Development of an innovative capsule with three-dimension honeycomb architecture via one-step titration-gel method for the removal of methylene blue

Effective enhancement of copper selective removal from sodium alginate-based gel adsorbent by dual construction of slit-shaped structure and internal channel

The Cu(II) treatment in water environment by adsorption has become a major strategy for water pollution control and water resource protection. In view of the planar configuration characteristics of Cu(II) complex, the construction and optimization of adsorbent's internal structure to achieve improved adsorption performance is still a problem worth exploring. Herein, polyvinyl alcohol (PVA) is introduced into graphene oxide/sodium alginate (GO/SA) gel system to obtain PVA/GO/SA gel material, which not only achieves the construction of slit-shaped structure by self-interlayer stacking for GO nanosheets and its cross-linking with SA, but effectively promotes formation of high cross-linking density internal channels by the introduction of PVA, thus achieving the efficacious and selective Cu(II) removal. Maximum adsorption capacity for PVA/GO/SA can reach 96.81 mg/g, and it also shows excellent selective removal rates in various real water environments. Molecular dynamics simulation is used to explore the key roles of each component of PVA/GO/SA on gel formation, slit-shaped structure and internal channel construction, and adsorption reaction activity, and to validate the efficacy components and adsorption mechanism of PVA/GO/SA in Cu(II) adsorption based on density-functional theory (DFT) and simulation calculations. Our study can provide a new structural design idea for the efficient selective Cu(II) adsorption materials.

Superoleophobic Hierarchical Honeycomb Hydrogels for Effective Heavy Metal Removal in Crude Oil Emulsion

Here, we designed a bioinspired hydrogel surface with underwater superoleophobicity for heavy metal adsorption, effectively addressing the challenge of adsorption site clogging caused by crude oil emulsions. Mimicking the reentrant structures of lotus leaf undersides, silica dioxide (SiO2) nanoparticles were self-assembled on the hydrogel surface, forming a stable hydration layer that imparts unique superoleophobic properties in an aqueous environment. The poly(vinyl alcohol)-sodium alginate-SiO2 capsule (PSSC) exhibited a hierarchical honeycomb pore structure with a nano screen mesh, achieving excellent adsorption capacities for typical cationic heavy metals (Pb2+, Cu2+, Cd2+, and Cr3+) in both aqueous solutions and crude oil emulsions. The optimal pH for heavy metal adsorption was determined to be between 4 and 5, while increasing temperature significantly inhibited the adsorption process. Maximum adsorption capacities of Pb2+, Cd2+, Cu2+, and Cr3+ reached 291.5 mg/g, 278.7 mg/g, 259.4 mg/g, and 171.4 mg/g in crude oil emulsions. Competitive adsorption was observed in multicomponent systems, with Cr3+ being adsorbed preferentially. The adsorption mechanisms were primarily governed by chemical adsorption, physical adsorption, and electrostatic attraction, with functional groups such as -COOH and -OH on the hydrogel surface playing a key role in metal ion binding. This study demonstrates the potential of PSSC as an efficient, cost-effective adsorbent for removing heavy metals from complex matrices, such as wastewater and crude oil emulsions, and highlights its applicability in various environmental remediation scenarios.

Chitosan-based composite featuring dual cross-linking networks for the removal of aqueous Cr(VI)

To avoid the environmental detriment caused by Cr(VI) waste, this study constructs a dual cross-linking network structure using sodium alginate (SA) and polyvinyl alcohol (PVA). Chitosan (CS) is further introduced through electrostatic attraction and hydrogen bonding and SA/PVA/CS (SPC) composite with porous structure is successfully prepared for the removal of Cr(VI) from wastewater. Batch adsorption experiments show that SPC has excellent adsorption capacity and practical usability with a broad pH applicability range. Under optimal adsorption conditions (pH = 2, t = 150 min, T = 35 °C, m/V = 2 g/L, C0 = 10 mg/L), the Cr(VI) removal rate of SPC achieves 89.2 %. Adsorption kinetics and isotherm models indicate that the adsorption process is primarily multi-layer and chemical adsorption. Additionally, FT-IR and XPS reveal that the adsorption mechanism of SPC for Cr(VI) involves a synergy of electrostatic attraction, reduction, ion exchange and complexation. Density functional theory (DFT) simulations also confirm the dominant role of CS in the Cr(VI) adsorption. In summary, SPC shows great potential for Cr(VI) wastewater treatment.

One-step fabrication of millimeter-scale hollow vesicles with chitosan /DADMAC/ sodium alginate graft copolymer for enhanced anionic dye adsorption

Hollow vesicles are promising in water treatment due to their unique structure of the membrane and inner cavity. However, the adsorption capacity needs to be improved for targeted pollutants. Herein, millimeter-scale hollow vesicles were prepared with a one-step process of sequential stirring and grafting using chitosan, diallyldimethylammonium chloride, and sodium alginate as raw materials with the purpose of efficient removal of anionic dyes from wastewater. The composite vesicles were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction. The hollow vesicles showed the structure of the cationic membrane and the inner cavity, facilitating the dye adsorption. The adsorption capacity for the anionic dye Reactive Black 5 reached 698.1 mg/g, more than twice that of the binary composite vesicles without graft. The adsorption kinetics and isotherm data coincided with the pseudo-second-order and Langmuir models, respectively, and the adsorption mechanism was monolayer chemisorption. Moreover, the vesicles worked well in wide ranges of environment pH, temperature, and co-existing pollutants. They also possessed excellent cyclic regeneration performance, in which 93 % of the initial adsorption capacity was maintained after four cycles. These results indicate that the millimeter-scale hollow vesicles exhibit broad application prospects for wastewater purification.

Electrospinning Novel Sodium Alginate/MXene Nanofiber Membranes for Effective Adsorption of Methylene Blue

Understanding how to develop highly efficient and robust adsorbents for the removal of organic dyes in wastewater is crucial in the face of the rapid development of industrialization. Herein, d-Ti₃C₂T_x nanosheets (MXene) were combined with sodium alginate (SA), followed by electrospinning and successive Ca²⁺-mediated crosslinking, giving rise to a series of SA/MXene nanofiber membranes (NMs). The effects of the MXene content of the NMs on the adsorption performance for methylene blue (MB) were investigated systemically. Under the optimum MXene content of 0.74 wt.%, SA/MXene NMs possessed an MB adsorption capacity of 440 mg/g, which is much higher than SA/MXene beads with the same MXene content, pristine MXene, or electrospinning SA NMs. Furthermore, the optimum SA/MXene NMs showed excellent reusability. After the adsorbent was reused ten times, both the MB adsorption capacity and removal rate could remain at 95% of the levels found in the fresh samples, which indicates that the electrospinning technique has great potential for developing biomass-based adsorbents with high efficiency.

Gum katira-silver nanoparticle-based bionanocomposite for the removal of methyl red dye

The present study aimed to synthesize gum katira-silver nanoparticle-based bionanocomposite. Different characterization techniques were used to analyze the synthesized bionanocomposite, such as Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM), thermo-gravimetric analysis (TGA), and transmission electronic microscopy (TEM). AgNPs were formed and were 6-20 nm in size. Thermo-gravimetric analysis showed that synthesized nanocomposites are more thermally stable than gum katira. All the reaction conditions, such as time, temperature, pH, solvent, amount of nanoparticles, the concentration of the initiator, crosslinker, and monomer were optimized with respect to swelling. The results showed that the highest percentage swelling (Ps) of Gk-cl-poly(AA) was 796%, and 867% of AgNPs were imbibed by Gk-cl-poly(acrylic acid)-AgNPs. Synthesized bionanocomposite was used as an adsorbent material for the adsorption of methyl red (MR) dye. The effects of different reaction conditions were also optimized to attain maximum adsorption of MR dye. The maximum dye adsorption through Gk-cl-poly(AA)-AgNPs bionanocomposite was 95.7%. Diverse kinetic and isotherm models were used to study the adsorption data. The R 2 value was established as 0.987 and k2 was .02671. The greater R 2 value of second-order kinetics over first-order kinetics suggested that MR adsorption by nanocomposite is best explained by pseudo-second-order kinetics, indicating that dye adsorption occurred through chemisorption. The R 2 value was determined to be .9954. The correlation coefficient values of Gk-cl-poly(AA)-AgNPs were best fitted by the Freundlich adsorption isotherm. Overall, synthesized bionanocomposite is a proficient material for removing of MR dye from wastewater.

Development of novel MOF-mixed matrix three-dimensional membrane capsules for eradicating potentially toxic metals from water and real electroplating wastewater

The stability and applicability of UiO-66-(NH₂)₂ metal-organic framework (MOF) nanoparticles (NPs) were successfully improved in this study by incorporating them into alginate biopolymer during the manifestation of crosslinking agents-calcium chloride and glutaraldehyde-via a simple, environment-friendly, and facile approach to eradicate potentially toxic metals (PTMs) such as Cr⁶⁺, Cr³⁺, Cu²⁺, and Cd²⁺ from water and real electroplating wastewater. Hydrophilic functional groups (i.e., -OH, -COOH, and -NH₂) are imperative in the smooth loading of UiO-66-(NH₂)₂ MOF- NPs into three-dimensional (3-D) membrane capsules (MCs). The X-ray photoelectron spectroscopy (XPS) results suggested that UiO-66-(NH₂)₂ MOF was effectively bonded in/on the capsule via electrostatic crosslinking between -H₃N⁺ and -COO^-. Scanning electron microscopy results revealed a porous honeycomb configuration of the 3-D SGMMCs (S: sodium alginate, G: glutaraldehyde, M: MOF NPs, and MCs: membrane capsules). The maximum monolayer absorption capacities for Cr⁶⁺, Cr³⁺, Cu²⁺, and Cd²⁺ were 495, 975, 1295, and 1350 mg/g, respectively. The results of Fourier transform infrared spectroscopy and XPS analyses showed that electrostatic attraction and ion exchange were the main processes for PTM removal used by the as-developed 3-D SGMMCs. The as-developed 3-D SGMMCs exhibited outstanding selectivity for removing the targeted PTMs under the specified pH/conditions and maintained >80% removal efficiency for up to six consecutive treatment cycles. Notably, > 60% removal efficiencies for Cr⁶⁺ and Cu²⁺ were observed when treating real electroplating wastewater. Therefore, the as-developed 3-D SGMMCs can be used as an exceptional multifunctional sorbent to remove and recover PTMs from real electroplating wastewater.

Quality assessment of lemon (Citrus aurantifolia, swingle) coated with self-healed multilayer films based on chitosan/carboxymethyl cellulose under cold storage conditions

The polyelectrolyte multilayer self-healing coating film of chitosan and carboxymethyl cellulose (PEM-SH) tended to maintain high sensory quality and control physiological and pathological decay of lemon fruits under cold storage. The PEM-SH film was characterized by ATR-IR, XRD, X-ray photoelectron spectroscopy, SEM analysis, swelling ratio, self-healing, and mechanical characteristics. The 3-layered film (3L) exhibited the optimum barrier properties; WVP: 3.32 ± 0.06 g. mm. k Pa-1.h-1.m-2 and GTR: 0.256 ± 0.032 cc.M-2.day-1. The moisture sorption isotherm data were fitted with BET, GAB, and Peleg models and three models showed applicability. The coated fruits exhibit superior features of fruit quality such as reduced weight loss %, respiration rate, and decay symptoms appearance. The 3L-coated fruit showed the lower pectinase enzyme activity (0.689 Ug-1 FW) up to 60 days. As well as, increased total soluble solids, keeping vitamin C of loss and decreasing percentage acidity of juice up to 60 days.

Fabrication of polyethylenimine functionalized magnetic cellulose nanofibers for the sorption of Ni(II), Cu(II) and Cd(II) in single-component and multi-component systems

Novel polyethyleneimine functionalized cellulose nanofiber magnetic composites (PEI-CNFs@Fe₃O₄) were prepared using banana peels as the raw materials for the sorption of Ni(II), Cu(II) and Cd(II) in single-component and multi-component systems. The batch experiments, spectral analyses and model fittings were used to reveal the sorption properties. The sorption of Ni(II), Cu(II) and Cd(II) on PEI-CNFs@Fe₃O₄ all conformed to the Langmuir isotherm and pseudo-second-order kinetic models. And the maximum sorption capacities of PEI-CNFs@Fe₃O₄ towards Ni(II), Cu(II) and Cd(II) were 134.38, 93.71 and 173.56 mg g^-1, respectively. The main sorption mechanism of Ni(II), Cu(II) and Cd(II) on PEI-CNFs@Fe₃O₄ is the strong surface complexation of the amino, carboxyl and hydroxyl groups with Ni(II), Cu(II) and Cd(II) ions. Especially, the introduction of PEI contributed to the improvement in the sorption capacities of PEI-CNFs@Fe₃O₄ towards the heavy metals. Besides, the size of the ionic radius and the strength of the surface complexing ability with PEI-CNFs@Fe₃O₄ are the reasons for the difference in the sorption capacities of Ni(II), Cu(II) and Cd(II) (Cd(II) > Ni(II) > Cu(II)). In conclusion, PEI-CNFs@Fe₃O₄ has shown the advantages of low cost, simple preparation, easy magnetic separation, environmental friendliness and high sorption capacity, thus having a broad application prospect in the treatment of multi-heavy metals polluted water.

Control of the pore size of honeycomb polymer film from micrometers to nanometers via substrate-temperature regulation and its application to photovoltaic and heat-resistant polymer films

Honeycomb porous polystyrene (PS) films with an aspect ratio of pore depth to pore diameter at approximately 1.0 were fabricated using the breath figure (BF) method. Two modes of water droplet coalescence in the pore growth were observed in real-time by optical microscopy. Pore size significantly increases with the increase in humidity and the decrease in substrate temperature. The porous pattern could emerge even at room temperature under high humidity of 80%. Boiling point and solvent density significantly influence the pore distribution and pore depth. Chloroform and tetrahydrofuran achieve more uniform hexagonal patterns than benzene and dichloromethane. Subsequently, to obtain nanometer porous PS film, the fast-evaporation BF process was designed by regulating the gradient substrate temperature and evaporation time, and porous mesoscopic PS film was obtained. The minimum pore diameter and corresponding pore depth are about 120 nm and 27 nm, respectively. Finally, the fast-evaporation BF process was applied to the honeycomb film formation of photovoltaic polymer poly(3-hexylthiophene) (P3HT), and the heat-resistant polymers polysulfone (PSF) and polyimide (PI).