Rapid enrichment of rare-earth metals by carboxymethyl cellulose-based open-cellular hydrogel adsorbent from HIPEs template

Advancements in functional adsorbents for sustainable recovery of rare earth elements from wastewater: A comprehensive review of performance, mechanisms, and applications

Rare earth elements (REEs) are crucial metallic resources that play an essential role in national economies and industrial production. The reclaimation of REEs from wastewater stands as a significant supplementary strategy to bolster the REEs supply. Adsorption techniques are widely recognized as environmentally friendly and sustainable methods for the separation of REEs from wastewater. Despite the growing interest in adsorption-based REEs separation, comprehensive reviews of both traditional and novel adsorbents toward REEs recovery remain limited. This review aims to provide a thorough analysis of various adsorbents for the recovery of REEs. The types of adsorbents examined include activated carbons, functionalized silica nanoparticles, and microbial synthetic adsorbents, with a detailed evaluation of their adsorption capacities, selectivity, and regeneration potential. This study focuses on the mechanisms of REEs adsorption, including electrostatic interactions, ion exchange, surface complexation, and surface precipitation, highlighting how surface modifications can enhance REEs recovery efficiency. Future efforts in designing high-performance adsorbents should prioritize the optimization of the density of functional groups to enhance both selectivity and adsorption capacity, while also maintaining a balance between overall capacity, cost, and reusability. The incorporation of covalently bonded functional groups onto mechanically robust adsorbents can significantly strengthen chemical interactions with REEs and improve the structural stability of the adsorbents during reuse. Additionally, the development of materials with high specific surface areas and well-defined porous structures is benifitial to facilitating mass transfer of REEs and maximizing adsorption efficiency. Ultimately, the advancement of the design of efficient, highly selective and recyclable adsorbents is critical for addressing the growing demand for REEs across diverse industrial applications.

Glycopolymer-Mediated Selective Separation of Middle Rare Earth Elements

The selective separation of rare earth elements (REEs) remains a formidable challenge due to limitations of current methodologies, which struggle to achieve the separation efficiency required for their critical industrial applications. Middle REEs (MREEs), characterized by their intermediate ionic radii, are particularly challenging to separate without size-specific trapping mechanisms. In this study, we report a novel approach that synergistically combines heavy metal sequestration with size-selective separation, utilizing negatively charged glycopolymers to achieve the targeted separation of MREEs. We systematically investigated the binding affinities of these glycopolymers for various REEs, focusing on the selective isolation of MREEs through a controlled variation of glycopolymer properties, including degree of polymerization (DP) and charge density. Our findings reveal a distinctive U-shaped selectivity profile, with a marked preference for Samarium (Sm) and Europium (Eu) over other REEs such as Cerium (Ce), Gadolinium (Gd), and Holmium (Ho). This selectivity underscores the potential for designing tailored separation processes optimized for specific MREEs. Moreover, enrichment experiments demonstrated the practical viability of our methodology, achieving over 10 % selectivity for Sm in a Ce/Sm mixture with a 10 : 1 Ce/Sm ratio, a trend that held for Sm in a Ho/Sm Mixture with a 10 : 1 Ho/Sm ratio, indicating significant selectivity over both light and heavy REEs. A subsequent separation experiment using a 1 : 1 Ce/Sm mixture yielded a 15 % enrichment after only five passes through a filter containing minimal amounts of glycopolymer, highlighting the promise of further refinement for enhanced separation efficiency.

Efficient Recovery of Rare Earth Elements from Acidic Wastewater by a Green β-CDs-Functionalized Nanosponge

The recovery of rare earth elements (REEs) from acidic wastewater is crucial to sustainable development, industrial processes, and human health. In this research, β-cyclodextrin-based nanosponges (β-CD/PVA-SA NSs) have been proposed as potential adsorbents for europium (Eu), dysprosium (Dy), and gadolinium (Gd) recovery. The nanosponges are synthesized by cross-linking β-cyclodextrin (β-CD) functionalized polyvinyl alcohol (PVA) and sodium alginate (SA). Experimental results indicate that β-CD/PVA-SA NSs exhibit favorable selectivity for Eu, Dy, and Gd, with the maximum adsorption capacity of 222, 217, and 204 mg/g, respectively, in addition to stability and cyclicity. β-CD/PVA-SA NSs maintain selective adsorption effects towards RE ions that are present in acidic mine drainage (AMD), thereby highlighting their potential for practical applications. Furthermore, density functional theory (DFT) simulations have unveiled the fundamental interactions between the functional groups anchored in β-CD/PVA-SA NSs and the REEs, providing vital insights into their adsorption mechanism. Hence, the utilization of β-CD/PVA-SA NSs has the potential to advance initiatives in remediating acidic water pollution and facilitating the sustainable recycling of RE resources.

Enhancement of Cerium Sorption onto Urea-Functionalized Magnetite Chitosan Microparticles by Sorbent Sulfonation—Application to Ore Leachate

The recovery of strategic metals such as rare earth elements (REEs) requires the development of new sorbents with high sorption capacities and selectivity. The bi-functionality of sorbents showed a remarkable capacity for the enhancement of binding properties. This work compares the sorption properties of magnetic chitosan (MC, prepared by dispersion of hydrothermally precipitated magnetite microparticles (synthesized through Fe(II)/Fe(III) precursors) into chitosan solution and crosslinking with glutaraldehyde) with those of the urea derivative (MC-UR) and its sulfonated derivative (MC-UR/S) for cerium (as an example of REEs). The sorbents were characterized by FTIR, TGA, elemental analysis, SEM-EDX, TEM, VSM, and titration. In a second step, the effect of pH (optimum at pH 5), the uptake kinetics (fitted by the pseudo-first-order rate equation), the sorption isotherms (modeled by the Langmuir equation) are investigated. The successive modifications of magnetic chitosan increases the maximum sorption capacity from 0.28 to 0.845 and 1.25 mmol Ce g−1 (MC, MC-UR, and MC-UR/S, respectively). The bi-functionalization strongly increases the selectivity of the sorbent for Ce(III) through multi-component equimolar solutions (especially at pH 4). The functionalization notably increases the stability at recycling (for at least 5 cycles), using 0.2 M HCl for the complete desorption of cerium from the loaded sorbent. The bi-functionalized sorbent was successfully tested for the recovery of cerium from pre-treated acidic leachates, recovered from low-grade cerium-bearing Egyptian ore.

Green Preparation of Aminated Magnetic PMMA Microspheres via EB Irradiation and Its Highly Efficient Uptake of Ce(III)

The modification of polymers can significantly improve the ability to remove rare earth ions from wastewater, but so far few studies have focused on the irradiation-induced grafting method. In this study, a novel magnetic chelating resin for Ce(III) uptake was first synthesized by suspension polymerization of PMMA@Fe₃O₄ microspheres followed by irradiation-induced grafting of glycidyl methacrylate (GMA) and subsequent amination with polyethyleneimine (PEI). The FT-IR, SEM, TG and XRD characterization confirmed that we had successfully fabricated magnetic PMMA-PGMA-PEI microspheres with a well-defined structure and good thermal stability. The obtained adsorbent exhibited a satisfactory uptake capacity of 189.81 mg/g for Ce(III) at 318.15 K and an initial pH = 6.0. Additionally, the impact of the absorbed dose and GMA monomer concentration, pH, adsorbent dosage, contact time and initial concentration were thoroughly examined. The pseudo-second order and Langmuir models were able to describe the kinetics and isotherms of the adsorption process well. In addition, the thermodynamic data indicated that the uptake process was spontaneous and endothermic. Altogether, this research enriched the Ce(III) trapping agent and provided a new method for the removal rare earth pollutants.

Probing and Manipulating Noncovalent Interactions in Functional Polymeric Systems

Noncovalent interactions, which usually feature tunable strength, reversibility, and environmental adaptability, have been recognized as driving forces in a variety of biological and chemical processes, contributing to the recognition between molecules, the formation of molecule clusters, and the establishment of complex structures of macromolecules. The marriage of noncovalent interactions and conventional covalent polymers offers the systems novel mechanical, physicochemical, and biological properties, which are highly dependent on the binding mechanisms of the noncovalent interactions that can be illuminated via quantification. This review systematically discusses the nanomechanical characterization of typical noncovalent interactions in polymeric systems, mainly through direct force measurements at microscopic, nanoscopic, and molecular levels, which provide quantitative information (e.g., ranges, strengths, and dynamics) on the binding behaviors. The fundamental understandings of intermolecular and interfacial interactions are then correlated to the macroscopic performances of a series of noncovalently bonded polymers, whose functions (e.g., stimuli-responsiveness, self-healing capacity, universal adhesiveness) can be customized through the manipulation of the noncovalent interactions, providing insights into the rational design of advanced materials with applications in biomedical, energy, environmental, and other engineering fields.

Simultaneously Remove and Visually Detect Ce4+ Based on Nanocomposite of UiO-66-NH2/CPA-MA

Effective strategies to deal with rare earth pollution are urgently needed due to the overexploitation of rare earths resource. In this study, a novel nanocomposite of UiO-66-NH2/CPA-MA denoted as UA was successfully synthesized, which can simultaneously remove and detect Ce4+ in water. The hybrid consists of UiO-66-NH2 and CPA-MA. Based on the high adsorption performance of UiO-66-NH2, it can remove Ce4+ with high capacity by adsorption. Moreover, it can change its color from olive drab to light cyan depending on the adsorbed Ce4+ concentration, and the chroma is linearly related to the Ce4+ concentration. So, UA can be used to qualitatively and quantitatively detect Ce4+ by its color changing. The kinetics of adsorption course was investigated in details. The anti-inference ability of the nanocomposite in coexisting systems was carefully evaluated. The results indicate that UiO-66-NH2/CPA-MA is highly potential to deal with Ce4+ pollutions due to its bifunctionality.

Characterization and physicochemical aspects of novel cellulose-based layered double hydroxide nanocomposite for removal of antimony and fluoride from aqueous solution

A series of novel adsorbents composed of cellulose (CL) with Ca/Al layered double hydroxide (CC_xA; where x represent the Ca/Al molar ratio) were prepared for the adsorption of antimony (Sb(V)) and fluoride (F^-) ions from aqueous solutions. The CC_xA was characterized by Fourier-transform infrared spectroscopy (FTIR), Brunauer-Emmett-Teller (BET), elemental analysis (CHNS/O), thermogravimetric analysis (TGA-DTA), zeta potential, X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) analysis. The effects of varying parameters such as dose, pH, contact time, temperature and initial concentration on the adsorption process were investigated. According to the obtained results, the adsorption processes were described by a pseudo-second-order kinetic model. Langmuir adsorption isotherm model provided the best fit for the experimental data and was used to describe isotherm constants. The maximum adsorption capacity was found to be 77.2 and 63.1 mg/g for Sb(V) and F^-, respectively by CC₃A (experimental conditions: pH 5.5, time 60 min, dose 15 mg/10 mL, temperature 298 K). The CC₃A nanocomposite was able to reduce the Sb(V) and F^- ions concentration in synthetic solution to lower than 6 μg/L and 1.5 mg/L, respectively, which are maximum contaminant levels of these elements in drinking water according to WHO guidelines.

Recent advances in separation applications of polymerized high internal phase emulsions

Polymerized high internal phase emulsions as highly porous adsorption materials have received increasing attention and wide applications in separation science in recent years due to their remarkable merits such as highly interconnected porosity, high permeability, good thermal and chemical stability, and tailorable chemistry. In this review, we attempt to introduce some strategies to utilize polymerized high internal phase emulsions for separation science, and highlight the recent advances made in the applications of polymerized high internal phase emulsions for diverse separation of small organic molecules, carbon dioxide, metal ions, proteins, and other interesting targets. Potential challenges and future perspectives for polymerized high internal phase emulsion research in the field of separation science are also speculated at the end of this review.

Preparation of a Hydrogel-Based Adsorbent for Metal Ions through High Internal Phase Emulsion Polymerization

In this work, a porous hydrogel-based adsorbent for metal ions was prepared through the copolymerization of acrylic acid and 2-hydroxyethyl methacrylate using a high internal phase emulsion (HIPE) method. Stretched molecular chains in the hydrogel ensure the excellent accessibility of functional sites by the metal ions. A highly open cellular structure endows the P(AANa-co-HEMA) gel with high transport rates as a promising adsorbent. Adsorption properties were investigated by three isotherm models and two kinetic models. X-ray photoelectron spectroscopy analysis proved a chelating interaction between -COO^- and metal ions. The adsorption capacity reached 630 mg·g^-1 for Pb²⁺ under 303 K and a 400 μg·mL^-1 initial concentration. The results show that the as-prepared PolyHIPE-based P(AANa-co-HEMA) gel possesses an open cellular structure, high adsorption capacity, and high selectivity for Pb²⁺.

Preparation of Carboxymethyl Cellulose-g- Poly(acrylamide)/Attapulgite Porous Monolith With an Eco-Friendly Pickering-MIPE Template for Ce(III) and Gd(III) Adsorption

Due to their high specific surface and metal-binding functional groups in their crosslinked polymeric networks, monolithic materials incorporating a porous structure have been considered one of the most efficient kinds of adsorbents for rare earth element recovery. Herein, a facile and novel monolithic multi-porous carboxymethyl cellulose-g-poly(acrylamide)/attapulgite was synthesized by free radical polymerization via green vegetable oil-in-water Pickering medium internal phase emulsion (O/W Pickering-MIPEs), which was synergically stabilized by attapulgite and tween-20. The homogenizer rotation speed and time were investigated to form stable Pickering-MIPEs. The effects of different types of oil phase on the formation of Pickering-MIPEs were investigated with stability tests and rheological characterization. The structure and composition of the porous material when prepared with eight kinds of vegetable oil were characterized by FTIR and SEM. The results indicate that the obtained materials, which have abundant interconnected porosity, are comparable to those fabricated with Pickering-HIPE templates. The adsorption experiment demonstrated that the prepared materials have a fast capture rate and high adsorption capacities for Ce(III) and Gd(III), respectively. The saturation adsorption capacities for Ce(III) and Gd(III) are 205.48 and 216.73 mg/g, respectively, which can be reached within 30 min. Moreover, the monolithic materials exhibit excellent regeneration ability and reusability. This work provides a feasible and eco-friendly pathway for the construction of a multi-porous adsorbent for adsorption and separation applications.

Synthesis of novel adsorbent by intercalation of biopolymer in LDH for the removal of arsenic from synthetic and natural water

This study focuses on the synthesis of nanocomposites named CCA and CZA that were prepared by the incorporation of cellulose (CL) in the Ca/Al and Zn/Al layered double hydroxide (LDH), respectively. These materials were then used for the uptake of As(III) and As(V) from aqueous medium. Characterization of both nanocomposites (CCA and CZA) was done using FTIR and Raman analysis to identify the functional groups, N₂ adsorption-desorption isotherms to determine the specific surface area and pore geometry and XPS analysis to obtain the surface atomic composition. Some other characters were investigated using simultaneous TGA and DTA and elemental chemical analysis (CHNS/O). The crystallinity of the prepared nanocomposites was displayed by XRD patterns. Furthermore, the sheet-like structure of the LDHs and the irregularity of surface morphology with porous structure were observed by TEM and SEM microphotographs. Optimization of maximum adsorption capacity was adjusted using different parameters including pH, contact time and adsorbent dosage. The pseudo-second-order model was in good fitting with kinetics results. The adsorption isotherm results showed that CZA exhibits better adsorption capacity for As(III) than CCA and the Langmuir isotherm model described the data well for both nanocomposites. Thermodynamic studies illustrated the endothermic nature of CCA and exothermic nature on CZA, as well as the fact that the adsorption process is spontaneous. A real water sample collected from well located in Gabes (Tunisia), has also been treated. The obtained experimental results were confirmed that these sorbents are efficient for the treatment of hazardous toxic species such as.

Nanocellulose-based composites for the removal of contaminants from wastewater

Polymers derived from plant and animal sources are of great interest in wastewater remediation due to their cost-effectiveness and renewable adsorption capabilities, one such polymer is nanocellulose (NC). NC has gained a lot of attention in various research fields due to its abundance in nature, nano-dimension, high surface area, stability and bio-compatibility. As a result, NC has emerged as a great potential adsorbent for the removal of contaminants such as heavy metals, organic dyes, oils, pharmaceutical and etc. in the environmental remediation. This review focuses on the description of the building blocks, structure, properties, isolation and also discusses the potential of nanocellulose based composites materials with reinforcements such as activated carbon, carbon nanotube, graphene oxides, metals, non-metals and ceramics that were effectively used as an adsorbents for diverse organic and inorganic contaminants in water.

Preparation of porous adsorbent via Pickering emulsion template for water treatment: A review

Porous materials as emerging potential adsorbents have received much more attention because they are capable of capturing various pollutants with fast adsorption rate, high adsorption capacity, good selectivity and excellent reusability. In order to prepare porous materials with decent porous structure, Pickering emulsion template method has been proved to be one of the most effective technologies to create pore structure. This paper reviewed comprehensively the latest research progress on the preparation of porous materials from various Pickering emulsions and their applications in the decontamination of pollutants (e.g., heavy metal ions, organic pollutants) and in the oil/water separation. It was expected that the summaries and discussions in this review will provide insights into the design and fabrication of new efficient porous adsorbents, and also give us a better understanding of the subject.

Preparation of Carboxymethyl Cellulose-Based Macroporous Adsorbent by Eco-Friendly Pickering-MIPEs Template for Fast Removal of Pb2+ and Cd2

Recently, Pickering high internal phase emulsions (Pickering HIPEs) have been widely used to fabricate macroporous materials. However, the high usage of poisonous organic solvent in HIPEs not only greatly increases the cost but also is harmful to human health and environment, which leads to limited large-scale applications. In this study, we prepared a novel monolithic macroporous material of carboxymethyl cellulose-g-poly(acrylamide)/montmorillonite (CMC-g-PAM/MMT) by the free radical polymerization via oil-in-water Pickering medium internal phase emulsions (Pickering MIPEs), which used the non-toxic and eco-friendly flaxseed oil as continuous phase, MMT, and Tween-20 (T-20) as stabilizer. The pore structure of the resulting macroporous materials could be tuned easily by adjusting the content of MMT, co-surfactant T-20, and the oil phase volume fraction. The maximal adsorption capacities of the prepared macroporous material for Pb²⁺ and Cd²⁺ were 456.05 and 278.11 mg/g, respectively, and the adsorption equilibrium can be reached within 30 min. Otherwise, the macroporous monolith exhibited excellent reusability through five adsorption–desorption cycles. Thus, the eco-friendly Pickering-MIPEs is a potential alternative method to be used to fabricate multi-porous adsorption materials for environmental applications.

Cryogels of carboxyalkylchitosans as a universal platform for the fabrication of composite materials

Here we report a new simple method for fabrication of supermacroporous beads and monoliths via cross-linking of carboxyalkylated chitosan derivatives with hexamethylene diisocyanate in aqueous solution at subzero temperature. These materials provide high filtration rate and good mass-transfer that in combination with high binding capacity toward metal ions allows their application as a universal platform for fabrication of composite catalysts, sorbents, and metal-affine chromatography stationary phases. Using N-(2-carboxyethyl)chitosan (CEC), we have demonstrated that optimum chitosan carboxylation degree for cryogels synthesis is close to 1.0. Cu(II)-chelated CEC cryogels have shown high efficiency as metal-affinity sorbents for ciprofloxacin recovery. Co(II)-chelated CEC cryogels have been used for fabrication of Co(II) ferrocyanide-containing composite with the distribution coefficient for ¹³⁷Cs of 140,000 ml/g and the adsorption capacity of ˜1 mmol/g. Composite Pd-catalysts supported on CEC cryogel provided tenfold higher reaction rate in 4-nitrophenol reduction in comparison with Pd-catalyst supported on chitosan beads.

Understanding the factors affecting the adsorption of Lanthanum using different adsorbents: A critical review

Over the past few decades, removal and recovery of Lanthanum (La) have received great attention due to its significance in different industrial processes. In this review, the application of various adsorbents viz. biosorbents, commercial and hybrid materials, nanoparticles, nanocomposites etc. have been summarized in terms of the removal and recovery of La. The influence of various operating parameters including pH, dosage, contact time, temperature, coexisting ions, adsorption kinetics, isotherm and thermodynamics were investigated. Statistical analysis of the obtained data revealed that 60% and 70% of the authors reported an optimum pH of 4-6 and a dose of 1-2 g/L, respectively. It can be concluded on the basis of an extensive literature survey that the adsorbent materials (especially hybrids nanocomposites) containing carboxyl, hydroxyl and amine groups offered efficient La removal over a wide range of pH with higher adsorption capacity as compared to other adsorbents (e.g., biosorbents and magnetic adsorbents). Also, in most cases, equilibrium and kinetics were followed by Langmuir and pseudo second-order model and adsorption was endothermic in nature. To evaluate the adsorption efficiency of several adsorbents towards La, desorption and regeneration of adsorbents should be given due consideration. The main objective of the review is to provide an insight into the important factors that may affect the recovery of La using various adsorbents.

Fabrication of novel metal ion imprinted xanthan gum-layered double hydroxide nanocomposite for adsorption of rare earth elements

The work focus to enhance the properties of xanthan gum (XG) by anchoring metal ions (Fe, Zr) and encapsulating inorganic matrix (M@XG-ZA). The fabricated nanocomposite was characterized by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR), surface area (BET) and zeta potential analysis. The adsorption of Sc, Nd, Tm and Yb was investigated after screening of synthesized materials in detail to understand the influence of pH, contact time, temperature and initial REE (rare earth element) concentration both in single and multicomponent system via batch adsorption. The adsorption mechanism was verified by FTIR, SEM and elemental mapping. The SEM images of Zr@XG-ZA demonstrate scutes structure, which disappeared after adsorption of REEs. The maximum adsorption capacities were 132.30, 14.01, 18.15 and 25.73 mg/g for Sc, Nd, Tm and Yb, respectively. The adsorption efficiency over Zr@XG-ZA in multicomponent system was higher than single system and the REEs followed the order: Sc > Yb > Tm > Nd. The Zr@XG-ZA demonstrate good adsorption behavior for REEs up to five cycles and then it can be used as photocatalyst for the degradation of tetracycline. Thus, the work adds a new insight to design and preparation of efficient bifunctional adsorbents from sustainable materials for water purification.

2-Methylol-12-crown-4 ether immobilized PolyHIPEs toward recovery of lithium(i)

A facile strategy to fabricate crown ether (2-methylol-12-crown-4, 2M12C4) immobilized porous polymers (PGMA-CE) was reported toward lithium(i) (Li⁺) recovery.

Magnetic chitosan-based adsorbent prepared via Pickering high internal phase emulsion for high-efficient removal of antibiotics

A novel magnetic chitosan-g-poly(2-acrylamide-2-methylpropanesulfonic acid) (CTS-g-AMPS) porous adsorbent was prepared by grafting the AMPS onto the CTS in the Fe₃O₄ stabilized Pickering high internal phase emulsions (Pickering-HIPEs) and used for the adsorptive removal of the antibiotics tetracycline (TC) and chlorotetracycline (CTC). The results of the structure characterization showed that porous structure of the adsorbent can be tuned easily by altering amount of Fe₃O₄-MNPs-M and the electrostatic attraction of between SO₃^- and CTC, TC was the main adsorption driving force. The adsorption capacities of the adsorbent for TC and CTC can be reached to 806.60 and 876.60mg/g in a wide pH ranged from 3.0 to 11.0, respectively. And the adsorption equilibrium can be reached within 90min for TC and 50min for CTC. The magnetic porous adsorbent had good reusability, which can still attain a high adsorption capacity of 759.82 and 842.99mg/g for TC and CTC after five consecutive adsorption cycles, respectively. Therefore, the as-prepared CTS-g-AMPS magnetic adsorbent is potential to be used for adsorption removal of antibiotics from water.

Fabrication of CMC-g-PAM Superporous Polymer Monoliths via Eco-Friendly Pickering-MIPEs for Superior Adsorption of Methyl Violet and Methylene Blue

A series of superporous carboxymethylcellulose-graft-poly(acrylamide)/palygorskite (CMC-g-PAM/Pal) polymer monoliths presenting interconnected pore structure and excellent adsorption properties were prepared by one-step free-radical grafting polymerization reaction of CMC and acrylamide (AM) in the oil-in-water (O/W) Pickering-medium internal phase emulsions (Pickering-MIPEs) composed of non-toxic edible oil as a dispersion phase and natural Pal nanorods as stabilizers. The effects of Pal dosage, AM dosage, and co-surfactant Tween-20 (T-20) on the pore structures of the monoliths were studied. It was revealed that the well-defined pores were formed when the dosages of Pal and T-20 are 9–14 and 3%, respectively. The porous monolith can rapidly adsorb 1,585 mg/g of methyl violet (MV) and 1,625 mg/g of methylene blue (MB). After the monolith was regenerated by adsorption-desorption process for five times, the adsorption capacities still reached 92.1% (for MV) and 93.5% (for MB) of the initial maximum adsorption capacities. The adsorption process was fitted with Langmuir adsorption isotherm model and pseudo-second-order adsorption kinetic model very well, which indicate that mono-layer chemical adsorption mainly contribute to the high-capacity adsorption for dyes. The superporous polymer monolith prepared from eco-friendly Pickering-MIPEs shows good adsorption capacity and fast adsorption rate, which is potential adsorbent for the decontamination of dye-containing wastewater.

Emulsion-derived hierarchically porous polystyrene solid foam for oil removal from aqueous environment

A novel co-stabilizer consisting of Span 20 and Fe₃O₄ particles stabilized the emulsions well and generated the hierarchically porous Fe₃O₄/polystyrene foams.

Synthesis and characterization of poly(carboxymethyl)-cellulose for enhanced La(III) sorption

The grafting of amino and carboxylic acid groups on cellulose increased La(III) sorption efficiency of cellulose: maximum sorption capacity increased from 38mgLag^-1 for cellulose to 101 and 170mgLag^-1 for amino derivative (PAC) and amino-carboxylic derivative (PCMC). Langmuir equation successfully fits sorption isotherms while uptake kinetics are effectively modeled using the pseudo-first order rate equation (though resistance to intraparticle diffusion plays a significant role in the control of metal recovery). Uptake equilibrium occurred within 150-180min. The thermodynamic study shows that the reaction is spontaneous, endothermic and entropic. Nitric acid solutions (0.5M concentration) can be efficiently used for metal recovery and sorbent can be recycled for at least 5 cycles with limited decrease in sorption performance for the three sorbents. The materials were characterized by elemental analysis, acid-base titration, FTIR spectrometry, x-ray diffraction analysis, X-ray photoelectron spectroscopy, SEM-EDX analysis and also by TGA.

Deep-Eutectic Solvents as MWCNT Delivery Vehicles in the Synthesis of Functional Poly(HIPE) Nanocomposites for Applications as Selective Sorbents

We report an alternative green strategy based on deep-eutectic solvents (DES) to deliver multiwalled carbon nanotubes (MWCNTs) for a bottom-up approach that allows for the selective interfacial functionalization of nonaqueous poly(high internal phase emulsions), poly(HIPEs). The formation and polymerization of methacrylic and styrenic HIPEs were possible through stabilization with nitrogen doped carbon nanotube (CN_X) and surfactant mixtures using a urea-choline chloride DES as a delivering phase. Subtle changes in CN_X concentration (less than 0.2 wt % to the internal phase) produced important changes in the macroporous monolith functionalization, which in turn led to increased monolith hydrophobicity and pore openness. These materials displayed great oleophilicity with water contact angles as high as 140° making them apt for biodiesel, diesel, and gasoline fuel sorption applications. Overall, styrene divinylbenzene (StDvB) based poly(HIPEs) showed hydrophobicity and fuel sorption capacities as high as 4.8 (g/g). Pore hierarchy, namely pore openness, regulated sorption capacity, and sorption times where greater openness resulted in faster sorption and increased sorption capacity. Monoliths were subject to 20 sorption-desorption cycles demonstrating recyclability and stable sorption capacity. Finally, CN_X/surfactant hybrids made it possible to reduce surfactant requirements for successful HIPE formation and stabilization during polymerization. All poly(HIPEs) retained acceptable conversion as a function of CN_X loading nearing 90% or better with thermal stability as high as 283 °C.