Highly efficient removal of antibiotic from biomedical wastewater using Fenton-like catalyst magnetic pullulan hydrogels

Tackling antibiotic contaminations in wastewater with novel Modified-MOF nanostructures: A study of molecular simulations and DFT calculations

The contamination of wastewater with antibiotics has emerged as a critical global challenge, with profound implications for environmental integrity and human well-being. Adsorption techniques have been meticulously investigated and developed to mitigate and alleviate their effects. In this study, we have investigated the adsorption behaviour of Erythromycin (ERY), Gentamicin (GEN), Levofloxacin (LEVO), and Metronidazole (MET) antibiotics as pharmaceutical contaminants (PHCs) on amide-functionalized (RC (=O)NH2)/MIL-53 (Al) (AMD/ML53A), using molecular simulations and density functional theory (DFT) calculations. Based on our DFT calculations, it becomes apparent that the adsorption tendencies of antibiotics are predominantly governed by the presence of AMD functional groups on the adsorbent surface. Specifically, hydrogen bonding (HB) and van der Waals (vdW) interactions between antibiotics and AMD groups serve as the primary mechanisms facilitating adsorption. Furthermore, we have observed that the adsorption behaviors of these antibiotics are influenced by their respective functional groups, molecular shapes, and sizes. Our molecular simulations delved into how the AMD/ML53A surfaces interact with antibiotics as PHCs. Moreover, various chemical quantum descriptors based on Frontier Molecular Orbitals (FMO) were explored to elucidate the extent of AMD/ML53A adsorption and to assess potential alterations in their electronic properties throughout the adsorption process. Monte Carlo simulation showed that ERY molecules adsorb stronger to the adsorbent in acidic and basic conditions than other contaminants, with high energies: -404.47 kcal/mol in acidic and -6375.26 kcal/mol in basic environments. Molecular dynamics (MD) simulations revealed parallel orientation for the ERY molecule's adsorption on AMD/ML53A with 80% rejection rate. In conclusion, our study highlighted the importance of modeling in developing practical solutions for removing antibiotics as PHCs from wastewater. The insights gained from our calculations can facilitate the design of more effective adsorption materials, ultimately leading to a more hygienic and sustainable ecosystem.

Crystalline nanoxylan from hot water extracted wood xylan at multi-length scale: Molecular assembly from nanocluster hydrocolloids to submicron spheroids

As a contribution to expand accessibility in the territory of bio-based nanomaterials, we demonstrate a novel material strategy to convert amorphous xylan preserved in wood biomass to hierarchical assemblies of crystalline nanoxylan on a multi-length scale. By reducing the end group in pressurized hot water extracted (PHWE) xylan to primary alcohol as a xylitol form with borohydride reduction, the endwise-peeling depolymerization is effectively impeded in the alkali-catalyzed hydrolytic cleavage of side substitutions in xylan. Nanoprecipitation by a gradual pH decrease resulted in a stable hydrocolloid dispersion in the form of worm-like nanoclusters assembled with primary crystallites, owing to the self-assembly of debranched xylan driven by strong intra- and inter-chain H-bonds. With evaporation-induced self-assembly, we can further construct the hydrocolloids as dry submicron spheroids of crystalline nanoxylan (CNX) with a high average elastic modulus of 47-83 GPa. Taking the advantage that the chain length and homogeneity of PHWE-xylan can be tailored, a structure-performance correlation was established between the structural order in CNX and the phosphorescent emission of this crystalline biopolymer. Rigid clusterization and high crystallinity that are constructed by strong intra- and inter-molecule interactions within the nanoxylan effectively restrict the molecular motion, thereby promoting the emission of ultralong organic phosphorescence.

Surface modified of chitosan by TiO2@MWCNT nanohybrid for the efficient removal of organic dyes and antibiotics

Considering the increase in the discharge of industrial effluents containing dyes and antibiotic resistance as a consequence of increasing the prescription and easy distribution of antibiotic drugs at the global level, designing efficient, biodegradable and non-toxic absorbents is necessary to reduce environmental harm effects. Herein, we present a series of novel eco-friendly ternary hybrid nanocomposite hydrogels CS/TiO2@MWCNT (CTM) composed of chitosan (CS), TiO2, and multiwalled carbon nanotube (MWCNT) for removal of methylene blue (MB) and methyl orange (MO) and common antibiotic ciprofloxacin (CIP) in aqueous medium. The combination of MWCNT and TiO2 improves the physicochemical properties of CS hydrogel and increases the adsorption capacity toward pollutants in the presence of different loadings. CTM hydrogel showed a specific surface area of 236.45 m2 g-1 with a pore diameter of 7.89 nm. Adsorption mechanisms were investigated in detail using kinetic, isotherm, and thermodynamic studies of adsorption as well as various spectroscopic techniques. Adsorption of these pollutants by CTM nanocomposite hydrogel occurred using various interactions at different pHs, which showed the obvious dependence of CTM adsorption capacity on pH. Electrostatic attractions, complex formation, π-π stacking and hydrogen bonds played a key role in the adsorption process. The adsorption of MB, MO, and CIP was fitted with the Langmuir isotherm with maximum adsorption capacities of 531.91, 1763.6, and 1510.5 mg g-1, respectively. CTM had a minor decrease in adsorption strength and showed good structural stability even after 8 adsorptions-desorption cycles. The total cost of producing a 1 kg adsorbent was calculated to be $ 450, which helped us determine the economic feasibility of the adsorbent in large-scale applications.

Polymer-Supported Heterogeneous Fenton Catalysts for the Environmental Remediation of Wastewater

Materials based on polymer hydrogels have demonstrated potential as innovative Fenton catalysts for treating water. However, developing these polymer-supported catalysts with robust stability presents a significant challenge. This paper explores the development and application of polymer-supported heterogeneous Fenton catalysts for the environmental remediation of wastewater, emphasizing the enhancement of metal incorporation into catalysts for improved efficiency. The study begins with an introduction to the heterogeneous Fenton process and its relevance to wastewater treatment. It further delves into the specifics of polymer-supported heterogeneous Fenton catalysts, focusing on iron oxide, copper complexes/nanoparticles, and ruthenium as key components. The synthesis methods employed to prepare these catalysts are discussed, highlighting the innovative approaches to achieve substantial metal incorporation. Operational parameters such as catalyst dosage, pollutant concentration, and the effect of pH on the process efficiency are thoroughly examined. The catalytic performance is evaluated, providing insights into the effectiveness of these catalysts in degrading pollutants. Recent developments in the field are reviewed, showcasing advancements in catalyst design and application. The study also addresses the stability and reusability of polymer-supported heterogeneous Fenton catalysts, critical factors for their practical application in environmental remediation. Environmental applications are explored, demonstrating the potential of these catalysts in addressing various pollutants. The Conclusions offers future perspectives, underlining the ongoing challenges and opportunities in the field, and the importance of further research to enhance the efficacy and sustainability of polymer-supported heterogeneous Fenton catalysts for wastewater treatment.

Iron-coated nutshell waste bioadsorbents: Synthesis, phosphate remediation, and subsequent fertilizer application

The increasing incidence of freshwater nutrient pollution worldwide has highlighted the need for improved phosphate capture technologies. Successful phosphate recovery from agricultural sources and commercial wastewater can help prevent freshwater algal bloom contamination, while also reducing the dependency on finite phosphate reserves. Biodegradable biosorbents have the potential to remove phosphate from water; however, their potential as slow-release fertilizers has not been tested. Novel biosorbents were developed by coating pistachio and walnut shells with iron oxides; batch and column experiments were conducted to investigate their adsorption capacities and performances. Surface characterization studies were also conducted to investigate changes in the surface area and morphology. The potential of using iron-coated shells loaded with phosphorus as slow-release fertilizers was also evaluated. Advanced characterization techniques (scanning electron microscopy, Brunauer-Emmett-Teller (BET) physisorption analysis, and x-ray diffraction) showed that hematite was successfully coated onto the surface, resulting in increased surface area and roughness. The iron-coated pistachio and walnut shell phosphate removal capacity was 12.63 mg g-1 and 9.25 mg g-1, respectively. The phosphate sorption data fitted well with the Freundlich isotherm model and pseudo-second-order kinetics. Inner sphere complex formation, coprecipitation, diffusion, and electrostatic attraction were the main uptake mechanisms. Results from sequential release experiments with simulated pore water suggested both fast and slow desorption components. The Mehlich-3 extraction revealed that more than 90% of the released phosphate was available for plant uptake. In addition, nutrient priming showed that corn seed shoot growth increased by more than 43% when pretreated with phosphate-loaded biosorbents, demonstrating that the released phosphate could be used for plant growth. This research provides a pathway for two important zero-waste, cyclical economic goals: (1) the beneficial use of agricultural waste, and (2) a low-cost technology that can recover phosphorus from waste streams while potentially adding an additional unconventional phosphate source to apatite mineral ores.

An electronic tongue based on conjugated polymers for the discrimination and quantitative detection of tetracyclines

A fluorescent sensor array has been developed based on conjugated polymers (CPs) having six different skeletons for the detection of tetracyclines (TCs), which are known as environmental pollutants. CPs were synthesized from confined nanoreactors in a controlled manner. The fluorescent response occurs through the fluorescence resonance energy transfer (FRET) effect. By utilizing linear discriminant analysis (LDA), effective differentiation of TCs was accomplished with a very low detection concentration (66 nM). Moreover, the sensor array exhibited a highly sensitive ability to quantitatively distinguish different concentrations of TCs. Finally, the sensor array's potential for detecting TCs in aqueous solutions has been successfully demonstrated, widening its applications in practical environments. With simple preparation process, a low cost of detection and high sensitivity, the experimental results indicate that the CP-based sensor array is a promising platform for the sensitive and quantitative detection of TCs, and provides a good reference for future scientific research.

A multifunctional recyclable adsorbent based on engineered MIL-125 (Ti) magnetic mesoporous composite for the effective removal of pathogens

The elimination of pathogenic bacteria from water sources is currently crucial for obtaining drinkable water. Therefore, the development of platforms with the ability to interact with pathogens and remove them is a potential future tool for medicine, food and water safety. In this work, we have grafted a layer of NH2-MIL-125 (Ti) on Fe3O4@SiO2 magnetic nanospheres for the removal of multiple pathogenic bacteria from water. The synthesized Fe3O4@SiO2@NH2-MIL-125 (Ti) nano adsorbent was characterized by FE-SEM, HR-TEM, FT-IR, XRD, BET surface analysis, magnetization tests, respectively, which illustrated its well-defined core-shell structure and magnetic behaviour. The prepared magnetic-MOF composite sorbent was attractive towards capturing a wide range of pathogens (S. typhimurium, S. aureus, E. coli, P. aeruginosa and K. pneumoniae) under experimental conditions. Influence factors such as adsorbent dosage, bacterial concentration, pH and incubation time were optimized for enhanced bacterial capture. The application of an external magnetic field removed Fe3O4@SiO2@NH2-MIL-125 (Ti) nano adsorbent from the solution along with sweeping the attached pathogenic bacteria. The non-specific removal efficiency of S. typhimurium for magnetic MOF composite was 96.58%, while it was only 46.81% with Fe3O4@SiO2 particles. For specific removal, 97.58% of S. typhimurium could be removed selectively from a mixture with monoclonal anti- Salmonella antibody conjugated magnetic MOF at a lower concentration of 1.0 mg/mL. The developed nano adsorbent may find great potential in microbiology applications and water remediation.

Flocculation synergistic with nano zero-valent iron augmented attapulgite @ chitosan as Fenton-like catalyst for the treatment of landfill leachate

In this study, nano-zero-valent iron (NZVI) was added to attapulgite/chitosan and used as a catalyst in the heterogeneous Fenton process to degrade stabilized landfill leachate. Landfill leachate has serious environmental impacts due to the complexity and diversity of its pollutants. A magnetic catalyst (NZVI@PATP/CS) was prepared by a liquid-phase reduction method. The NZVI@PATP/CS were characterized by XRD, FTIR and SEM. The pH of leachate and the dosage of catalyst and H2O2 were changed to determine the best-operating conditions for the effective removal of chemical oxygen demand (COD) and total phosphorus(TP). To understand the adsorption degradation mechanism, the quenching experiments of free radicals were carried out. The results showed that the degradation rates of COD and TP were 66% and 92%, respectively, under the optimum pH value of 8, the dosage of H2O2 of 5 mL, and the dosage of the catalyst of 0.25 g for 60 min.

Graphitic carbon nitride alleviates cadmium toxicity to microbial communities in soybean rhizosphere

Cadmium (Cd) contamination has led to various harmful impacts on soil microbial ecosystem, agricultural crops, and thus human health. Nanomaterials are promising candidates for reducing the accumulation of heavy metals in plants. In this study, graphitic carbon nitride (g-C3N4), a two-dimensional polymeric nanomaterial, was applied for ameliorating Cd phytotoxicity to soybean (Glycine max (L.) Merr.). Its impacts on rhizosphere variables, microorganisms, and metabolism were examined. It was found that g-C3N4 increased carbon/nitrogen/phosphorus (C/N/P) content, especially when N contents were averagely 4.2 times higher in the g-C3N4-treated groups. g-C3N4 significantly induced alterations in microbial community structures (P < 0.05). The abundance of the probiotics class Nitrososphaeria was enriched (on average 70% higher in the g-C3N4-treated groups) as was Actinobacteria (226% higher in the g-C3N4 group than in the CK group). At the genus level, g-C3N4 recruited more Bradyrhizobium (122% higher) in the Cd + g-C3N4 group than in the Cd group and more Sphingomonas (on average 24% higher) in the g-C3N4-treated groups. The changes of microbial clusters demonstrated the potential of g-C3N4 to shape microbial functions, promote plant growth, and enhance Cd resistance, despite observing less pronounced modifications in microbial communities in Cd-contaminated soil compared to Cd-free soil. Moreover, abundance of functional genes related to C/N/P transformation was more significantly promoted by g-C3N4 in Cd-contaminated soil (increased by 146%) than in Cd-free one (increased by 32.8%). Therefore, g-C3N4 facilitated enhanced microbial survival and adaptation through the amplification of functional genes. These results validated the alleviation of g-C3N4 on the microbial communities in the soybean rhizosphere and shed a new light on the application of environmental-friendly nanomaterials for secure production of the crop under soil Cd exposure.

Bio-fabricated bismuth-based materials for removal of emerging environmental contaminants from wastewater

Although rapid industrialization has made life easier for humans, several associated issues are emerging and harming the environment. Wastewater is regarded as one of the key problems of the 21st century due to its massive production every year and requires immediate attention from all stakeholders to protect the environment. Since the introduction of nanotechnology, bismuth-based nanomaterials have been used in variety of applications. Various techniques, such as hydrothermal, solvo-thermal and biosynthesis, have been reported for synthesizing these materials, etc. Among these, biosynthesis is eco-friendly, cost-effective, and less toxic than conventional chemical methods. The prime focuses of this review are to elaborate biosynthesis of bismuth-based nanomaterials via bio-synthetic agents such as plant, bacteria and fungi and their application in wastewater treatment as anti-pathogen/photocatalyst for pollutant degradation. Besides this, future perspectives have been presented for the upcoming research in this field, along with concluding remarks.

Waste self-heating bag derived iron-based composite with abundant oxygen vacancies for highly efficient Fenton-like degradation of micropollutants

In this study, iron-rich waste self-heating bag was reutilized as the raw material to prepare oxygen vacancies (OV) functionalized iron-based composite (iron oxide (Fe₃O₄)-carbon-vermiculite, viz. OV-ICV), which exhibited excellent performance in the Fenton-like degradation of micropollutants via peroxydisulfate (PDS) activation. Above 95% of 1.0 mg/L carbaryl (CB) was efficiently eliminated in the presence of 0.1 g/L of OV-ICV and 0.5 mmol/L of PDS over a wide pH range of 3-10 within 30 min. Besides, OV-ICV also showed acceptable adaptability, stability, and renewability. Imbedding OV into Fe₃O₄ structure significantly generated more active iron sites and localized electrons, promoted the charge transfer ability, and assisted the redox cycle of ≡Fe(III)/≡Fe(II) for PDS activation. Mechanism investigation demonstrated that superoxide radicals (O₂^•-) derived from the activation of molecular oxygen mediated the generation of H₂O₂, and both of them further enhanced the formation of more sulfate radicals (SO₄^•-) and hydroxyl radicals (^•OH), which led to the efficient degradation and mineralization of CB. Furthermore, the degradation pathways of CB were proposed based on the intermediates identification. This work lays a foundation for the rational reutilization of iron-containing wastes modified with defect engineering in heterogeneous Fenton-like catalysis for the remediation of micropollutants wastewater.

Poly(vinyl alcohol)/sodium alginate/magnetite composites: magnetic force microscopy for tracking magnetic domains

Hydrogels of poly(vinyl alcohol) (PVA)/sodium alginate (SA), and magnetic nanoparticles (MNPs) were prepared by solvent casting in the absence and in the presence of magnets, in order to obtain MNPs distributed randomly (PVA/SA-rMNP) and magnetically oriented MNPs (PVA/SA-gMNP) in the polymer matrix. Atomic force microscopy (AFM) and magnetic force microscopy (MFM) techniques were used to evaluate the topography and to map the distribution of magnetic domains in the polymer matrix, respectively. The tip-surface distance (lift distance) of 50 nm during the MFM analyses facilitated the mapping of magnetic domains because the van der Waals forces were minimized. The magnetic signal stemming from clusters of MNPs were more easily identified than that from isolated MNPs. PVA and SA, PVA/SA, PVA/SA-rMNP, and PVA/SA-gMNP coatings with surface roughness (R_a) values of 3.8 nm, 28.7 nm, and 49.8 nm, respectively, were tested for the proliferation of mouse hippocampal HT-22 cells. While PVA/SA, PVA/SA-rMNP, and PVA/SA-gMNP coatings preserved cell viability >70% in comparison to the control (plastic plate) over 48 h, cell proliferation tended to decrease on surfaces with higher R_a values (PVA/SA-gMNP). These findings showed that the orientation of magnetic domains led to an increase of surface roughness, which decreased the viability of HT-22 cells. Thus, these results might be interesting for situations, where the control of cell proliferation is necessary.

From Fenton and ORR 2e−-Type Catalysts to Bifunctional Electrodes for Environmental Remediation Using the Electro-Fenton Process

Currently, the presence of emerging contaminants in water sources has raised concerns worldwide due to low rates of mineralization, and in some cases, zero levels of degradation through conventional treatment methods. For these reasons, researchers in the field are focused on the use of advanced oxidation processes (AOPs) as a powerful tool for the degradation of persistent pollutants. These AOPs are based mainly on the in-situ production of hydroxyl radicals (OH•) generated from an oxidizing agent (H2O2 or O2) in the presence of a catalyst. Among the most studied AOPs, the Fenton reaction stands out due to its operational simplicity and good levels of degradation for a wide range of emerging contaminants. However, it has some limitations such as the storage and handling of H2O2. Therefore, the use of the electro-Fenton (EF) process has been proposed in which H2O2 is generated in situ by the action of the oxygen reduction reaction (ORR). However, it is important to mention that the ORR is given by two routes, by two or four electrons, which results in the products of H2O2 and H2O, respectively. For this reason, current efforts seek to increase the selectivity of ORR catalysts toward the 2e− route and thus improve the performance of the EF process. This work reviews catalysts for the Fenton reaction, ORR 2e− catalysts, and presents a short review of some proposed catalysts with bifunctional activity for ORR 2e− and Fenton processes. Finally, the most important factors for electro-Fenton dual catalysts to obtain high catalytic activity in both Fenton and ORR 2e− processes are summarized.

NIR-induced improvement of catalytic activity and antibacterial performance over AuAg nanorods in Rambutan-like Fe3O4@AgAu@PDA magnetic nanospheres

Pathogenic bacteria and difficult-to-degrade pollutants in water have been serious problems that always plague people. Therefore, finding a "one stone-two birds" method that can quickly catalyze the degradation of pollutants and show effective antibacterial behavior become an urgent requirement. This work reports a facile one-step strategy for fabricating a Rambutan-like Fe₃O₄@AgAu@PDA (Fe₃O₄@AgAu@Polydopamine) core/shell nanosphere with both catalytic and antibacterial activities which can be critically improved by externally applying an NIR laser irradiation (NIR, 808 nm) and a rotating magnetic field. Typically, the Rambutan-like Fe₃O₄@AgAu@PDA nanosphere have a rather rough surface due to the AuAg bimetallic nanorods sandwiched between the Fe₃O₄ core and the PDA shell. Owing to the penetrated PDA shell, AgAu nanorods show high and magnetically recyclable photothermal-enhanced catalytic activity for the reduction of 4-nitrophenol to 4-aminophenol and they can also be applied to initiate TMB oxidation under the help of NIR heating condition. Moreover, Fe₃O₄@AgAu@PDA shows a moderate antibacterial activity due to the weak release of Ag⁺. Under applying a rotating external magnetic field, the rough-surface Fe₃O₄@AgAu@PDA nanospheres produce a controllable magnetolytic force on the bacterial due to their good affinity. As a result, the Fe₃O₄@AgAu@PDA nanospheres show a "magnetolytic-photothermal-Ag⁺" synergistic antibacterial behavior against E. coli and S. aureus.

Profile and actual transmissibility of Carbapenem resistance genes: Intracellular and extracellular DNA in hospital wastewater

The current worldwide spread of carbapenem resistance genes (CRGs) has posed a major public health threat, which continues to grow in severity. Hospital wastewaters (HWWs) are major reservoirs for antibiotic resistance genes, while resistomes in HWWs are still poorly characterized when it comes to CRGs. We comprehensively characterized the profile and actual transmissibility of extracellular CRGs (eCRGs) and intracellular CRGs (iCRGs) in HWWs for the first time. In this study, CRGs showed similar relative abundance in treated and untreated HWWs. Meanwhile, HWWs treatments led to the enrichment of bla_IMP-8, probably attributed to the promotion of Novosphingobium and Prosthecobacter after treatment. To evaluate the transmission potential of CRGs, extracellular and intracellular carbapenem-resistant plasmids were captured from HWWs by transformation and conjugation, respectively. We found an interesting phenomenon regarding the transmission characteristics of CRGs: bla_KPC-carrying plasmids could only be captured by transformation, while bla_NDM-carrying plasmids were captured by conjugation. Further experiments showed that HWW treatments increased the conjugation ability of bla_NDM. In conclusion, our study demonstrated that HWWs are significant reservoirs of CRGs and various CRGs exhibit different modes of transmission in HWWs. CRGs cannot be removed by membrane bioreactor and chlorine disinfection. An urgent need is to develop more efficient wastewater treatments to limit CRG dissemination.

pH-responsive magnetic Fe3O4/carboxymethyl chitosan/aminated lignosulfonate nanoparticles with uniform size for targeted drug loading

In order to improve the effect of anti-tumor drugs, a magnetic delivery system for targeted drug was reported. Firstly, aminated lignosulfonate (ALS) and carboxymethyl chitosan (CMCS) were used to fabricate nano Fe₃O₄ to obtain pH-responsive magnetic Fe₃O ₄ /CMCS/ALS nanoparticles. Then the nanoparticles were loaded with doxorubicin hydrochloride (DOX), realizing the targeted delivery and controlled release of anti-tumor drugs. It was found that the amount of crosslinking agent and emulsifier were the key factors affecting the morphology and size of the magnetic nanoparticles. Under optimized conditions, the particle size was about 79.9-169.9 nm, exhibiting excellent pH responsiveness. When the drug-to-material ratio was 11:10, the DOX loading rate and the encapsulation rate of the nanoparticles was 48.68 % and 86.23 %. While the Fe₃O₄ /CMCS/ALS-DOX particles could release 63.14 %, 56.71 %, and 14.28 % of DOX at pH 4.0, 5.3, and 7.4, respectively. The results showed that the Fe₃O₄ /CMCS/ALS particles exhibited excellent drug loading and release behavior based on the pH responsiveness, which could be described by Langmuir adsorption model and Fick's law of diffusion respectively. MTT assay and Live/dead staining experiments also showed that the drug-loaded particles had obvious growth inhibition on cancer cells.

Reduced Graphene Oxide-Coated CuFeO2 with Fenton-like Catalytic Degradation Performance for Terramycin

A novel Fenton-like catalyst made of reduced graphene oxide-coated CuFeO₂ (rGO-coated CuFeO₂) was synthesized by the hydrothermal reaction method to remove terramycin from aqueous solutions. The catalytic degradation performance of rGO-coated CuFeO₂ for terramycin was verified with H₂O₂ activation. The characterization reveals that rGO-coated CuFeO₂ has a micro- and mesoporous structure, with groups such as C=C/C-C, CH₂-CO, and HO-C=O found on the surface. The Fenton-like catalytic degradation of terramycin by rGO-coated CuFeO₂ was in line with the pseudo-second-order kinetic model, and the elevated temperature accelerated the reaction. Terramycin was catalytically degraded by rGO-coated CuFeO₂ in two steps: terramycin was first adsorbed by rGO, and then Fenton-like degradation took place on its surface. This research presents new insight into the design and fabrication of Fenton-like catalysts with enhanced performance.

Direct Z-Scheme Heterojunction α-MnO2/BiOI with Oxygen-Rich Vacancies Enhanced Photoelectrocatalytic Degradation of Organic Pollutants under Visible Light

The degradation efficiency of photoelectrocatalytic (PEC) processes for the removal of organic pollutants is highly dependent on the performance of the photoelectroanode catalyst. The design of PEC systems with a direct Z-scheme charge transfer mechanism and visible light excitation is essential to enhance the degradation efficiency of organic compounds. Here, a α-MnO2/BiOI direct Z-scheme heterojunction photocatalyst was successfully synthesized through a convenient and feasible method. It is remarkable that the photoanode exhibited excellent PEC performance under visible light irradiation; a 95% removal rate of tetracycline (TC) pollutants was achieved within 2 h, and it had excellent stability and reusability, which was expected to degrade antibiotics efficiently and environmentally in harsh environments. The presence of oxygen vacancies (OVs) in the α-MnO2/BiOI heterojunction was confirmed by electron spin resonance technique, and the OVs acted as electron traps that contributed substantially to the separation efficiency of photogenerated carriers. ESR characterization showed that the main reactive radicals during TC degradation were –OH and –O2−. By analyzing the intermediates, the possible degradation pathways of TC were further analyzed and a suitable degradation mechanism was proposed. The toxicity changes in the degradation process were explored by evaluating the toxicity of the intermediates. This study provides a new way to enhance the performance of Bi-based semiconductor photocatalysts for the effective degradation of TC in water.

Polydopamine-mediated modification of ZIF-8 onto magnetic nanoparticles for enhanced tetracycline adsorption from wastewater

Magnetic nanoparticle materials which could be used to remove tetracycline were confined seriously due to their poor stability and unsatisfactory reusability. Here, we facilely prepared novel zeolitic imidazolate framework-8 (ZIF-8) functionalized magnetic nanoparticles (Fe₃O₄@PDA-ZIF-8) adsorbent utilizing polydopamine as a bond to establish a connection between zeolitic imidazolate framework-8 and Fe₃O₄, which could improve the stability of magnetic nanoparticles and enhance the tetracycline adsorption capacity simultaneously. The prepared nanocomposites were characterized and their TC adsorption abilities under various experiment conditions (contact time, TC initial concentration and pH values) were also investigated. Experimental results proved that the prepared adsorbent showed superior TC adsorption capacities (92.01 mg/g at pH = 7). Further, the adsorption mechanisms were comprehensively studied and the prepared adsorbent showed satisfactory stability and reusability during the cycle experiment. Altogether, our findings provided a feasible way to design and construct functional magnetic MOF materials for enhancing tetracycline adsorption from wastewater.

Structure and Adsorption Performance of Cationic Entermorpha prolifera Polysaccharide-Based Hydrogel for Typical Pollutants: Methylene Blue, Cefuroxime, and Cr (VI)

Hydrogels with polysaccharides as high polymer substrates have surprising advantages in wastewater treatment with complex components. Therefore, in this study, polysaccharides named EPS were extracted from Enteromorpha prolifera, a coastal pollutant with a wide range of sources, and cationic modification was performed to obtain CAEPS, the hydrogel with a double network structure was prepared based on EPS and CAEPS. Meanwhile, the structural characteristic of EPS and CAEPS-based hydrogel were identified by HPLC, AFM, FT-IR, TGA, SEM-EDS, Pore size distribution, and WCA, which showed that the porosity, apparent (skeletal) density, and hydrophilicity of CAEPS-hydrogels. We used nonlinear isotherms to uncover the adsorption mechanism of hydrogel applied to the water environment containing three typical pollutants (Methylene blue, Cefuroxime, and Cr (VI)). The results showed that the adsorption isotherm of the two hydrogels fit the Langmuir isotherm model, which indicated the monolayer adsorption of the pollution factor onto EPS- and CAEPS-hydrogels. The maximum adsorption capacities of CAEPS-hydrogels were higher than EPS-hydrogels, which indicated the microstructure and adsorption performance of the CAEPS-hydrogel are strengthened.

Dispersible CdS1-xSex solid-solution nanocrystal photocatalysts: Photoinduced self-transformation synthesis and enhanced hydrogen-evolution activity

Modulating the electronic structure of Cadmium sulfide (CdS) by non-metallic elements to produce solid-solution photocatalysts serves as a potential route to improve its performance of photocatalytic hydrogen (H₂) evolution. However, exploring an effective synthetic route of CdS-based solid solution is still a great challenge. Herein, the CdS_1-xSe_x solid-solution nanocrystals were successfully synthesized by an accessible photoinduced self-transformation route, including the direct formation of dispersible CdS_1-x(SeS)_x and the in situ self-transformation of selenosulfide ((SeS)^2-) to Se^2- by photoexcited electrons. The prepared CdS_1-xSe_x solid-solution photocatalysts possess a small crystallite size of ca. 5 nm and their bandgaps can be easily tuned in a wide range of 1.84-2.28 eV by tailoring the mole ratio of Se/S. The resultant CdS_0.90Se_0.10 solid-solution photocatalyst realizes the highest H₂-production tempo of 94.6 μmol·h^-1, which is 1.6 folds higher than that of CdS. The experimental and theoretical studies supported that the incorporation of Se atoms could not only narrow the bandgap value to reinforce visible-light absorption, but also tune its electronic structure to optimize interfacial H₂-evolution dynamics, thus achieving an efficient photocatalytic H₂-production rate of the dispersible CdS_1-xSe_x solid solution. This study may deliver advanced inspirations for optimizing the electronic structure of photocatalysts towards sustainable H₂ production.

Sustainable Mitigation of Paracetamol with a Novel Dual-Functionalized Pullulan/Kaolin Hydrogel Nanocomposite from Simulated Wastewater

In the present investigation, a novel, green, and economical dual-functionalized pullulan/kaolin hydrogel nanocomposite (f-PKHN) was fabricated and subsequently applied for the liquid-phase decontamination of paracetamol (PCT), a pharmaceutical pollutant. Pullulan and kaolin were functionalized with l-asparagine and gallic acid, respectively. The physicochemical facets of the functionalized pullulan/kaolin hydrogel nanocomposite and its interactive behavior with PCT were elucidated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and elemental mapping. The process parameters along with the isotherm, kinetics, and thermodynamics were methodically appraised via a batch technique to unveil the adsorption performance of the as-fabricated hydrogel nanocomposite. The adsorption isotherm and kinetics of PCT uptake by f-PKHN conform well to Freundlich and pseudo-second-order models, respectively. Relying on hydrogen bonding, n-π, and van der Waals interactions, the maximum adsorption capacity was 332.54 mg g^-1, higher than for most of the previous adsorbents reported in the literature for PCT removal. Thermodynamic calculations corroborated endothermic, spontaneous, and feasible adsorption phenomena. The maintenance of a high uptake percentage (69.11%) in the fifth consecutive adsorption-desorption cycle implied the significant reusable potential of f-PKHN. Swelling studies exhibited 90% swelling within 200 min, indicating the successful fabrication of a cross-linked hydrogel network. The real water (distilled water, tap water, and river water) samples spiked with PCT specified a significant uptake of PCT (>85%), and the minor influence of ionic strength on the adsorptive potential of f-PKHN validated its potentiality for the decontamination of real effluents. In conclusion, f-PKHN with substantial adsorption capacity, green characteristics, and excellent reusability can be reckoned with as a promising adsorbent for the de-escalation of PCT from aquatic sources as well as at the industrial level.

Synthesis of magnetic/pH dual responsive dextran hydrogels as stimuli-sensitive drug carriers

Hydrogels loaded with magnetic nanoparticles have been widely researched recently as biomaterials, due to their good biocompatibility and unique magnetic characteristics. In this study, water-soluble superparamagnetic iron oxide nanoparticles (Fe₃O₄) prepared by coprecipitation were physically doped into the dextran hydrogels which were formed via Schiff base reactions between ethylenediamine and oxidized dextran. The combination of magnetic nanoparticles and chemical cross-linked hydrogels leads to magnetic/pH dual-sensitive hydrogels which can be used as stimuli-responsive carrier. Magnetic properties, swelling, and rheology behaviors of the resulted magnetic hydrogels were strongly affected by the Fe₃O₄ nanoparticle content. Moreover, doxorubicin (DOX⋅HCl) was embedded into the magnetic hydrogels and pH/magnetic sensitive release profiles were identified. The release mechanism analysis indicated that the release behaviors of DOX⋅HCl were controlled by the diffusion, swelling, and erosion processes simultaneously. The prepared hydrogel/Fe₃O₄ composites with dual magnetic/pH stimuli-responsiveness hold the promise to be used in various applications such as drug release.

Recent Advances in Polysaccharide-Based Physical Hydrogels and Their Potential Applications for Biomedical and Wastewater Treatment

Polysaccharides have been widely employed to fabricate hydrogels owing to their intrinsic properties including biocompatibility, biodegradability, sustainability, and easy modification. However, a considerable amount of polysaccharide-based hydrogels are prepared by chemical crosslinking method using organic solvents or toxic crosslinkers. The presence of reaction by-products and residual toxic substances in the obtained materials cause a potential secondary pollution risk and thus severely limited their practical applications. In contrast, polysaccharide-based physical hydrogels are preferred over chemically derived hydrogels and can be used to address existing drawbacks of chemical hydrogels. The polysaccharide chains of such hydrogel are typically crosslinked by dynamic non-covalent bonds, and the co-existence of multiple physical interactions stabilize the hydrogel network. This review focuses on providing a detailed outlook for the design strategies and formation mechanisms of polysaccharide-based physical hydrogels as well as their specific applications in tissue engineering, drug delivery, wound healing, and wastewater treatment. The main preparation principles, future challenges, and potential improvements are also outlined. The authors hope that this review could provide valuable information for the rational fabrication of polysaccharide-based physical hydrogel. The specific research works listed in the review will provide a systematic and solid research basis for the reliable development of polysaccharide-based physical hydrogel. This article is protected by copyright. All rights reserved.

Adsorption removal and photocatalytic degradation of azithromycin from aqueous solution using PAC/Fe/Ag/Zn nanocomposite

The improper use of antibiotics and their discharge into the environment can have serious and hazardous consequences. The purpose of this research is to synthesize an activated carbon impregnated magnetite composite (PAC/Fe), prepare PAC/Fe/Ag/Zn nanocomposites, and innovate by simultaneously synthesizing two metals, zinc and silver, on magnetically activated carbon and check its ability to remove azithromycin antibiotic (AZT) from an aqueous solution via UV system. PAC/Fe/Ag/Zn nanocomposites were characterized by various techniques including XRD, FESEM, and EDX. A series of batch experiments were carried out under various experimental conditions such as pH of the solution (3-11), contact time (0-120 min), initial concentration of AZT (10-40 ppm), amount of PAC/Fe/Ag/Zn nano-absorbent (0.01-0.04 g/l), and recoverability and reuse. Some common isotherm models were used for the study of AZT adsorption removal and finding the best model. Also, kinetic studies of AZT removal were performed by fitting the experimental data on first-order and second-order models. In this system, under optimal conditions of pH = 9, 120 min with 0.04 g/l of PAC/Fe/Ag/Zn, 99.5% of 10 ppm AZT were degraded under UV-C irradiation. Furthermore, the obtained results of isotherm and kinetic studies revealed that Langmuir (R² = 0.9336) isotherm model, and the pseudo-first-order kinetic model (R² = 0.9826) had the highest correlation with the experimental data of AZT antibiotic adsorption. Finally, the reusability experiments showed that PAC/Fe/Ag/Zn nanocomposites have a high ability of antibiotic adsorption and high stability after four cycles of application (99.5 to 40%).

Hydrogels and Hydrogel Nanocomposites: Enhancing Healthcare through Human and Environmental Treatment

Humans are constantly exposed to exogenous chemicals throughout their life, which can lead to a multitude of negative health impacts. Advanced materials can play a key role in preventing or mitigating these impacts through a wide variety of applications. The tunable properties of hydrogels and hydrogel nanocomposites (e.g., swelling behavior, biocompatibility, stimuli responsiveness, functionality, etc.) have deemed them ideal platforms for removal of environmental contaminants, detoxification, and reduction of body burden from exogenous chemical exposures for prevention of disease initiation, and advanced treatment of chronic diseases, including cancer, diabetes, and cardiovascular disease. In this review, three main junctures where the use of hydrogel and hydrogel nanocomposite materials can intervene to positively impact human health are highlighted: 1) preventing exposures to environmental contaminants, 2) prophylactic treatments to prevent chronic disease initiation, and 3) treating chronic diseases after they have developed.

UV-assisted ultrafast construction of robust Fe3O4/polydopamine/Ag Fenton-like catalysts for highly efficient micropollutant decomposition

Fenton-like catalysts represent a family of promising materials to degrade micropollutants from contaminated water. However, the practical applications of Fenton-like catalysts are mainly limited by low catalytic degradation efficiency and stability. Herein, for the first time, rapid fabrication of Ag-decorated Fe₃O₄/polydopamine (FPA) microspheres was achieved via the help of UV irradiation, and the designed FPA microspheres were employed as Fenton-like catalysts to degrade micropollutants. Results showed that UV irradiation could activate the generation of the polydopamine shell and accelerate the Ag deposition, which played a crucial role in the rapid synthesis of highly active and stable FPA catalysts. Relative to reported catalysts, these FPA microspheres exhibited outstanding catalytic degradation performance, achieving 94.38% removal of tetracycline within 60 min. This work will provide a convenient strategy in the sustainable and efficient purification of wastewater to improve the quality of human life.

Facile formation of injectable quaternized chitosan/tannic acid hydrogels with antibacterial and ROS scavenging capabilities for diabetic wound healing

The wound healing process of the diabetic wound is often hindered by excessive oxygen free radicals and infection. An ideal wound dressing should possess great reactive oxygen species (ROS) scavenging property and considerable antibacterial ability. In this study, we facilely constructed a novel hydrogel dressing with excellent ROS scavenging property and outstanding antibacterial performance by introducing tannic acid (TA) into quaternized chitosan (QCS) matrix. Attributing to the suitable physical crosslinking between TA and QCS, this QCS/TA hydrogel was endowed with injectable and self-healing properties, which could avoid the various external squeezing on the irregular shape by wound dressing. The results showed that it could promote coagulation, suppress inflammation and expedite collagen deposition in the skin defect model of diabetic rats. This study provides a facile and convenient method for constructing injectable hydrogel dressing, which has application potentials in the clinical management of diabetic wounds.

Biogenic Synthesis of Iron Oxide Nanoparticles Using Enterococcus faecalis: Adsorption of Hexavalent Chromium from Aqueous Solution and In Vitro Cytotoxicity Analysis

The biological synthesis of nanoparticles is emerging as a potential method for nanoparticle synthesis due to its non-toxicity and simplicity. In the present study, a bacterium resistant to heavy metals was isolated from a metal-contaminated site and we aimed to report the synthesis of Fe3O4 nanoparticles via co-precipitation using bacterial exopolysaccharides (EPS) derived from Enterococcus faecalis_RMSN6 strains. A three-variable Box-Behnken design was used for determining the optimal conditions of the Fe3O4 NPs synthesis process. The synthesized Fe3O4 NPs were thoroughly characterized through multiple analytical techniques such as XRD, UV-Visible spectroscopy, FTIR spectroscopy and finally SEM analysis to understand the surface morphology. Fe3O4 NPs were then probed for the Cr(VI) ion adsorption studies. The important parameters such as optimization of initial concentration of Cr(VI) ions, effects of contact time, pH of the solution and contact time on quantity of Cr(VI) adsorbed were studied in detail. The maximum adsorption capacity of the nanoparticles was found to be 98.03 mg/g. The nanoparticles could retain up to 73% of their efficiency of chromium removal for up to 5 cycles. Additionally, prepared Fe3O4 NPs in the concentration were subjected to cytotoxicity studies using an MTT assay. The investigations using Fe3O4 NPs displayed a substantial dose-dependent effect on the A594 cells. The research elucidates that the Fe3O4 NPs synthesized from EPS of E. faecalis_RMSN6 can be used for the removal of heavy metal contaminants from wastewater.

ε‑Polylysine-stabilized agarose/polydopamine hydrogel dressings with robust photothermal property for wound healing

Polydopamine (PDA) is emerging as an attractive photothermal agent due to its good photothermal performance and excellent biocompatibility. However, without chemical modification, PDA is normally unstable and usually leached out from the constructed biomaterials, realistically limiting its application space. Here, we constructed a new hydrogel dressing with robust and stable photothermal performance by introduction of ε-Polylysine (ε-PL) into agarose/PDA matrix to efficiently lock PDA. By optimizing PDA/ε-PL rational dose in agarose network structure, a hybrid agarose/PDA/ε-PL hydrogel (ADPH) with stable photothermal functionality and desirable physicochemical properties could be achieved. ADPH possessed satisfactory microbicidal efficacy in vivo, which enabled the bacteria-infected skin wound to be cured quickly by successful suppressing inflammation, accelerating collagen deposition and promoting angiogenesis in a bacterial-infected wound model. Collectively, this study illustrates a simple, convenient but powerful strategy to design functionally stable ADPH dressing for treating dermal wounds, which could open vistas in clinical wound management.