Polydopamine-assisted grafting of chitosan on porous poly (L-lactic acid) electrospun membranes for adsorption of heavy metal ions

Chitosan-blended membranes for heavy metal removal from aqueous systems: A review of synthesis, separation mechanism, and performance

The environmental pollution caused by heavy metal ions has become a serious global environmental issue. Heavy metal contaminants released from industrial effluents, agricultural runoff, and human activities, can enter into water resources. The toxicity of these heavy metal ions even at trace concentrations presents a substantial hazard to both aquatic systems and human well-being. The membrane separation processes have become more promising sustainable techniques for the separation of metal ions from the effluent. The research efforts have been concentrated on improving the synthesis of membranes and membrane materials to facilitate the sustainable separation of heavy metals. The application of chitosan in the fabrication of membranes is getting more attention. Chitosan, a natural polysaccharide derived from chitin, is abundant in nature and has active hydroxyl and amino groups suitable for the separation of heavy metal ions. It exhibits excellent chelating tendency, biocompatibility, and biodegradability. The functionalization of chitosan to improve its mechanical strength, chemical stability, and antifouling properties has become an ongoing area of research. This review examines the synthesis and efficient applications of chitosan blended membranes. The review concludes by outlining the current challenges and proposing future research prospects to enhance the applicability of chitosan-blended membranes in environmental remediation.

The role of chitosan grafted copolymer/zeolite Schiff base nanofiber in adsorption of copper and zinc cations from aqueous media

The objective of this research was to develop and assess chitosan-grafted copolymer/HZSM5 zeolite Schiff base nanofibers for Cu2+ and Zn2+ adsorption from aqueous media. Nanofibers were prepared via electrospinning and characterized using XRD, FTIR, 1H NMR, FESEM, TGA, BET, and XPS. The study evaluated the effect of unmodified HZSM5 and Schiff base functionalization on adsorption capacities. Incorporating 10.0 wt% zeolite Schiff base as the optimum content into the chitosan-grafted copolymer significantly enhanced adsorption, achieving increases of 98.2 % for Zn2+ and 42.2 % for Cu2+. Specifically, Zn2+ adsorption increased from 27.6 to 54.7 mg/g, and Cu2+ from 67.1 to 95.4 mg/g. Factors such as temperature, pH, adsorption time, and initial cation concentration were analyzed. Kinetic studies revealed a double-exponential model, and isotherm analysis indicated a good fit with the Redlich-Peterson model, showing maximum monolayer capacities of 310.1 mg/g for Cu2+ and 97.8 mg/g for Zn2+ (pH 6.0, 240 min, 45 °C). The adsorption thermodynamics indicated a spontaneous and endothermic adsorption. Reusability tests showed minimal capacity loss (4.91 % for Cu2+ and 5.59 % for Zn2+) after five cycles. The nanofiber displayed greater selectivity for Cu2+ over Zn2+ in multi-ion systems and real electroplating wastewater, highlighting its potential for targeted heavy metal removal.

Bioactive chitosan/polydopamine nanospheres coating on carbon fiber towards strengthening epoxy composites

This paper initially examines the feasibility and effectiveness on interfacial adhesion of composites when grafting nanoparticle-structured polydopamine (PDA) and chitosan around carbon fiber periphery. The resulting interfacial shear strength was maximized as 92.3 MPa, delivering 50.1 % and 15.7-16.2 % gains over those of control fiber and only polydopamine nanospheres (PDANPs) or only chitosan modified fiber composites. Measuring surface morphology and thermal stability of fibers found that abundant PDANPs well adhered with the help of chitosan, highlighting nanoscale size effects and intrinsic adhesiveness of PDA. Under good wettability, rich and dense interfacial interactions (covalent and hydrogen bond, electrostatic interaction, and π conjugation) caused by PDANPs/chitosan coating provides impetus for effective stress transfer. Additionally, the stable "soft-rigid" combination of chitosan and PDANPs adds the efficiency of crack passivation. As such, it is hoped that this work could fully explore the possibility of PDA geometry in interphase engineering of fiber composites.

Enhancing Encapsulation Efficiency of Chavir Essential Oil via Enzymatic Hydrolysis and Ultrasonication of Whey Protein Concentrate-Maltodextrin

This study focused on the characterization of emulsions and microparticles encapsulating Chavir essential oil (EO) by application of modified whey protein concentrate-maltodextrin (WPC-MD). Different physical, chemical, morphological, thermal, and antioxidant properties and release behavior of spray-dried microparticles were assessed. Antioxidant, solubility, emulsifying, and foaming activities of modified WPC were increased compared to those of primary material. The results indicated that the particle size distribution varied depending on the type of carriers used, with the smallest particles formed by hydrolyzed WPC (HWPC). Binary blends of modified WPC-MD led to improved particle sizes. The spray-drying yield ranged from 64.1% to 85.0%, with higher yields observed for blends of MD with sonicated WPC (UWPC). Microparticles prepared from primary WPC showed irregular and wrinkled surfaces with indentations and pores, indicating a less uniform morphology. The UWPC as a wall material led to microparticles with increased small cracks and holes on their surface. However, HWPC negatively affected the integrity of the microparticles, resulting in broken particles with irregular shapes and surface cracks, indicating poor microcapsule formation. Encapsulating EO using WPC-MD increased the thermal stability of EO significantly, enhancing the degradation temperature of EO by 2 to 2.5-fold. The application of primary WPC (alone or in combination with MD) as wall materials produced particles with the lowest antioxidant properties because the EO cannot migrate to the surface of the particles. Enzymatic hydrolysis of WPC negatively impacted microparticle integrity, potentially increasing EO release. These findings underscore the crucial role of wall materials in shaping the physical, morphological, thermal, antioxidant, and release properties of spray-dried microparticles, offering valuable insights for microencapsulation techniques.

Computational AI to predict and optimize the relationship between dye removal efficiency and Gibbs free energy in the adsorption process utilizing TiO2/chitosan-polyacrylamide composite

Building a model that can accurately anticipate and optimize the dynamics of dye removal and Gibbs free energy within the framework of an adsorption process is the main goal of this research. Furthermore, it has been determined that a correlation exists between the efficacy of dye removal and the behavior of Gibbs free energy throughout the process of adsorption. The study utilized a composite material consisting of chitosan-polyacrylamide/TiO2 as an adsorbent to remove anionic dye from a mainly aqueous solution. The parameters have been analyzed using response surface methodology (RSM), artificial neural networks (ANN), and machine learning (ML) techniques in this particular context. The obtained F-value of 814.62 for the RSM model, which assesses dye removal efficiency, suggests that the model under examination is statistically significant. Furthermore, based on the RSM data, the proposed model demonstrates a significant level of accuracy in predicting the performance of the TiO2/chitosan-polyacrylamide composite as an adsorbent during the dye removal adsorption process. The ANN model achieved a high level of accuracy, as evidenced by its R2 value of 0.999455. Through the utilization of neural networks and machine learning, the intended objective of forecasting dye removal efficiency and Gibbs free energy behavior in the adsorption process was effectively accomplished.

Biodegradable Electrospun Membranes for Sustainable Industrial Applications

The escalating demand for sustainable industrial practices has driven the exploration of innovative materials, prominently exemplified by biodegradable electrospun membranes (BEMs). This review elucidates the pivotal role of these membranes across diverse industrial applications, addressing the imperative for sustainability. Furthermore, a comprehensive overview of biodegradable materials underscores their significance in electrospinning and their role in minimizing the environmental impact through biodegradability. The application of BEMs in various industrial sectors, including water treatment, food packaging, and biomedical applications, are extensively discussed. The environmental impact and sustainability analysis traverse the lifecycle of BEMs, evaluating their production to disposal and emphasizing reduced waste and resource conservation. This review demonstrates the research about BEMs toward an eco-conscious industrial landscape for a sustainable future.

PVDF Nanofiber Modified with ZnO Nanowires/Polydopamine for the Treatment of Sewage Containing Heavy Metals, Organic Dyes, and Bacteria

In various countries worldwide, the issue of wastewater contamination poses a significant threat due to its intricate composition of heavy metals, organic dyes, and microorganisms, thereby complicating the purification process. Consequently, researchers have expressed considerable interest in materials capable of eliminating organic, heavy metal, and microbial pollutants. This study focuses on the fabrication of a water purification membrane (PDA/ZnO-NWs/PVDF) with a hierarchical structure and the ability to remove multiple pollutants. The membrane was created by modifying poly(vinylidene fluoride) (PVDF) nanofiber with zinc oxide nanowires (ZnO-NWs) and reinforcing it with polydopamine (PDA). The experimental results demonstrate that the PDA/ZnO-NWs/PVDF membrane exhibits a range of functionalities, including long-lasting superhydrophilicity, Cu(II) adsorption, photocatalytic degradation, and antibacterial ability. The manipulation of the DA synthesis procedure allows for the adjustment of the wettability, adsorption, and photocatalytic and antibacterial activities of the PDA/ZnO-NWs/PVDF composite. According to the Langmuir isotherm, the maximum Cu(II) adsorption capacity of the PDA/ZnO-NWs/PVDF membrane is determined to be 65.75 mg/g, which is significantly higher (27.26 mg/g) than that of the ZnO-NWs/PVDF membrane (38.49 mg/g). The PDA/ZnO-NWs/PVDF composite exhibited a notable degradation capacity toward rhodamine B under natural sunlight, reaching a maximum of 5.97 mg/g. Additionally, the degradation rate achieved during daylight hours was as high as 90.42%. Furthermore, the antibacterial efficacy of the PDA/ZnO-NWs/PVDF composite against both Gram-positive and Gram-negative bacteria approached 100%. This work presents a promising approach for the treatment of wastewater containing various coexisting contaminants.

Development of polydopamine functionalized porous starch for bleeding control with the assistance of NIR light

Efficient hemorrhage control of severe wound injuries is an urgent medical need, deserving agents with promising blood coagulation and biocompatible characteristics. Current work developed polydopamine (PDA) functionalized porous starch powder (PS-PDA) for emergency bleeding treatment. The micro-morphology and elements, chemical groups, and porosity of PS-PDA were systematically characterized. Its comparison with porous starch (PS) revealed the promising potential of this composite in medical practice. On one hand, PS-PDA showed superior surface area and biomineralization affinity over PS, along with comparable hemo/cyto-compatibility. On the other hand, the photothermal effect of PDA under near Infrared (NIR) light paved the possibility to accelerate blood coagulation in situ. In vivo studies indicated PS-PDA can significantly reduce blood loss and improvement of hemostasis efficiency accompanied by NIR light exposure. These results suggest that this newly developed PS-PDA powder can serve as a promising hemostatic material for bleeding wound control.

Preparation of biochar@chitosan-polyethyleneimine for the efficient removal of uranium from water environment

A novel chitosan-based composite with rich active sites was synthesized by uniformly dispersing biochar into the cross-linked network structure formed by chitosan and polyethyleneimine. Due to the synergistic effect of biochar (minerals) and chitosan-polyethyleneimine interpenetrating network (amino and hydroxyl), the chitosan-based composite possessed an excellent adsorption performance for uranium(VI). It could rapidly (<60 min) achieve a high adsorption efficiency (96.7 %) for uranium(VI) from water and a high static saturated adsorption capacity (633.4 mg/g), which was far superior to other chitosan-based adsorbents. Moreover, the separation for uranium(VI) on the chitosan-based composite was suitable for a variety of actual water environments and the adsorption efficiencies all exceeded 70 % in different water bodies. The soluble uranium(VI) could be completely removed by the chitosan-based composite in the continuous adsorption process, which could meet the permissible limits of the World Health Organization. In sum, the novel chitosan-based composite could overcome the bottleneck of current chitosan-based adsorption materials and become a potential adsorbent for the remediation of actual uranium(VI) contaminated wastewater.

Facile synthesis of chitosan-tartaric acid biosorbents for removal of Cu(II) and Cd(II) from water and tea beverages

Consumption of water and tea beverages leads to the intake of heavy metals by humans. Development of technology for decontamination greatly reduces the risks of the heavy metal exposure. In this study, environment-friendly chitosan-tartaric acid biosorbents (CTBs) were synthesized by a facile one-step cross-linking strategy to mitigate the Cu(II) and Cd(II) contamination in water and tea beverages. The cross linkage of tartaric acid and chitosan endowed CTBs with excellent properties in aspects of surface roughness, mechanical strength, and acid resistance. Adsorption performance and mechanism of CTBs were studied, and the Langmuir isotherm model and pseudo-second-order kinetic model were adhered during adsorption. Up to 90 % removal efficiencies of Cu(II) and Cd(II) from water and tea beverages by CTBs were achieved. Moreover, the adsorption showed only a slight reduction in the quality of tea beverages. This study offers a new insight for reduction of heavy metals-pollution in beverages.

Oxidized dextran-crosslinked ferrocene-chitosan-PEI composite porous material integrating adsorption and degradation to malachite green

Treating wastewater containing malachite green (MG) using porous materials with both adsorption and degradation functions have become a major challenge in achieving the carbon neutrality goal. Herein by incorporating the ferrocene (Fc) group as a Fenton active center, a novel composite porous material (DFc-CS-PEI) was prepared using chitosan (CS) and polyethyleneimine (PEI) as skeletons and oxidized dextran as a crosslinker. DFc-CS-PEI not only possesses satisfactory adsorption performance to MG but also excellent degradability in the presence of a minor amount of H₂O₂ (3.5 mmol/L) without any additional assistance, due to high specific surface area and active Fc group. The maximum adsorption capacity is ca. 177.73 ± 3.11 mg/g, outperforming most CS-based adsorbents. The removal efficiency of MG is significantly enhanced from 20 % to 90 % as DFc-CS-PEI and H₂O₂ coexist, due to ^·OH-dominated Fenton reaction, and remained in a wide pH range (2.0-7.0). Cl^- exhibits notable suppression on the degradation of MG because of quenching effects. Note that DFc-CS-PEI has a very small iron leaching (0.2 ± 0.015 mg/L), and can be rapidly recycled by simple water-washing, without any harmful chemicals and potential second pollution. Such versatility, high stability, and green recyclability make the as-prepared DFc-CS-PEI a promising porous material for the treatment of organic wastewater.

Research Progress of Water Treatment Technology Based on Nanofiber Membranes

In the field of water purification, membrane separation technology plays a significant role. Electrospinning has emerged as a primary method to produce nanofiber membranes due to its straightforward, low cost, functional diversity, and process controllability. It is possible to flexibly control the structural characteristics of electrospun nanofiber membranes as well as carry out various membrane material combinations to make full use of their various properties, including high porosity, high selectivity, and microporous permeability to obtain high-performance water treatment membranes. These water separation membranes can satisfy the fast and efficient purification requirements in different water purification applications due to their high filtration efficiency. The current research on water treatment membranes is still focused on creating high-permeability membranes with outstanding selectivity, remarkable antifouling performance, superior physical and chemical performance, and long-term stability. This paper reviewed the preparation methods and properties of electrospun nanofiber membranes for water treatment in various fields, including microfiltration, ultrafiltration, nanofiltration, reverse osmosis, forward osmosis, and other special applications. Lastly, various antifouling technologies and research progress of water treatment membranes were discussed, and the future development direction of electrospun nanofiber membranes for water treatment was also presented.

Recent development and application of membrane chromatography

Membrane chromatography is mainly used for the separation and purification of proteins and biological macromolecules in the downstream processing process, also applications in sewage disposal. Membrane chromatography is recognized as an effective alternative to column chromatography because it significantly improves chromatography from affinity, hydrophobicity, and ion exchange; the development status of membrane chromatography in membrane matrix and membrane equipment is thoroughly discussed, and the applications of protein capture and intermediate purification, virus, monoclonal antibody purification, water treatment, and others are summarized. This review will provide value for the exploration and potential application of membrane chromatography.

Preparation of a Chitosan/Coal Gasification Slag Composite Membrane and Its Adsorption and Removal of Cr (VI) and RhB in Water

At present, there are many kinds of pollutants, including dyes and heavy metal ions, in wastewater. It is very important to develop adsorbents that can simultaneously remove heavy metal ions and dyes. In this study, a renewable composite membrane material was synthesized using chitosan and treated coal gasification slag. The Cr (VI) maximum adsorption capacity of the composite membrane was 50.0 mg/L, which was 4.3~8.8% higher than that of the chitosan membrane. For the adsorption of RhB, the removal rate of the chitosan membrane was only approximately 5.0%, but this value could be improved to 95.3% by introducing coal gasification slag. The specific surface area of the chitosan membrane could also be increased 16.2 times by the introduction of coal gasification slag. This is because coal gasification slag could open the nanopores of the chitosan membrane (from 80 μm to 110 μm). Based on the adsorption kinetics and adsorption mechanism analysis, it was found that the adsorption of Cr (VI) occurred mainly through the formation of coordination bonds with the amino groups on the molecular chains of chitosan. Meanwhile, RhB adsorption occurred through the formation of hydrogen bonds with the surface of coal gasification slag. Additionally, coal gasification slag can improve the mechanical properties of the chitosan membrane by 2.2 times, which may facilitate the practical application of the composite membrane. This study provides new insight into the adsorbent design and the resource utilization of coal gasification slag.

The effects of process parameters on polydopamine coatings employed in tissue engineering applications

The biomaterials’ success within the tissue engineering field is hinged on the capability to regulate tissue and cell responses, comprising cellular adhesion, as well as repair and immune processes’ induction. In an attempt to enhance and fulfill these biomaterials’ functions, scholars have been inspired by nature; in this regard, surface modification via coating the biomaterials with polydopamine is one of the most successful inspirations endowing the biomaterials with surface adhesive properties. By employing this approach, favorable results have been achieved in various tissue engineering-related experiments, a significant one of which is the more rapid cellular growth observed on the polydopamine-coated substrates compared to the untreated ones; nonetheless, some considerations regarding polydopamine-coated surfaces should be taken into account to control the ultimate outcomes. In this mini-review, the importance of coatings in the tissue engineering field, the different types of surfaces requiring coatings, the significance of polydopamine coatings, critical factors affecting the result of the coating procedure, and recent investigations concerning applications of polydopamine-coated biomaterials in tissue engineering are thoroughly discussed.

Research progress in the removal of heavy metals by modified chitosan

Chitosan and its modifiers have been widely studied for their good biocompatibility and excellent adsorption properties for heavy metal ions. The synthesis and application of modified chitosan, the effects of process variables (such as pH, amount of adsorbent, temperature, contact time, etc.), adsorption kinetics, thermodynamics and the adsorption mechanism on the removal of heavy metal ions are reviewed. The purpose is to provide the latest information about chitosan as adsorbent and to promote the synthesis of modified chitosan and its application in the removal of heavy metals.

Sustainable and efficient technologies for removal and recovery of toxic and valuable metals from wastewater: Recent progress, challenges, and future perspectives

Due to their numerous effects on human health and the natural environment, water contamination with heavy metals and metalloids, caused by their extensive use in various technologies and industrial applications, continues to be a huge ecological issue that needs to be urgently tackled. Additionally, within the circular economy management framework, the recovery and recycling of metals-based waste as high value-added products (VAPs) is of great interest, owing to their high cost and the continuous depletion of their reserves and natural sources. This paper reviews the state-of-the-art technologies developed for the removal and recovery of metal pollutants from wastewater by providing an in-depth understanding of their remediation mechanisms, while analyzing and critically discussing the recent key advances regarding these treatment methods, their practical implementation and integration, as well as evaluating their advantages and remaining limitations. Herein, various treatment techniques are covered, including adsorption, reduction/oxidation, ion exchange, membrane separation technologies, solvents extraction, chemical precipitation/co-precipitation, coagulation-flocculation, flotation, and bioremediation. A particular emphasis is placed on full recovery of the captured metal pollutants in various reusable forms as metal-based VAPs, mainly as solid precipitates, which is a powerful tool that offers substantial enhancement of the remediation processes' sustainability and cost-effectiveness. At the end, we have identified some prospective research directions for future work on this topic, while presenting some recommendations that can promote sustainability and economic feasibility of the existing treatment technologies.

In situ polydopamine functionalized poly-L-lactic acid nanofibers with near-infrared-triggered antibacterial and reactive oxygen species scavenging capability

The development of a new multi-functional poly(L)-lactide (PLLA) nanofibrous scaffold with excellent antibacterial and reactive oxygen species (ROS) scavenging capability is quite important in tissue engineering. In this study, polydopamine (PDA)/PLLA nanofibers were prepared by combining electrospinning and post in-situ polymerization. The post in-situ polymerization of PDA on the PLLA nanofiber enable PDA uniformly distribute on PLLA nanofiber surface. PDA/PLLA nanofibrous composites also achieved stronger mechanical strength, hydrophilicity, good oxidation resistance and enhanced near-infrared photothermal effect. The near-infrared photothermal effect from PDA made the PDA/PLLA a good antibacterial material. The in vitro ROS scavenging ability of the PDA made PDA/PLLA be beneficial to damaged tissue repair. These results indicate that PDA/PLLA nanofibrous scaffold can be used as a tissue engineering scaffold material with versatile biomedical applications.

Polydopamine treatment of chitosan nanofibers for the conception of osteoinductive scaffolds for bone reconstruction

We report the influence of treatment time of electrospun chitosan nanofibers (CHT NFs) in dopamine hydrochloride bath (2 mg.mL^-1 in 10 mM Tris buffer, pH 8.5) on the extent of the polydopamine (pDA) coating on NFs surface. The reaction was characterized by FTIR and SEM analysis and the cytocompatibility of the scaffolds toward MT3C3-E1 cells was assessed. Biomimetic deposition of hydroxyapatite (HA) in 1.5xSBF batch was investigated by SEM-EDS and XRD. Samples treated in dopamine bath during 2 h promoted the structural stability of NFs in PBS, provided optimal cytocompatibility and induced the in vitro biomineralization from 6 days in 1.5xSBF. The XRD and SEM-EDS investigations confirmed formation of spherical-shaped particles composed of apatitic phase. Finally, this study shows that these NFs-pDA scaffolds prepared in the optimal experimental conditions defined here are promising candidates for application as osteoinductive scaffolds for bone regeneration applied to orthopedic and dental applications.

Amphiphilic chitosan-g-poly(trimethylene carbonate) - A new approach for biomaterials design

The paper presents the synthesis and characterization of poly(trimethylene carbonate) grafted chitosan as a new water soluble biopolymer suitable for in vivo applications. The synthesis was performed via ring-opening polymerization of 1,3-dioxan-2-one (trimethylene carbonate) (TMC) monomer, initiated by the functional groups of chitosan in the presence of toluene as solvent/swelling agent. By varying the molar ratio between the glucosamine units of chitosan and TMC, a series of chitosan derivatives with different content of poly(trimethylene carbonate) chains was synthetized. The structural characterization of the polymers was realized by FTIR and ¹H NMR spectroscopy and their solubility was assessed in water and in organic solvents as well. The biocompatibility was investigated by MTS assay on Normal Human Dermal Fibroblasts, and the biodegradability was evaluated in lysozyme buffer solution. Further, the surface properties of the polymer films were analyzed by polarized optical microscopy, atomic force microscopy and water-to-air contact angle measurements. It was established that, by 5% substitution of chitosan with poly(trimethylene carbonate) chains having an average polymerization degree of 7, a water soluble polymer can be attained. Compared to the pristine chitosan, it has improved biocompatibility in solution and moderate wettability and higher biodegradability rate in solid state, pointing its suitability for in vivo applications.

Flocculation of combined contaminants of dye and heavy metal by nano-chitosan flocculants

In this study, two multifunctional nano-chitosan flocculants (CPAM-NCS1 and CPAM-NCS2) were made through the graft modification of cationic monomer and carboxymethylchitosan (CMCTS) to remove combined contaminants. The effects of various factors (pH, flocculant dosage and hydraulic mixing conditions) on the flocculation performance under single and composite pollution conditions were systematically investigated, the optimal chemical oxygen demand (COD) and the chromaticity removal rates in the dye wastewater were 79.9% and 83.9% at wastewater pH 7, the fast stirring rate 300 rpm, the fast stirring time 8 min, and the dosage of CPAM-NCS1 80 mg/L, respectively. The optimal removal rates of Cu (II) obtained by CPAM-NCS1 and CPAM-NCS2 at were 80.3% and 75.2% at 60 mg/L and the wastewater pH 7, respectively. The optimal removal rates of Cu (II) and disperse orange were 85.3% and 89.4%, respectively, in a composite pollutant system in which Cu (II) and disperse orange coexisted when the pH of the composite system was 9 and the dosage of CPAM -NCS1 was 60 mg/L. This study proved that nanoflocculants made by modifying CMCTS with different structures can demonstrate ideal flocculation removal performance for dye and heavy metal wastewaters.

Decoration of Citrus limon wood carbon with Fe3O4 to enhanced Cd2+ removal: A reclaimable and magnetic nanocomposite

In the present study, the activated carbon of lemon (ACL) was generated from Citrus limon wood waste and composited with Fe₃O₄ nanoparticles. The ACL/Fe₃O₄ magnetic composite was effectively used to eliminate Cd²⁺ from an aqueous solution. The active surface area values for ACL and ACL/Fe₃O₄ magnetic composite were 25.99 m²/g and 38.70 m²/g, respectively indicating the effectiveness of Fe₃O₄ nanoparticles in improving ACL active surface area. The response surface methodology with central composite design (RSM-CCD) was used to determine optimal values of pH, ACL/Fe₃O₄ dose, contact time, and Cd²⁺ concentration on the decontamination efficiency. The Langmuir and Freundlich isotherm models had more potential to describe the adsorption process using ACL and ACL/Fe₃O₄, respectively. The Langmuir-based adsorption capacity was obtained as 28.2 mg/g (ACL) and 39.6 mg/g (ACL/Fe₃O₄). A pseudo-second order (PSO) model was successfully applied to evaluate the adsorption process kinetic behavior. A higher value of α parameter for ACL/Fe₃O₄ (5.7 mg/g.min) than that of ACL (3.5 mg/g.min) indicated that the magnetic composite had a greater tendency to absorb Cd²⁺. In addition, the Weber-Morris model showed that various mechanisms such as intraparticle diffusion and boundary layer effects may have a role in the adsorption process. The study of ad(de)sorption behavior showed that the adsorbents have a good ability to adsorb Cd²⁺ and no significant change in their performance has been made up to 4 times of reuse. Our results showed that ACL modification using Fe₃O₄ nanoparticles improved the adsorption efficiency of ACL to remove Cd²⁺ from the aqueous solutions.

Hierarchical Porous Recycled PET Nanofibers for High-Efficiency Aerosols and Virus Capturing

Plastic crisis, especially for poly(ethylene terephthalate) (PET) bottles, has been one of the greatest challenges for the earth and human beings. Processing recycled PET (rPET) into functional materials has the dual significance of both sustainable development and economy. Providing more possibilities for the engineered application of rPET, porous PET fibers can further enhance the high specific surface area of electrospun membranes. Here, we use a two-step strategy of electrospinning and postprocessing to successfully control the surface morphology of rPET fibers. Through a series of optical and thermal characterizations, the porous morphology formation mechanism and crystallinity induced by solvents of rPET fibers were discussed. Then, this work further investigated both PM2.5 air pollutants and protein filtration performance of rPET fibrous membrane. The high capture capability of rPET membrane demonstrated its potential application as an integrated high-efficiency aerosol filtering solution.

Novel amidinothiourea-modified chitosan microparticles for selective removal of Hg(II) in solution

Glutaraldehyde-crosslinked chitosan microparticles (CGP) prepared via the inversed-phase emulsification were successively modified by epichlorohydrin (ECH) and amidinothiourea (AT) as novel adsorbent (CGPET) for selective removal of Hg(II) in solution. FTIR, EA, XPS, SEM-EDX, TG, DTG, and XRD results indicated that CGPET had ample -NH₂ and CS, relative rough surface, mean diameter of ~40 μm, great thermal stability, and crystalline degree of 2.4%, beneficial to the uptake of Hg(II). The optimum parameters (pH 5, dosage 1 g/L, contact time 4 h, and initial concentration 150 mg/L) were acquired via batches of adsorption experiments. Adsorption behavior was well described by the Liu isothermal and pseudo-second-order kinetics models, and the maximum adsorption capacity was 322.51 mg/g, surpassing many reported adsorbents. Regeneration and coexisting-ion tests demonstrated that CGPET had outstanding reusability (R_r > 86.89% at the fifth cycle) and selectivity (R_s > 93%). Besides, its potential adsorption sites and mechanisms were proposed.