Organic silicone sol-gel polymer as a noncovalent carrier of receptor proteins for label-free optical biosensor application

Fabrication of melamine formaldehyde/graphene oxide composite for efficient static and dynamic adsorption of lead ions from aqueous medium

The present work discusses the synthesis, characterization, and environmental applications of graphene oxide (GO), melamine formaldehyde resin (MF), and melamine formaldehyde/graphene oxide composite (MGO) for the efficient removal of Pb2+ from aqueous medium via batch and column procedures. TGA, XRD, TEM, zeta potential, nitrogen adsorption/desorption, ATR-FTIR, and other characterization techniques revealed that MGO is characterized by a greater surface area (609 m2/g), total pore volume (1.0106 cm3/g), pHPZC (6.5), and the presence of various surface chemical functional groups. The synthesized solid adsorbents were used in both static and dynamic adsorption processes to remove Pb2+, with varying application parameters such as pH, starting concentration, adsorbent dosage, and shaking time in the case of static adsorption method. While through the column adsorption process the effects of column bed height, flow rate, and starting Pb2+ were taken into consideration. Results of the batch adsorption demonstrated that MGO had the highest Langmuir adsorption capacity (201.5 mg/g), and the adsorption fit the nonlinear Langmuir adsorption model and Elovich kinetic models. The adsorption of Pb2+ onto all prepared solid materials is endothermic, spontaneous, and physical in nature, as demonstrated by thermodynamic studies. Column adsorption of Pb2+ well fitted by Thomas and Yoon Nelson nonlinear adsorption models. MGO showed a maximum column adsorption capacity of 168 mg/g when applying 4 cm, 15 mL/min, and 150 mg/L as bed height, flow rate, and initial Pb2+, respectively. With only a 12.6% reduction in its adsorption capacity, column regeneration showed that MGO exhibited a high degree of reusability even after five cycles of adsorption/desorption studies.

Nanoarchitectonics Design Strategy of Metal-Organic Framework and Bio-Metal-Organic Framework Composites for Advanced Wastewater Treatment through Adsorption

Freshwater depletion is an alarm for finding an eco-friendly solution to treat wastewater for drinking and domestic applications. Though several methods like chlorination, filtration, and coagulation-sedimentation are conventionally employed for water treatment, these methods need to be improved as they are not environmentally friendly, rely on chemicals, and are ineffective for all kinds of pollutants. These problems can be addressed by employing an alternative solution that is effective for efficient water treatment and favors commercial aspects. Metal organic frameworks (MOFs), an emerging porous material, possess high stability, pore size tunability, greater surface area, and active sites. These MOFs can be tailored; thus, they can be customized according to the target pollutant. Hence, MOFs can be employed as adsorbents that effectively target different pollutants. Bio-MOFs are a kind of MOFs that are incorporated with biomolecules, which also possess properties of MOFs and are used as a nontoxic adsorbent. In this review, we elaborate on the interaction between MOFs and target pollutants, the role of linkers in the adsorption of contaminants, tailoring strategy that can be employed on MOFs and Bio-MOFs to target specific pollutants, and we also highlight the effect of environmental matrices on adsorption of pollutants by MOFs.

Advances in boron nitride-based nanomaterials for environmental remediation and water splitting: a review

Boron nitride has gained wide-spread attention globally owing to its outstanding characteristics, such as a large surface area, high thermal resistivity, great mechanical strength, low density, and corrosion resistance. This review compiles state-of-the-art synthesis techniques, including mechanical exfoliation, chemical exfoliation, chemical vapour deposition (CVD), and green synthesis for the fabrication of hexagonal boron nitride and its composites, their structural and chemical properties, and their applications in hydrogen production and environmental remediation. Additionally, the adsorptive and photocatalytic properties of boron nitride-based nanocomposites for the removal of heavy metals, dyes, and pharmaceuticals from contaminated waters are discussed. Lastly, the scope of future research, including the facile synthesis and large-scale applicability of boron nitride-based nanomaterials for wastewater treatment, is presented. This review is expected to deliver preliminary knowledge of the present state and properties of boron nitride-based nanomaterials, encouraging the future study and development of these materials for their applications in various fields.

Ion-retention properties of graphene oxide/zinc oxide nanocomposite membranes at various pH and temperature conditions

Laminar graphene oxide (GO) is a promising candidate material for next-generation highly water-permeable membranes. Despite extensive research, there is little information known concerning GO's ion-sieving properties at high acidic/basic pH and temperatures. In this study, the ion-blockage properties of the pristine GO and GO/zinc oxide (ZnO) nanocomposite membranes were tested using a non-pressure-driven filtration setup over a wide range of pH and temperatures. The ZnO nanoparticles within the composite membranes were synthesized via the room-temperature oxidation of zinc acetate and zinc acrylate precursors and were uniformly distributed across the composite membrane. It is observed that partially replacing the zinc acetate precursor with zinc acrylate improves the blockage performance of the composite membranes under extreme basic conditions by 42%. Moreover, photocatalytically-reduced composite membranes blocked copper sulfate ions 28% more than as-prepared composite membranes. Further, it was discovered that the composition of the membrane plays a vital role in its ion blockage performance at higher temperatures.

Recent Advances on Porous Siliceous Materials Derived from Waste

In recent years, significant efforts have been made in view of a transition from a linear to a circular economy, where the value of products, materials, resources, and waste is maintained as long as possible in the economy. The re-utilization of industrial and agricultural waste into value-added products, such as nanostructured siliceous materials, has become a challenging topic as an effective strategy in waste management and a sustainable model aimed to limit the use of landfill, conserve natural resources, and reduce the use of harmful substances. In light of these considerations, nanoporous silica has attracted attention in various applications owing to the tunable pore dimensions, high specific surface areas, tailorable structure, and facile post-functionalization. In this review, recent progress on the synthesis of siliceous materials from different types of waste is presented, analyzing the factors influencing the size and morphology of the final product, alongside different synthetic methods used to impart specific porosity. Applications in the fields of wastewater/gas treatment and catalysis are discussed, focusing on process feasibility in large-scale productions.

Improved water purification by PVDF ultrafiltration membrane modified with GO-PVA-NaAlg hydrogel

This work presents a modified polyvinylidene fluoride (PVDF) ultrafiltration membrane blended with graphene oxide-polyvinyl alcohol-sodium alginate (GO-PVA-NaAlg) hydrogel (HG) and polyvinylpyrrolidone (PVP) prepared by the immersion precipitation induced phase inversion approach. Characteristics of the membranes with different HG and PVP concentrations were analyzed by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), contact angle measurement (CA), and Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). The FESEM images showed an asymmetric structure of the fabricated membranes, and possessing a thin dense layer over the top and a layer finger-like. With increasing HG content, membrane surface roughness increases so that highest surface roughness for the membrane containing 1wt% HG is with a Ra value of 281.4 nm. Also, the contact angle of the membrane reaches from 82.5° in bare PVDF membrane to 65.1° in the membrane containing 1wt% HG. The influences of adding HG and PVP to the casting solution on pure water flux (PWF), hydrophilicity, anti-fouling ability, and dye rejection efficiency were evaluated. The highest water flux reached 103.2 L/m² h at 3 bar for the modified PVDF membranes containing 0.3 wt% HG and 1.0wt% PVP. This membrane exhibited a rejection efficiency of higher than 92%, 95%, and 98% for Methyl Orange (MO), Conge Red (CR), and Bovine Serum Albumin (BSA), respectively. All nanocomposite membranes possessed a flux recovery ratio (FRR) higher than bare PVDF membranes, and the best anti-fouling performance of 90.1% was relevant to the membrane containing 0.3 wt% HG. The improved filtration performance of the HG-modified membranes was due to the enhanced hydrophilicity, porosity, mean pore size, and surface roughness after introducing HG.

Development of sustainable strontium ferrite graphene nanocomposite for highly effective catalysis and antimicrobial activity

Graphene oxide (GO) has layered structure with carbon atoms that are highly coated with oxygen-containing groups, increasing the interlayer distance while simultaneously making hydrophilic atomic-thick layers. It is exfoliated sheets that only have one or a few layers of carbon atoms. In our work, Strontium Ferrite Graphene Composite (SF@GOC) has been synthesized and thoroughly characterized by physico-chemical methods like XRD, FTIR, SEM-EDX, TEM, AFM, TGA and Nitrogen adsorption desorption analysis. A very few catalysts have been manufactured so far that are capable of degrading Eosin-Y and Orange (II) dyes in water by heterogeneous catalytic method. The current study offers an overview of the recyclable nanocomposite SF@GOC used in mild reaction conditions to breakdown the hazardous water pollutant dyes Eosin-Y (96.2%) and Orange (II) (98.7%). The leaching experiment has demonstrated that the use of the transition metals strontium and iron have not result in any secondary contamination. Moreover, antibacterial and antifungal assay have been investigated. SF@GOC has shown greater activity with bacterial and fungal species while compared with GO. FESEM analysis shows that the bactericidal mechanism for SF@GOC is same in both gram-negative bacteria. The difference in the antifungal activity among the candida strains can be correlated with the movement of ions release (slower and faster) of synthesized nanoscrolls in SF@GOC. In comparison to previous reports, this new environmentally safe and novel catalyst showed substantial degrading activity. It can also be applied to new multifunctional processes such as in the fields of composite materials, solar energy, heterogeneous catalysis and biomedical applications.

Reusable Sugar-Based Gelator for Marine Oil-Spill Recovery and Waste Water Treatment

In this work, the gelation ability of a series of novel pyridine-based glucose tailored gelators (DPHAEN, DPHABN, and DPHAHN) with a flexible alkyl chain has been examined in binary solvent mixtures using a number of techniques, for example, UV spectroscopy, FT-IR spectroscopy, NMR spectroscopy, rheology measurement, SEM, XRD, and computational study. Proposed herein is an environment-friendly method to realize toxic dye separation and oil/water separation. It has been found that gels in a selective binary solvent mixture are efficient reusable absorbers of toxic dye molecules. A new gravitational force-driven, simple one-step, toxic dye removal and oil-water separation method is presented for sustainable filtration of waste water and simultaneous collection of oil. The gel column also showed high stability and reusability over repeated use and can be easily scaled for efficient clean-up of a large number of toxic dyes and oil spills present in water. Studies also exposed that the gel column can simultaneously separate dye molecules and mineral oils from water. This simple, green, and efficient method overcomes a nontrivial hurdle for environmentally safe separation of toxic dyes as well as oil/water mixtures and offers insights into the design of advanced materials for practical oil/water separation.

ZnO/Graphene Composite from Solvent-Exfoliated Few-Layer Graphene Nanosheets for Photocatalytic Dye Degradation under Sunlight Irradiation

ZnO/graphene nanocomposites were prepared using a facile approach. Graphene nanosheets were prepared by ultrasonication-based liquid phase exfoliation of graphite powder in a low boiling point organic solvent, 1,2-Dichloroethane, for the preparation of ZnO/graphene nanocomposites. Structural properties of the synthesized ZnO/graphene nanocomposites were studied through powder XRD and micro-Raman analysis. The characteristic Raman active modes of ZnO and graphene present in the micro-Raman spectra ensured the formation of ZnO/graphene nanocomposite and it is inferred that the graphene sheets in the composites were few layers in nature. Increasing the concentration of graphene influenced the surface morphology of the ZnO nanoparticles and a flower shape ZnO was formed on the graphene nanosheets of the composite with high graphene concentration. The efficiencies of the samples for the photocatalytic degradation of Methylene Blue dye under sunlight irradiation were investigated and 97% degradation efficiency was observed. The stability of the nanocomposites was evaluated by performing five cycles, and 92% degradation efficiency was maintained. The observed results were compared with that of ZnO/graphene composite derived from other methods.

A Facile Synthesis and Properties of Graphene Oxide-Titanium Dioxide-Iron Oxide as Fenton Catalyst

Textile industries discharge wastewater in huge amount that contains several toxic contaminants, especially organic dyes. Organic dyes present in wastewater have many adverse effects on environment as well as on living organisms including human beings. The generation of a nanocomposite to trap the toxic organic dyes from wastewater is highly recommended. Herein, we report the preparation of graphene-iron-titanium oxide (GFT) nanocomposite using simple, practical, and cost-effective protocol. The prepared tri-nanocomposite was successfully recognized by employing several analytical techniques. Morphology of the prepared nanocomposites was assessed by SEM coupled with EDS (energy dispersive spectroscopy). HRTEM was used to measure the size of the nanocomposites with shape and morphology. The UV-visible absorption spectra of the nanocomposites were recorded by a UV-visible spectrophotometer. Finally, the crystal structures of the nanocomposites were confirmed by XRD. Moreover, we proposed a plausible mechanism to demonstrate the catalytic activity of GFT oxide nanocomposite for the degradation auramine (AM) dye via a heterogeneous Fenton process.

SnS2 Nanoparticles and Thin Film for Application as an Adsorbent and Photovoltaic Buffer

Energy consumption and environmental pollution are major issues faced by the world. The present study introduces a single solution using SnS₂ for these two major global problems. SnS₂ nanoparticles and thin films were explored as an adsorbent to remove organic toxic materials (Rhodamine B (RhB)) from water and an alternative to the toxic cadmium sulfide (CdS) buffer for thin-film solar cells, respectively. Primary characterization tools such as X-ray photoelectron spectroscopy (XPS), Raman, X-ray diffraction (XRD), and UV-Vis-NIR spectroscopy were used to analyze the SnS₂ nanoparticles and thin films. At a reaction time of 180 min, 0.4 g/L of SnS₂ nanoparticles showed the highest adsorption capacity of 85% for RhB (10 ppm), indicating that SnS₂ is an appropriate adsorbent. The fabricated Cu(In,Ga)Se₂ (CIGS) device with SnS₂ as a buffer showed a conversion efficiency (~5.1%) close to that (~7.5%) of a device fabricated with the conventional CdS buffer, suggesting that SnS₂ has potential as an alternative buffer.

Graphene Oxide-Doped Polymer Inclusion Membrane for Remediation of Pharmaceutical Contaminant of Emerging Concerns: Ibuprofen

The application of polymer inclusion membranes (PIMs) for the aquatic remediation of several heavy metals, dyes, and nutrients has been extensively studied. However, its application in treating organic compounds such as Ibuprofen, an emerging pharmaceutical contaminant that poses potential environmental problems, has not been explored satisfactorily. Therefore, graphene oxide (GO) doped PIMs were fabricated, characterized, and applied to extract aqueous Ibuprofen at varied pH conditions. The doped PIMs were synthesized using a low concentration of Aliquat 336 as carrier and 0, 0.15, 0.45, and 0.75% GO as nanoparticles in polyvinyl chloride (PVC) base polymer without adding any plasticizer. The synthesized PIM was characterized by SEM, FTIR, physical, and chemical stability. The GO doped PIM was well plasticized and had an optimal Ibuprofen extraction efficiency of about 84% at pH of 10 and 0.75% GO concentration. Furthermore, the GO doped PIM's chemical stability indicates better stability in acidic solution than in the alkaline solution. This study demonstrates that the graphene oxide-doped PIM significantly enhanced the extraction of Ibuprofen at a low concentration. However, further research is required to improve its stability and efficiency for the remediation of the ubiquitous Ibuprofen in the aquatic environment.

Advanced Photocatalysts Based on Conducting Polymer/Metal Oxide Composites for Environmental Applications

Photocatalysts provide a sustainable method of treating organic pollutants in wastewater and converting greenhouse gases. Many studies have been published on this topic in recent years, which signifies the great interest and attention that this topic inspires in the community, as well as in scientists. Composite photocatalysts based on conducting polymers and metal oxides have emerged as novel and promising photoactive materials. It has been demonstrated that conducting polymers can substantially improve the photocatalytic efficiency of metal oxides owing to their superior photocatalytic activities, high conductivities, and unique electrochemical and optical properties. Consequently, conducting polymer/metal oxide composites exhibit a high photoresponse and possess a higher surface area allowing for visible light absorption, low recombination of charge carriers, and high photocatalytic performance. Herein, we provide an overview of recent advances in the development of conducting polymer/metal oxide composite photocatalysts for organic pollutant degradation and CO2 conversion through photocatalytic processes.

Cadmium oxide nanoparticles/graphene composite: synthesis, theoretical insights into reactivity and adsorption study

Graphene-based metal oxide nanocomposites are interesting and promising kinds of nanocomposites due to their large specific area, fast kinetics, and specific affinity towards heavy metal contaminants. In this work, a facile and cost-effective route was used to synthesize CdO nanoparticles (CdO NPs) and graphene-based CdO nanocomposite (G-CdO). The prepared nanomaterials were characterized and explored for lead removal from water. Both CdO NPs and G-CdO composite exhibited excellent sorption capacity of 427 and 398 mg g-1, respectively, at pH 4.8 and T = 298 K, which was superior to individual graphene and many other adsorbents. The results indicated that the recovered nanomaterials endure 4 times recyclability retaining up to 89% lead uptake efficiency. To complement the experimental study, DFT calculations were performed to investigate the stability of the formed G-CdO composite compared to CdO NPs; the reactivity of G-CdO compared to plain graphene as well as the interaction insights between graphene and CdO clusters were studied using natural-bond-orbital (NBO), electron-localization-function (ELF) and reduced-density-gradient (RDG) analyses.

Photocatalytic self-cleaning properties of m-phenylene isophthalamide membranes enhanced by immobilization of GO-ZnO-Ag for dye wastewater disposal

Drawing self-cleaning technology into polymer membranes offers an extensive solution to overcome the membrane fouling obstacle. Herein, the GO-ZnO-Ag nano-hybrid particles with photocatalytic activity prepared via the microwave hydrothermal method were immobilized in poly(m-phenylene isophthalamide) (PMIA) membranes. Not only was the thorny issue in catalyst recovery avoided, but also the satisfactory photocatalytic self-cleaning performance of the polymer membrane was awarded. GO and noble metal silver nanoparticles (AgNPs) acted as a conductive electron transfer carrier and an electron host, respectively, which hindered the recombination rate of excited electrons and holes on ZnO under UV light. The UV-driven PMIA membrane photodegradation rates of MB and Cr(VI) were up to 97.2% and 94.3%, respectively, at 150 min on photodegradation kinetics. Also, MB was completely degraded at 180 min. For MB and Cr(VI) mix solutions, their degradation efficiencies were 78.1% and 71%, respectively. The BSA rejection rate of the modified polymer membrane was 93.8%, and the water flux was 408.8 (L·m−2·h−1). Permeability was maintained at a high level after repeated use. Therefore, the newly designed PMIA/GO-ZnO-Ag series membranes could expand the application of polymers in wastewater disposal industry.

Removal of Mn(II) from Acidic Wastewaters Using Graphene Oxide-ZnO Nanocomposites

Pollution due to acidic and metal-enriched waters affects the quality of surface and groundwater resources, limiting their uses for various purposes. Particularly, manganese pollution has attracted attention due to its impact on human health and its negative effects on ecosystems. Applications of nanomaterials such as graphene oxide (GO) have emerged as potential candidates for removing complex contaminants. In this study, we present the preliminary results of the removal of Mn(II) ions from acidic waters by using GO functionalized with zinc oxide nanoparticles (ZnO). Batch adsorption experiments were performed under two different acidity conditions (pH1 = 5.0 and pH2 = 4.0), in order to evaluate the impact of acid pH on the adsorption capacity. We observed that the adsorption of Mn(II) was independent of the pH_PZC value of the nanoadsorbents. The qmax with GO/ZnO nanocomposites was 5.6 mg/g (34.1% removal) at pH = 5.0, while with more acidic conditions (pH = 4.0) it reached 12.6 mg/g (61.2% removal). In turn, the results show that GO/ZnO nanocomposites were more efficient to remove Mn(II) compared with non-functionalized GO under the pH2 condition (pH2 = 4.0). Both Langmuir and Freundlich models fit well with the adsorption process, suggesting that both mechanisms are involved in the removal of Mn(II) with GO and GO/ZnO nanocomposites. Furthermore, adsorption isotherms were efficiently modeled with the pseudo-second-order kinetic model. These results indicate that the removal of Mn(II) by GO/ZnO is strongly influenced by the pH of the solution, and the decoration with ZnO significantly increases the adsorption capacity of Mn(II) ions. These findings can provide valuable information for optimizing the design and configuration of wastewater treatment technologies based on GO nanomaterials for the removal of Mn(II) from natural and industrial waters.

Preparation of Carbon-Covered Phosphorus-Modified Alumina with Large Pore Size and Adsorption of Rhodamine B

In this study, phosphorus-modified alumina with large pore size was synthesized through a coprecipitation method. The carbon-covered, phosphorus-modified alumina with large pores was prepared by impregnating with glucose and carbonizing to further improve the adsorption of organic dyes. The morphology and structure of these composites were characterized by various analysis methods, and Rhodamine B (RhB) adsorption was also examined in aqueous media. The results showed that the specific surface area and pore size of the phosphorus-modified alumina sample AP7 (prepared with a P/Al molar ratio of 0.07) reached 496.2 m²·g⁻¹ and 21.9 nm, while the specific surface area and pore size of the carbon-covered phosphorus-modified alumina sample CAP7–27 (prepared by using AP7 as a carrier for glucose at a glucose/Al molar ratio of 0.27) reached 435.3 m²·g⁻¹ and 21.2 nm. The adsorption experiment of RhB revealed that CAP7–27 had not only an equilibrium adsorption capacity of 198 mg·g⁻¹, but also an adsorption rate of 162.5 mg·g⁻¹ in 5 min. These superior adsorption effects can be attributed to the similar pore structures of CAP7–27 with those of alumina and the specific properties with those of carbon materials. Finally, the kinetic properties of these composites were also studied, which were found to be consistent with a pseudo-second-order kinetic model and Langmuir model for isothermal adsorption analysis. This study indicates that the prepared nanomaterials are expected to be promising candidates for efficient adsorption of toxic dyes.

rGO-ZnO nanocomposites as efficient photocatalyst for degradation of 4-BP and DEP using high temperature refluxing method in in-situ condition

Persistent organic pollutants (mainly aromatic compounds) such as bromophenol and diethyl phthalate are dangerous and act as primary contaminants in aqueous system. In this study, efficient reduced graphene oxide zinc oxide (rGO-ZnO) nanocomposites were synthesized by using a simple and facile method for photocatalytic degradation of 4-Bromophenol (4-BP) and diethyl phthalate (DEP). The rGO-ZnO (rGZ) nanocomposites (NCs) with different weight ratio of rGO and ZnO (coded as rGZ-1, rGZ-2, rGZ-5 and rGZ-10) were synthesized via high temperature refluxing method. The crystalline structure and phase, surface morphological study, optical properties, crystal defects and existence of functional groups in rGZ NCs were studied by X-ray diffraction (XRD), field-emission-scanning electron microscope (FE-SEM), UV-Visible diffuse reflectance spectroscopy (DRS), Raman spectroscopy and FT-IR analysis, respectively. The elimination of 4-BP and DEP from water by UV-light exposure was considered to estimate the photocatalytic efficiency of prepared rGZ NCs. The maximum elimination of 4-BP and DEP via photodegradation (advanced oxidation process) was found about 99.04% and 98.63% over rGZ NCs after 180 min UV irradiation, respectively. The photodegradation study was examined by using high performance liquid chromatography (HPLC) technique. This study confirms the efficient photocatalytic activity of rGZ-5 towards degradation of 4-BP and DEP. Finally, degradation mechanism has been proposed for the degradation of 4-BP and DEP.

Experimental and theoretical investigations of methyl orange adsorption using boron nitride nanosheets

Fractions of dyes, that are used in large quantities for various applications, are lost during the dying process and contaminate water. In order to avoid their harmful effect on human health, boron nitride nanosheets (BNNSs) have been synthesized in this work and their adsorption behavior for the removal of anionic methyl orange (MO) dye from aqueous solution has been reported. The effect of pH, contact time, and initial dye concentration has been investigated on MO to find the optimum pH, equilibrium and adsorption capacity of the synthesized BNNSs. The adsorption kinetics and isotherm models showed that pseudo-second-order (PSO) kinetic and Freundlich isotherm models were being followed during the adsorption, respectively. The experimental maximum adsorption capacity of the synthesized adsorbent was found to be 575.0 mg g-1, which is due to the strong electrostatic attraction between the negatively charged MO and positively charged BNNSs. Furthermore, density functional theory (DFT) calculations have also been performed to investigate the nature and feasibility of the adsorption process, the interactions of MO dye molecules with the adsorbent, and the adsorption capacity of BNNSs. The theoretical and experimental studies suggest that the adsorption process is physical in nature. It was found that negative charge transfer occurred from MO to BNNSs with high chemical potential suggesting high chemical activity and a decrease in band gap after the adsorption process. These theoretical and experimental findings demonstrate the potential of BNNSs as adsorbents for commercial applications.

Photocatalytic performance improvement by utilizing GO_MWCNTs hybrid solution on sand/ZnO/TiO2-based photocatalysts to degrade methylene blue dye

In this work, sand/zinc oxide (ZnO)/titanium dioxide (TiO₂)-based photocatalysts were hybridized with graphene oxide (GO) and GO_multi-walled carbon nanotubes (MWCNTs) hybrid solution. The novel hybrid was then used in photocatalysis to degrade dye contamination. The nanocomposite photocatalyst was initially fabricated by growing ZnO nanorods (NRs) via sol-gel immersion followed by synthesizing TiO₂ NRs for different times (5 and 20 h) using a hydrothermal method on sand as a substrate. Prior to the hybridization, the initial GO was synthesized using electrochemical exfoliation and further mixed with 1 wt% MWCNTs to form GO_MWCNTs hybrid solution. The synthesized GO and GO_MWCNTs hybrid solution were then incorporated onto sand/ZnO/TiO₂ nanocomposite-based photocatalysts through immersion. Various sand/ZnO/TiO₂-based photocatalysts were then tested for methylene blue (MB) dye degradation within 3 days. On the basis of UV-Vis measurement, the highest MB degradation was achieved by using sand/ZnO NRs/TiO₂ NRs (5 h)/GO_MWCNTs (92.60%). The high surface area and high electrical conductivity of GO_MWCNTs prolonged the lifetime of electron/hole separation and thus enhanced the photocatalytic performance.

Electronic structure modelling of the edge-functionalisation of graphene by MnxOy particles

The use of graphenic carbon is attractive as a basal or intermediate support for catalytic particles in advanced catalytic electrodes. This popularity is motivated by its excellent electrical properties and ability to form foliated conformal coatings of exceptional surface area and flexibility. Surface- and edge-functionalisation of graphene sheets affords diverse routes to the covalent attachment of candidate catalytic species. Of particular interest to advanced water oxidation is the possibility of covalent attachment of MnxOy species partially recapitulating the chemistry of the Mn4O5Ca active site of Photosystem II (PSII), which achieves the four-electron oxidation of water under physiological conditions. Here, we report aperiodic density functional theory (DFT) investigations of candidate attachment geometries for a variety of manganese oxide particles to graphene sheets. We find that the flexibility of graphene sheets as well as the conformational degrees of freedom of candidate edge functionalisation permits a large variety of realistic attachment geometries that can act as attachment sites for molecular manganese-oxide species or nuclei for the growth of periodic manganese oxides. We find that substantially simplified models of graphene attachment afford an excellent compromise between computational efficiency, tractability, and accuracy, and characterise the accuracy of these models in detail.

Application of graphene-based materials for removal of tetracyclines using adsorption and photocatalytic-degradation: A review

Tetracyclines are extensively used to treat human and animal infectious diseases due to its effective antimicrobial activities. About 70-90% of its parent materials are released into the environment through urine and feces, implying they are the most frequently detected antibiotics in the environment with high ecological risks. Adsorption and photocatalysis have been promising techniques for the removal of tetracyclines due to effectiveness and efficiency. Graphene-based materials provide promising platforms for adsorptive and photocatalytic removal of tetracyclines from aqueous environment owning to distinctive remarkable physicochemical, optical, and electrical characteristics. Herein, we intensively reviewed the available literatures in order to provide comprehensive insight about the applications and mechanisms of graphene-based materials for removal of tetracyclines via adsorption and phototocatalysis. The synthesis methods of graphene-based materials, the tetracycline adsorption and photocatalytic-degradation conditions, and removal mechanisms have been extensively discussed. Finally concluding remarks and future perspectives have been deduced and recommended to stimulate further researches in the subject. The review study can be used as theoretical guideline for further researchers to improve the current approaches of material synthesis and application towards tetracyclines removal.

Catalytic degradation of chlorpheniramine over GO-Fe3O4 in the presence of H2O2 in water: The synergistic effect of adsorption

Chlorpheniramine is a pharmaceutical widely used and found in water environments. Besides hormone disruption and adverse environmental effects, chlorpheniramine forms carcinogenic nitrosamines during disinfection. We have demonstrated previously the efficient adsorption of chlorpheniramine from aqueous solution onto graphene oxide-magnetite composite (GO-Fe₃O₄). The present study focused on the elimination of chlorpheniramine and the formation of nitrosamine byproducts during reaction with H₂O₂ over GO-Fe₃O₄ catalyst. The effects of the morphology of GO-Fe₃O₄ in terms of iron fraction, pH, concentrations of H₂O₂ and organic matters on chlorpheniramine removal in the GO-Fe₃O₄-H₂O₂ system were investigated. Chlorpheniramine was efficiently removed at pH 9 when GO-Fe₃O₄ had a higher micropore volume and surface area. Kinetics study showed that both oxidation (k = 5.1(±0.2) × 10^-3 (mg g^-1)^-1 min^-1) and adsorption reactions (k = 2.7(±0.1) × 10^-3 (mg g^-1)^-1 min^-1) fitted well with the second-order kinetics model. The adsorption sites on the GO-Fe₃O₄ surface could be different from those involved during catalytic oxidation. Chlorpheniramine removal decreased by 44.9% in the 5th cycle without regeneration due to the structural fracture of GO-Fe₃O₄. A tentative pathway of chlorpheniramine degradation and nitrosamine formation by GO-Fe₃O₄-H₂O₂ was proposed. GO-Fe₃O₄ was an adsorbent and effective catalyst in chlorpheniramine degradation by H₂O₂ that exhibited limited nitrosamine formation at moderate reaction time.

Reduced Graphene Oxide/ZnIn2S4 Nanocomposite Photocatalyst with Enhanced Photocatalytic Performance for the Degradation of Naproxen under Visible Light Irradiation

The development of photocatalysts with visible light response is of great significance to cope with energy crisis and environmental remediation. In this study, a visible light-driven photocatalyst reduced graphene oxide/ZnIn2S4 (rGO/ZIS) was prepared by a facile one-pot hydrothermal method. The photocatalyst was used for the degradation of naproxen under visible light illumination and it exhibited remarkably degradation efficiency (nearly 99% within 60 min). The improved photocatalytic degradation performance can be attributed to the enhancement of light adsorption capacity and effective separation of photoinduced electron–hole pairs. The reactive species quenching experiments and EPR measurements demonstrated that superoxide radical (–O2−) and hole (h+) play a dominant role in the photocatalytic degradation reactions. In addition, the degradation intermediates were identified and the degradation pathway was suggested.

Removal of Pharmaceutical Contaminants in Wastewater Using Nanomaterials: A Comprehensive Review

BACKGROUND

The limitless presence of pharmaceutical contaminants in discharged wastewater has emerged as a threat to aquatic species and humans. Their presence in drinking water has although raised substantial concerns, very little is known about the fate and ecological impacts of these pollutants. As a result, these pollutants are inevitably introduced to our food chain at trace concentrations. Unfortunately, the conventional wastewater treatment techniques are unable to treat pharmaceuticals completely with practical limitations. The focus has now been shifted towards nanotechnology for the successful remediation of these persistent pollutants. Thus, the current review specifically focuses on providing readers brief yet sharp insights into applications of various nanomaterials for the removal of pharmaceutical contaminants.

METHODS

An exhaustive collection of bibliographic database was done with articles having high impact and citations in relevant research domains. An in-depth analysis of screened papers was done through standard tools. Studies were categorized according to the use of nanoscale materials as nano-adsorbents (graphene, carbon nanotubes), nanophotocatalysts (metal, metal oxide), nano-filtration, and ozonation for promising alternative technologies for the efficient removal of recalcitrant contaminants.

RESULTS

A total of 365 research articles were selected. The contemporary advancements in the field of nanomaterials for drinking and wastewater treatment have been thoroughly analyzed along with their future perspectives.

CONCLUSION

The recommendations provided in this article will be useful to adopt novel strategies for on-site removal of the emerging contaminants in pharmaceutical effluents and related industries.

Sulfonated polyaniline-encapsulated graphene@graphitic carbon nitride nanocomposites for significantly enhanced photocatalytic degradation of phenol: a mechanistic study

The photocatalytic degradation of phenol through -s-PANI@g-C₃N₄ and its nanocomposites with graphene.

Progress in biomimetic leverages for marine antifouling using nanocomposite coatings

Because of the environmental and economic casualties of biofouling on maritime navigation, modern studies have been devoted toward formulating advanced nanoscale composites in the controlled development of effective marine antifouling self-cleaning surfaces.

Three-dimensional zinc oxide nanostars anchored on graphene oxide for voltammetric determination of methyl parathion

The two-step microwave method was used to synthesize zinc oxide nanostars linked to graphene oxide (GO) nanosheets. The material was used to modify a screen printed carbon electrode (SPCE) and then explored as a binder-free electrocatalyst for the electrochemical determination of methyl parathion (MP). The morphology and crystallinity of the material were characterized by various techniques. The modified SPCE shows extraordinary electrochemical performances for sensitive determination of MP. Figures of merit include (a) a wide linear dynamic range (0.03-670 μM), (b) a low detection limit (1.2 nM; at S/N = 3), (c) a comparably low working voltage (-0.69 V vs. Ag/AgCl); and (d) an excellent sensitivity (16.5 μA μM^-1 cm^-2) that surpasses other modified electrodes. The sensor was successfully applied to the determination of MP, even in the presence of other common electroactive interference, in (spiked) fruits and vegetables. Graphical abstractGraphene oxide anchored three-dimensional zinc oxide nanostars were used to coat electrode for the sensing of methyl parathion (MP) by voltammetry.

Adsorptive removal and photocatalytic degradation of organic pollutants using metal oxides and their composites: A comprehensive review

Metal oxide nanomaterials and their composites are comprehensively reviewed for water remediation. The controlled morphological and textural features, variable surface chemistry, high surface area, specific crystalline nature, and abundant availability make the nanostructured metal oxides and their composites highly selective materials for efficient removal of organic pollutants based on adsorption and photocatalytic degradation. A wide range of metal oxides like iron oxides, magnesium oxide, titanium oxides, zinc oxides, tungsten oxides, copper oxides, metal oxides composites, and graphene-metal oxides composites having variable structural, crystalline and morphological features are reviewed emphasizing the recent development, challenges, and opportunities for adsorptive removal and photocatalytic degradation of organic pollutants viz. dyes, pesticides, phenolic compounds, and so on. It also covers the deep discussion on the photocatalytic mechanism of metal oxides and their composites along with the properties relevant to photocatalysis. High photodegradation efficiency, economically-viable approaches for the preparation of photocatalytic materials, and controlled band-gap engineering make metal oxides highly efficient photocatalysts for degradation of organic pollutants. The review would be an excellent resource for researchers who are currently focusing on metal oxides-based materials for water remediation as well as for those who are interested in adsorptive and photocatalytic applications of metal oxides and their composites.

Graphene oxide-based materials for efficient removal of heavy metal ions from aqueous solution: A review

Graphene with atomic layer of sp²-hybridized carbon atoms in a hexagonal structure has attracted multidisciplinary attention since its discovery. Due to the inherent advantages of large specific surface area and abundant functional groups, its derivative graphene oxide (GO) nanomaterials have achieved large-scale development in effective pollution treatment. In the past few years, novel GO-based nanomaterials through coupling with other nanomaterials have been synthesized with significant process and applied for efficient elimination of different kinds of pollutants. This paper aims to summarize recent research results on the excellent removal ability of GO-based nanomaterials for various heavy metal ions in aqueous solutions. The synthesis, adsorption process characteristics and interaction mechanism of the adsorbent are emphasized and discussed. The effects of various environmental conditions are outlined. At last, a brief summary, perspective and outlook are presented. This review is intended to provide some thrilling information for the design and manufacture of GO-based nanomaterials for the elimination of heavy metal ions from wastewater in environmental pollution management.

Comparative toxicity evaluation of graphene oxide (GO) and zinc oxide (ZnO) nanoparticles on Drosophila melanogaster

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Synthesis and complete characterization of Green and Chemical Zinc Oxide nanoparticles and Graphene Oxide nanoparticles.

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Comparison of Graphene Oxide nanoparticles with Zinc oxide nanoparticles formed through both Green and Chemical route of synthesis.

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Comparative toxicity evaluation of these real world nanoparticles on Drosophila melanogaster using various assays.

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Observations revealed that different biological responses were caused in the flies due to these nanomaterials that proved their toxicity at different concentrations upon prolonged exposures.

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Cues to the prospect of these nanoparticles in the field of insect and pest management.

Engineered nanomaterials consisting of multiple nanoparticles (NPs) are finding their use in fields as wide and diverse as medicine, environment, cosmetics, energy and electronics. However, health and environmental impacts of these NPs need to be discerned individually to understand their true toxicity. Due to the promising application of upcoming material like GO-ZnO nanocomposite, the toxicity of ZnO and GO NPs was evaluated and compared individually in our study. This study compares the toxicity of Graphene Oxide (GO) NPs and Zinc Oxide (ZnO) NPs synthesized by Green method and Chemical method on Drosophila melanogaster. The GO, Chemical ZnO and Green ZnO NPs were synthesized and characterized using SEM, HR-TEM, FT-IR, UV–vis, EDX, XRD and DLS studies. NPs were comparatively analyzed for their cytotoxic and neurotoxic behaviors using different assays like MTT assay, mortality rate, larval crawling and climbing assay, total protein content analysis for evaluating the toxic potential of each of these NPs at different concentrations of use. Green ZnO were found to be least cytotoxic while Chemical ZnO caused the most cell damage. GO were found to have intermediary cytotoxicity. However, a different trend was observed with neurotoxicity wherein Green ZnO reportedly affected the neuromuscular coordination the most, while GO was found to have the least affect. This study provided insights into the different toxic effects caused by GO and ZnO NPs on Drosophila as well as comparative toxic effects of Chemical vs Green ZnO NPs.

Graphene based adsorbents for remediation of noxious pollutants from wastewater

The contamination of water resources with noxious pollutants is a serious issue. Many aquatic systems are contaminated with different toxic inorganic and organic species; coming to wastewater from various anthropogenic sources such as industries, agriculture, mining, and domestic households. Keeping in view of this, wastewater treatment appears to the main environmental challenge. Adsorption is one of the most efficient techniques for removing all most all types of pollutants i.e. inorganics and organics. Nowadays, graphene and its composite materials are gaining importance as nano adsorbents. Graphene; a two-dimensional nanomaterial having single-atom graphite layer; has attracted a great interest in many application areas (including wastewater treatment) due to its unique physico-chemical properties. The present paper is focused on the remediation of noxious wastes from wastewater using graphene based materials as adsorbents, and it contains all the details on materials - i.e., from their synthesis to application in the field of wastewater treatment (removal of hazardous contaminants of different chemical nature - heavy and rare-earth metal ions, and organic compounds - from wastewater effluents. The efficiency of the adsorption and desorption of these substances is considered. Certainly, this article will be useful for nano environmentalist to design future experiments for water treatment.

Enhanced photocatalytic degradation of methyl orange by porous graphene/ZnO nanocomposite

Degrading aquatic organic pollutants efficiently is very important but strongly relied on the design of photocatalysts. Porous graphene could increase photocatalytic performance of ZnO nanoparticles by promoting the effective charge separation of electron-hole pairs if they can be composited. Herein, porous graphene, ZnO nanoparticles and porous graphene/ZnO nanocomposite were prepared by fine tuning of partial combustion, which graphene oxide imperfectly covered by the layered Zn salt was combusted under muffle furnace within few minutes. Resulting ZnO nanoparticles (32-72 nm) are dispersed uniformly on the surface of graphene sheets, the pore sizes of porous graphene are in the range from ∼3 to ∼52 nm. The synthesized porous graphene/ZnO nanocomposite was confirmed to show enhanced efficiency under natural sunlight irradiation compared with pure ZnO nanoparticles. Using porous graphene/ZnO nanocomposite, 100% degradation of methyl orange can be achieved within 150 min. The synergetic effect of photocatalysis and adsorption is main reason for excellent MO degradation of PG/ZnO nanocomposite. This work may offer a new route to accurately prepare porous graphene-based nanocomposite and open a door of their applications.

Advances in the applications of graphene adsorbents: from water treatment to soil remediation

Graphene, a novel carbon allotrope, is single-layered graphite with honeycomb lattice. Its unique structure endows graphene many outstanding physical/chemical properties and a large surface area, which are beneficial to its applications in many areas. The potential applications of graphene in pollution remediation are adsorption, membrane separation, catalysis, environmental analysis, and so on. The adsorption efficiency of graphene adsorbents largely depends on its surface area, porous structure, oxygen-containing groups and other functional groups, adsorption conditions, and also the properties of adsorbates. With appropriate modifications, graphene materials are mostly efficient adsorbents for organic pollutants (e.g. dyes, pesticides, and oils) and inorganic pollutants (e.g. metal ions, nonmetal ions, and gas). Since our first report of graphene adsorbents in 2010, plenty of studies have been dedicated to developing various graphene adsorbents and to evaluating their performance in treating contaminated water. Recently, there is a growing trend in graphene adsorbents that could be applied in soil remediation, where the situation is much more complicated than in aqueous systems. Herein, we review the design of graphene adsorbents for water treatment and analyze their potential in soil remediation. Several suggestions to accelerate the research on graphene-based soil remediation technology are proposed.

An insight into Cadmium poisoning and its removal from aqueous sources by Graphene Adsorbents

Graphene alone, in modified form or its composites had find their explicit position in the field of adsorption technology and hence assist in detection and removal of heavy metals like Cd (permissible limit 0.1 mg/L), which can cause various physiological problems if entered in variety of biota. Attributed to their unique physiognomies graphene-based adsorbent had classed themselves superior as compared to other carbonaceous adsorbent like CNT's or activated carbon, etc. This assessment summarizes the validity of graphene and its composite as a superior adsorbent for decontamination of Cd from aqueous environment; in addition, this evaluation also pronounces the toxicity profile of trace graphene and necessity of regeneration of the adsorbent.