Functionalization of MCM-41 with titanium oxynitride deposited via PECVD for enhanced removal of methylene blue

Silica-supported ionic liquid for efficient gaseous arsenic oxide removal through hydrogen bonding

The emission of highly-toxic gaseous As2O3 (As2O3 (g)) from nonferrous metal smelting poses environmental concerns. In this study, we prepared an adsorbent (SMIL-X) by loading an ionic liquid (IL) ([HOEtMI]NTf2) into MCM-41 through an impregnation-evaporation process and then applied it to adsorb As2O3 (g). SMIL-20% exhibited an As2O3 (g) adsorption capacity of 35.48 mg/g at 400 °C, which was 490% times higher than that of neat MCM-41. Characterization of SMIL-X indicated that the IL was mainly supported on MCM-41 through O-H…O bonds formed between the hydroxyl groups (-OH) and the silanol groups (Si-OH) and the O-H…F bonds formed between the C-F groups and the Si-OH groups. The hydrogen bonds significantly contributed to the adsorption of As2O3 (g), with -NH and -OH groups forming hydrogen bonds with As-O species (i.e., N-H…O and O-H…O). This showed superior performance to traditional adsorbents that rely on van der Waals forces and chemisorption. Moreover, after exposure to high concentrations of SO2, the adsorption capacities remained at 76% of their initial values, demonstrating some sulfur resistance. This study presents an excellent adsorbent for the purification of As2O3 (g) and shows promising application potential for treating flue gas emitted by nonferrous metal smelting processes.

Anaerobic Membrane Bioreactor (AnMBR) for the Removal of Dyes from Water and Wastewater: Progress, Challenges, and Future Perspectives

The presence of dyes in aquatic environments can have harmful effects on aquatic life, including inhibiting photosynthesis, decreasing dissolved oxygen levels, and altering the behavior and reproductive patterns of aquatic organisms. In the initial phase of this review study, our aim was to examine the categories and properties of dyes as well as the impact of their toxicity on aquatic environments. Azo, phthalocyanine, and xanthene are among the most frequently utilized dyes, almost 70–80% of used dyes, in industrial processes and have been identified as some of the most commonly occurring dyes in water bodies. Apart from that, the toxicity effects of dyes on aquatic ecosystems were discussed. Toxicity testing relies heavily on two key measures: the LC50 (half-lethal concentration) and EC50 (half-maximal effective concentration). In a recent study, microalgae exposed to Congo Red displayed a minimum EC50 of 4.8 mg/L, while fish exposed to Disperse Yellow 7 exhibited a minimum LC50 of 0.01 mg/L. Anaerobic membrane bioreactors (AnMBRs) are a promising method for removing dyes from water bodies. In the second stage of the study, the effectiveness of different AnMBRs in removing dyes was evaluated. Hybrid AnMBRs and AnMBRs with innovative designs have shown the capacity to eliminate dyes completely, reaching up to 100%. Proteobacteria, Firmicutes, and Bacteroidetes were found to be the dominant bacterial phyla in AnMBRs applied for dye treatment. However, fouling has been identified as a significant drawback of AnMBRs, and innovative designs and techniques are required to address this issue in the future.

Hierarchically porous and mechanically stable monoliths from ordered mesoporous silica and their water filtration potential

Mechanically stable structures with interconnected hierarchical porosity combine the benefits of both small and large pores, such as high surface area, pore volume, and good mass transport capabilities. Hence, lightweight micro-/meso-/macroporous monoliths are prepared from ordered mesoporous silica COK-12 by means of spark plasma sintering (SPS, S-sintering) and compared to conventionally (C-) sintered monoliths. A multi-scale model is developed to fit the small angle X-ray scattering data and obtain information on the hexagonal lattice parameters, pore sizes from the macro to the micro range, as well as the dimensions of the silica population. For both sintering techniques, the overall mesoporosity, hexagonal pore ordering, and amorphous character are preserved. The monoliths' porosity (77-49%), mesopore size (6.2-5.2 nm), pore volume (0.50-0.22 g cm^-3), and specific surface area (451-180 m² g^-1) decrease with increasing processing temperature and pressure. While the difference in porosity is enhanced, the structural parameters between the C-and S-sintered monoliths are largely converging at 900 °C, except for the mesopore size and lattice parameter, whose dimensions are more extensively preserved in the S-sintered monoliths, however, coming along with larger deviations from the theoretical lattice. Their higher mechanical properties (biaxial strength up to 49 MPa, 724 MPa HV 9.807 N) at comparable porosities and ability to withstand ultrasonic treatment and dead-end filtration up to 7 bar allow S-sintered monoliths to reach a high permeance (2634 L m^-2 h^-1 bar^-1), permeability (1.25 × 10^-14 m²), and ability to reduce the chemical oxygen demand by 90% during filtration of a surfactant-stabilized oil in water emulsion, while indicating reasonable resistance towards fouling.

Removal of PFASs from water by carbon-based composite photocatalysis with adsorption and catalytic properties: A review

Per- and polyfluoroalkyl substances (PFASs) are a class of persistent organic pollutants widely distributed in aquatic environments. The adsorption and photocatalytic methods have been widely used to remove PFASs in water because of their respective advantages. Still, they have apparent defects when used alone. Therefore, the adsorption and photocatalytic technologies are combined through suitable preparation methods, and the excellent properties of the two are used to synergize the treatment of organic pollutants. This strategy of "concentrating" pollutants and then degrading them in a centralized manner plays an essential role in removing trace PFASs. Nevertheless, a review focusing on this kind of adsorption photocatalyst system is lacking. This review will fill this gap and provide a reference for developing a carbon-based composite photocatalyst. Firstly, different carbon-based composite photocatalysts are reviewed in detail, focusing on the differences in various composite materials' excellent adsorption and catalytic properties. Secondly, the factors influencing the removal effect of carbon-based composite photocatalysts are discussed. Thirdly, the removal mechanism of carbon-based composite photocatalysts is summarized in detail. The removal process involves two steps: adsorption and photodegradation. The adsorption process involves multiple cooperative adsorption mechanisms, and photocatalytic degradation includes oxidative and reductive degradation. Fourthly, the comparison of adsorption-photocatalysis with common treatment techniques (including removal rate, range of adaptation, cost, and the possibility of expanding application) is summarized. Finally, the prospects of carbon-based composite photocatalysts for repairing PFASs are given by evaluating the performance of different composites.

Mineral-Supported Photocatalysts: A Review of Materials, Mechanisms and Environmental Applications

Although they are of significant importance for environmental applications, the industrialization of photocatalytic techniques still faces many difficulties, and the most urgent concern is cost control. Natural minerals possess abundant chemical inertia and cost-efficiency, which is suitable for hybridizing with various effective photocatalysts. The use of natural minerals in photocatalytic systems can not only significantly decrease the pure photocatalyst dosage but can also produce a favorable synergistic effect between photocatalyst and mineral substrate. This review article discusses the current progress regarding the use of various mineral classes in photocatalytic applications. Owing to their unique structures, large surface area, and negatively charged surface, silicate minerals could enhance the adsorption capacity, reduce particle aggregation, and promote photogenerated electron-hole pair separation for hybrid photocatalysts. Moreover, controlling the morphology and structure properties of these materials could have a great influence on their light-harvesting ability and photocatalytic activity. Composed of silica and alumina or magnesia, some silicate minerals possess unique orderly organized porous or layered structures, which are proper templates to modify the photocatalyst framework. The non-silicate minerals (referred to carbonate and carbon-based minerals, sulfate, and sulfide minerals and other special minerals) can function not only as catalyst supports but also as photocatalysts after special modification due to their unique chemical formula and impurities. The dye-sensitized minerals, as another natural mineral application in photocatalysis, are proved to be superior photocatalysts for hydrogen evolution and wastewater treatment. This work aims to provide a complete research overview of the mineral-supported photocatalysts and summarizes the common synergistic effects between different mineral substrates and photocatalysts as well as to inspire more possibilities for natural mineral application in photocatalysis.

New alginic acid derivatives ester for methylene blue dye adsorption: kinetic, isotherm, thermodynamic, and mechanism study

In this paper, the application of ester materials prepared by grafting different carbon chain lengths of diols in alginic acid (AA) by a simple, fast and efficient method for the adsorption of methylene blue (MB) is studied. The AA ester derivatives are characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), derivative thermogravimetry (DTG), scanning electron microscopy (SEM), atomic force microscopy (AFM), and Zeta potential before and after MB adsorption. This study shows a significant improvement in the adsorption capacity of MB by AA after its esterification with a Q_max value up to 454.545 mg/g for the best adsorbent "Poly(AA-g-EG)". The experimental data are studied according to two isothermal models (Langmuir and Freundlich) and two kinetic models (pseudo-second order and intra-particle diffusion). The adsorption of MB is also evaluated thermodynamically. An adsorption mechanism of MB is established.

Enhanced Photocatalytic Activity of WS2/TiO2 Nanofibers for Degradation of Phenol under Visible Light Irradiation

Binary composite WS2/TiO2 nanofibers (WTN) were elaborated by electrospinning technique. The photocatalytic efficiency of the binary nanofibers was changed via different ratios between WS2 and TiO2. The structural, morphological and optical properties of the prepared nanofibers were evaluated by Raman spectroscopy, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and UV-Vis diffuse reflectance spectroscopy (UV-vis/DRS), respectively. The prepared nanofibers showed a remarkable performance in photocatalytic efficiency of phenol compound degradation under visible light. WTN nanofibers showed superior photocatalytic activity (83%) and high stability of several cycles under visible light. Therefore, WS2/TiO2 nanofibers have great prospects for the treatment of wastewater from toxic organic contamination due to their excellent photocatalytic performance reusability and recyclability.

Novel Natural Glycyrrhetinic Acid-Derived Super Metal Gel and Its Highly Selective Dyes Removal

Hydrogels play important roles in function materials, especially in wastewater treatment, that could solve the problems of microbial infections and dye pollutions. Herein, a natural glycyrrhetinic acid-derived gel was successfully constructed by forming hierarchical assemblies of the glycyrrhetinic acid derivatives (GA-O-09) with Cu²⁺. Interestingly, the GA-O-09/Cu²⁺ gel exhibited Cu²⁺-triggered shrinkage, which was helpful for spontaneous self-demolding through the shrinkage process with a precise amount of Cu²⁺. Moreover, the gel showed excellent antimicrobial activity against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA) with minimum inhibitory concentrations (MICs) at 2.5 μg/mL and 5.0 μg/mL, respectively. Furthermore, the resultant GA-O-09/Cu²⁺ gel showed an excellent performance in dyes removal; the adsorption capacity at equilibrium (q_e) could reach 82.91 mg/g according to a pseudo-second-order model, and it was better than most reported dye adsorbent materials. The experimental result suggested that the electrostatic interactions of the hydrogel with the cationic dyes and the hydrogel swelling were responsible for the possible dye removal mechanism of GA-O-09/Cu²⁺ gel. Therefore, our study holds the promise of a better future, for such a hydrogel could be used as an antibacterial and dye removal material.

Effect of Fomes fomentarius Cultivation Conditions on Its Adsorption Performance for Anionic and Cationic Dyes

Lab-cultivated mycelia of Fomes fomentarius (FF), grown on a solid lignocellulose medium (FF-SM) and a liquid glucose medium (FF-LM), and naturally grown fruiting bodies (FF-FB) were studied as biosorbents for the removal of organic dyes methylene blue and Congo red (CR). Both the chemical and microstructural differences were revealed using X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, zeta potential analysis, and scanning electron microscopy, illuminating the superiority of FF-LM and FF-SM over FF-FB in dye adsorption. The adsorption process of CR on FF-LM and FF-SM is best described by the Redlich-Peterson model with β constants close to 1, that is, approaching the monolayer Langmuir model, which reach maximum adsorption capacities of 48.8 and 13.4 mg g^-1, respectively, in neutral solutions. Adsorption kinetics follow the pseudo-second-order model where chemisorption is the rate-controlling step. While the desorption efficiencies were low, adsorption performances were preserved and even enhanced under simulated dye effluent conditions. The results suggest that F. fomentarius can be considered an attractive biosorbent in industrial wastewater treatment and that its cultivation conditions can be specifically tailored to tune its cell wall composition and adsorption performance.

Ultrahigh Adsorption Capacity and Kinetics of Vertically Oriented Mesoporous Coatings for Removal of Organic Pollutants

Highly efficient removal of organic pollutants currently is a main worldwide concern in water treatment, and highly challenging. Here, vertically oriented mesoporous coatings (MCs) with tunable surface properties and pore sizes have been developed via the single-micelle directing assembly strategy, which show good adsorption performances toward a wide range of organic pollutants. The micelle size and structure can be precisely regulated by oil molecules based on their n-octanol/water partition coefficients (Log P) in the oil-water diphase assembly system, which are critical to the pore size and pore surface property of the MCs. The affinity and steric effects of the MCs can be on-demand adjusted, as a result, the MCs show a ultrahigh adsorption capacity (263 mg g^-1 ), surface occupancy ratio (≈41.92%), and adsorption rate (≈10.85 mg g^-1  min^-1 ) for microcystin-LR, which is among the best performances up to date. The MCs also show an excellent universality to remove organic pollutants with different properties. Moreover, overcoming the challenges proposed by particulate absorbents, the MCs are stable and can be easily regenerated and reused without secondary contamination. This work paves a new route to the synthesis of high-quality MCs for water purification.

Cross-linked FeCl3-activated seaweed carbon/MCM-41/alginate hydrogel composite for effective biosorption of bisphenol A plasticizer and basic dye from aqueous solution

A FeCl₃-activated seaweed carbon/MCM-41/alginate hydrogel composite (ECAC/MCM-41/ ALG) cross-linked with calcium chloride (2% CaCl₂) was synthesized for the biosorption of bisphenol A (BPA) plasticizer and basic blue (BB) dye. Biosorption uptakes of BPA and BB were performed in a batch mode with varying solution pH from 3 to 11, initial sorbate concentration from 25 to 300 mg/L, reaction time from 0 to 10 h, and biosorption temperature from 30 to 50 °C. The maximum BPA and BB uptake mechanisms were fast, which occurred within contact times of 1 and 2 h with monolayer coverage capacities of 222.32 and 190.11 mg/g at 50 °C, respectively. Cyclic biosorption/desorption behavior was evaluated via an ethanol elution to evaluate the feasibility of the ECAC/MCM-41/ALG for long-term application. Results revealed the biosorption renewability for five cycles up to 80% of the newly synthesized hydrogel composite for the purification of industrial wastewater laden with emerging contaminants.

New Eco-Materials Derived from Waste for Emerging Pollutants Adsorption: The Case of Diclofenac

This work proposes new eco-materials for the adsorption of diclofenac (DCF). The large consumption of this nonsteroidal anti-inflammatory drug combined with the inefficiency of wastewater treatment plants (WWTPs) leads to its presence in aquatic environments as an emerging pollutant. The adsorption technique is widely used for pharmaceutical removal. Moreover, due to the large effect of commercial adsorbents, in the frame of the Azure Chemistry approach, new sustainable materials are mandatory for removal as emerging pollutants. The work proposes three adsorbents that were obtained from different stabilization methods of fly ash derived from an incinerator plant; the stabilization techniques involved the use of various industrial by-products such as bottom ash, flue gas desulphurization residues, coal fly ash, and silica fume. The best performance, although less than activated carbon, was obtained by COSMOS (COlloidal Silica Medium to Obtain Safe inert: the case of incinerator fly ash), with a removal efficacy of approximately 76% with 15 g/L of material. Several advantages are expected not only from the DCF removal but also from an economic perspective (the newly obtained adsorbents are eco-materials, so they are cheaper in comparison to conventional adsorbents) and in terms of sustainability (no toxic reagents and no heating treatment are involved). This work highlights the adsorption performance of the new eco-materials and their potential use in WWTPs.

Palladium/Carbon Nanofibers by Combining Atomic Layer Deposition and Electrospinning for Organic Pollutant Degradation

As organic dyes are a major source of pollution, it is important to develop novel and efficient heterogeneous catalysts with high activity for their degradation. In this work, two innovative techniques, atomic layer deposition and electrospinning, were used to prepare palladium nanoparticles (Pd NPs) supported on carbon nanofibers (CNFs). The sample morphology was investigated using scanning and transmission electron microscopy. This showed the presence of nanofibers of several micrometers in length and with a mean diameter of 200 nm. Moreover, the size of the highly dispersed Pd NPs was about 7 nm. X-ray photoelectron spectroscopy visually validated the inclusion of metallic Pd. The prepared nano-catalysts were then used to reduce methyl orange (MO) in the presence of sodium borohydride (NaBH₄). The Freundlich isotherm model was the most suitable model to explain the adsorption equilibrium for MO onto the Pd/CNF catalysts. Using 5 mL MO dye-solution (0.0305 mM) and 1 mL NaBH₄ (0.026 mM), a 98.9% of catalytic activity was achieved in 240 min by 0.01 g of the prepared nano-catalysts Pd/C (0.016 M). Finally, no loss of catalytic activity was observed when such catalysts were used again. These results represent a promising avenue for the degradation of organic pollutants and for heterogeneous catalysis.

Nitridation Temperature Effect on Carbon Vanadium Oxynitrides for a Symmetric Supercapacitor

In this work, porous carbon-vanadium oxynitride (C-V₂NO) nanostructures were obtained at different nitridation temperature of 700, 800 and 900 °C using a thermal decomposition process. The X-ray diffraction (XRD) pattern of all the nanomaterials showed a C-V₂NO single-phase cubic structure. The C-V₂NO obtained at 700 °C had a low surface area (91.6 m² g⁻¹), a moderate degree of graphitization, and a broader pore size distribution. The C-V₂NO obtained at 800 °C displayed an interconnected network with higher surface area (121.6 m² g⁻¹) and a narrower pore size distribution. In contrast, at 900 °C, the C-V₂NO displayed a disintegrated network and a decrease in the surface area (113 m² g⁻¹). All the synthesized C-V₂NO yielded mesoporous oxynitride nanostructures which were evaluated in three-electrode configuration using 6 M KOH aqueous electrolyte as a function of temperature. The C-V₂NO@800 °C electrode gave the highest electrochemical performance as compared to its counterparts due to its superior properties. These results indicate that the nitridation temperature not only influences the morphology, structure and surface area of the C-V₂NO but also their electrochemical performance. Additionally, a symmetric device fabricated from the C-V₂NO@800 °C displayed specific energy and power of 38 W h kg⁻¹ and 764 W kg⁻¹, respectively, at 1 A g⁻¹ in a wide operating voltage of 1.8 V. In terms of stability, it achieved 84.7% as capacity retention up to 10,000 cycles which was confirmed through the floating/aging measurement for up to 100 h at 10 A g⁻¹. This symmetric capacitor is promising for practical applications due to the rapid and easy preparation of the carbon-vanadium oxynitride materials.

Functionalized Porous Silica-Based Nano/Micro Particles for Environmental Remediation of Hazard Ions

The adsorption and separation of hazard metal ions, radioactive nuclides, or minor actinides from wastewater and high-level radioactive waste liquids using functional silica-based nano/micro-particles modified with various inorganic materials or organic groups, has attracted significant attention since the discovery of ordered mesoporous silica-based substrates. Focusing on inorganic and organic modified materials, the synthesis methods and sorption performances for specific ions in aqueous solutions are summarized in this review. Three modification methods for silica-based particles, the direct synthesis method, wetness impregnation method, and layer-by-layer (LBL) deposition, are usually adopted to load inorganic material onto silica-based particles, while the wetness impregnation method is currently used for the preparation of functional silica-based particles modified with organic groups. Generally, the specific synthesis method is employed based on the properties of the loading materials and the silicon-based substrate. Adsorption of specific toxic ions onto modified silica-based particles depends on the properties of the loaded material. The silicon matrix only changes the thermodynamic and mechanical properties of the material, such as the abrasive resistance, dispersibility, and radiation resistance. In this paper, inorganic loads, such as metal phosphates, molybdophosphate, titanate-based materials, and hydrotalcite, in addition to organic loads, such as 1,3-[(2,4-diethylheptylethoxy)oxy]-2,4-crown-6-Calix{4}arene (Calix {4}) arene-R14 and functional 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridines(BTP) are reviewed. More specifically, we emphasize on the synthesis methods of such materials, their structures in relation to their capacities, their selectivities for trapping specific ions from either single or multi-component aqueous solutions, and the possible retention mechanisms. Potential candidates for remediation uses are selected based on their sorption capacities and distribution coefficients for target cations and the pH window for an optimum cation capture.

Grafting and stabilization of ordered mesoporous silica COK-12 with graphene oxide for enhanced removal of methylene blue

Grafting of environmentally friendly produced ordered mesoporous silica (OMS) COK-12 with graphene oxide yields a superior OMS/GO adsorbent for methylene blue.

An ultrasonic method for the synthesis, control and optimization of CdS/TiO2 core–shell nanocomposites

In this study, an ultrasonic method was utilized in combination with microemulsion to synthesize CdS/TiO₂ core–shell nanoparticles and control their particle size and ultimately optimize the influential parameters. Moreover, response surface methodology (RSM) was used to optimize the thickness of the shell. Herein, four parameters, i.e. temperature (67–79 °C), synthesis retention time (45–105 min), TiO₂ : CdS ratio (1.5–7.5) and the power of ultrasound waves (37–53 watt), were optimized to synthesize nanoparticles with an average size of up to 10 nm. A correlation equation was introduced for the size range of 10–90 nm, which was then proven to have excellent predictions. To verify the proposed model, two different sets of combinations were selected to synthesize 10 nm composites, and consequently, nanocomposites with the sizes of 10.4 and 10.9 nm were successfully synthesized. The power of ultrasound waves and retention time had the most influence on the size of the particles. Further experiments proved that the optical absorption spectrum of the composite particles was extended to the visible region. Furthermore, the formation of CdS/TiO₂ core–shell nanocomposites was confirmed by different characterization techniques including XRD, TEM, EDAX, UV-vis, FTIR and DLS.

In this study, an ultrasonic method was utilized in combination with microemulsion to synthesize CdS/TiO₂ core–shell nanoparticles and control their particle size and ultimately optimize the influential parameters.