Polymeric Materials for Rare Earth Elements Recovery.

Rare earth elements (REEs) play indispensable roles in various advanced technologies, from electronics to renewable energy. However, the heavy global REEs supply and the environmental impact of traditional mining practices have spurred the search for sustainable REEs recovery methods. Polymeric materials have emerged as promising candidates due to their selective adsorption capabilities, versatility, scalability, and regenerability. This paper provides an extensive overview of polymeric materials for REEs recovery, including polymeric resins, polymer membranes, cross-linked polymer networks, and nanocomposite polymers. Each category is examined for its advantages, challenges, and notable developments. Furthermore, we highlight the potential of polymeric materials to contribute to eco-friendly and efficient REEs recovery, while acknowledging the need to address challenges such as selectivity, stability, and scalability. The research in this field actively seeks innovative solutions to reduce reliance on hazardous chemicals and minimize waste generation. As the demand for REEs continues to rise, the development of sustainable REEs recovery technologies remains a critical area of investigation, with the collaboration between researchers and industry experts driving progress in this evolving field.

Multicomponent Acrylic Formulation Design for Corrosion Casting with Controlled Mechanical Properties.

Corrosion casting based on the curing of acrylic resins enables one to create casts as replicas of body systems, enhancing our knowledge of veterinary medicine. The identification of the optimal chemical formulations as well as the processing conditions, the delivery of good control during the liquid state and the excellent macroscopic properties during solidification and after use are remaining challenges. In the present work, based on the identification of more qualitative trends, it is demonstrated that multicomponent comonomer mixtures are interesting materials that can be used to expand the range of mechanical properties and can specifically result in a better balance between stiffness and flexibility while guaranteeing dimensional stability. Emphasis is put on a large pool of formulations in the testing phase to then perform a detailed mechanical flexural analysis for the most promising cases during a more rigorous testing phase, accounting for a new pragmatic protocol for the pot life. This protocol consists of a vial-based turning test and a measurement of the viscosity variation up to 1000 mPa∙s and highlights the complex interplay between the overall initial concentrations and the impact of the absence of mixing once the system is at rest. It is demonstrated that the use of only low-molar-mass crosslinkers should be avoided, and overall, an intermediate amount of crosslinkers is recommendable.

Development of a chlorhexidine delivery system based on dental reline acrylic resins.

The high recurrence rate of common denture stomatitis after antifungal treatment is still concerning. This condition is caused by low patient compliance and incomplete local elimination of the main etiological factor - Candida albicans, often associated with other microorganisms, such as Streptococcus species. Impregnating denture materials with antimicrobials for local delivery is a strategy that can overcome the side effects and improve the efficacy of conventional treatments (topical and/or systemic). In this work, we describe the development of three hard autopolymerizing reline acrylic resins (Kooliner, Ufi Gel Hard, and Probase Cold) loaded with different percentages of chlorhexidine (CHX). The novel formulations were characterized based on their antimicrobial activity, mechanical, morphological and surface properties, in-vitro drug release profiles, and cytotoxicity. The addition of CHX in all resins did not change their chemical and mechanical structure. Among all the tested formulations, Probase Cold loaded with 5 wt% CHX showed the most promising results in terms of antimicrobial activity and lack of serious detrimental mechanical, morphological, surface, and biological properties.

Extending the Metabolite Diversity of the Endophyte Dimorphosporicola tragani.

Fungi are one of the most prolific sources of microbial secondary metabolites. The production of new metabolites can be achieved using multiple fermentation conditions and by adding small-molecule effectors, including epigenetic modifiers. In the framework of our Natural Product screening programme targeting the discovery of new antimicrobial compounds, we applied multiple fermentation conditions and adsorptive polymeric resins on a large collection of fungal endophytes, to increase and stimulate their fungal secondary metabolite production. During this work the endophytic fungus Dimorphosporicola tragani CF-090383 showed antimicrobial activity only when grown in presence of adsorptive polymeric resins. In addition, seven epigenetic modifiers were added to fermentations of this endophytic fungus, in an attempt to activate its cryptic pathways as well as to analyse the metabolites produced under these conditions. D. tragani was seen to produce three different mycotoxin dendrodolides when the epigenetic modifiers 5-azacytidine and valproic acid were added to the fermentations, and these compounds were further characterized. However, the fungus produced the fatty acid synthesis inhibitor cerulenin, a molecule not previously described to be produced by this fungal species, only when cultivated in presence of the XAD-16 resin. We have found that the addition of XAD-16 resin resulted in four-fold higher titers in the production of cerulenin when compared to the best production conditions described in literature for the original fungal producer strain, Cephalosporium caerulens KF-140 (=Sarocladium oryzae), in a zeolite-based fermentation, used as an ammonium ion-trapping agent. The production of cerulenin by this strain of D. tragani, represents an alternative source for the improved production of cerulenin with better yields.

Adsorption of micropollutants present in surface waters onto polymeric resins: Impact of resin type and water matrix on performance.

The occurrence of micropollutants in water resources is raising substantial concerns, worldwide. These pollutants may have adverse impacts on the aquatic ecosystem and human health. Even though activated carbon is commonly used as an adsorbent to remove micropollutants from water, its low removal of hydrophilic components, energy-intensive regeneration procedure and slow adsorption can impair its applicability. Polymeric resins have been suggested as an effective alternative adsorbent due to their high porosity and accessible adsorption sites, significant adsorption concentration and stable chemical properties. In this work, we evaluated the performance of five commercially available polymeric resins (including two ion exchange resins) for the removal of nine selected micropollutants in water. More specifically, we investigated the effect of polymeric resin type and concentration, contact time and water matrix on the removal efficiency of five pharmaceuticals, two pesticides and two endocrine disruptors of high current concern (diclofenac, sulfamethoxazole, fluoxetine, caffeine, carbamazepine, 17-ß estradiol, norethindrone, atrazine and desesthylatrazine). Results presented herein indicated that two hydrophobic polymeric resins can effectively adsorb over 80% of the targeted micropollutants within 30 min when the resin concentration was higher than 2.5 mL L-1. The adsorption data were well described with the Freundlich isotherm and the pseudo-second order kinetic model very well described the kinetic process of the selected micropollutants onto the polymeric resins. Moreover, we observed that increasing the synthetic water temperature from 4 to 22 °C led to a marginally higher micropollutant uptake and the presence of natural organic matter had no noted impact on the efficiency of the resins in removing the tested micropollutants when the resin dosage was 5.4 mL L-1. On the basis of these promising results, we conclude that polymeric resins are a promising alternative to activated carbon for micropollutants sorption in drinking water treatment.

Metamorphosis in the Porosity of Recycled Concretes Through the Use of a Recycled Polyethylene Terephthalate (PET) Additive. Correlations between the Porous Network and Concrete Properties.

In the field of construction, sustainable building materials are currently undergoing a process of technological development. This study aims to contribute to understanding the behavior of the fundamental properties of concretes prepared with recycled coarse aggregates that incorporate a polyethylene terephthalate (PET)-based additive in their matrix (produced by synthesis and glycolysis of recycled PET bottles) in an attempt to reduce their high porosity. Techniques to measure the gas adsorption, water porosity, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) were used to evaluate the effect of the additive on the physical, mechanical and microstructural properties of these concretes. Porosity reductions of up to 30.60% are achieved with the addition of 1%, 3%, 4%, 5%, 7% and 9% of the additive, defining a new state in the behavioral model of the additive (the overdosage point) in the concrete matrix; in addition, the porous network of these concretes and their correlation with other physical and mechanical properties are also explained.

Designing micro- and mesoporous carbon networks by chemical activation of organic resins.

Carbon xerogels with ultrahigh micro- and mesopore volumes were synthesized from the activation of polymeric resins prepared by sol-gel polycondensation of resorcinol/formaldehyde mixtures in basic medium and subcritical drying. Various activating conditions (e.g., agent, temperature, impregnation conditions) were used and it was found that the textural features of the resulting carbon xerogels are linked to the experimental procedure of the activation reaction to promote the porosity development. The shrinkage and structural collapse of the fragile resins typically obtained upon annealing at high temperatures (during carbonization and/or physical activation) is suppressed when the impregnation of the chemical activating agent is performed under controlled conditions. If the alkaline reagent (either KOH or K2CO3) is put in contact with the resin by wet impregnation (liquid/solid); under such conditions, the intimate contact between both compounds allows the formation of microporosity during the activation along with the enlargement and/or preservation of the mesoporosity of the pristine resin. Furthermore, the chemical activation via wet impregnation allows the combination of high surface areas and the preservation (even higher development) of the mesoporosity created during the synthesis of the resin. The effect of the impregnation method was found highly dependent of the reagent and activation temperature, highlighting the possibility to design micro-mesoporous carbon xerogels at low temperatures with a subtle control of the activation conditions.

Selective recovery of acidic and lactonic sophorolipids from culture broths towards the improvement of their therapeutic potential.

Sophorolipids (SLs) were produced by Starmerella bombicola. The separation and purification of SLs are a complex process, since they are produced as a mixture of compounds with few structural differences. Solvent extraction is commonly used in downstream processing. In this work, an environmental friendly approach was developed for SLs recovery and purification, based on neutral polymeric sorbents, Amberlite XAD16NTM, XAD18TM, and XAD1600NTM. In batch microassays, key parameters of sorption/desorption process (e.g., contact time, temperature, sorbents, and SLs concentrations) were optimized for separation of acidic and lactonic SLs. Sorption equilibrium was reached after 2-3 h, for all the sorbents tested. Among them XAD1600NTM showed a higher sorption capacity (q max 230 mg g-1), a higher removal (≈100 %) of acidic and lactonic SLs [1 and 2.5 % (w/v)], and the best selectivity. Methanol, ethanol, and acetone were suitable for SLs elution. A selective desorption of SLs was attained with acetonitrile aqueous solutions (v/v): (1) 25 % led to 88.3 % of acidic SLs and (2) 55 % followed by methanol solution (100 %) led to 93.2 % of purified lactonic SLs. This achievement was particularly important regarding SLs potential therapeutic applications, since acidic and lactonic SLs show different biologic activities. In fact, acid SLs show higher virucidal and pro-inflammatory cytokine activity, while lactonic SLs show stronger spermicidal and anti-cancer activity.

Sorption of the herbicides diquat and difenzoquat from aqueous medium by polymeric resins in the presence of sodium dodecylsulfate: Kinetic and mechanistic study.

The goal of this work was to propose a novel method for the solid-phase extraction of the herbicides diquat (DQT(2+)) and difenzoquat (DFQT(+)) from aqueous medium using polymeric Amberlite XAD-2 and XAD-4 resins in the presence of sodium dodecylsulfate (SDS). The addition of SDS to the medium was of fundamental importance in order to allow the formation of a negatively charged surface able to sorb the cationic solutes. Several factors that could influence the sorption process, such as SDS concentration in the medium, sorbent mass, pH, ionic strength, and initial concentration of the solutes were investigated. Kinetic studies were also performed to model the system and to identify the mechanisms that operate the sorption process of the herbicides. SDS concentration in the medium presented remarkable influence on the extraction efficiency, achieving maximum values when the ratios [SDS]/[herbicide] were approximately 90, for XAD-2, and 22 and 11 for DQT(2+) and DFQT(+), respectively, for XAD-4. The sorption process followed a pseudo second-order kinetic in all cases studied. It was also found that an intraparticle diffusion process controlled exclusively the sorption of the herbicides by the Amberlite XAD-2 and XAD-4 resins in the first 15 min, becoming less active with time.

Synthesis, characterization and evaluation of two crosslinked polymeric resins and their comparison with walnut shell in oil removal from water.

The aim of this paper was to compare two kinds of adsorbents (walnut shell and polymeric resins) in terms of their efficiency to remove oil from water, since walnut shell losses weight during the process requiring interruption, while polymeric resins do not. Polymeric resins based on glycidyl methacrylate and divinylbenzene (GMA-DVB) and styrene and divinylbenzene (STY-DVB) were synthesized and characterized. All adsorbents were tested by continuous flow process, eluting 3,000 bed volumes of synthetic oily water, and the oil content was monitored by fluorescence spectroscopy. Although the walnut shell presented high efficiency (∼94%), STY-DVB was even better (∼100%) besides presenting better mechanical resistance. Moreover, polymeric resins, mainly when based on GMA, can be chemically modified to remove specific contaminants still remaining in water after conventional treatment.

Removal of naphthalene from aqueous systems by poly(divinylbenzene) and poly(methyl methacrylate-divinylbenzene) resins.

Treatment of the oily wastewater from crude oil extraction is a growing challenge due to rising concern for the environment. Polyaromatic hydrocarbons (PAHs) deserve special attention because of their high toxicity. There is a need to develop processes able to minimize the discharge of these compounds and analytic techniques to monitor the levels of PAHs in aqueous media. In this study poly(methyl methacrylate-divinylbenzene) (MMA-DVB) and poly(divinylbenzene) (DVB) were assessed with respect to their capacity to retain naphthalene (NAF) in continuous flow and batch processes (adsorption equilibrium and kinetics). The analytic techniques applied were gas chromatography and spectrofluorimetry, which was adapted for quantification of NAF. The batch adsorption studies showed that DVB is more efficient in adsorption than MMA-DVB, and the Freundlich model and pseudo-second-order model better fitted the equilibrium data and adsorption kinetics, respectively. The elution results showed that both resins are highly efficient in removing NAF, with DVB outperforming MMA-DVB. However, MMA is cheaper raw material, making MMA-DVB more competitive for treatment of oily wastewater. The resins were regenerated by eluting about 7.2 and 2.5 L of methanol:water (70:30 v/v), respectively for DVB and MMA-DVB. Regarding to the useful life after regeneration, the resins presented a reduction about 30%, relating to zero concentration of NAF.

Iron-mediated oxidation of arsenic(III) by oxygen and hydrogen peroxide: dispersed versus resin-supported zero-valent iron.

The goal of this study is to assess the differences in As(III) removal kinetics and mechanisms between dispersed zero-valent iron (d-ZVI) and resin-supported zero-valent iron (D201-ZVI) in the presence of dissolved oxygen and hydrogen peroxide. Experimental results show that As(III) could be removed by all the studied systems (d-ZVI/O2, d-ZVI/H2O2, D201-ZVI/O2, D201-ZVI/H2O2). The d-ZVI/H2O2 system was more efficient than D201-ZVI/H2O2 for the oxidation of As(III). Similar trends were observed in O2 system for both solids. The kinetic behaviors as well as the influence of a hydroxyl radical scavenger (2-propanol) on the oxidation of As(III) at different pH suggest that the oxidation of As(III) in the d-ZVI/O2 and d-ZVI/H2O2 systems occurred mainly through Fenton-like reactions. The oxidation of As(III) in the D201-ZVI/O2 and D201-ZVI/H2O2 systems might be expected as follows: As(III) was firstly adsorbed onto the surface of the D201-ZVI, and then oxidation may proceed mainly through a non-Fenton mechanism that directly converts H2O2 into O2 and H2O. In addition, certain iron oxides in the D201-ZVI could also serve as oxidants for As(III) oxidation. The significant differences between the dispersed and supported ZVIs suggest that the supporting matrix interfered in the removal process, which deserves a further investigation.