Ionic liquid-modified composites for the adsorptive removal of emerging water contaminants: A review

Ionic liquid-modified magnetic covalent organic framework for the extraction of four pyrethroids in traditional Chinese herbs

Efficient enrichment of analytes and purification of matrices are crucial for the highly sensitive detection and monitoring of pesticides in traditional Chinese herbs. This work prepared magnetic ionic liquid-controlled covalent organic framework (IL-COF@Fe3O4) as the sorbent via a simple in-situ precipitation polymerization and thiolene "click" strategy. The IL-COF@Fe3O4 exhibited remarkable adsorption performance towards pyrethroids within 5 min. The adsorption of four pyrethroids on the surface of IL-COF@Fe3O4 was according with Langmuir model and pseudo-second-order kinetic model. The adsorption energies were theoretically calculated, which were permethrin>cypermethrin>fenvalerate>bifenthrin. The modification of ILs improved extraction capacity mainly because of the interaction of imidazole and Cl or F and the pore size effect. This method was developed for the rapid extraction of four pyrethroids in Codonopsis pilosula and Angelica sinensis. The linear range was 0.05-200 μg L-1. Matrix effects were ranging from -16.14% to 9.53%, indicating the strong matrix anti-interference ability of IL-COF@Fe3O4.

Adsorption of Pb(II) in water by modified chitosan-based microspheres and the study of mechanism

In this study, a fresh three-dimensional microsphere adsorbent (CATP@SA3) was successfully synthesized by Attapulgite (ATP) and combining Chitosan (CS), incorporating them into a Sodium alginate (SA) solution, and crosslinking them in a CaCl2 solution. Multiple analyses, including XRD, TGA, FTIR, XPS, SEM-EDS, and BET were utilized to comprehensively characterize the structural makeup of CATP@SA3. These analyses revealed the presence of beneficial functional groups like hydroxyl, amino, and carboxyl groups that enhance the adsorption efficiency in adsorption procedures. CATP@SA3 was evaluated by studying different factors, including material ratio, contact time, dosage, solution pH, Pb(II) concentration, temperature, ionic strength, and aqueous environment. Three adsorption models, including kinetic, isotherm, and thermodynamic, were fitted to the experimental data. The findings demonstrated that the maximum Pb(II) adsorption capacity of CATP@SA3 was 1081.36 mg/g, with a removal rate that exceeded 70 % even after 5 cycles of use. Furthermore, correlation adsorption models revealed that the adsorption process of Pb(II) with CATP@SA3 was driven by a chemical predominantly reaction.

A comparison between constructed wetland substrates: Impacts on microbial community and wastewater treatment

Constructed wetlands (CWs) can play a crucial role in treating wastewater, and in the context of this study, the distillation byproduct of the whisky industry known as 'spent lees'. Here, we assess several different CW substrates (pea gravel, LECA and Alfagrog), with and without the addition of 20% biochar, in mesocosms set up to treat spent lees. Among the substrates tested, LECA + biochar and gravel + biochar showed promising results, with greater dissolved copper (dissCu) reduction, chemical oxygen demand (COD) removal, organic carbon (OC) reduction, and pH modulation. These findings indicate a potentially beneficial role for biochar in enhancing treatment efficacy, particularly in facilitating dissCu remediation and the removal of organic pollutants. In terms of microbial diversity, mesocosms including biochar generally had reduced bacterial alpha diversity, suggesting that 'fresh' (uncolonized) biochar may negatively affect microbial diversity in wetland ecosystems in the short term. After continuously supplying spent lees to mesocosms for 2-months, microbial diversity in each mesocosm dropped substantially, and moderate levels of bacterial community differentiation and high levels of fungal community differentiation were detected among mesocosms. The bacterial and fungal communities were also found to differ between the substrate and outlet water samples. Among the bacterial classes present in the mesocosms that may play a crucial role in water treatment performance, Gammaproteobacteria, Bacteroidia and Alphaproteobacteria should be further investigated. In terms of fungal classes, the role of Sordariomycetes should be explored in greater depth.

Adsorption potential of ionic liquid-modified ZnO nanoparticles for highly efficient removal of azo dye: detailed isotherms and kinetics

In this study, bare and ionic liquid-modified ZnO nanoparticles have been fabricated using microwave irradiation method. The fabricated nanoparticles were characterized by different techniques, viz. XRD, FT-IR, FESEM, and UV-Visible spectroscopy, and were explored as adsorbent for effective sequestration of azo dye (Brilliant Blue R-250) from aqueous media. Various factors affecting the adsorption efficiency of synthesized nanoparticles (bare/ionic liquid-modified) such as concentration of dye, pH of reaction media, dose of nanoparticles, and reaction time were thoroughly investigated with varying experimental conditions; on a magnetic stirrer and in a sonicator. The results exhibited a high adsorption efficiency of ionic liquid-modified nanoparticles for removal of dye as compared to the bare one. Also, an enhanced adsorption was observed via sonication in comparison with magnetic stirring. Different isotherms such as Langmuir, Freundlich, and Tempkin were elaborated. Evaluation of adsorption kinetics showed a linear pseudo-second-order equation for adsorption process. The exothermic and spontaneous nature of adsorption was further confirmed by thermodynamic investigations. As per the results obtained, it is suggested that the fabricated ionic liquid-modified ZnO nanoparticles could successfully remediate the toxic anionic dye from aqueous media. Hence, this system can be utilized for large-scale industrial applications.

Enhanced dye sequestration with natural polysaccharides-based hydrogels: A review

Due to the expansion of industrial activities, the concentration of dyes in water has been increasing. The dire need to remove these pollutants from water has been heavily discussed. This study focuses on the reproducible and sustainable solution for wastewater treatment and dye annihilation challenges. Adsorption has been rated the most practical way of the several decolorization procedures due to its minimal initial investment, convenient utility, and high-performance caliber. Hydrogels, which are three-dimensional polymer networks, are notable because of their potential to regenerate, biodegrade, absorb bulky amounts of water, respond to stimuli, and have unique morphologies. Natural polysaccharide hydrogels are chosen over synthetic ones because they are robust, bioresorbable, non-toxic, and cheaply accessible. This study has covered six biopolymers, including chitosan, cellulose, pectin, sodium alginate, guar gum, and starch, consisting of their chemical architecture, origins, characteristics, and uses. The next part describes these polysaccharide-based hydrogels, including their manufacturing techniques, chemical alterations, and adsorption effectiveness. It is deeply evaluated how size and shape affect the adsorption rate, which has not been addressed in any prior research. To assist the readers in identifying areas for further research in this subject, limitations of these hydrogels and future views are provided in the conclusion.

Innovative strategies for enhancing gas separation: Ionic liquid-coated PES membranes for improved CO2/N2 selectivity and permeance

As a cost-effective advancement in membrane technology, this study investigates the impact of PEG additive and CBT on the structural, stability, and gas permeance properties of PES-coated membranes, utilizing 1-dodecyl-3-methylimidazolium chloride ionic liquid ([DDMI][Cl] IL) as a carrier liquid. BET and FT-IR analyses highlight the significant enhancement in performance through the immobilization of pores with [DDMIM][Cl] IL. The investigation focuses on PES-M5-coated membranes, revealing excellent stability in finger-like pore structures prepared through direct immersion and nitrogen pressure immobilization. PES-M5-coated membranes with [DDMIM][Cl] IL via direct immersion experience lower weight loss than those coated using nitrogen pressure, with critical pressures at 1.4 and 1.25 bar, respectively. The study identifies PES-coated membranes, particularly PES-M25 (20.88 GPU) with macro-void pores and PES-M5 (29 GPU) with finger-like pores, exhibiting the highest CO2 permeance and CO2/N2 selectivity. As a cost-effective advancement in membrane technology, ionic liquids are employed in support membranes to enhance gas separation. Employing pure PES membranes with varying pore structures, created through the NIPS method, the study immobilizes [DDMI][Cl] IL in membrane pores through nitrogen pressure and direct immersion. Results underscore the successful application of porous support materials coated with ionic liquids for continuous CO2 and sulfur compound separation, showcasing competitive permeability and selectivity compared to traditional polymer membranes.

Innovative Sol-gel functionalized polyurethane foam for sustainable water purification and analytical advances

Nanomaterial combined polymeric membranes such as polyurethane foams (PUFs) have garnered enormous attention in the field of water purification due to their ease of management and surface modification, cost-effectiveness, and mechanical, chemical, and thermal properties. Thus, this study reports the use of novel Sol-gel impregnated polyurethane foams (Sol-gel/PUFs) as new dispersive solid phase microextractors (d- µ SPME) for the efficient separation and subsequent spectrophotometric detection of Eosin Y (EY) textile dye in an aqueous solution with a pH of 3-3.8. The Sol gel, PUFs, and Sol gel-impregnated PUFs were characterized using scanning electron microscopy (SEM), goniometry measurements, dynamic light scattering (DLS), energy dispersive spectroscopy (EDS), UV-Visible, and FTIR spectra. Batch experiment results displayed a remarkable removal percentage (96% ± 5.4%) of the EY from the aqueous solution, with the total sorption time not exceeding 60 min. These data indicate rate-limited sorption via diffusion and/or surface complex ion associate formations after the rapid initial sorption steps. A pseudo-second order kinetic model thoroughly explained the sorption kinetics, providing a sorption capacity (qe) of 37.64 mg g-1, a half-life time (t1/2) of 0.8 ± 0.01 min, and intrinsic penetration control dye retention. The thermodynamic results revealed a negative value for ΔG⁰ (-78.07 kJ mol-1 at 293 K), clearly signifying that the dye uptake was spontaneous, as well as a negative value for ΔH⁰ (-69.58 kJ mol-1) and a positive value for ΔS⁰ (147.65 J mol-1 K-1), making clear the exothermic nature of EY adsorption onto the sorbent, with a growth in randomness at the molecular level. A ternary retention mechanism is proposed, involving the "weak base anion exchanger" of {(-CH2-OH+ -CH2-) (Dye anion)-}Sol-gel/PUF and/or {(-NH2 + -COO-) (Dye anion)-}Sol-gel/PUF via solvent extraction and "surface adsorption" of the dye anion on/in the Sol-gel/PUFs membranes in addition to H-bonding, including surface complexation and electrostatic π-π interaction, between the dye and the silicon/zirconium oxide (Si-O-Zr) and siloxane (Si-O-Si) groups on the sorbent. Complete extraction and recovery (93.65 ± 0.2, -102.28 ± 2.01) of EY dye with NaOH (0.5 M) as a proper eluting agent was achieved using a sorbent-packed mini column. In addition, the established extractor displayed excellent reusability and does not require organic solvents for EY enrichment in water samples, making it a talented nominee as a novel sorbent for EY sorption from wastewater. This study is of great consequence for expanding the applicatio1n of Sol-gel/PUFs in developing innovative spectrophotometric sensing strategies for dye determination. In view of this, it would also be remarkable to perform future studies to explore the analytical implications of this extractor regarding safety and environmental and public health issues associated to the pollutant.

Sol-Gel Functionalized Polyurethane Foam-Packed Mini-Column as an Efficient Solid Extractor for the Rapid and Ultra-Trace Detection of Textile Dyes in Water

Textile dyes widely used in industrial products are known as a major threat to human health and water ecological security. On the other hand, sol gel represents a principal driver of the adoption of dispersive solid-phase microextractors (d-µ SPME) for pollutants residues in water. Thus, the current study reports a new and highly rapid and highly efficient hybrid sol-gel-based sponge polyurethane foam as a dispersive solid-phase microextractor (d-µ-SPME) platform packed mini-column for complete preconcentration and subsequent spectrophotometric detection of eosin Y textile dye in wastewater. The unique porous structure of the prepared sol-gel immobilized polyurethane foams (sol-gel/PUF) has suggested its use for the complete removal of eosin Y dye (EY) from water. In the mini-column, the number (N) of plates, the height equivalent to the theoretical plates (HETP), the critical capacity (CC), and the breakthrough capacities (BC) of the hybrid sol-gel-treated polyurethane foams towards EY dye were determined via the breakthrough capacity curve at various flow rates. Under the optimum condition using the matrix match strategy, the linear range of 0.01-5 µg L-1, LODs and LOQs in the range of 0.006 µg L-1, and 0.01 µg L-1 for wastewater were achieved. The intra-day and inter-day precisions were evaluated at two different concentration levels (0.05 and 5 μg L-1 of dye) on the same day and five distinct days, respectively. The analytical utility of the absorbents packed in pulses and mini-columns to extract and recover EY dye was attained by 98.94%. The column could efficiently remove different dyes from real industrial effluents, and hence the sol-gel/PUF is a good competitor for commercial applications. The findings of this research work have strong potential in the future to be used in selecting the most suitable lightweight growing medium for a green roof based on stakeholder requirements. Therefore, this study has provided a convenient pathway for the preparation of compressible and reusable sponge materials from renewable biomass for efficient removal of EY from the water environment.

Manganese Removal Using Functionalised Thiosalicylate-Based Ionic Liquid: Water Filtration System Application

Aiming at the generation of new functionalised thiosalicylate-based ionic liquids, a polymeric hydrogel consisting of 1-hexylimidazole propionitrile thiosalicylate [HIMP][TS], with a solid biomaterial support based on polyvinyl alcohol (PVA)-alginate beads, was produced. This study aimed to develop a treatment method for removing manganese (Mn) heavy metal from industrial wastewater, which is known to be toxic and harmful towards the environment and human health. The method utilised an adsorption-based approach with an alginate adsorbent that incorporated a functionalised thiosalicylate-based ionic liquid. The synthesised smooth round beads of PVA-alginate-[HIMP][TS] adsorbent were structurally characterised using Fourier transform infrared spectroscopy (FTIR) and field emission scanning electron microscopy (FESEM). The Mn concentration and removal efficiency were evaluated using atomic absorption spectroscopy (AAS). Three important parameters were evaluated: pH, adsorbent dosage, and contact time. During optimisation using the interactive factor design of experiments through the Box-Behnken model, the results showed that the system achieved a maximum Mn removal efficiency of 98.91% at an initial pH of 7.15, with a contact time of 60 min, using a bead dosage of 38.26 g/L. The beads were also tested in an available water filtration prototype system to illustrate their industrial application, and the performance showed a removal efficiency of 99.14% with 0 NTU total suspended solid (TSS) and 0.13 mg/L turbidity analysis. The recyclability of PVA-alginate-[HIMP][TS] beads using 0.5 M HCl resulted in four cycles with constant 99% Mn removal. The adsorption capacity of Mn was also determined in optimum conditions with 56 mg/g. Therefore, the alginate-thiosalicylate-based ionic liquid system is considered an effective and environmentally friendly method for removing Mn heavy metal due to the high removal efficiency achieved.

Highly efficient degradation of ofloxacin and diclofenac by composite photocatalyst aloe-emodin/PMMA

Photocatalysis is one of the most effective methods to remove pollutants from water. Photocatalyst is the core of photocatalysis. The composite photocatalyst combines the photosensitizer with the support and uses the photosensitivity of the photosensitizer and the stability and adsorption of the support to achieve efficient and rapid degradation of pharmaceuticals in water. In this study, natural aloe-emodin with π-conjugated structure was used as photosensitizer to react with macroporous resin polymethylmethacrylate (PMMA) under mild conditions to prepare composite photocatalysts AE/PMMAs. The photocatalyst underwent photogenerated electron migration under visible light to form ^•O₂^- and holes with high oxidation activity, which could realize efficient photocatalytic degradation of ofloxacin and diclofenac sodium and showed excellent stability, recyclability and industrial feasibility. This research has developed an efficient method of composite photocatalyst and realized the application of a natural photosensitizer in pharmaceutical degradations.

Insight into the adsorptive removal of ibuprofen using porous carbonaceous materials: A review

Over the last decade, the removal of pharmaceuticals from aquatic bodies has garnered substantial attention from the scientific community. Ibuprofen (IBP), a non-steroidal anti-inflammatory drug, is released into the environment in pharmaceutical waste as well as medical, hospital, and household effluents. Adsorption technology is a highly efficient approach to reduce the IBP in the aquatic environment, particularly at low IBP concentrations. Due to the exceptional surface properties of carbonaceous materials, they are considered ideal adsorbents for the IBP removal of, with high binding capacity. Given the importance of the topic, the adsorptive removal of IBP from effluent using various carbonaceous adsorbents, including activated carbon, biochar, graphene-based materials, and carbon nanostructures, has been compiled and critically reviewed. Furthermore, the adsorption behavior, binding mechanisms, the most effective parameters, thermodynamics, and regeneration methods as well as the cost analysis were comprehensively reviewed for modified and unmodified carbonaceous adsorbents. The compiled studies on the IBP adsorption shows that the IBP uptake of some carbon-based adsorbents is significantly than that of commercial activated carbons. In the future, much attention is needed for practical utilization and upscaling of the research findings to aid the management and sustainability of water resource.

Chitosan Nanoparticles as Potential Nano-Sorbent for Removal of Toxic Environmental Pollutants

Adsorption is the most widely used technique for advanced wastewater treatment. The preparation and application of natural renewable and environmentally friendly materials makes this process easier and more profitable. Chitosan is often used as an effective biomaterial in the adsorption world because of its numerous functional applications. Chitosan is one of the most suitable and functionally flexible adsorbents because it contains hydroxyl (-OH) and amine (-NH₂) groups. The adsorption capacity and selectivity of chitosan can be further improved by introducing additional functions into its basic structure. Owing to its unique surface properties and adsorption ability of chitosan, the development and application of chitosan nanomaterials has gained significant attention. Here, recent research on chitosan nanoparticles is critically reviewed by comparing various methods for their synthesis with particular emphasis on the role of experimental conditions, limitations, and applications in water and wastewater treatment. The recovery of pollutants using magnetic nanoparticles is an important treatment process that has contributed to additional development and sustainable growth. The application of such nanoparticles in the recovery metals, which demonstrates a "close loop technology" in the current scenarios, is also presented in this review.

Highly efficient decontamination of tetracycline and pathogen by a natural product-derived Emodin/HAp photocatalyst

To address the water pollution induced by pharmaceuticals, especially antibiotics, and pathogens, natural product emodin, a traditional Chinese medicine with the characteristic large π-conjugation anthraquinone structure, was used to rationally develop a novel Emodin/HAp photocatalyst by integrating with a thermally stable and recyclable support material hydroxyapatite (HAp) through a simple preparation method. It was found that its photocatalytic activity to generate reactive oxygen species (ROS) was greatly improved due to the migration of photogenerated electrons and holes between emodin and HAp upon visible light irradiation. Thus, this Emodin/HAp photocatalyst not only quickly photodegraded tetracycline with 99.0% removal efficiency but also exhibited complete photodisinfection of pathogenic bacteria Staphylococcus aureus upon visible light irradiation. Therefore, this study offers a new route for the design and preparation of multifunctional photocatalysts using widely available natural products for environmental remediation.

Fe/C materials prepared by one-step calcination of acidified municipal sludge and their excellent adsorption of Cr(VI)

Biochar derived from municipal sludge can be applied to adsorption. But it usually requires activation and pickling due to the generation of impurities such as metal oxide particles, which is uneconomical. Here, a facile strategy, acidification-one-step calcination, was developed and sludge-based Fe-C materials with good Cr(VI) removal effect were obtained by regulating the amount of hydrochloric acid. The results show that the adsorption capacity of Fe/C-5 (the best sample) for Cr(VI) was 150.84 mg g^-1. According to the Langmuir isotherm and pseudo-second-order kinetic model, the removal of Cr(VI) by Fe/C-5 is spontaneous and endothermic chemisorption process. In addition, Fe/C-5 has good ability to remove Cr(VI) under the interference of coexisting ions, and has good cycle stability. The removal of Cr(VI) by Fe/C-5 is considered to be synergistic process of adsorption and reduction. The Fe atoms were highly dispersed in Fe/C-5 and tightly bonded with C atoms, which not only strengthened the Cr(VI) adsorption by electrostatic attraction, but also activated the C atoms in the biochar material, so that the C atoms can reduce Cr(VI) to Cr(III) under acidic conditions. This may be due to the fact that acid pretreatment converted the iron in municipal sludge in the form of Fe-O/OH to free Fe³⁺ and entered the C lattice during the calcination process. In this work, Fe-C materials with excellent Cr(VI) adsorption capacity were prepared by one-step calcination method, which has important reference significance for the resource utilization of municipal sludge.

Preparation and characterization of polyethyleneimine functionalized magnetic graphene oxide as high uptake and fast removal for Hg (II)

Polyethyleneimine functionalized magnetic graphene oxide adsorbent (PEI-mGO) was synthesized by introducing polyethyleneimine onto Fe₃O₄/graphene oxide. The structures and morphologies of PEI-mGO was identified by using Fourier-tranform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) methods. Quantities of bar-like Fe₃O₄ nanoparticles were observed on the surfaces of PEI-mGO. The adsorption of PEI-mGO for Cu(II), Pb(II), Hg(II), Co(II) and Cd(II) was compared. The adsorption results indicated that PEI-mGO showed higher uptake for Hg(II) than the other ions. The influence of various variables for the adsorption of Hg(II) on PEI-mGO was explored. The adsorption kinetics and isotherm could be described well by the pseudo-second-order and Langmuir models. The maximal uptake of PEI-mGO for Hg(II) from Langmuir model was 857.3 mg g^-1, which was higher than that reported previously. The adsorption removal was a fast and endothermic process governed by the chemical process. The uptake increased with increasing temperature. PEI-mGO showed an excellent performance for removal of Hg(II) with 93.3% removal efficiency from simulated wastewater. Adsorption-desorption cycled experiments indicated that PEI-mGO could be recycled. PEI-mGO could be easily separated from the adsorbed solution by using a magnet. Hence, this novel adsorbent would be promising for the removal of Hg(II) from wastewater.

Ionic Liquid-Based Polymer Nanocomposites for Sensors, Energy, Biomedicine, and Environmental Applications: Roadmap to the Future

Current interest toward ionic liquids (ILs) stems from some of their novel characteristics, like low vapor pressure, thermal stability, and nonflammability, integrated through high ionic conductivity and broad range of electrochemical strength. Nowadays, ionic liquids represent a new category of chemical-based compounds for developing superior and multifunctional substances with potential in several fields. ILs can be used in solvents such as salt electrolyte and additional materials. By adding functional physiochemical characteristics, a variety of IL-based electrolytes can also be used for energy storage purposes. It is hoped that the present review will supply guidance for future research focused on IL-based polymer nanocomposites electrolytes for sensors, high performance, biomedicine, and environmental applications. Additionally, a comprehensive overview about the polymer-based composites' ILs components, including a classification of the types of polymer matrix available is provided in this review. More focus is placed upon ILs-based polymeric nanocomposites used in multiple applications such as electrochemical biosensors, energy-related materials, biomedicine, actuators, environmental, and the aviation and aerospace industries. At last, existing challenges and prospects in this field are discussed and concluding remarks are provided.

Ultrasound-assisted dispersive magnetic solid-phase extraction of cadmium, lead and copper ions from water and fruit juice samples using DABCO-based poly (ionic liquid) functionalized magnetic nanoparticles

A poly (ionic liquid) (PIL) functionalized magnetic nanoparticles methodology was developed and utilized as an efficient adsorbent for the simultaneous extraction of cadmium, lead, and copper ions from water and fruit juice samples. The novel adsorbent was fabricated by grafting DABCO-based PIL onto silica-coated Fe₃O₄ nanoparticles via copper (0)-mediated reversible-deactivation radical polymerization. Different techniques properly characterized the developed nanoparticles. The central composite design was used to analyze the simultaneous effects of various parameters on the extraction efficiency. The detection limits for water samples ranged between 3.2 and 9.2 ng.L^-1, and fruit juice samples varied from 0.0103 to 0.1082 μg.kg^-1. The recovery ranged from 94.1 to 101.3% and 93.6 to 105.1% for water and fruit juice samples, respectively. The relive measurement uncertainty ranged from 7.7 to 13.6%. The proposed method is rapid, sensitive, environmentally friendly, and useful for monitoring the residues of heavy metal ions in water and fruit juice samples.

Adsorptive removal of fluoride using ionic liquid-functionalized chitosan - Equilibrium and mechanism studies

In this study, novel biosorbents, based on chitosan and imidazolium ionic liquid, were prepared for the removal of fluoride from aqueous solutions. The adsorbents were characterized by FTIR, SEM-EDS and low-temperature nitrogen adsorption-desorption. To investigate the adsorption mechanism and behavior of chitosan adsorbents, batch experiments were conducted under different adsorbent dosages (2, 4, 10 g/L), pH (4, 7, 9) and initial concentration (0.5-25.0 mg/L). The influence of the method of synthesis of ionic liquid on the adsorption performance were also studied. Experimental data were evaluated by Freundlich, Langmuir and Sips models. The introduction of ionic liquid significantly improved the uptake of fluoride compared to pure chitosan. The adsorption was influenced by the experimental conditions, as well as the method of ionic liquid synthesis. The highest fluoride removal was observed at pH 4 and found to decrease with increasing pH. The removal efficiency and adsorption capacity values indicated that the dose of 4 g/L was the optimum adsorbent dosage. The equilibrium data fitted best with the Sips isotherm and the maximum adsorption capacity reached 8.068 mg/g for modified chitosan beads. The mechanism of fluoride adsorption onto ionic liquid-modified chitosan involves electrostatic attraction, ion exchange and ion pair interaction.

Effectiveness of ionic liquid-supported membranes for carbon dioxide capture: a review

The world's population explosion creates a need for natural resources for energy, which will become a significant contributor to global climate change. As we all know, carbon dioxide (CO₂) is one of the most critical elements of the global greenhouse gas effect. CO₂ capture and storage innovations have piqued researchers' attention in recent decades. Compared to other methods, membrane separation has some positive performance in CO₂ capture. CO₂ capture with membrane separation using enhanced ionic liquids (ILs) is described in this review. ILs have made an appearance in CO₂ capture work as the potential additive, and companies and academics have been interested in CO₂ separation for the past two decades. This article comprehensively analyzes the current modern approach in ILs and IL-based membranes for gas separation processes. Based on the latest literature and performance data, this work provides a complete compressive examination of types of ILs and IL-supported membrane performances. ILs for CO₂ capture were also explored, and IL-based membranes for different ILs were also studied. This study emphasizes the supremacy of novel ILs for CO₂ capture in membrane separation.

Zeolitic imidazolate framework (ZIF-8)/polyacrylonitrile derived millimeter-sized hierarchical porous carbon beads for peroxymonosulfate catalysis

Well dispersed nanocatalysts on porous substrate with macroscopic morphology are highly desired for the application of heterogeneous catalysis. Traditional fabrication process suffers from multiple steps for controlling the structure on nanocatalysts and matrix or both. Herein, we report a facile strategy for the synthesis of millimeter-sized hierarchical porous carbon beads (HPCBs) which containing well dispersed hollow-nano carbon boxes for peroxymonosulfate catalysis. Specially, the precursors of HPCBs were prepared by phase inversion method, which involving introduction of zeolitic imidazolate framework (ZIF-8) nanocubes into polyacrylonitrile (PAN) solutions followed by solidification of the mixture. After pyrolysis, nitrogen doped and hierarchical porous HPCBs with diameter of about 1.2 mm were obtained. The merits of our synthesis strategy lie in that synchronizes the hollow microstructure evolution with the shaping of ZIF-8 nanocubes into millimeter scale beads. Attribute to its special structure feature and the appropriate chemical composition, the resultant millimeter-sized HPCBs exhibit enhanced catalytic performance by activation of peroxymonosulfate (PMS) for tetracycline degradation. The degradation efficiency of TC is up to 85.1% within 120 min, which is 18% higher than that of ZIF8-Solid/PAN carbon bead (SPCBs). In addition, the possible decomposition pathways, main reactive oxygen species, and reasonable enhanced mechanism for the HPCBs/PMS system are systematically investigated by quenching experiments, electron paramagnetic resonance (EPR) and liquid chromatography-mass spectrometry (LC-MS). This work addresses the issue of easy aggregation and recycling of carbon materials in industrial productions and extends the prospects of carbon materials in engineering applications.

Adsorption of Cetylpyridinium Chloride at Silica Nanoparticle/Water Interfaces (II): Dependence of Surface Aggregation on Particle Size

Herein, we report a thermodynamic model that relates the adsorption (aggregation) parameters of surfactants at solid/liquid interfaces to particle radius (r). The adsorption (aggregation) parameters include adsorption amounts, equilibrium constants (or the standard Gibbs free energy changes), the critical surface micelle concentration (csmc), and the average aggregation number of surface micelles (n). The model predicts the size dependence of the surface aggregation of surfactants, which is determined by the changes in the interfacial tension and the molar volume of surface components caused by adsorption. In addition, the adsorption of cetylpyridinium chloride (CPyCl), a cationic surfactant, on silica nanoparticles with different r values (ca. 6-61 nm) was determined at 298 K and pH 4, showing an obvious size dependence, consistent with the prediction of the model. With an increase in r, the adsorption isotherm changes from the double-plateau type to the Langmuir type, accompanied by obvious changes in the adsorption parameters. The size-dependent adsorption data can be well described using the model equations, indicating that the model presented here is acceptable. In addition, the model can extract information on the interfacial tensions from adsorption data. We think that the model deepens the understanding of the aggregation phenomena of surfactants at solid/liquid interfaces.

High Performance of Ionic-Liquid-Based Materials to Remove Insecticides

Neonicotinoids are systemic insecticides commonly used for pest control in agriculture and veterinary applications. Due to their widespread use, neonicotinoid insecticides (neonics) are found in different environmental compartments, including water, soils, and biota, in which their high toxicity towards non-target organisms is a matter of great concern. Given their widespread use and high toxicity, the development of strategies to remove neonics, while avoiding further environmental contamination is of high priority. In this work, ionic-liquid-based materials, comprising silica modified with tetraalkylammonium cations and the chloride anion, were explored as alternative adsorbent materials to remove four neonics insecticides, namely imidacloprid, acetamiprid, thiacloprid, and thiamethoxam, from aqueous media. These materials or supported ionic liquids (SILs) were first synthesized and chemically characterized and further applied in adsorption studies. It was found that the equilibrium concentration of the adsorbate in the solid phase decreases with the decrease in the SIL cation alkyl chain length, reinforcing the relevance of hydrophobic interactions between ionic liquids (ILs) and insecticides. The best-identified SIL for the adsorption of the studied insecticides corresponds to silica modified with propyltrioctylammonium chloride ([Si][N3888]Cl). The saturation of SILs was reached in 5 min or less, showing their fast adsorption rate towards all insecticides, in contrast with activated carbon (benchmark) that requires 40 to 60 min. The best fitting of the experimental kinetic data was achieved with the Pseudo Second-Order model, meaning that the adsorption process is controlled at the solid-liquid interface. On the other hand, the best fitting of the experimental isotherm data is given by the Freundlich isotherm model, revealing that multiple layers of insecticides onto the SIL surface may occur. The continuous removal efficiency of the best SIL ([Si][N3888]Cl) by solid-phase extraction was finally appraised, with the maximum adsorption capacity decreasing in the following sequence: imidacloprid > thiacloprid > thiamethoxam > acetamiprid. Based on real reported values, under ideal conditions, 1 g of [Si][N3888]Cl is able to treat at least 106 m3 of wastewater and water from wetland contaminated with the studied neonics. In summary, the enhanced adsorption capacity of SILs for a broad diversity of neonics was demonstrated, reinforcing the usefulness of these materials for their removal from aqueous matrices and thus contributing to preventing their introduction into the ecosystems and reducing their detrimental effects in the environment and human health.

Substantial improvement in the adsorption behavior of montmorillonite toward Tartrazine through hexadecylamine impregnation

In the present work, the surface of montmorillonite K10 was successfully modified by hexadecylamine surfactant (Mt-HDA) and its intercalation and characteristics were assessed by XRD, FTIR, SEM, EDX and BET methods. Also, its adsorption performance was systematically examined in the removal of Tartrazine (TZ), as a sulfonated azo dye model, from aqueous phase. Our results showed that the HDA modification remarkably improved the adsorption ability of montmorillonite toward TZ molecules. The highest adsorption efficiency was achieved >98% at the pH range of 4-6 within a fast process (less than 30 min). The maximum adsorption capacity Mt-HDA toward TZ molecules was found to be ~59 mg/g at 45 °C. The kinetic study indicated that the adsorption kinetic follows pseudo-second-order model, which shows the chemisorption process between Mt-HDA and TZ molecules. Besides, the adsorption isotherm showed the monolayer coverage of Mt-HDA surface adsorption sites, which was fitted with the Langmuir isotherm model in an exothermic process. The adsorption mechanism was studied.

The surfactant-ionic liquid bi-functionalization of chitosan beads for their adsorption performance improvement toward Tartrazine

In this study, the ionic liquid (Aliquat-336) and anionic surfactant (cetyltrimethylammonium bromide, CTAB) bi-functionalized chitosan beads were prepared and characterised using different techniques, including FTIR, XRD, SEM, EDS and BET surface area analysis. The characteristic analysis confirmed the successful conjugation of chitosan beads with both surfactant and ionic liquid. The novel fabricated beads (CS-CTAB-AL) were efficiently employed, as a high-performance adsorbent, for the removal of Tartrazine (TZ), an anionic food dye, from polluted water. The optimum adsorption of TZ onto the CS-CTAB-AL was found at 2 g L^-1 of adsorbent in the wide pH range of 4-11, whereas just 45 min was required to reach more than 90% adsorption efficiency in the studied conditions. Also, the adsorption and kinetic studies showed that the experimental data well fitted the pseudo-first-order kinetic model and the Langmuir isotherm model. The maximum adsorption capacity of prepared beads was found to be 45.95 mg g^-1 at 45 °C. The adsorption properties of enabling CS-CTAB-AL conjugation introduced a new type of adsorbents, exploited the combination of ionic liquid and surfactant capabilities for wastewater treatment.

A Model for the Structure of Adsorbed Layers at Solid/Liquid Interfaces

Understanding the structure of adsorbed layers, including their composition (the mole fraction of sorbate, x_A) and thickness (d_al), is of great significance for revealing the nature of adsorption and guiding its applications. Many techniques have been used to estimate the structure of adsorbed layers of organics at solid/liquid interfaces. However, there is still a lack of feasible thermodynamic models to describe the correlation between the structure (more precisely, x_A and d_al) and the equilibrium adsorption amount (Γ_e). Herein, a thermodynamic model, called the dynamic bonding equilibrium (DBE) model, was developed on the basis of the adsorption equilibrium thermodynamics with an assumption that, at adsorption equilibrium, the sorbate and solvent within the adsorbed layer both exist in different bonding states. The DBE model relates x_A and d_al with Γ_e and thus can predict or describe the structure (x_A and d_al) of adsorbed layers from Γ_e. Its rationale was confirmed by the literature-reported adsorption data of organics, including surfactants, proteins, and polymers, on hydrophilic and hydrophobic surfaces in water. This work provides a feasible approach for obtaining information about the structure of adsorbed layers at solid/liquid interfaces.

Removal of metal ions using a new magnetic chitosan nano-bio-adsorbent; A powerful approach in water treatment

In this study, a magnetic chitosan/Al₂O₃/Fe₃O₄ (M-Cs) nanocomposite was developed by ethylenediaminetetraacetic acid (EDTA) functionalization to enhance its adsorption behavior for the removal of Cd(II), Cu(II) and Zn(II) metal ions from aqueous solution. The results revealed that the EDTA functionalization of M-Cs increased its adsorption capacity ~9.1, ~5.6 and ~14.3 times toward Cu, Cd and Zn ions. The maximum adsorption capacity followed the order of Cd(II) > Cu(II) > Zn(II) and the maximum adsorption efficiency was achieved at pH of 5.3 with the removal percentage of 99.98, 93.69 and 83.81 %, respectively, for the removal of Cu, Cd and Zn ions. The metal ions adsorption kinetic obeyed pseudo-second-order equation and the Langmuir isothermal was found the most fitted model for their adsorption isothermal experimental data. In addition, the thermodynamic study illustrated that the adsorption process was exothermic and spontaneous in nature.

Mussel-inspired triple bionic adsorbent: Facile preparation of layered double hydroxide@polydopamine@metal-polyphenol networks and their selective adsorption of dyes in single and binary systems

To effectively address the serious human health challenges and ecological damage caused by organic dyes in wastewater, we developed a novel bionic adsorbent (LDH@PDA@MPNs) for the selective adsorption and removal of malachite green (MG) and crystalline violet (CV). The adsorbent was prepared using a facile two-step method based on mussel-inspired chemistry and metal complexation. The physicochemical structure, surface morphology, and composition of the LDH@PDA@MPNs were characterized by scanning electron microscopy, Fourier-transform infrared spectrometry, X-ray photoelectron spectroscopy, and thermogravimetric analysis. Adsorption of MG and CV with the LDH@PDA@MPNs was evaluated. Under optimal conditions, the maximum adsorption of MG and CV by the adsorbent was 89.608 and 40.481 mg/g, respectively. The adsorption kinetics showed that the experimental data were in good agreement with the pseudo-second-order kinetic model, and the equilibrium adsorption isotherm data fitted well with the Freundlich model. The thermodynamic results indicated that the adsorption of the dyes on LDH@PDA@MPNs was a spontaneous endothermic process. Importantly, the bionic adsorbent not only shows high removal efficiency by easy regeneration with low-cost reagents but also exhibits high selectivity for dyes in both single and binary systems. Therefore, LDH@PDA@MPNs have the potential to adsorb and remove dyes from complex wastewater solutions.

Evaluating the Effect of Ionic Liquid on Biosorption Potential of Peanut Waste: Experimental and Theoretical Studies

Peanut skin having polyphenols as major constituents is a natural, abundant, and environmentally friendly potent biosorbent for aquatic pollutants such as heavy metals. Its natural potential can be enhanced several times by treating it with ionic liquids-the green solvents. This report presents a complete study on biosorption of divalent cadmium ions using ionic liquid-treated peanut skin. Initially, both peanut biomasses, skin and shells, were tested, and peanut skin was used for thorough experimentation because of its higher adsorption potential (q _e values). Ionic liquids are highly green and designed solvents with vast adjustable striking features such as high thermal and chemical stability, insignificant vapor pressure, wide electrochemical assortment, non-volatility, non-flammability, less toxicity, and high recycling ability. Peanut skin after treatment with ionic liquids was characterized via FTIR, TGA, SEM, and XRD. The biosorption process was optimized with respect to time, temperature, metal ion concentrations, agitation speed, pH, and adsorbent dose. Data obtained were interpreted by kinetic, isothermal, and thermodynamic models. The biosorbent and ionic liquid both are regenerated and recycled up to three times, so cost effectiveness is a promising thing.

A novel graphene oxide-dicationic ionic liquid composite for Cr(VI) adsorption from aqueous solutions

A novel graphene oxide-dicationic ionic liquid composite (GO-DIL) was prepared by modifying graphene oxide (GO) with a dicationic ionic liquid (DIL), 3,3'-(butane-1,4-diyl) bis (1-methyl-1H-imidazol-3-ium) chloride ([C₄(MIM)₂]Cl₂). GO and GO-DIL were characterized by SEM, BET, FTIR, and XPS, and the materials were used for Cr(VI) adsorption. Batch adsorption studies showed that adsorption reached equilibrium within 40 min, and the optimal pH was 3, where the electrostatic attraction between GO-DIL and Cr(VI) was maximized. The maximum theoretical Cr(VI) adsorption capacity (q_m) was 271.08 mg g^-1, and q_m remained above 228.00 mg g^-1 after five cycles. The adsorption data were fitted well by both the pseudo-first-order kinetic model and the Langmuir model. Furthermore, thermodynamics calculations revealed that adsorption was a spontaneous endothermic process. Importantly, electrostatic attraction between Cr(VI) and the protonated imidazole N⁺ of GO-DIL played a critical role in Cr(VI) adsorption, and Cr(VI) was reduced to Cr(III). Thus, GO-DIL is predicted to be an effective adsorbent for Cr(VI) and other heavy metal ions in wastewater.

Ionic liquid-based antimicrobial materials for water treatment, air filtration, food packaging and anticorrosion coatings

Efforts to widen the scope of ionic liquids applications across diverse research areas have flourished in the last two decades with developments in understanding and tailoring their physical, chemical, and biological properties. The promising applications of ionic liquids-based materials as antimicrobial systems is due to their ability and flexibility to be tailored in varying sizes, morphologies, and surface charges. Ionic liquids are also considered as greener materials. Common methods for the preparation of ionic liquid-based materials include crosslinking, loading, grafting, and combination of ionic liquids with other polymeric materials. Recent research focuses on the tuning of the biological properties to design novel ionic liquids-based antimicrobial materials. Here, the properties, synthesis and applications of ionic liquids and ionic liquids-based materials are reviewed with focus on antimicrobial activities applied to water treatment, air filtration, food packaging, and anticorrosion.

Adsorption of Cetylpyridinium Chloride at Silica Nanoparticle/Water Interfaces (I): Dependence of Adsorption Equilibrium on Particle Size

In the current work, a size-effect model was developed to describe the particle size-dependence of adsorption at solid/liquid interfaces. A parameter, ΔQ_ad, was introduced, defined as the change of the product of the solid/liquid interfacial tension and the molar volume of solid surface components caused by adsorption. The model predicts that with a decrease in particle radius (r), the saturation adsorption amount per unit area (Γ_m, mol/m²) decreases, while the change of the adsorption equilibrium constant (K_ad) is determined by the ΔQ_ad, namely, it decreases if ΔQ_ad > 0 but increases if ΔQ_ad < 0. There exists a critical r at which the saturation adsorption amount per unit mass (Γ_m^g, mol/g) attains a maximum. In addition, the adsorption of cetylpyridinium chloride (CPyCl), a cationic surfactant, on silica nanoparticles with different r (ca. 6-61 nm) values was determined at 298 K and pH 9, showing an obvious size-dependence. With a decrease in r, K_ad and Γ_m decrease, indicating a decrease in the affinity of silica particles toward CPyCl. The size-dependent adsorption data can be well described using our model. Adsorption can affect the molar volume of the solid surface phase, which plays an important role in the size-dependence of adsorption. This work provides a better understanding of the size-dependent adsorption phenomenon at solid/liquid interfaces.

Removal of extracellular antibiotic resistance genes using magnetic biochar/quaternary phosphonium salt in aquatic environments: A mechanistic study

The proliferation and spread of antibiotic resistance genes (ARGs) is becoming a worldwide crisis. Extracellular DNA encoding ARGs (eARGs) in aquatic environment plays a critical role in the dispersion of antimicrobial resistance genes. Strategies to control the dissemination of eARGs are urgently required for ecological safety and human health. Towards this goal, magnetic biochar/quaternary phosphonium salt (MBQ), was used to investigate the efficiency and removal mechanism for eARGs. Magnetic biochar modified by quaternary phosphonium salt enhanced the adsorption capacity of extracellular DNA to approximately 9 folds, compared to that of the unmodified. DNA adsorption by MBQ was mainly dominated by chemisorption in heterogeneous systems and was promoted in acidic and low-salt environment. The generation of •OH and MBQ colloid jointly cleaved DNA into fragments, facilitating the adsorption of the phosphate backbone of DNA onto MBQ through electrostatic force as well as the conformational transition of DNA. Furthermore, quantification of extracellular DNA after MBQ was applied in water demonstrated that over 92.7% of resistance genes were removed, indicating a significantly reduced risk of propagation of antimicrobial resistance in aquatic environments. These findings have a practical significance in the application of MBQ in mitigating the spread of ARGs in aquatic environment.

Novel 1-butyl-3-methylimidazolium bromide impregnated chitosan hydrogel beads nanostructure as an efficient nanobio-adsorbent for cationic dye removal: Kinetic study

In the present study, a novel 1-butyl-3-methylimidazolium bromide (BmImBr) impregnated chitosan beads were prepared and characterized using different methods, including XRD, FT-IR, EDX, SEM and BET. The FTIR analysis revealed that the BmImBr was successfully conjugated with the chitosan in the beads structure. The prepared beads were used as an efficient sorbent for the fast removal of methylene blue, as cationic dye model, from aqueous solution, whereas just 25 min was required to reach 86% removal efficiency. The increasing of BmImBr amount improved the adsorption performance of prepared beads. Also, it was found that the dye can be higher adsorbed on the beads surface by increasing the sorbent dosage and pH of solution, while the optimum dosage and pH were obtained 3 mg/L and 11, respectively. The kinetic study showed that the MB adsorption onto the CS-BmImBr beads follows the pseudo-fist order model and the intrinsic penetration controls the adsorption process. The properties of prepared chitosan- BmImBr IL conjugation confirmed that it can be exploited as an efficient adsorbent in the wastewater treatment.

A Review on Ionic Liquid Gas Separation Membranes

Ionic liquids have attracted the attention of the industry and research community as versatile solvents with unique properties, such as ionic conductivity, low volatility, high solubility of gases and vapors, thermal stability, and the possibility to combine anions and cations to yield an almost endless list of different structures. These features open perspectives for numerous applications, such as the reaction medium for chemical synthesis, electrolytes for batteries, solvent for gas sorption processes, and also membranes for gas separation. In the search for better-performing membrane materials and membranes for gas and vapor separation, ionic liquids have been investigated extensively in the last decade and a half. This review gives a complete overview of the main developments in the field of ionic liquid membranes since their first introduction. It covers all different materials, membrane types, their preparation, pure and mixed gas transport properties, and examples of potential gas separation applications. Special systems will also be discussed, including facilitated transport membranes and mixed matrix membranes. The main strengths and weaknesses of the different membrane types will be discussed, subdividing them into supported ionic liquid membranes (SILMs), poly(ionic liquids) or polymerized ionic liquids (PILs), polymer/ionic liquid blends (physically or chemically cross-linked 'ion-gels'), and PIL/IL blends. Since membrane processes are advancing as an energy-efficient alternative to traditional separation processes, having shown promising results for complex new separation challenges like carbon capture as well, they may be the key to developing a more sustainable future society. In this light, this review presents the state-of-the-art of ionic liquid membranes, to analyze their potential in the gas separation processes of the future.

Adsorption and desorption of malachite green by using chitosan-deep eutectic solvents beads

Chitosan-deep eutectic solvent (DES) beads were prepared from chitosan and DESs. The DESs used were choline chloride-urea (DES A) and choline chloride-glycerol (DES B). Both chitosan-DES beads were used to remove malachite green (MG) dye from an aqueous solution. The optimum pH for chitosan-DES A was recorded at pH 8.0 while optimum pH for chitosan-DES B was pH 9.0. The maximum adsorption capacity obtained for chitosan-DES A and chitosan-DES B were 6.54 mg/g and 8.64 mg/g, respectively. The optimum conditions for both chitosan-DES beads to remove MG were 0.08 g of adsorbent and 20 min of agitation time. Five kinetic models were applied to analyse the data and the results showed that the pseudo-second-order and intraparticle diffusion model fitted best with R² > 0.999. For the adsorption capacity, results show that the Freundlich and Langmuir adsorption isotherms fitted well with chitosan-DES A and chitosan-DES B, respectively. The maximum adsorption capacities (q_max) obtained from chitosan-DES A and chitosan-DES B were 1.43 mg/g and 17.86 mg/g, respectively. Desorption indicated good performance in practical applications.

One-step fabrication of photoluminescent SiC quantum dots through a radiation technique

The fabrication of PL SiC-QDs by using ionic liquid-based microemulsions combined with electron beam radiation.