Facile preparation of microscale hydrogel particles for high efficiency adsorption of bisphenol A from aqueous solution

Enhanced sorption and fluorescent detection of bisphenol A by using sodium alginate/cellulose nanofibrils/ZIF-8 composite hydrogel

To address the issue of bisphenol A (BPA) contamination in wastewater, a novel hydrogel, sodium alginate/cellulose nanofibrils/ZIF-8 composite hydrogel (SCZC), was synthesized for efficient BPA removal. The SCZC exhibited an exceptional adsorption capacity of 1696 mg/g, aligning well with both Langmuir and pseudo-second-order models. Furthermore, it exhibited remarkable regeneration properties, maintaining 89.1 % of its adsorption capacity even after undergoing five adsorption-desorption cycles. The synthesized SCZC also acted as a fluorescent sensor for detecting BPA, employing dynamic quenching and offering linear detection ranges of 10-100 mg/L and 0.2-1.0 μg/L, with a low detection limit of 0.06 μg/L. Analysis of adsorption and detection mechanisms revealed that SCZC's exceptional performance could be attributed to the three-dimensional (3D) porous structure formed by sodium alginate and cellulose nanofibrils. Economic analysis indicated that SCZC, in comparison to commercially activated carbon, was relatively inexpensive. This study introduces a novel approach for designing and preparing a sodium alginate-based hydrogel incorporating metal-organic frameworks, offering simultaneous BPA detection and removal capabilities.

Self-regeneration hybrid hydrogel for bisphenol a adsorption in water

Hybrid hydrogel was synthesized by immobilizing TiO₂ in polyethylene glycol diacrylate (TiO₂@PEGDA) as an efficient adsorbent with photocatalysis property for bisphenol A (BPA) elimination. TiO₂@PEGDA exhibited spherical and rough structure with limited crystallinity and abundant functional groups. The contact angle increased to 61.96° (TiO₂@PEGDA) from 46.73° (pristine PEGDA), indicating that hydrogel hydrophilicity decreased due to the presence of TiO₂. The swelling capacity of TiO₂@PEGDA (9.0%) was decreased compared with pristine PEGDA (15.6%). Adsorption results demonstrated that the maximum adsorption capacity of TiO₂@PEGDA (101.4 mg/g) for BPA was slightly higher than that of pristine PEGDA (97.68 mg/g). The adsorption capacity was independent with pH below 8 and decreased obviously when the value of pH was higher than 8. The adsorption behavior was fitted well with the pseudo-second-order kinetic and the Langmuir isotherm model. Both ΔG₀ and ΔH₀ were negative, indicating that BPA adsorbed on TiO₂@PEGDA was an exothermic and spontaneous process. Regeneration study was performed by photocatalysis, and the adsorption capacity was 85.6% compared with the initial capacity after four-cycle use, indicating that TiO₂@PEGDA could be recycled without significant adsorption capacity loss. Consequently, TiO₂@PEGDA can serve as an eco-friendly and promising material for efficiently adsorbing BPA with self-clean property.

Application of Microgel as a Sorbent for Bisphenol Analysis in Liquid Food Samples

Bisphenols are well-known endocrine disruptors that can easily migrate from plastic and can containers to food. Due to the complicated matrix and ultra-low concentrations of bisphenols in food, samples require extensive preparation before instrumental analysis. In this paper, an environmental sensitive microgel was employed as a sorbent for the preconcentration of four bisphenols, bisphenol A (BPA), bisphenol B (BPB), bisphenol E (BPE) and bisphenol F (BPF), from liquid food samples. Liquid chromatography with fluorescence detection (LC-FLD) was used for the quantification of bisphenols. By applying microgel solid-phase extraction procedure, the limits of detections achieved in liquid food samples can be lowered to 0.9 µg·L−1 for BPF and BPA, 2.3 µg·L−1 for BPE and 2.9 µg·L−1 for BPB. Only 5 mg of microgel was sufficient to achieve good recoveries (70.5–109%) with precision (RSD 0.21–5.01%, n = 3) for different analyzed liquid food samples spiked at concentration levels of 50 µg·L−1. In five out of twelve of the analyzed samples (pineapple, mandarin, peach, mushroom and pickles), they were contaminated with BPA, and the determined concentration was in the range of 6.2–22 µg·L−1; however, these results are below the specific migration limit (SML) set for BPA (50 µg·kg−1).

Processing and modification of hydrogel and its application in emerging contaminant adsorption and in catalyst immobilization: a review

Due to the wonderful property of hydrogels, they can provide a platform for a wide range of applications. Recently, there is a growing research interest in the development of potential hydrogel adsorbents in wastewater treatment due to their adsorption ability toward aqueous pollutants. It is important to prepare such a hydrogel that possesses appropriate robustness, adsorption capacity, and adsorption efficiency to meet the need of water treatment. In order to improve the property of hydrogels, much effort has been made by researchers to modify hydrogels, among which incorporating inorganic components into the polymeric networks is the most common method, which can reduce the product cost and simplify the preparation procedure. Not only can hydrogel be applied as adsorbent, but it also can be used as matrix for catalyst immobilization. In this review, the key advancement on the preparation and modification of hydrogels is discussed, with special emphasis on the introduction of inorganic materials into polymeric networks and consequential changes in the properties of mechanical strength, swelling, and adsorption. Besides, hydrogels used as adsorbents for removal of dyes and inorganic pollutants have been widely explored, but their use for adsorbing emerging contaminants from aqueous solution has not received much attention. Thus, this review is mainly focused on hydrogels' application in removing emerging contaminants by adsorption. Furthermore, hydrogels can be also applied in immobilizing catalysts, such as enzyme and photocatalyst, to remove pollutants completely and avoid secondary pollution, so their progress as catalyst matrix is overviewed.

In Situ Formation of Ionic Liquid by Metathesis Reaction for the Rapid Removal of Bisphenol A from Aqueous Solutions

In this work we present a rapid and easy method to remove the totality of bisphenol A from aqueous solutions using ionic liquid (IL). Dispersive liquid–liquid microextraction is employed. The IL 1-octyl-3-methylimidazolium bis((trifluoromethane)sulfonyl)imide ([C8C1im] [NTf2]) is formed in situ because of the mixture of 1-octyl-3-methylimidazolium chloride ([C8C1im]Cl) and lithium bis(trifluoromethanesulfonyl)imide (Li[NTf2]) aqueous solutions. A cloud of microdroplets of IL formed by the dispersion generated through the precursors metathesis reaction allows the rapid and total extraction of bisphenol A (BPA). After centrifugation, the formed IL phase is deposited at the bottom of the flask and the total amount of BPA is extracted in the sedimented phase. The volume of IL is very low, in the order of microliters, which enables us to remove all the BPA from the solution. The technique studied is highly efficient, cost-effective, and presents less environmental impact than other extraction techniques, thus becoming an outstanding alternative to the most commonly used methods. BPA concentration is determined by high performance liquid chromatography by injecting the IL phase directly. An extraction kinetic model for the kinetic profile has been tested for this method, which allows to infer the ideal experimental conditions to execute the extraction method.

Hydrophobic-force-driven adsorption of bisphenol A from aqueous solution by polyethylene glycol diacrylate hydrogel microsphere

Polyethylene glycol diacrylate (PEGDA) hydrogel microsphere was synthesized by UV-assisted reverse emulsion polymerization as an efficient adsorbent for water purification. Optical microscopy and TEM proved its spherical and hollow structure, while XRD pattern proved that it was amorphous with limited crystallinity. Abundant oxygen-containing functional groups such as hydroxyl were detected by FTIR. The hydrogels exhibited low swelling capacities ranging from 0.19 to 0.77 g/g in water and would decrease in salty solutions. The effects of operation parameters on the bisphenol A (BPA) adsorption were studied, including the polymer composition between PEGDA and polyethylene glycol methacrylate (PEGMA), initial concentration of BPA, pH, and operation temperature. The resulting hydrogel, especially for PDM₂ (the ratio between PEGDA and PEGMA is 2), was able to effectively enrich BPA in water. The adsorption capacity was nearly stable below pH 8.0 and decreased when beyond 8.0. Thermodynamic parameters reflected that BPA adsorbed by hydrogel was a spontaneous (ΔG⁰ < 0) and exothermic (ΔH⁰ < 0) progress. The adsorption capacity increased with the increase of the concentration of NaCl, exhibiting salinity-enhanced adsorption capacity driven by hydrophobic force. Excellent results were also achieved by applying hydrogel for spiked real surface waters, which accounted for more than 91% compared to simulated solution. As-prepared hydrogel was expected to be good candidate for treatment of endocrine disruptors with lower solubility in water.