Surface modification of electrospun polyester nanofibers with cyclodextrin polymer for the removal of phenanthrene from aqueous solution

Applications of macrocycle-based solid-state host-guest chemistry

Macrocyclic molecules have been used in various fields owing to their guest binding properties. Macrocycle-based host-guest chemistry in solution can allow for precise control of complex formation. Although solution-phase host-guest complexes are easily prepared, their limited stability and processability prevent widespread application. Extending host-guest chemistry from solution to the solid state results in complexes that are generally more robust, enabling easier processing and broadened applications. Macrocyclic compounds in the solid state can encapsulate guests with larger affinities than their soluble counterparts. This is crucial for use in applications such as separation science and devices. In this Review, we summarize recent progress in macrocycle-based solid-state host-guest chemistry and discuss the basic physical chemistry of these complexes. Representative macrocycles and their solid-state complexes are explored, as well as potential applications. Finally, perspectives and challenges are discussed.

A novel multifunctional β-cyclodextrin polymer as a promising sorbent for rapid removal of methylene blue from aqueous solutions

Production wastewater has evolved with dye and printing technology to become one of the major sources of soil and water contamination. The majority of dyes are carcinogenic, teratogenic, and mutagenic compounds. As a result, dealing with the dye in the wastewater is a critical issue. Insoluble polymers of β-cyclodextrin (β-CD), an inexpensive, sustainably produced macrocycle of glucose, have potential to remove dyes from water/wastewater via sorption due to formation of well-defined host-guest complexes. A novel polymeric sorbent based on cyclodextrin was successfully synthesized in a one-step reaction with few reagents. The polymer is characterized by multifunctionality and cross-linked network structure. The sorption studies aimed at the removal of methylene blue (MB) from aqueous solutions. The dominant model was Langmuir isotherm which indicated a sorption capacity of 96.15 mg/g. The rapid removal has already been obtained after 1 min, around 84 % of efficiency. The molecular mechanism of MB sorption by poly(β-CD-BPDA) network is found mostly on the electrostatic interactions and partially on the inclusion of complexation inside supramolecular pores based on cyclodextrins' cavities, hydrogen bonding and slightly π-stacking. The presented polymer seems to be a promising sorbent for the removal of hazardous organic pollutants from water/wastewater.

Adsorption of Fatty Acid on Beta-Cyclodextrin Functionalized Cellulose Nanofiber

Fatty acids in wastewater contribute to high chemical oxygen demand. The use of cellulose nanofiber (CNF) to adsorb the fatty acids is limited by its strong internal hydrogen bonding. This study aims to functionalize CNF with β-cyclodextrin (β-CD) and elucidate the adsorption behaviour which is yet to be explored. β-CD functionalized CNF (CNF/β-CD) was achieved by crosslinking of β-CD and citric acid. Functionalization using 7% (w/v) β-CD and 8% (w/v) citric acid enhanced mechanical properties by increasing its thermal decomposition. CNF/β-CD was more efficient in removing palmitic acid, showcased by double adsorption capacity of CNF/β-CD (33.14% removal) compared to CNF (15.62% removal). CNF/β-CD maintained its adsorption performance after five cycles compared to CNF, which reduced significantly after two cycles. At 25 °C, the adsorption reached equilibrium after 60 min, following a pseudo-second-order kinetic model. The intraparticle diffusion model suggested chemical adsorption and intraparticle interaction as the controlling steps in the adsorption process. The maximum adsorption capacity was 8349.23 mg g−1 and 10485.38 mg g−1 according to the Sips and Langmuir isotherm model, respectively. The adsorption was described as monolayer and endothermic, and it involved both a physisorption and chemisorption process. This is the first study to describe the adsorption behaviour of palmitic acid onto CNF/β-CD.

Removal of organic micropollutans by adsorptive membrane

Various emerging organic micropollutants, such as pharmaceuticals, have attracted the interest of the water industry during the last two decades due to their insufficient removal during conventional water and wastewater treatment methods and increasing demand for pharmaceuticals projected to climate change-related impacts and COVID-19, nanosorbents such as carbon nanotubes (CNTs), graphene oxides (GOs), and metallic organic frameworks (MOFs) have recently been extensively explored regarding their potential environmental applications. Due to their unique physicochemical features, the use of these nanoadsorbents for organic micropollutans in water and wastewater treatment processes has been a rapidly growing topic of research in recent literature. Adsorptive membranes, which include these nanosorbents, combine the benefits of adsorption with membrane separation, allowing for high flow rates and faster adsorption/desorption rates, and have received a lot of publicity in recent years. The most recent advances in the fabrication of adsorptive membranes (including homogeneous membranes, mixed matrix membranes, and composite membranes), as well as their basic principles and applications in water and wastewater treatment, are discussed in this review. This paper covers ten years, from 2011 to 2021, and examines over 100 published studies, highlighting that micropollutans can pose a serious threat to surface water environments and that adsorptive membranes are promising, particularly in the adsorption of trace substances with fast kinetics. Membrane fouling, on the other hand, should be given more attention in future studies due to the high costs and restricted reusability.

Zein adsorbents with micro/nanofibrous membrane structure for removal of oils, organic dyes, and heavy metal ions in aqueous solution

Developing multi-functional media for effectively removing different contaminants coexisted in wastewater system is highly desired. Herein, zein, a natural protein possessing abundant functional groups in molecule, is chosen to be fabricated into micro/nanofibrous membranes as adsorbents and separation media. Zein fibers with novel groove ribbon structures, which possess better structural characteristics, are designed for obtaining good adsorption performance. The adsorption performances of zein fiber membranes are evaluated. The results show that zein fiber membranes have the adsorption capacities up to 94 g/g for motor oil, 168 mg/g for Congo red, and 189 mg/g for Pb²⁺ ion for 1000 mg/L initial solution concentration, showing considerable competitiveness as compared with the reported adsorbents. The zein membrane with groove ribbon fiber morphology exhibits optimal adsorption capability and can be attractive multi-functional separation media.

Multifunctional β-Cyclodextrin-EDTA-Chitosan polymer adsorbent synthesis for simultaneous removal of heavy metals and organic dyes from wastewater

Heavy metals and organic dyes are the major source of water pollution. Herein, a trifunctional β-cyclodextrin-ethylenediaminetetraacetic acid-chitosan (β-CD-EDTA-CS) polymer was synthesized using an easy and simple chemical route by the reaction of activated β-CD with CS through EDTA as a cross-linker (amidation reaction) for the removal of inorganic and organic pollutants from aqueous solution under different parameters such as pH, time effect, initial concentration, reusability, etc. The synthesized adsorbent was characterized using powder X-ray diffraction, Fourier transform infrared spectroscopy, field scanning electron microscopy, energy dispersive spectroscopy, Brunauer-Emmett-Teller (BET), thermogravimetric analyzer techniques to investigate their structural, functional, morphological, elemental compositions, surface area and thermal properties, respectively. Two types of heavy metals, i.e., mercury (Hg²⁺) and cadmium (Cd²⁺), and three organic dyes, i.e., methylene blue (MB), crystal violet (CV) and safranin O (SO) were chosen as inorganic and organic pollutants, respectively, to study the adsorption capacity of β-CD-EDTA-CS in aqueous solution. The β-CD-EDTA-CS shows monolayer adsorption capacity 346.30 ± 14.0 and 202.90 ± 13.90 mg g^-1 for Hg²⁺ and Cd²⁺, respectively, and a heterogeneous adsorption capacity 107.20 ± 5.70, 77.40 ± 5.30 and 55.30 ± 3.60 mg g^-1 for MB, CV and SO, respectively. Kinetics results followed pseudo-second order (PSO) kinetics behavior for both metal ions and dyes, and higher rate constants values (0.00161-0.00368 g mg^-1 min^-1) for dyes confirmed the cavitation of organic dyes (physisorption). In addition, we have also demonstrated the performance of β-CD-EDTA-CS for the of four heavy metals Hg²⁺, Cd²⁺, Ni²⁺, and Cu²⁺ and three dyes MB, CV, and SO in secondary treated wastewater. Findings of this study indicate that β-CD-EDTA-CS simple and essay to synthesize and can be use in wastewater treatment.

Modification of cyclodextrin and use in environmental applications

Water pollution, which has become a global problem in parallel with environmental pollution, is a problem that needs to be solved urgently, considering the gradual depletion of water resources. The inadequacy of the water treatment methods and the materials used somehow directed the researchers to look for dual character structures such as biocompatible and biodegradable β-cyclodextrin (β-CD). β-CD, which is normally insoluble in water, is used in demanding wastewater applications by being modified with the help of different agents to be water soluble or transformed into polymeric adsorbents as a result of co-polymerization via cross-linkers. In this way, in addition to the host-guest interactions offered by β-CD, secondary forces arising from these interactions provide advantages in terms of regeneration and reusability. However, the adsorption efficiency and synthesis steps need to be improved. Based on the current studies presented in this review, in which cross-linkers and modification methods are also mentioned, suggestions for novel synthesis methods of new-generation β-CD-based materials, criticisms, and recent methods of removal of micropollutants such as heavy metals, industrial dyes, harmful biomolecules, and pharmaceutics wastes are mentioned.

Simultaneous Removal of Heavy Metals and Ciprofloxacin Micropollutants from Wastewater Using Ethylenediaminetetraacetic Acid-Functionalized β-Cyclodextrin-Chitosan Adsorbent

The current study pertains to the synthesis of an EDTA-functionalized β-cyclodextrin-chitosan (β-CD-CS-EDTA) composite via a two-step process for the adsorptive removal of toxic heavy metallic ions (i.e., Pb(II), Cu(II), and Ni(II)) and antibiotic micropollutant, i.e., ciprofloxacin (CIP), from water. Different batch adsorption experiments such as pH, reaction time and initial pollutant concentration effects were carried out to identify the adsorption condition to attain the maximum removal efficiency. Kinetics results fit well with the pseudo-second order (PSO) kinetics model for both inorganic and organic pollutants. However, adsorption of heavy metal ions to the adsorbent was faster than that of CIP. Isotherms results showed excellent monolayer adsorption capacities of 330.90, 161, and 118.90 mg g^-1 for Pb(II), Cu(II), and Ni(II), respectively, with a heterogeneous adsorption capacity of 25.40 mg g^-1 for CIP. The adsorption mechanism was investigated using energy dispersive X-ray (EDX), elemental mapping, and Fourier transform infrared (FTIR) techniques. More significantly, the synthesized adsorbent gave good removal efficiencies when it was applied to simultaneously adsorb metal ions and CIP from real wastewater. Furthermore, excellent reusability could be obtained, making it a viable alternative to remove the inorganic and organic micropollutants for wastewater treatment.

Polymer-free cyclodextrin and natural polymer-cyclodextrin electrospun nanofibers: A comprehensive review on current applications and future perspectives

The present review discusses the use of cyclodextrins and their derivatives to prepare electrospun nanofibers with specific features. Cyclodextrins, owing to their unique capability to form inclusion complexes with hydrophobic and volatile molecules, can indeed facilitate the encapsulation of bioactive compounds in electrospun nanofibers allowing fast-dissolving products for food, biomedical, and pharmaceutical purposes, filtering materials for wastewater and air purification, as well as a variety of other technological applications. Additionally, cyclodextrins can improve the processability of naturally occurring biopolymers helping the fabrication of "green" materials with a strong industrial relevance. Hence, this review provides a comprehensive state-of-the-art of different cyclodextrins-based nanofibers including those made of pure cyclodextrins, of polycyclodextrins, and those made of natural biopolymer functionalized with cyclodextrins. To this end, the advantages and disadvantages of such approaches and their possible applications are investigated along with the current limitations in the exploitation of electrospinning at the industrial level.

Film-like bacterial cellulose/cyclodextrin oligomer composites with controllable structure for the removal of various persistent organic pollutants from water

The adsorptive removal of persistent organic pollutants (POPs) is reckoned as a simple, convenient, and practical technology, especially in decentralized systems and remote areas. For this purpose, it is important to design new adsorbents, with controllable structure and convenient shape, for the highly efficient removal of POPs. In this study, we describe a strategy for film-like water purifier, prepared by loading cyclodextrin (CD) oligomer onto the ultrafine nanofibers of 3D bacterial cellulose. The optimum product exhibits remarkable removal ability toward various target pollutants such as phenol, bisphenol A (BPA), glyphosate and 2,4-Dichlorophenol (2,4-DCP), with capacities higher than most adsorbents including porous carbon based materials reported previously. Moreover, our sample demonstrated stable adsorption ability over a broad pH range and under more complex water conditions, and more importantly excellent reusability. A rough cost analysis highlights the commercial potential of our sample. We reckon our study provides new insight for the design of adsorbent with high yet stable adsorption ability and controllable structure. Furthermore, the product can be used to treat actual sewage with its convenient film-like shape and excellent performance, which improves its potential in complex systems and large-scale applications.

Electrospun polyurethane/phytic acid nanofibrous membrane for high efficient removal of heavy metal ions

Polyurethane (PU) nanofibers possess large specific surface area and excellent mechanical properties which have been used as the matrix for many applications. Phytic acid is the biocompatible and environment-friendly organic acid with excellent chelating ability of heavy metal ions due to it contains 6 phosphate groups. In this study, the PU/phytic acid nanofibrous membrane has been successfully produced by electrospinning which was used for Pb²⁺ removal. Though phytic acid would improve the hydrophilicity and reduce the mechanical properties to a certain extent, the phytic acid-modified PU nanofibrous membrane still possessed excellent mechanical properties. The PU/phytic acid nanofibrous membrane achieved the highest adsorption capacity (136.52 mg/g) of Pb²⁺ under the condition of the pH of Pb²⁺ solution was 6 and the adsorption temperature and time were 20°C and 10 h which was over 6 times higher the unmodified one's (21.06 mg/g). These results demonstrated that the electrospun PU/phytic acid nanofibrous membrane could obtain high adsorption capacity of Pb²⁺ and it would achieve the potential application in the fields of the removal of heavy metal ions.

Cyclodextrin Polymers and Cyclodextrin-Containing Polysaccharides for Water Remediation

Chemical pollution of water has raised great concerns among citizens, lawmakers, and nearly all manufacturing industries. As the legislation addressing liquid effluents becomes more stringent, water companies are increasingly scrutinized for their environmental performance. In this context, emergent contaminants represent a major challenge, and the remediation of water bodies and wastewater demands alternative sorbent materials. One of the most promising adsorbing materials for micropolluted water environments involves cyclodextrin (CD) polymers and cyclodextrin-containing polysaccharides. Although cyclodextrins are water-soluble and, thus, unusable as adsorbents in aqueous media, they can be feasibly polymerized by using different crosslinkers such as epichlorohydrin, polycarboxylic acids, and glutaraldehyde. Likewise, with those coupling agents or after substituting hydroxyl groups with more reactive moieties, cyclodextrin units can be covalently attached to a pre-existing polysaccharide. In this direction, the functionalization of chitosan, cellulose, carboxymethyl cellulose, and other carbohydrate polymers with CDs is vastly found in the literature. For the system containing CDs to be used for remediation purposes, there are benefits from a synergy that arises from (i) the ability of CD units to interact selectively with a broad spectrum of molecules, forming inclusion complexes and higher-order supramolecular assemblies, (ii) the functional groups of the crosslinker comonomers, (iii) the three-dimensional structure of the crosslinked network, and/or (iv) the intrinsic characteristics of the polysaccharide backbone. In view of the most recent contributions regarding CD-based copolymers and CD-containing polysaccharides, this review discusses their performance as adsorbents in micropolluted water environments, as well as their interaction patterns, addressing the influence of their structural and physicochemical properties and their functionalization.

Polycyclodextrins: Synthesis, functionalization, and applications

Cyclodextrins (CDs) are cyclic oligosaccharides with unique conical structure enabling host-guest inclusion complexes. However, virgin CDs sufferfrom low solubility, lack of functional groups and its inability to strong complexation with the guests. One of the most efficient ways to improve the properties of cyclodextrins is the synthesis of polycyclodextrins. Generally, there are two types of polycyclodextrins: 1) polymers containing CD units as parts of the main backbone; and 2) polymers with CD units as side chains. These polycyclodextrins are produced (i) from direct copolymerization of virgin cyclodextrins or cyclodextrins derivatives with various monomers including isocyanates, epoxides, carboxylic acids, anhydrides, acrylates, acrylamides and fluorinated aromatic compounds, or (ii) by post-functionalization of other polymers with CDs or CD derivatives.. By selecting the proper derivatives of CDs and controlling the polymerization, polycyclodextrins with linear, hyperbranched, and crosslinked structures have been synthesized. Polycyclodextrins have found significant applications in numerous areas, as adsorbents for removal of organic pollutants, carriers in gene/drug delivery, and for preparation of supramolecular based hydrogels. The focus of this review paper is placed on the synthesis, characterization, and applications of CDs so as to highlight challenges as well as the promising features of the future ahead of material developments based on CDs.

Analytical techniques to recognize inclusion complexes formation involving monoterpenes and cyclodextrins: A study case with (-) borneol, a food ingredient

Monoterpenes are non-polar secondary metabolites widely used by industry due to their excellent therapeutic, food-ingredient and cosmetic properties. However, their low solubility in water limits their use. In this sense, cyclodextrins (CDs) have been widely used to solve these technological challenges. Thus, this study aims to use (-)-borneol as a monoterpene model to prepare inclusion complexes between β-CD and hydroxypropyl-β-CD (HP-β-CD) through different ways and characterize them in order to choose the best inclusion method to improve physicochemical properties of monoterpenes. To achieve this goal, the samples were prepared by physical mixture (PM), paste complex (PA) and freeze-drying complex (FD) and then, extensively characterized by thermal analysis, Fourier-transform infrared spectroscopy, scanning electron microscopy, size particle, X-ray diffraction and nuclear magnetic resonance. The physicochemical results showed that freeze-drying was more effective to form inclusion complexes between (-)-borneol with both CDs. This research highlights the importance of recognizing the best method to prepare inclusion complexes, including food additives as (-)-borneol, to achieve better results in food preparations.

Biofunctionalized nanomaterials for in situ clean-up of hydrocarbon contamination: A quantum jump in global bioremediation research

Interfacing organic or inorganic nanoparticles with biological entities or molecules or systems with the aim of developing functionalized nano-scale materials or composites for remediation of persistent organic hydrocarbon pollutants (such as monocyclic and polycyclic aromatic hydrocarbons, MAH/PAH) has generated great interest and continues to grow almost unabated. However, the usefulness and potency of these materials or conjugates hinges over several key barriers, including structural assembly with fine-tuned control over nanoparticle/biomolecule ratio, spatial orientation and activity of biomolecules, the nano/bio-interface strategy and hierarchical architecture, water-dispersibility and long term colloidal stability in environmental media, and non-specific toxicity. The present review thus critically analyses, discusses and interprets recently reported attempts and approaches to functionalize nanoparticles with biomolecules. Since there is no comprehensive and critical reviews on the applications of nanotechnology in bioremediation of MAHs/PAHs, this overview essentially captures the current global scenario and vision on the use and future prospects of biofunctionalized nanomaterials with respect to their strategic interactions involved at the nano/bio-interface essential to understand and decipher the structural and functional relationships and their impact on persistent hydrocarbon remediation.

Development of Water-Compatible Molecularly Imprinted Polymers Based on Functionalized β-Cyclodextrin for Controlled Release of Atropine

Herein, a novel method for molecularly imprinted polymers (MIPs) using methacrylic acid functionalized beta-cyclodextrin (MAA-β-CD) monomer is presented, which was designed as a potential water-compatible composite for the controlled release of atropine (ATP). The molecularly imprinted microspheres with pH-sensitive characteristics were fabricated using thermally-initiated precipitation polymerization, employing ATP as a template molecule. The effects of different compounds and concentrations of cross-linking agents were systematically investigated. Uniform microspheres were obtained when the ratio between ATP, MAA-β-CD, and trimethylolpropane trimethacrylate (TRIM) was 1:4:20 (mol/mol/mol) in polymerization system. The ATP loading equilibrium data was best suited to the Freundlich and Langmuir isotherm models. The in vitro drug release study was assessed under simulated oral administration conditions (pH 1.5 and 7.4). The potential usefulness of MIPs as drug delivery devices are much better than non-molecularly imprinted polymers (NIPs). The study shows that the prepared polymers are a pH stimuli-responsive system, which controlled the release of ATP, indicating the potential applications in the field of drug delivery.

Fabrication of a PAN–PA6/PANI membrane using dual spinneret electrospinning followed by in situ polymerization for separation of oil-in-water emulsions

A polyacrylonitrile–polyamide 6/polyaniline (PAN–PA6/PANI) doped membrane was prepared using dual spinneret simultaneous electrospinning of PAN and PA6 and in situ polymerization of aniline at low temperature.

Efficient Removal of Polycyclic Aromatic Hydrocarbons and Heavy Metals from Water by Electrospun Nanofibrous Polycyclodextrin Membranes

Here, a highly efficient membrane based on electrospun polycyclodextrin (poly-CD) nanofibers was prepared and exploited for the scavenging of various polycyclic aromatic hydrocarbons (PAHs) and heavy metals from water. The poly-CD nanofibers were produced by the electrospinning of CD molecules in the presence of a cross-linker (i.e., 1,2,3,4-butanetetracarboxylic acid), followed by heat treatment to obtain an insoluble poly-CD nanofibrous membrane. The membrane was used for the removal of several PAH compounds (i.e., acenaphthene, fluorene, fluoranthene, phenanthrene, and pyrene) and heavy metals (i.e., Pb²⁺, Ni²⁺, Mn²⁺, Cd²⁺, Zn²⁺, and Cu²⁺) from water over time. Experiments were made on the batch sorption of PAHs and heavy metals from contaminated water to explore the binding affinity of PAHs and heavy metals to the poly-CD membrane. The equilibrium sorption capacity (q _e) of the poly-CD nanofibrous membrane was found to be 0.43 ± 0.045 mg/g for PAHs and 4.54 ± 0.063 mg/g for heavy metals, and the sorption kinetics fitted well with the pseudo-second-order model for both types of pollutants. The membrane could be recycled after treatment with acetonitrile or a 2% nitric acid solution and reused up to four times with similar performance. Further, dead-end filtration experiments showed that the PAH removal efficiencies were as high as 92.6 ± 1.6 and 89.9 ± 4.8% in 40 s for the solutions of 400 and 600 μg/L PAHs, respectively. On the other hand, the removal efficiencies for heavy metals during the filtration were 94.3 ± 5.3 and 72.4 ± 23.4% for 10 and 50 mg/L solutions, respectively, suggesting rapid and efficient filtration of heavy metals and PAHs by the nanofibrous poly-CD membrane.

β-Cyclodextrin modified electrospinning fibers with good regeneration for efficient temperature-enhanced adsorption of crystal violet

Novel β-cyclodextrin modified fibers with highly insoluble infraction and temperature enhanced adsorption performance were fabricated via electrospinning technology and followed thermo-crosslinking. The fabricated fibers were characterized by FT-IR, ¹H NMR, TGA and SEM. In the fibers, β-CD was crosslinked with methacrylic acid (MAA) units to maintain morphologies of fibers and further be utilized for the adsorption of Crystal Violet through complex and electrostatic interaction. In particular, N-isopropyl acrylamide (NIPAM) units were introduced to create thermo-responsively hydrophobic internal cavity within the swelling fibers at high temperatures. Benefiting from that, the maximum adsorption amount could reach to 1253.78 mg g^-1, enhanced by 20% than that at low temperatures. The adsorption data of the fibers fit well the pseudo-second-order model and Langmuir isotherm model. Moreover, the fibers could maintain high regeneration efficiency even after four adsorption-desorption cycles. These results indicated the practical application values of the β-cyclodextrin modified fibers in the dye wastewater treatment field.

Cyclodextrin modified filter paper for removal of cationic dyes/Cu ions from aqueous solutions

A filter paper was functionalized with β-cyclodextrin and citric acid via esterification reaction for the removal of dyes and Cu ions from aqueous solutions. The adsorption capacity and removal performance of the modified filter paper (MFP) was investigated using static and dynamic adsorption experiments. The static adsorption data fit well the Langmuir and pseudo-second-order models, and the adsorption capacity of Methylene Blue (MB), Brilliant Green (BG), Rhodamine-B (RB) and Cu(II) over the MFP were 124.6 mg/g, 130.4 mg/g, 99.7 mg/g and 39.1 mg/g, respectively, which are much higher than the unmodified filter paper (below 2 mg/g). Even better, the decolorization performance and Cu(II) removal of MFP are remarkable in dynamic adsorption. The effluent can reach the National Standard for dyeing and finishing of textile industry of China after three cycles in a continuous filtration-adsorption system. This method provides a new pathway to achieve high efficiency removal of dyes and metal ions from wastewater.

Poly(butylene succinate-co-terephthalate) nanofibrous membrane composited with cyclodextrin polymer for superhydrophilic property

Tailoring the wetting properties of nanofibrous membranes and endowing them with expected wettability provides new ways in extending the application field of these materials. In this study, we first performed the in situ fabrication of poly(butylenes succinate-co-terephthalate) (PBST) composite nanofibrous membrane with cyclodextrin polymer (CDP) using a combination of electrospinning and heating processes. Then, the morphologies, crystallization and mechanical properties of the PBST composite membrane were investigated. It was found that the CDP was uniformly dispersed on the PBST nanofibers instead of merely covering the surface of the membrane. Moreover, the introduction of additives brought about a decreased crystallinity and tensile strength of the resultant membrane due to its restraining role in the crystallization of PBST. Furthermore, the wettability of the PBST composite membranes with various amounts of additives was explored and the evolution of water spread on top of the membranes was also recorded. The membrane became superhydrophilic from hydrophobic upon increasing the amount of additives and the water droplet could completely spread within 0.2 s, which was attributed to the enlarged roughness and increased contact area of CDP on the nanofibers. A comparison between the two fabrication methods used for PBST composite nanofibrous membranes is also presented and studies on the preparation and wetting properties may shed light on polymer composite membranes that exhibit potential application in more fields.

We present a facile fabrication method for a PBST composite nanofibrous membrane with cyclodextrin polymer via electrospinning and heating processes. The membrane is superhydrophilic and water can completely spread on the surface within just 0.2 s.

One-pot synthesis of trifunctional chitosan-EDTA-β-cyclodextrin polymer for simultaneous removal of metals and organic micropollutants

The global contamination of water resources with inorganic and organic micropollutants, such as metals and pharmaceuticals, poses a critical threat to the environment and human health. Herein, we report on a bio-derived chitosan-EDTA-β-cyclodextrin (CS-ED-CD) trifunctional adsorbent fabricated via a facile and green one-pot synthesis method using EDTA as a cross-linker, for the adsorption of toxic metals and organic micropollutants from wastewater. In this system, chitosan chain is considered as the backbone, and the immobilized cyclodextrin cavities capture the organic compounds via host-guest inclusion complexation, while EDTA-groups complex metals. The thoroughly characterized CS-ED-CD was employed for batch adsorption experiments. The adsorbent displayed a monolayer adsorption capacity of 0.803, 1.258 mmol g-1 for Pb(II) and Cd(II) respectively, while a heterogeneous sorption capacity of 0.177, 0.142, 0.203, 0.149 mmol g-1 for bisphenol-S, ciprofloxacin, procaine, and imipramine, respectively. The adsorption mechanism was verified by FT-IR and elemental mapping. Importantly, the adsorbent perform is effective in the simultaneous removal of metals and organic pollutants at environmentally relevant concentrations. All these findings demonstrate the promise of CS-ED-CD for practical applications in the treatment of micropollutants. This work adds a new insight to design and preparation of efficient trifunctional adsorbents from sustainable materials for water purification.

Fabrication of cellulose acetate/polybenzoxazine cross-linked electrospun nanofibrous membrane for water treatment

Herein, polybenzoxazine based cross-linked cellulose acetate nanofibrous membrane exhibiting enhanced thermal/mechanical properties and improved adsorption efficiency was successfully produced via electrospinning and thermal curing. Initially, suitable solution composition was determined by varying the amount of the benzoxazine (BA-a) resin, cellulose acetate (CA) and citric acid (CTR) to obtain uniform nanofibrous membrane via electrospinning. Subsequently, thermal curing was performed by step-wise at 150, 175, 200 and 225°C to obtain cross-linked composite nanofibrous membranes. SEM images and solubility experiments demonstrated that most favorable result was obtained from the 10% (w/v) CA, 5% (w/v) BA-a and 1% (w/v) CTR composition and cross-linked nanofibrous membrane (CA10/PolyBA-a5/CTR1) was obtained after the thermal curing. Chemical structural changes (ring opening) occurred by thermal curing revealed successful cross-linking of BA-a in the composite nanofibrous membrane. Thermal, mechanical and adsorption performance of pristine CA and CA10/PolyBA-a5/CTR1 nanofibrous membranes were studied. Char yield of the pristine CA nanofibrous membrane has increased notably from 12 to 24.7% for composite CA10/PolyBA-a5/CTR1 membrane. When compared to pristine CA membrane, CA10/PolyBA-a5/CTR1 nanofibrous membrane has shown superior mechanical properties having tensile strength and Young's modulus of 8.64±0.63MPa and 213.87±30.79MPa, respectively. Finally, adsorption performance of pristine CA and CA10/PolyBA-a5/CTR1 nanofibrous membranes was examined by a model polycyclic aromatic hydrocarbon (PAH) compound (i.e. phenanthrene) in aqueous solution, in which CA10/PolyBA-a5/CTR1 nanofibrous membrane has shown better removal efficiency (98.5%) and adsorption capacity (592μg/g).

Electrospun crosslinked poly-cyclodextrin nanofibers: Highly efficient molecular filtration thru host-guest inclusion complexation

Water pollution is a serious concern for public health and environment in today’s world; hence, there exists a strong demand to develop cost-effective, sustainable and eco-friendly membranes. Here, we produce a highly efficient molecular filter membrane based on bio-renewable material; cyclic oligosaccaharides known as cyclodextrins (CD). Crosslinked insoluble poly-CD nanofibers are produced by using electrospinning technique in the absence of any additional polymeric carrier. Poly-CD nanofibrous membrane exhibit significant affinity to a common class of organic pollutant (i.e. methylene blue (MB)). Remarkably, the electrospun poly-CD nanofibrous web can outdistance the commonly used filter material (i.e. activated carbon) in terms of removal capacity. The flexible and free-standing poly-CD nanofibrous membrane depicted outstanding filtration performance. We estimate of above 90% removal efficiency for highly concentrated solutions of MB pollutant (40 mg/L) under extremely high flux (3840 Lm⁻²h⁻¹). Essentially, these poly-CD nanofibrous webs demonstrate quite rapid uptake of MB from liquid environment. Overall, bio-based flexible electrospun poly-CD nanofibrous membrane represents a highly efficient molecular filter for wastewater treatment.

Poly-cyclodextrin cryogels with aligned porous structure for removal of polycyclic aromatic hydrocarbons (PAHs) from water

Cyclodextrins (CDs) are sugar-based cyclic oligosaccharides, which form inclusion complexes with small guest molecules through their hydrophobic cavity. Here we successfully synthesized highly porous poly-cyclodextrin (poly-CD) cryogels, which were produced under cryogenic conditions by the cross-linking of amine-functional CDs with PEG-based diepoxide cross-linker. The poly-CD cryogels showed aligned porous network structures owing to the directional freezing of the matrix, of which the pore size and architecture exposed variations depending on the composition of the reactants. The cryogels were employed for the removal of genotoxic polycyclic aromatic hydrocarbons (PAHs) from aqueous solutions. They reached PAH sorption capacities as high as 1.25mg PAH per gram cryogel. This high sorption performance is due to interactions between PAHs and the complete swollen network, and thus, is not restricted by interfacial adsorption. Given that the hydrophilic nature of the components, the sorption performance could only be attributed to the inclusion complex formation of CDs with PAH molecules. The poly-CD cryogels could be recycled with an exposure to ethanol and reused without any significant loss in the sorption capacity of PAHs.

Electrospun Fibers of Cyclodextrins and Poly(cyclodextrins)

Cyclodextrins (CDs) can endow electrospun fibers with outstanding performance characteristics that rely on their ability to form inclusion complexes. The inclusion complexes can be blended with electrospinnable polymers or used themselves as main components of electrospun nanofibers. In general, the presence of CDs promotes drug release in aqueous media, but they may also play other roles such as protection of the drug against adverse agents during and after electrospinning, and retention of volatile fragrances or therapeutic agents to be slowly released to the environment. Moreover, fibers prepared with empty CDs appear particularly suitable for affinity separation. The interest for CD-containing nanofibers is exponentially increasing as the scope of applications is widening. The aim of this review is to provide an overview of the state-of-the-art on CD-containing electrospun mats. The information has been classified into three main sections: (i) fibers of mixtures of CDs and polymers, including polypseudorotaxanes and post-functionalization; (ii) fibers of polymer-free CDs; and (iii) fibers of CD-based polymers (namely, polycyclodextrins). Processing conditions and applications are analyzed, including possibilities of development of stimuli-responsive fibers.

Pentynyl Ether of β-Cyclodextrin Polymer and Silica Micro-Particles: A New Hybrid Material for Adsorption of Phenanthrene from Water

A new hybrid material for the removal of polycyclic aromatic hydrocarbons (PAH) from water was prepared by the polymerization of pentynyl beta-cyclodextrin (PyβCD) and silica micro-particles (SMP). Phenanthrene, being one of the important members of the PAH family and a potential risk for environmental pollution, was selected for this study. Results show that phenanthrene removal efficiency of the SMP was improved significantly after hybridization with PyβCD-polymer. Approximately 50% of the phenanthrene was removed in the first 60 min and more than 95% was removed in less than 7 h when 25 mL of the 2 ppm aqueous phenanthrene solution was incubated with the 100 mg of SMP-PyβCD-polymer material. Infrared spectroscopy and thermal gravimetric analysis show that the enhanced efficiency of the SMP-PyβCD-polymer compared to the unmodified SMP was due to the formation of the inclusion complexation of phenanthrene with the PyβCD. These results indicate that SMP-PyβCD polymers have a potential to be applied as molecular filters in water purification systems and also for waste water treatment.