball milling on the adsorption/removal capacity of biochar for contaminants in aqueous solutions, and to investigate whether ball milling effects are related to biochar production, ball milling, and other experimental variables. Overall, ball milling significantly increased biochar adsorption capacity towards both inorganic and organic contaminants, by 69.9% and 561.9%, respectively. This could be attributed to ball milling increasing biochar surface area by 2.05-fold, pore volume by 2.39-fold, and decreasing biochar pH by 0.83-fold. The positive adsorption effects induced by ball milling varied widely, with the most effective being ball milling for 12 to 24 h at 300 to 400 rpm with a biochar:ball mass ratio of 1:100 on biochars produced at 400–550 °C from wood residues. Based on this meta-analysis, we conclude that ball milling could effectively enhance biochar's ability to remove organic and inorganic contaminants from aquatic systems.

Carbon Nanostructures-Silica Aerogel Composites for Adsorption of Organic Pollutants.

Silica aerogels are a class of materials that can be tailored in terms of their final properties and surface chemistry. They can be synthesized with specific features to be used as adsorbents, resulting in improved performance for wastewater pollutants' removal. The purpose of this research was to investigate the effect of amino functionalization and the addition of carbon nanostructures to silica aerogels made from methyltrimethoxysilane (MTMS) on their removal capacities for various contaminants in aqueous solutions. The MTMS-based aerogels successfully removed various organic compounds and drugs, achieving adsorption capacities of 170 mg⋅g-1 for toluene and 200 mg⋅g-1 for xylene. For initial concentrations up to 50 mg⋅L-1, removals greater than 71% were obtained for amoxicillin, and superior to 96% for naproxen. The addition of a co-precursor containing amine groups and/or carbon nanomaterials was proven to be a valuable tool in the development of new adsorbents by altering the aerogels' properties and enhancing their adsorption capacities. Therefore, this work demonstrates the potential of these materials as an alternative to industrial sorbents due to their high and fast removal efficiency, less than 60 min for the organic compounds, towards different types of pollutants.

Rapid and selective removal of toxic and radioactive anionic pollutants using an ionic covalent organic framework (iCOF-2)

The schematic representation of iCOF-2 as an effective adsorbent for trapping of toxic and radioactive species from aqueous solutions.

Facile copper ferrite/carbon quantum dot magnetic nanocomposite as an effective nanocatalyst for reduction of para-nitroaniline and ortho-nitroaniline

Para-nitroaniline (PNA) and ortho-nitroaniline (ONA) are highly toxic contaminants in aqueous solution and must be treated. In the current investigation, novel magnetic nanocomposites containing copper ferrite (CuFe2O4) and gelatin-derived carbon quantum dots (CQDs) were successfully synthesized. The prepared nanocatalyst was characterized by scanning electron microscopy, x-ray diffraction, transmission electron microscopy, Brunauer–Emmet–Teller (BET), Fourier transform infrared and ultraviolet–visible techniques. The mesoporous structure of the CuFe2O4/CQD nanocomposite was shown using the BET/Barrett–Joyner–Halenda technique. The catalytic performance of the nanocatalyst during the reduction of PNA and ONA was assessed in an aqueous medium at 25 °C. The complete reduction of PNA and ONA using the CuFe2O2/CQDs nanocomposite occurred in 13 s and 35 s, respectively. The pseudo-second-order rate constant (K app) was obtained as 2.89 × 10−1 s−1 and 9.3 × 10−2 s−1 for reducing PNA and ONA, respectively. Moreover, the magnetic nanocatalyst was easily separated from the reaction solution and recycled for up to six consecutive cycles without significant loss of catalytic activity.

Adsorption characteristics of lead, copper, cadmium, methylene blue, phenol, and toluene in water using composite synthesized from titanium dioxides and carbon spheres through hydrothermal method

Titanium nanotubes (TNT) are commonly synthesized from TiO2 P25 under hydrothermal reaction (HTR) using 10 M NaOH). Composite adsorbents derived from TiO2 and carbon spheres (CS) were synthesized via a facile two-stage HTR process. CS was firstly synthesized from glucose through HTR. The mixture (CS, TiO2, and NaOH) was then transferred to a Teflon-lined autoclave for another HTC process to generate TNT/CS. The TNT/CS composite was calcined from 300 to 800 °C to evaluate the changes in its surface properties (functional group, morphology, and external charge), textural parameters, crystallinity, cation exchange capacity, and adsorption capacity. Results indicated that the Brunauer–Emmett–Teller surface area and total pore volume of composites were 25.0–131.9 m2/g and 0.099–0.33 cm3/g, respectively. The composites exhibited a negatively charged surface within pH 4.0–9.0, with their zeta potentials at pH 5.0 ranging from −54.60 to −31.1 mV. The result of X-ray photoelectron spectroscopy demonstrated that the main components (%atomic) in the composites were carbon (29.07%–60.75%), oxygen (29.09%–49.16%), titanium (2.93%–17.52%), and sodium (0.56%–9.48%). During the preparation of TNT/CS, CS (its negatively charged surface) can well absorb Na+ ions in the mixture. This phenomenon prevented the performance of tubular morphology in TNT/CS. The synthesized composites were regarded as multifunctional adsorbents for adsorbing various contaminants (Pb2+, Cd2+, Cu2+, cationic methylene blue dye, phenol, and toluene) in water. Equilibrium adsorption at pH 5.0 was carried out to estimate their adsorption capacities toward the selected contaminants. The Langmuir maximum adsorption capacities of Pb, Cd, Cu, methylene blue, phenol, and toluene were 534, 518, 514, 690, 329, 138 mg/g for TNT/CS and 334–523, 384–477, 297–453, 394–677, 303–416, 118–260 mg/g for the calcinated TNT/CS composites, and 26.3, 23.8, 21.4, 285, 239, 188 mg/g for commercial activated carbon, respectively. The adsorption mechanisms were elucidated based on the adsorption experiments and surface characteristics of TNT/CS. Ion exchange was the primary adsorption mechanism for the test cationic contaminants. The van der Waals force was an important adsorption mechanism for phenol and toluene. The developed TNT/CS composite can be employed as an effective adsorbent for adsorbing cationic and non-ionic contaminants in aqueous solutions.

Fabrication of Hydroxyl‐Carboxyl Bifunctional Hyper‐Crosslinked Polymers for Selective Adsorption of Methylene Blue

AbstractDyes are usual contaminants in aqueous solution. Some of them are carcinogenic and toxic. Hydroxyl‐carboxyl bifunctional hyper‐crosslinked polymers (HCHCP) carrying hydroxyl and carboxyl groups on their surface were fabricated for methylene blue (MB) adsorption by Friedel‐Crafts alkylation, using 3,4‐dihydroxyphenylacetic acid as a monomer. The maximum adsorption amount of MB was 751.88 mg g−1 according to the Langmuir isotherm model. The adsorption kinetics results demonstrated that the adsorption of MB followed the pseudo‐second‐order kinetic mode. In addition, the results of selective adsorption displayed that the HCHCP could separate MB from Acid Red 91 and methyl orange. Thus, HCHCP are promising adsorbents for cationic dyes.

Nanocomposite Electrodes for Detection of Hexavalent Chromium

Metal cations, when present in appropriate concentrations, serve an essential physiological function, however, their presence in larger concentrations has proven to be detrimental to human health. Modern industrial processes such as alloy treatment, coatings, and leather pigmentation, often result in the release of the heavy metal cations, causing adverse biological and ecological consequences. Amongst many, hexavalent chromium (Cr6+) is a major concern because of its carcinogenic properties. Therefore, it is imperative to develop a sophisticated technique for the early detection of Cr present in aqueous solutions. Numerous methods use techniques such as mechanical, optical, spectroscopic, and electrochemical for the detection of contaminants in aqueous solutions. Electrochemistry driven sensors have shown promise due to their possibility of miniaturization and low-cost. However, early and trace detection of such contaminants remains a challenge. Recently, atomically thin allotropes of carbon such as graphene or graphene oxide have been used to fabricate ultra-responsive and selective sensor platforms, owing to its excellent electrical conductivity, high surface area for functionalization, and physicochemical stability. In this work, we examine the use of electrically conducting polymer and atomically thin carbon materials as electrodes for the development of electrochemical sensors. Nanocomposite electrode films have been synthesized, and its performance as a function of number of cycles of deposition were analyzed. A capacitive microcomb sensor device has been fabricated, and the device performance using electrochemical, chemical, and morphological tests on electrodes as a function of deposition and electrolyte solutions will be highlighted. A fundamental understanding of reaction kinetics and identification of the rate-limiting steps will lead a path forward for developing robust sensors.

Mn3O4 Catalysts for Advanced Oxidation of Phenolic Contaminants in Aqueous Solutions

Water-soluble organic pollutants, such as phenolic compounds, have been exposed to environments globally. They have a significant impact on groundwater and surface water quality. In this work, different Mn3O4 catalysts were prepared for metal oxide activation of peroxymonosulfate (PMS) to remove the phenolic compound from the water environment. The as-prepared catalysts were characterized using thermogravimetric-differential thermal analysis (TG-DTA), powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. Furthermore, the effect of temperature and reusability of the as-prepared Mn3O4 catalysts is also investigated. The Mn3O4 nanoparticles (NPs) catalyst reveals an excellent performance for activating PMS to remove phenol compounds. Mn3O4 NPs exhibits 96.057% efficiency in removing 25 ppm within 60 min. The kinetic analysis shows that Mn3O4 NPs fitted into pseudo-first order kinetic model and exhibited relatively low energy activation of 42.6 kJ/mol. The reusability test of Mn3O4 NPs displays exceptional stability with 84.29% efficiency after three-sequential cycles. The as-prepared Mn3O4 NPs is proven suitable for phenolic remediation in aqueous solutions.

High potential of amine rice husk magnetic biocomposites for Cu(II) ion adsorption and heterogeneous degradation of contaminants in aqueous solution

High potential of amine rice husk magnetic biocomposites for Cu(II) ion adsorption and heterogeneous degradation of contaminants in aqueous solution

Hydrophilic PAA-g-MWCNT/TiO2@PES nano-matrix composite membranes: Anti-fouling, antibacterial and photocatalytic

The synthesis of composite nano-matrix membranes from a variety of nanoscale materials will impair the comprehensive properties of the materials. Therefore, it is not easy to prepare multifunctional nano-matrix membranes with excellent performance. Carbon nanotubes (CNTs) have superiority in absorption of impurities and contaminants in aqueous solution. Therefore, Polyethersulfone (PES) ultrafiltration membrane modified by CNTs and PAA-g-MWCNT/TiO2 (AMT) organic-inorganic hybrid particles is synthesized. And a new nano-matrix composite membrane PAA-g-MWCNT/TiO2@PES (AMTP) is prepared after the combination of the two particles, which endows the new composite membrane with three major effects of fouling resistance, photocatalysis and antibacterial properties. When the amount of AMT was 1 wt%, AMTP had the highest anti-pollution rate (31.21%); the best flux recovery rate (85.76%) and the degradation efficiency of MB and MO reached 90.03%, 62.36% within 2 h; the antibacterial rate was 98.12 %. When the dosage was 2 wt%, the antibacterial rate of AMTP reached 100 %. AMTP nano-matrix composite membranes have considerable adaptability and practicability of a wide application in the wastewater recovery and recycling.

Cobalt doped bismuth oxysulfide with abundant oxygen vacancies towards tetracycline degradation through peroxymonosulfate activation

Herein, Co doped Bi2O2S catalysts (denoted as CBOS) with different Co doping contents were successfully fabricated through a facile hydrothermal reaction and Co species could be uniformly distributed in the crystal structure of Bi2O2S. The catalytic performance of CBOS catalyst for the degradation of tetracycline (TC) is ca. 2.1-fold higher than that of pristine Bi2O2S by peroxymonosulfate (PMS) activation and its catalytic activity could be enhanced with the increase of catalyst loading, PMS concentration, reaction temperature and the decrease of TC concentration, while the CBOS catalyst also showed high catalytic activity at the pH range of 3–9 and for other contaminants in aqueous solution. The suitable content of Co doping, the rich oxygen vacancies and the redox property of Co species on CBOS surface could be attributed to its highly enhanced performance via the experimental analysis and DFT calculations. Radical scavenging and ESR experiments confirmed the formation of reactive radical species (SO4–, O2−and 1O2) and the possible catalytic degradation pathways for TC were given according to the LC-MS analysis of degradation intermediates in CBOS/PMS system finally. The present work provides a promising perspective for the preparation of Co-based catalysts aiming at the treatment of contaminated water through the PMS activation.

Self-supported 3D reduced graphene oxide for solid-phase extraction: An efficient and low-cost sorbent for environmental contaminants in aqueous solution

A 3D reduced graphene oxide (3D-rGO), a self-supported, efficient, and low-cost sorbent, was synthesised and employed in a solid-phase extraction (SPE) cartridge. As a proof of concept, it was applied to remove diclofenac from aqueous solution. After applying statistical methods to systematically investigate key parameters for optimizing the 3D-rGO cartridge performance, it reached removal and elution efficiencies of 100 % and 90 %, respectively. This SPE cartridge presented advantages compared to traditional ones as the smaller amount of material into the cartridge (mass twenty times smaller), in addition to the ability of eliminating sorbent preconditioning, reducing the use of solvents, and making the process environmentally friendly with a faster operation. Also, it presented improved reproducibility after several cycles of reuse, and finally a lower cost of production unveiled by a cost-benefit analysis. Analysis with scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectrometry, Raman, and Fourier transform infrared spectroscopy in attenuated total reflectance mode suggested that the 3D framework morphology with a high content of carbon at the surface and some residual oxygen-containing groups are the protagonists in this performance. Therefore, 3D-rGO has the potential to be a highly efficient sorbent in analytical procedures using SPE for environmental contaminants in water and effluent samples.