Removal Of Environmental Pollutants Research Articles

One-pot synthesis of flower-like SnS2/SnO2 heterojunction with enhanced visible light photocatalytic performance

Herein, the combined strategy of coupling SnS2 was adopted to modify SnO2 nanoparticles to construct SnS2/SnO2 heterostructure. The as-prepared SnS2/SnO2 composites were characterized by XRD, TEM, XPS, UV–vis, transient photocurrent and photoluminescence spectra technologies. TEM results proved SnS2/SnO2 composites showed flower-like structure. UV–vis spectra suggested that the introduction of SnS2 can prolong light absorption range to visible region. The photocatalytic activity of SnS2/SnO2 composites were measured by degrading methyl orange and Cr (VI). The SnS2/SnO2 heterojunction exhibited excellent photodegradation activity compared with pure SnO2 and SnS2, and the MO degradation rates were up to 98% and 96% after 120 min irradiation under UV and visible, and 98% and 95% of Cr (VI) were degraded by the composites in 120 min, respectively. The superior photocatalytic performance was due to the effective separation of photoinduced carriers and enhanced light absorption, which was proved by the transient photocurrent, photoluminescence, and UV–vis spectra. Photocatalytic mechanism was further studied through free radical capture experiments and theoretical calculations. Our research provides a novel design for the synthesis of SnO2-based composites with effective removal of environmental pollutants.

Biological responses of Eisenia fetida towards the exposure and metabolism of tris (2-butoxyethyl) phosphate

The toxicity of various organophosphorus flame retardants (OPFRs) is of increasing concern. However, there is still a lack of research on the toxicity of OPFRs to terrestrial invertebrates and its metabolism in vivo. Herein, earthworms (Eisenia fetida) were exposed to soil spiked with 0, 0.05, 0.5, and 5 mg/kg tris(2-butoxyethyl) phosphate (TBOEP, a typical alkyl OPFRs) for 28 d to study the biological responses to the exposure and metabolism of TBOEP. TBOEP exposure inhibited the activity of acetyl-cholinesterase (64.4–68.6% of that in the control group), increased the energy consumption level, and affected calcium-dependent pathways of E. fetida, which caused a 3.6–12.4% reduction in the weight gain rate (developmental toxicity), a 10.6–69.4% reduction in the number of juveniles (reproduction toxicity), and neurotoxicity to E. fetida. The 5 mg/kg TBOEP exposure caused a significant accumulation of malondialdehyde (1.68 times higher than that in the control group) in E. fetida, which indicated that the balance of oxidation and anti-oxidation of E. fetida was broken. Meanwhile, E. fetida maintained the absorption and metabolic abilities to TBOEP under the environmental condition. The removal rate of soil TBOEP was increased by 25.1–35.5% by the presence of E. fetida. Importantly, TBOEP could accumulate in E. fetida (0.09–76.0 μg/kg) and the activation of cytochrome P450 and glutathione detoxification pathway promoted the metabolism of TBOEP in E. fetida. These findings link the biological responses and metabolic behavior of earthworms under pollution stress and provide fundamental data for the environmental risk assessment and pollution removal of OPFRs in soil.

MXenes-A New Class of Two-Dimensional Materials: Structure, Properties and Potential Applications.

A new class of two-dimensional nanomaterials, MXenes, which are carbides/nitrides/carbonitrides of transition and refractory metals, has been critically analyzed. Since the synthesis of the first family member in 2011 by Yury Gogotsi and colleagues, MXenes have quickly become attractive for a variety of research fields due to their exceptional properties. Despite the fact that this new family of 2D materials was discovered only about ten years ago, the number of scientific publications related to MXene almost doubles every year. Thus, in 2021 alone, more than 2000 papers are expected to be published, which indicates the relevance and prospects of MXenes. The current paper critically analyzes the structural features, properties, and methods of synthesis of MXenes based on recent available research data. We demonstrate the recent trends of MXene applications in various fields, such as environmental pollution removal and water desalination, energy storage and harvesting, quantum dots, sensors, electrodes, and optical devices. We focus on the most important medical applications: photo-thermal cancer therapy, diagnostics, and antibacterial treatment. The first results on obtaining and studying the structure of high-entropy MXenes are also presented.

Glycerol-assisted degradation of dibenzothiophene by Paraburkholderia sp. C3 is associated with polyhydroxyalkanoate granulation

Glycerol is a biodiesel byproduct. In the present study, glycerol was used as a co-substrate during biodegradation of dibenzothiophene (DBT) by Paraburkholderia sp. C3. Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent, ubiquitous and carcinogenic chemicals found in the environment. DBT is a major sulfur-containing PAH. The chemical properties of DBT make it an ideal model pollutant for examining the bioremediation of higher molecular weight PAHs. Bioremediation uses microbial catalysis for removal of environmental pollutants. Environmental microorganisms that encounter aromatic substrates such as heterocyclic PAHs develop unique characteristics that allow the uptake and assimilation of these cytotoxic substrates. Microbial adaptations include changes in membrane lipid composition, secretion of surface-active compounds and accumulation of lipid granules to withstand chemical toxicity. Biostimulation using more readily metabolized substrates can increase the biodegradation rate of PAHs, but the molecular mechanisms are not well understood. We analyzed the DBT biodegradation kinetics in C3, proteome changes and TEM micrographs in different culturing conditions. We utilized 2-bromoalkanoic lipid metabolic inhibitors to establish a correlation between polyhydroxyalkanoate (PHA) granule formation and the enhancement of DBT biodegradation induced by glycerol. This is the first description linking PHA biosynthesis, DBT biodegradation and 2-bromoalkanoic acids in a Paraburkholderia species.

Copper-based composites derived from metal-organic frameworks on carbohydrates-rich corncobs as efficient catalysts for organic compounds removal

It is of great significance to exploit environmentally friendly, efficient and economical catalysts for dealing with wastewater and other aquatic environments. In this study, a series of P-doped Cu/Cu2O/C heterostructures were obtained by controlled calcination of corncobs supported Cu-MOF in different temperature. Comprehensive structural characterizations indicate the polyhedron morphology and high porosity of HKUST-1-P@corncob-400. The composites were further explored as an efficient catalyst for catalytic reduction of 4-nitrophenol (4-NP). Remarkably, HKUST-1-P@corncob-400 could efficiently catalyze the reduction of 4-NP, and the reduction could be finished within 90 s with a 4-aminophenol (4-AP) selectivity of >99%, demonstrating the excellent performance of Cu-based catalysts for 4-NP reduction. The application scope could be further expanded to the catalytic reduction of ofloxacin and a conversion of 95.7% could be achieved within 10 min. Reproducibility studies and characterizations comprehensively demonstrate the promising potential of HKUST-1-P@corncob-400 acting as efficient catalyst for the reductive removal of environmental pollutants. This work provides a facile strategy for the fabrication of highly active catalysts for high-performance environmental purification, and the employment of renewable bioresources and functional MOFs represents a promising strategy for design and synthesis of highly active catalysts towards various advanced applications.

Study of photocatalytic activity of green synthesized nickel oxide nanoparticles in the degradation of acid orange 7 dye under visible light.

Environmental pollution is one of the most important problems that human beings face. Today, nanotechnology has played an important role in green chemistry and the use of nanoparticles in the removal of environmental pollutants is one of the newest methods of removing pollutants in the world. So, in this study, Nickel oxide nanoparticles (NiO NPs) of this work were successfully synthesizedviaa green method by the usage of nickel nitrate hexahydrate as the source of metal and Biebersteinia multifida extract as the stabilizing agent throughout different annealing temperatures. The physicochemical properties of the obtained NiO NPs were characterized through the application of scanning electron microscopy (SEM), energy dispersive X-ray (EDX), powder X-ray diffraction (PXRD), ultraviolet visible (UV-vis), and Raman analysis. According to the results of SEM and PXRD, the prepared product contained a satisfying distribution and very fine cubic structure with minimal accumulation. The average crystal size of prepared nanoparticles was obtained 54-58nm. The energy band gap of synthesized NiO NPs was calculated 3-3.7 using Tauc equation. The photocatalytic performance of NiO NPs was investigated under visible light through the decolourization reaction of acid orange 7 (AO7) dye in aqueous solution. Being composed at 300°C of annealing temperature, these nanoparticles exhibited excellent adsorption and photocatalytic activity (90.2%) toward AO7 dye. Therefore, it can be indicated that the synthesized NiO NPs demonstrated an excellent dispersion in dye solution, as well as considerable photocatalytic activity.

A Titania-Supported Polyoxometalate and Au Cocatalyst for Efficient Photocatalytic Environmental Remediation

Photocatalysis has been considered an effective method for environmental purification and pollutant removal, with many experiments having being performed. The sustainable development of environmentally friendly materials that can photocatalytically oxidize and degrade contaminants is widely studied. Here, we report the results of the photocatalytic oxidation of contaminants (over 99% conversion of the contaminants was achieved) on a tri-component photocatalyst by the simultaneous decoration of Au nanoparticles and a new type of Sn-substituted Keggin structure polyoxometalate (POM) on a TiO2 semiconductor (denoted as AuPT). The light absorption and the electron–hole pair separation capacity of TiO2 was significantly ameliorated on AuPT. The synergistic effect of the Au resonance energy transfer (RET) course and the POM redox transformation can be advantageous to the efficient transmission of photogenerated electrons and holes in a way that achieves efficient photocatalytic oxidation of contaminants.

Crude Oil Bioremediation - Genetically Modified Microorganisms for Poly-Aromatic Hydrocarbon Degradation

The process of Bioremediation uses the microorganisms/their enzymes to aid the degradation and removal of contaminants present in the environment. The microbial metabolic ability is used for degradation and removal of environmental pollutants providing an economically safer alternative compared to the rest of physicochemical methodologies. One of the hazardous organic priority pollutants are the Polyaromatic hydrocarbons (PAHs). There are a lot of public concerns and critical environmental challenges in the world because of being carcinogenically toxic and mutagenic properties, their ubiquitous distribution, recalcitrance and their environmental presence. The understanding about harmful effects of PAHs on ecosystems and human health has resulted in an interest of researchers on their degradation. Many types of microbes like bacteria, fungi, and algae are capable to use PAHs as carbon and energy source under aerobic and anaerobic conditions leading to their degradation or transformation. Microbial genetic makeup having genes conceal catabolic enzymes results in PAH-degradation mechanism. From the past twenty years, PAH- biodegradation mechanism, catabolic gene system encoding catabolic enzymes, and adaptation through genetics and regulations have been investigated in detail. This review is to attain an overview of the present knowledge of the genetically modified organisms in crude oil spills using PAH degradation mechanism.

Mechanisms for hydroxyl radical production and arsenic removal in sulfur-vacancy greigite (Fe3S4)

Herein, we systematically investigated the mechanisms of OH production and arsenic (As(III)) oxidation induced by sulfur vacancy greigite (Fe3S4) under anoxic and oxic conditions. Reactive oxygen species analyses revealed that sulfur vacancy-rich Fe3S4 (SV-rich Fe3S4) activated molecular oxygen to produce hydrogen peroxide (H2O2) via a two-electron reduction pathway under oxic conditions. Subsequently, H2O2 was decomposed to OH via the Fenton reaction. Additionally, H2O was directly oxidized to OH by surface high-valent iron (Fe(IV)) resulting from the abundance of sulfur vacancies in Fe3S4 under anoxic/oxic conditions. These differential OH-generating mechanisms of Fe3S4 resulted in higher OH production of SV-rich Fe3S4 compared to sulfur vacancy-poor Fe3S4 (SV-poor Fe3S4). Moreover, the OH production rate of SV-rich Fe3S4 under oxic conditions (19.3 ± 1.0 μM•h−1) was 1.6 times greater than under anoxic conditions (11.8 ± 0.4 μM•h−1). As(III) removal experiments and X-ray photoelectron spectra (XPS) showed that both OH production pathways were favorable for As(III) oxidation, and a higher concentration of As(V) was immobilized on the surface of SV-rich Fe3S4 under oxic conditions. This study provides new insights concerning OH production and environmental pollutants removal mechanisms on surface defects of Fe3S4 under anoxic and oxic conditions.

Novel fumed silica/g‐C3N4 composites for highly efficient removal of rhodamine B under visible light emitting diodes light irradiation

AbstractGraphitic carbon nitride (g‐C3N4) is a fascinating nonmetallic photocatalyst for the removal of environmental pollutants. The fumed silica/g‐C3N4 (gCN‐FS) composite photocatalysts were successfully fabricated by a combination of solvent volatilization and post‐annealing methods. The introduction of SiO2 not only widens the absorption range of visible light, but also enhances the specific surface area of g‐C3N4. The gCN‐FS‐3 composite has a BET surface area of 129.89 m2/g, which is ~3.3 times as much as that of g‐C3N4 (39.54 m2/g). The gCN‐FS composites have markedly improved rhodamine B (RhB) photodegradation activity in comparison to pure g‐C3N4, bulk g‐C3N4 and P25 under 557 nm yellow‐green light emitting diode light irradiation. The gCN‐FS‐3 has the highest RhB photodegradation rate, which is ~9.67‐, 11.81‐folds as compared to bare g‐C3N4 and bulk g‐C3N4, respectively. The coupling effect between the increase in specific surface areas and the inhibition effect of SiO2 on photogenerated electron/hole pairs recombination is responsible for the enhanced visible light photocatalytic activity of gCN‐FS composite. Superoxide and holes are responsible for the RhB photocatalytic degradation. Furthermore, no apparent loss of photocatalytic activity over five cycles is observed, which indicates that the gCN‐FS composites have considerable stability and reusability in the photodegradation process. The gCN‐FS composites show great promise in visible light driven photocatalysis for environmental applications.

Green photocatalyst Cu/NiO doped zirconia for the removal of environmental pollutants

Three distinct copper/nickel oxide doped zirconia (Cu-NiO-ZrO2) photocatalysts were synthesized using one pot hydrothermal method. In these synthesized photocatalysts Cu-NiO ratio were 1:1, 1:2, 2:1 while CuNiO to ZrO2 ratio was kept constant (1:4). It was observed that these prepared materials displayed strong photocatalytic properties for the reduction of 4-nitrophenol (NP) and degradation of methylene blue (MB) and methyl orange (MO) respectively. XRD pattern, BET surface area, SEM and EDX have determined the physical properties of these synthesized photocatalysts. The effect of initial dye concentration, photocatalyst dose, pH, and time on the efficiency of degradation were evaluated by selecting efficient catalyst for 4-nitrophenol (4-NP) reduction, methylene blue (MB) and methyl orange (MO) degradation respectively. It was found that the degradation efficiency of these pollutants decreased with increase in the solution’s pH and the initial concentration of dye while it enhanced by increasing the catalyst dose and irradiation reaction time during photocatalysis. Almost complete reduction of 4-NP was accomplished while using 20 mg/L of 4-NP and 0.02 g of catalyst within 5 min using 25 Mm NaBH4 solution. The reduction of 4-NP to 4-AP using Cu/NiO-ZrO2 photocatalyst follows pseudo-first order kinetics having a rate constant 0.882 min−1 with R2 value of 0.9957. In reactions of MB (50 mg/L) and MO (50 mg/L), approximately 99% degradation efficiency was achieved by using 0.03 g of catalyst dose with reaction time of 10 and 35 min, respectively.

Methods of synthesis, characteristics, and environmental applications of MXene: A comprehensive review

MXene, comprised of two-dimensional transition metal carbides/nitride, has emerged as a novel material suitable for environmental remediation of toxic compounds. Due to their inherent and superior physical and chemical properties, MXene is employed in separation techniques like photocatalysis, adsorption, and membrane separation. MXene is equipped with a highly hydrophilic surface, ion exchange property, and robust surface functional groups. In this review paper, a comprehensive discussion on the structural patterns, preparation, properties of MXene and its application for the removal of toxic pollutants like Radionuclide, Uranium, Thorium, and dyes is presented. The mechanism of removal of the pollutants by MXene is extensively reviewed. Synthesis of MXene based membranes, their properties, and application for water purification and properties were also discussed. This review will be highly helpful to understand critically the methods of synthesis and use of MXene material for priority environmental pollutants removal. In addition, the challenges behind the synthesis and use of MXene for decontamination of pollutants were reviewed and reported.

Microbial fuel cells for remediation of environmental pollutants and value addition: Special focus on coupling diatom microbial fuel cells with photocatalytic and photoelectric fuel cells

With the advent of global industrialisation and adaptation of smart life there is rise in anthropogenic pollution especially in water. Remediation of the pollutants (such as metals, and dyes) present in industrial effluents is possible via microbes and algae present in the environment. Microbes are used in a microbial fuel cell (MFC) for remediation of various organic and inorganic pollutants. However, for industrial scale application coupling the MFCs with photocatalytic and photoelectric fuel cell has a potential in improving the output of power. It can also be used for remediation of pollutants more expeditiously, conserving fossil fuels, cleaning environment, hence making the coupled hybrid fuel cell to run economically. Furthermore, such MFC inbuilt with algae in living or powder form give additional value addition products like biofuel, polysaccharides, biopolymers, and polyhydroxy alkanoates etc. This review provides bird’s eye view on the removal of environmental pollutants by different biological sources like bacteria and algae. The article is focussed on diatoms as potential algae since they are rich source of crude oil and high value added products in a hybrid photocatalytic MFC. It also covers bottle necks, challenges and future in this field of research.

Advances in biosorbents for removal of environmental pollutants: A review on pretreatment, removal mechanism and future outlook

Environmental pollutants are a serious threat for decades causing contamination of soil and water systems. The release from various industries is the main source of these pollutants. Biosorption has been accepted as an alternative eco-friendly green technology for the removal of various pollutants utilizing microbes such as bacteria, fungi and algae, and yeasts. This review features on overview of studies on materials as biosorbents, their pretreatment process, desorption of adsorbed pollutants from biosorbents, and safe disposal of biosorbent material in detail. Pretreatment is mainly performed for increasing the efficiency and adsorption rate which can be performed using various methods. Desorbing eluents can be used for recovering adsorbed pollutants and regeneration of biosorbents can be performed chemically, thermally, or electrochemical methods. In the case of large-scale commercial utilization of biosorbents, final disposal of biosorbents without any effects has paid better attention. Cost is also one of the major factors and it has an impact on the overall economy of the biosorption process. Additional efforts are required for discovering novel biosorbent materials and desorbing eluents for an economically feasible and efficient treatment process.

Co-regulation of dispersion, exposure and defect sites on CeO2 (111) surface for catalytic oxidation of Hg0

The additional cost of Hg0 capture in coal-fired power plants has facilitated the demand for environmental pollutants mitigation material for Hg0 oxidation to Hg2+ for an ultra-low Hg emission technology. Herein, a suite of CeO2-based catalysts were investigated aiming at ultra-low gaseous Hg0 emission at coal-fired power stations. Gaseous elemental mercury is feasible to be catalytically oxidized to Hg2+. The co-regulated dispersion, exposure and defect sites on CeO2 (111) surface with 2 wt% Ce and 8 wt% Mo compositions on γ-Al2O3 was found to be the most promising catalyst demonstrating a high catalytic oxidation efficiency, a broad operating temperature range and a low activation energy. Specifically, it is shown that the oxidation of Hg0 on the Ce-based catalysts can be enhanced by the addition of Mo (up to 8 wt%) via promoting the CeO2 (111) surface dispersion and exposure. Moreover, insights into the Ce and Mo synergistic interactions showed that it facilitated the formation of defect-containing surface sites. Besides, the co-regulation of dispersion, exposure and defect sites on CeO2 (111) surface was further studied by DFT calculations. This study provides a feasible approach in optimization of CeO2-based catalysts for catalytic oxidation of Hg0 to achieve efficient removal of environmental pollutants.

Co‐doping of P(V) and Ti(III) in leaf‐architectured TiO2 for enhanced visible light harvesting and solar photocatalysis

AbstractExtending the absorption spectrum of TiO2 to include more visible light is of great importance to boost the photocatalytic efficiency for hydrogen generation and environmental pollution removal. Chemical doping and microstructure optimization are both effective. However, integrating them into one system at a low cost is a big challenge. Herein, we reported that phosphorus(V) and Titanium(III) were codoped into leaf‐architectured TiO2 via a facile sol‐gel biotemplating approach, which leads to significantly enhanced visible light harvesting and solar photocatalysis. P(V) doping at a moderate level (1.76 atm%) stabilized Ti(III) to achieve heavy self‐doping (Ti(III):Ti(IV) = 1:44) and concurrent oxygen vacancies of high concentration. The bandgap was narrowed to be only 1.9~2.3 eV. The synergistic co‐doping, coupling with the leaf‐architecture, allows efficient light absorption of less than 539~653 nm, as well as improved charge separation/transfer. The solar photocatalytic degradation rate is 2.6 times higher than that for a commercial TiO2 of P25 towards crystal violet. This work would push forward leaf‐architectured TiO2 toward practical application in photocatalysis, given the abundance, low cost, and renewability of green leaves. The codoping strategy combining sol‐gel and biotemplating approaches is potential for the synthesis of photo‐response materials or systems beyond photocatalysis.

Gamma-ray initiated polymerization from polydopamine-modified MoS2 nanosheets with poly (ionic liquid) and their utilization for adsorptive organic dyes with enhanced efficiency

In this paper, we report the fabrication of ionic liquid (IL)-modified molybdenum disulfide (MoS2) composites via a simple but effective method, that relied on Gamma-ray-initiated polymerization of polydopamine (PDA) modified MoS2 nanosheets using IL as a monomer. The adsorptive removal of Congo red (CR) from aqueous medium by MoS2@PDA@IL composites was investigated. Batch experiments were carried out thoroughly to explore the effects of various experimental factors, such as contact time, containment initial concentration, and the function of pH and system temperature on the adsorption of MoS2@PDA@IL composites towards CR. Based on the experimental data, the adsorption kinetics, isotherms (Langmuir and Freundlich) and thermodynamics were also studied. We demonstrated that the adsorption of CR on MoS2@PDA@IL is a spontaneous and endothermic process. The amount of adsorbed CR of the MoS2@PDA@IL composites (Qe, max = 112.16 mg/g) is 2.77 times that of pristine MoS2 (Qe, max = 40.54 mg/g). The above results demonstrated that PIL functionalized MoS2 nanosheets are promising for adsorptive removal of environmental pollutants. More importantly, owing to the universal adhesion capability of polydopamine, the method might also be extended for the fabrication of other polymeric composites with different functions for various applications. Therefore, this work will attract interest from scientists in the materials, chemistry and environmental fields.

Toward broader applications of iron ore waste in pollution control: Adsorption of norfloxacin

Norfloxacin, a kind of antibiotic frequently detected in environments, represents a group of non-persistent organic pollutants with latent risks to the ecosystem. Iron ore waste, generated and accumulated in large quantities from the iron/steel industry, was evaluated as a potential sorbent for norfloxacin removal. Kinetics analysis showed that the adsorption process reached equilibrium at 72 h, and the adsorption process could be best defined by the pseudo-second-order kinetics with the primary mechanism of norfloxacin adsorption suggested to be cation exchange. Further, adsorption of norfloxacin to iron ore waste was shown to be facilitated by the pH range of 2–10, low cation concentration, and low temperature, which are characteristic of natural surface waters, suggesting the potential of practical applications in aquatic environments. These findings provide new insight into the potentials of beneficial reuse for iron ore waste in the adsorptive removal of environmental pollutants.

Nanozymes: A Promising Horizon for Medical and Environmental Applications

Nanozymes are nanomaterials that exhibited high enzymatic activities and considered as a better alternative to natural enzymes. These nanoparticles are characterized by unique properties such as high catalytic activity with high stability, easy and low cost preparation. The multi-functional feature of nanozymes enables them to be applied in a wide range of applications such as biosensing, immunoassays, diseases diagnosis and therapeutics as well environmental management. In this context, this review provides a comprehensive overview about these nanoparticles, especially their types, preparation, characterization and enzymatic activities. In addition, some of their potential applications in the biocontrol of multi-drug resistant bacteria, medical field as well as environmental pollutants detection and removal have been highlighted. Nanozymes with both unique physicochemical properties of nanoparticles and enzyme-mimicking catalytic properties will attract a broad interest of scientists and offer promising strategies for diagnosis and treatment of many diseases and handling current environmental problems.

A Review in Tetracycline Removal from Water Environment by Carbon Nanotubes Adsorption

Owing to the unique properties, carbon nanotubes (CNTs) have been widely reported as a desirable adsorbent for environmental pollutants removal. In this paper, the synthetic strategies of different kinds of CNTs and CNTs based composites, as well as their application in tetracycline antibiotics (TCs) removal were discussed. The adsorption process, performance, influence factors involved in the adsorption of tetracycline (TC) are highlighted in this review. In addition, the adsorption mechanism and limitations in adsorption TCs with CNTs are discussed.