Carboxymethyl chitosan-modified magnetic-cored dendrimer as an amphoteric adsorbent

Preparation of porous silica materials using a eucalyptus template method and its efficient adsorption of methylene blue

Methylene blue (MB) is a prevalent pollutant in organic wastewater. For this research, eucalyptus wood was used as a template, into which quartz powder dissolved in NaOH was grown, resulting in a low-cost and efficient porous silica adsorbent material (PSAM). This PSAM successfully replaces expensive materials for MB removal from water. Through the application of Scanning Electron Microscopy (SEM) and Brunauer-Emmett-Teller (BET) analysis, it became evident that PSAM displays a porous slit pore structure characterized by numerous active sites, leading to an impressive maximum specific surface area of 88.05 m²/g. The central objective of this research was to investigate the impact of experimental temperature, initial dye concentration, and pH on the adsorption process. The adsorption kinetics were analyzed using the pseudo-first-order and pseudo-second-order models, as well as the Langmuir model. Remarkably, PSAM exhibited a substantial maximum adsorption capacity of 90.01 mg/g at 293 K, achieving an adsorption rate of over 85% within a mere 10-minute timeframe. The thermodynamic analysis revealed that the adsorption of MB onto PSAM was characterized by spontaneity and accompanied by heat absorption. Fourier Transform Infrared (FTIR) and SEM comparisons of PSAM before and after adsorption indicated that MB adsorption primarily occurred through electrostatic gravitational binding. In comparison to other adsorbents, PSAM exhibited exceptional efficacy in removing MB from water.

Advances in functionalization and conjugation mechanisms of dendrimers with iron oxide magnetic nanoparticles

Iron oxide magnetic nanoparticles (MNPs) are crucial in various areas due to their unique magnetic properties. However, their practical use is often limited by instability and aggregation in aqueous solutions. This review explores the advanced technique of dendrimer functionalization to enhance MNP stability and expand their application potential. Dendrimers, with their symmetric and highly branched structure, effectively stabilize MNPs and provide tailored functional sites for specific applications. We summarize key synthetic modifications, focusing on the impacts of dendrimer size, surface chemistry, and the balance of chemical (e.g., coordination, anchoring) and physical (e.g., electrostatic, hydrophobic) interactions on nanocomposite properties. Current challenges such as dendrimer toxicity, control over dendrimer distribution on MNPs, and the need for biocompatibility are discussed, alongside potential solutions involving advanced characterization techniques. This review highlights significant opportunities in environmental, biomedical, and water treatment applications, stressing the necessity for ongoing research to fully leverage dendrimer-functionalized MNPs. Insights offered here aim to guide further development and application of these promising nanocomposites.

Highly Efficient Biosorption of Cationic Dyes via Biopolymeric Adsorbent-Material-Based Pectin Extract Polysaccharide and Carrageenan Grafted to Cellulosic Nonwoven Textile

Water scarcity and contamination have emerged as critical global challenges, requiring the development of effective and sustainable solutions for the treatment of contaminated water. Recently, functionalized polymer biomaterials have garnered significant interest because of their potential for a wide range of water treatment applications. Accordingly, this paper highlights the design of a new adsorbent material based on a cellulosic nonwoven textile grafted with two extracted biopolymers. The layer-by-layer grafting technique was used for the polyelectrolyte multi-layer (PEM) biosorbent production. Firstly, we extracted a Suaeda fruticosa polysaccharide (SFP) and confirmed its pectin-like polysaccharide structure via SEC, NMR spectroscopy, and chemical composition analyses. Afterward, the grafting was designed via an alternating multi-deposition of layers of SFP polymer and carrageenan crosslinked with 1,2,3,4-butanetetracarboxylic acid (BTCA). FT-IR and SEM were used to characterize the chemical and morphological characteristics of the designed material. Chemical grafting via polyesterification reactions of the PEM biosorbent was confirmed through FT-IR analysis. SEM revealed the total filling of material microspaces with layers of grafted biopolymers and a rougher surface morphology. The assessment of the swelling behavior revealed a significant increase in the hydrophilicity of the produced adsorbent system, a required property for efficient sorption potential. The evaluation of the adsorption capabilities using the methylene blue (MB) as cationic dye was conducted in various experimental settings, changing factors such as the pH, time, temperature, and initial concentration of dye. For the untreated and grafted materials, the greatest adsorbed amounts of MB were 130.6 mg/g and 802.6 mg/g, respectively (pH = 4, T = 22 C, duration = 120 min, and dye concentration = 600 mg/L). The high adsorption performance, compared to other reported materials, was due to the presence of a large number of hydroxyl, sulfonate, and carboxylic functional groups in the biosorbent polymeric system. The adsorption process fitted well with the pseudo-first-order kinetic model and Langmuir/Temkin adsorption isotherms. This newly developed multi-layered biosorbent shows promise as an excellent adsorption resultant and cheap-cost/easy preparation alternative for treating industrial wastewater.

Retention of Phthalates in Wine Using Nanomaterials as Chemically Modified Clays with H20, H30, H40 Boltron Dendrimers

The presence of phthalic acid esters in wines presents a major risk to human health due to their very toxic metabolism. In this paper, aluminosilicate materials were used, with the aim of retaining various pollutants and unwanted compounds in wine. The pollutants tested were di-butyl and di-ethyl hexyl phthalates. They were tested and detected using the gas chromatography-mass spectrometry (CG-MS) analytical technique. Nanomaterials were prepared using sodium bentonite, and were chemically modified via impregnation using three types of Boltron dendrimers of second, third and fourth generations (NBtH20, NBtH30 and NBtH40). The synthesized nanomaterials were characterized using the Brunauer-Emmett-Teller (BET) method, Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. In this paper, two aspects were addressed: the first related to the retention of phthalate-type pollutants (phthalic acid esters-PAEs) and the second related to the protein and polyphenol levels in the white wine of the Aligoté grape variety. The results obtained in this study have a major impact on PAEs in wine, especially after treatment with NBtH30 and NBtH40 (volumes of 250-500 μL/10 mL wine), with the retention of the pollutants being up to 85%.

Chitosan-Based Architectures as an Effective Approach for the Removal of Some Toxic Species from Aqueous Media

Modified uncrosslinked and crosslinked chitosan derivatives were investigated as green sorbents for the removal of copper (Cu²⁺) and lead (Pb²⁺) cations from simulated solutions. In this regard, N, O carboxymethyl chitosan (N, O CMC), chitosan beads (Cs-g-GA), chitosan crosslinked with glutaraldehyde/methylene bisacrylamide (Cs/GA/MBA), and chitosan crosslinked with GA/epichlorohydrin (Cs/GA/ECH) were prepared and characterized by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, and scanning electron microscopy analyses. Atomic force microscopy investigation was carried out to compare the surface topography of the prepared samples before and after the metal uptake. The kinetics of the removal process were investigated by pseudo-first-order and -second-order models. Moreover, the adsorption isotherms were carefully studied by applying Langmuir and Freundlich models. The data reveal that upon adsorption of copper(II) metal ions, all chitosan-modified products followed the Langmuir isotherm except for Cs/GA/ECH which followed the Freundlich isotherms, and the highest adsorption capacity (q _e) was obtained for Cs/GA/MBA due to the formation of stable chelate structures between the metal cation and the functional groups present on the modified chitosan product. The order of metal uptake at the optimum pH value is as follows: Cs/GA/MBA (Cu: 95.7 mg/g, Pb: 99.15 mg/g), Cs/GA/ECH (Cu: 80.4 mg/g, Pb: 93.14 mg/g), Cs-g-GA (Cu: 77 mg/g, Pb: 88.4 mg/g), and N, O CMCh (Cu: 30.2 mg/g, Pb: 44.8 mg/g). The AFM data confirmed the metal uptake process by comparing the roughness and height measurements of the free sorbents and the metal-loaded sorbents.

Modified magnetic chitosan materials for heavy metal adsorption: a review

Magnetic chitosan materials have the characteristics of both chitosan and magnetic particle nuclei, showing the characteristics of easy separation and recovery, strong adsorption capacity and high mechanical strength, and have received extensive attention in adsorption, especially in the treatment of heavy metal ions. In order to further improve its performance, many studies have modified magnetic chitosan materials. This review discusses the strategies for the preparation of magnetic chitosan using coprecipitation, crosslinking, and other methods in detail. Besides, this review mainly summarizes the application of modified magnetic chitosan materials in the removal of heavy metal ions in wastewater in recent years. Finally, this review also discusses the adsorption mechanism, and puts forward the prospect of the future development of magnetic chitosan in wastewater treatment.

Thermosensitive poly(N-isopropylacrylamide)-grafted magnetic-cored dendrimers for benzene uptake

A series of thermosensitive and magneto-responsive dendrimers was synthesized based on magnetic-cored dendrimers (MCD) and carboxylic end-capped poly(N-isopropylacrylamide) (PNIPAM) to obtain PNIPAM-g-MCD. Thermo-response profiles of the PNIPAM-g-MCD from dynamic light scattering within the temperature range of 25-45 °C indicated that the lower critical solution temperature (LCST) of the PNIPAM-g-MCD was 32 °C. The physical size of the PNIPAM-g-MCD decreased as the temperature increased above the LCST. The initial hydrodynamic size of the PNIPAM-g-MCDs at 25 °C was 298.6 nm and reached 226.4 nm at 45 °C upon heating. Adsorption of benzene onto the PNIPAM-g-MCD at 25 °C was assessed, and the results showed that hydrophobic benzene was included within the internal cavities of lipophilic PNIPAM-g-MCD to maintain a thermodynamically stable state. Entrapment effects of the PNIPAM-g-MCD were confirmed at 45 °C, and the removal efficiency of benzene increased considerably to 50% when benzene was adsorbed, and the entrapment process was added. The shrunken PNIPAM terminal groups aggregated and trapped benzenes within the cavities of PNIPAM-g-MCD to prevent escape into the aqueous solution. Un-trapped benzene was removed through coalescence with PNIPAM-g-MCD because hydrophobic interactions prevailed with increasing temperature. PNIPAM-g-MCD were also able to form emulsions below the LCST and disrupted emulsions above the LCST in oil-water emulsions.

Citric, succinic, and vanillic acid-functionalized magnetic-cored dendrimer for methylene blue adsorption

A new functional composite was synthesized in this study comprising magnetic-cored dendrimer (MCD) modified with citric acid (CA), succinic acid (SA), and vanillic acid (VA) terminal groups. The CA-MCD, SA-MCD, and VA-MCD exhibited average particle size of 8-18 nm and superparamagnetic behavior. Adsorption potential of the composite was assessed by monitoring methylene blue (MB) removal from contaminated water. The CA-MCD attained adsorption equilibrium in 30 min while SA-MCD and VA-MCD achieved equilibrium in 60 min. The Langmuir model better fitted the adsorption results than the Freundlich model, indicating a monolayer mode of MB adsorption on the composite. Maximum adsorption capacity of CA-MCD, SA-MCD, and VA-MCD was 216.30 mg/g, 184.29 mg/g, and 196.58 mg/g, respectively. The CA-MCD exhibited best adsorption performance by removing 99% MB at pH = 11. In reusability experiments, the CA-MCD, SA-MCD, and VA-MCD maintained over 90% MB adsorption for both 15 mg/L and 50 mg/L solutions in the third cycle. Overall, the organic acid-functionalized MCDs with high adsorption capacity and reusability potential showed utility for practical application for wastewater decontamination.

Graphene oxide modified magnetic polyamidoamide dendrimers based magnetic solid phase extraction for sensitive measurement of polycyclic aromatic hydrocarbons

In this study, graphene oxide modified magnetic polyamidoamine dendrimers (MNPs@PAMAM-G2.0@GO) nanoparticles were successfully prepared by amidation method. The obtained MNPs@PAMAM-G2.0@GO nanocomposites were examined by fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), scanning electron microscope (SEM) and transmission electron microscopy (TEM), etc. MNPs@PAMAM-G2.0@GO exhibited excellent adsorption property and was investigated for magnetic solid phase extraction (MSPE) of polycyclic aromatic hydrocarbons (PAHs) from water. The detection of extracted PAHs was accomplished by high performance liquid chromatography (HPLC) and gas chromatography tandem mass spectrometry (GC-MS/MS). The target PAHs included anthracene (ANT), pyrene (PYR), fluoranthene (FLT), carbazole (CB), 7-methylquinoline (7-MQL), 9-methylcarbazole (9-MCB), dibenzothiophene (DBT) and 4,6-dimethyldibenzothiophene (4,6-DBT). Important operation parameters for MSPE that could affect the extraction efficiencies of PAHs were investigated in detail. Under optimal parameters, the constructed method demonstrated excellent linear range with 0.001-10 μg L^-1 for analytes and low limits of detection within the range of 0.11-0.9 ng L^-1. The spiked average recoveries of PAHs in natural water samples ranged from 92.5% to 105.2%. The promising results indicated that MNPs@PAMAM-G2.0@GO could be employed to efficiently extract PAHs from aqueous samples.

Magnetic chitosan microspheres: An efficient and recyclable adsorbent for the removal of iodide from simulated nuclear wastewater

The efficient and recyclable magnetic chitosan microspheres (MCMs) were successfully synthesized to remove iodide from nuclear wastewater and characterized through XRD, FTIR, SEM, EDS, VSM, TGA and XPS. The characterization results indicated that the MCMs exhibited smooth spherical morphology and good magnetic properties. The removal potential of MCMs was investigated for iodide (I^-) anions at different conditions. From pH 3 to pH 9, MCMs performed the high I^- removal efficiency (>90%). The maximum I^- removal capacity of MCMs was up to 0.8087 mmol g^-1 at 298 K, well-fitting with the pseudo-second-order and Sips models. Furthermore, the I^- removal efficiency of MCMs still maintained more than 91% after five adsorption-desorption cycles, performing good regeneration and reusability. This study is expected to prompt the MCMs to become an efficient and recyclable biosorbent for iodide removal from nuclear wastewater.

Simultaneous adsorption for cationic and anionic dyes using chitosan/electrospun sodium alginate nanofiber composite sponges

The coexistence of anionic and cationic dyes in dye wastewater has highlighted a great necessity to develop amphoteric adsorbents for their simultaneous removal. Herein, an amphoteric composite sponge was successfully fabricated by combining chitosan with electrospun sodium alginate nanofiber using lyophilization in acetic acid/water/dioxane mixed solvents, which owned the abundant functional groups and superior microstructure of interconnected pores and nanoscale fibers, beneficial for the adsorption capacity improvement. The optimum adsorption capacities for Acid Blue-113 and Rhodamine B were 926.2 ± 25.7 mg/g and 695.4 ± 17.0 mg/g, respectively, much higher than that of the controlled sample prepared with chitosan and non-spinning sodium alginate in traditional acetic acid/water solvents. Meanwhile, the sponge provided with the superior adsorption performance under various pH environment and cyclic adsorption. Importantly, it had considerable simultaneous adsorption capacity for binary system containing anionic and cationic dyes. Overall, the chitosan/electrospun sodium alginate nanofiber composite sponge shows potential for complex wastewater treatment.

Recent Advances in Functional Polymer Materials for Energy, Water, and Biomedical Applications: A Review

Academic research regarding polymeric materials has been of great interest. Likewise, polymer industries are considered as the most familiar petrochemical industries. Despite the valuable and continuous advancements in various polymeric material technologies over the last century, many varieties and advances related to the field of polymer science and engineering still promise a great potential for exciting new applications. Research, development, and industrial support have been the key factors behind the great progress in the field of polymer applications. This work provides insight into the recent energy applications of polymers, including energy storage and production. The study of polymeric materials in the field of enhanced oil recovery and water treatment technologies will be presented and evaluated. In addition, in this review, we wish to emphasize the great importance of various functional polymers as effective adsorbents of organic pollutants from industrial wastewater. Furthermore, recent advances in biomedical applications are reviewed and discussed.

Adsorption Behavior of Methylene Blue Dye by Novel CrossLinked O-CM-Chitosan Hydrogel in Aqueous Solution: Kinetics, Isotherm and Thermodynamics

The chemical cross-linking of carboxymethyl chitosan (O-CM-chitosan), as a method for its modification, was performed using trimellitic anhydride isothiocyanate to obtain novel cross-linked O-CM-chitosan hydrogel. Its structure was proven using FTIR, XRD and SEM. Its adsorption capacity for the removal of Methylene Blue (MB) dye from aqueous solution was studied. The effects of different factors on the adsorption process, such as the pH, temperature and concentration of the dye, in addition to applications of the kinetic studies of the adsorption process, adsorption isotherm and thermodynamic parameters, were studied. It was found that the amount of adsorbed MB dye increases with increasing temperature. A significant increase was obtained in the adsorption capacities and removal percentage of MB dye with increasing pH values. An increase in the initial dye concentration increases the adsorption capacities, and decreases the removal percentage. It was found that the pseudo-second-order mechanism is predominant, and the overall rate of the dye adsorption process appears to be controlled by more than one step. The Langmuir model showed high applicability for the adsorption of MB dye onto O-CM-chitosan hydrogel. The value of the activation energy (E_a) is 27.15 kJ mol⁻¹ and the thermodynamic parameters were evaluated. The regeneration and reuse of the investigated adsorbent was investigated.

Preparation of Polyamidoamine Dendrimer Modified Magnetic Nanoparticles and Its Application for Reliable Measurement of Sudan Red Contaminants in Natural Waters at Parts-Per-Billion Levels

The health threat from Sudan red dyes has been the subject of much attention in recent years and is crucial to design and establish reliable measurement technologies. In the present study, a new magnetic nanomaterial, polyamidoamine dendrimer-modified magnetic nanoparticles (Gn-MNPs), was synthesized and characterized. The nanomaterials had good adsorption capacity for Sudan dyes from natural waters. G1.5-MNPs possessed excellent adsorption capacity and a linear adsorption relationship over the range from 0.02 to 300 μg L⁻¹ of Sudan dyes with relative coefficients all larger than 0.996. The sensitivity of the proposed method was excellent with detection limits over the range from 1.8 to 5.5 ng L⁻¹ and the precision was less than 3.0%. G1.5-MNPs showed a remarkable application potential for the enrichment of trace environment pollutants in aqueous samples and the developed method based on this nanomaterial could be a robust and reliable alternative tool for routine monitoring of such pollutants.

Sequestration of p-nitrophenol from liquid phase by poly(acrylonitrile-co-acrylic acid) containing thioamide group

In this paper, the adsorptive performance of synthesized thiourea (TU) modified poly(acrylonitrile-co-acrylic acid) (TU-P(AN-co-AA)) polymeric adsorbent for capturing p-nitrophenol (PNP) from aqueous solution was investigated. TU-P(AN-co-AA) was synthesized via the redox polymerization method with acrylonitrile (AN) and acrylic acid (AA) as the monomers, then modified chemically with thiourea (TU). Characterization analysis with Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), elemental microanalysis for CHNS, zeta potential measurement, Brunauer-Emmett-Teller (BET) surface analysis and thermal analyses were carried out to determine the morphology and physico-chemical properties of the synthesized polymer. The characterization results indicated successful surface modification of polymer with TU. The performance of TU-P(AN-co-AA) for the removal of PNP was investigated under various experimental parameters (adsorbent dosage, initial adsorbate concentration, contact time and temperature). The results demonstrated that the Freundlich isotherm model and pseudo-second-order kinetic model best described the equilibrium and kinetic data, respectively. Thermodynamic studies showed that the uptake of PNP by TU-P(AN-co-AA) was spontaneous and exothermic in nature. The results of the regeneration studies suggested that the TU-P(AN-co-AA) polymer is a reusable adsorbent with great potential for removing PNP from wastewater.

Electrochemical and Electrochemiluminescence Dendrimer-based Nanostructured Immunosensors for Tumor Marker Detection: A Review

The usage of dendrimers or cascade molecules in the biomedical area has recently attracted much attention worldwide. Furthermore, dendrimers are interesting in clinical and pre-clinical applications due to their unique characteristics. Cancer is one of the most widespread challenges and important diseases, which has the highest mortality rate. In this review, the recent advances and developments (from 2009 up to 2019) in the field of electrochemical and electroluminescence immunosensors for detection of the cancer markers are presented. Moreover, this review covers the basic fabrication principles and types of electrochemical and electrochemiluminescence dendrimer-based immunosensors. In this review, we have categorized the current dendrimer based-electrochemical/ electroluminescence immunosensors into five groups: dendrimer/ magnetic particles, dendrimer/ferrocene, dendrimer/metal nanoparticles, thiol-containing dendrimer, and dendrimer/quantum dots based-immunosensors.

A regenerable ion-imprinted magnetic biocomposite for selective adsorption and detection of Pb2+ in aqueous solution

A regenerable ion-imprinted magnetic biocomposite (IIMB) was successfully synthesized for simultaneous removal of Pb²⁺ using Serratia marcescens and carboxymethyl chitosan (CMC) as functional carriers, Pb²⁺ was utilized as the imprinted ion, while Fe₃O₄ served as the magnetic component. The structure and properties of IIMB were characterized by various techniques. The adsorption kinetics, isotherms and thermodynamics were applied to interpret the Pb²⁺ adsorption process on IIMB. The results showed the IIMB possessed prominent uptake ability toward Pb²⁺. The pseudo-second-order kinetic (R² = 0.9989) and Langmuir models (R² = 0.9555) fitted the data well. Adsorption thermodynamics revealed that the adsorption was a spontaneous endothermic reaction. The possible adsorption mechanisms involved physical adsorption, electrostatic attraction and complexing. Moreover, because Pb²⁺ can be specifically and strongly adsorbed on IIMB, a simple method for detection of Pb²⁺ was established by coupling IIMB with flame atomic absorption spectrometry (IIMB-FAAS). The developed IIMB-FAAS assay can sensitively detect Pb²⁺ with a linear range from 5.0 to 500.0 μg/L. The detection limit (LOD) of 0.95 μg/L as well as a quantification limit (LOQ) of 3.20 μg/L were obtained. This work proved that the IIMB could selective and efficient adsorb Pb²⁺, which provided some insights into wastewater treatment, water quality inspection and environmental remediation.

Magnetic polyamidoamine dendrimer grafted with 4-mercaptobenzoic acid as an adsorbent for preconcentration and sensitive determination of polycyclic aromatic hydrocarbons from environmental water samples

Polyamidoamine dendrimer decorated Fe₃O₄ magnetic nanoparticles was synthesized and grafted with 4-mercaptobenzoic acid (4-MBA). The resulting material was utilized to develop an effective magnetic solid phase extraction method in combination with high performance liquid chromatography for trace determination of polycyclic aromatic hydrocarbons including phenanthrene (PHE), anthracene (ANT), fluoranthene (FLT), pyrene (PYR) and benzo(a)pyrene (BaP). The MNPs@G3.0@4-MBA exhibited to be an efficient extracting medium due to the existence of terminal benzene ring groups, the internal pores, and strong hydrophobic interactions and π-π interactions. The experiments demonstrated that the proposed method possessed excellent linearity in the concentration range of 0.1-300 μg L^-1 with correlation coefficients (R) larger than 0.997, and the limits of detection (LODs, S/N = 3) according to the ratio of signal to noise equal to three of PHE, ANT, FLT, PYR and BaP were 0.014 μg L^-1, 0.032 μg L^-1, 0.055 μg L^-1, 0.027 μg L^-1 and 0.039 μg L^-1, respectively. The proposed method was applied to real water samples and the spiked recoveries were over the range of 92-99%. The results showed that the method earned good repeatability and high sensitivity, and the as-prepared materials were stable and reusable, which displayed that the proposed method would have a wonderful application prospect.

Using a Modified Polyamidoamine Fluorescent Dendrimer for Capturing Environment Polluting Metal Ions Zn2+, Cd2+, and Hg2+: Synthesis and Characterizations

One of the most pressing global concerns is how to provide a clean environment for future generations given the exacerbation of urban, agricultural, industrial, and economic activities due to the escalating size of the global population. A polyamidoamine (PAMAM) dendrimer peripherally modified with 4-N,N′-dimethylethylenediamine-1,8-naphthalmide as a chromophore was synthesized and utilized to capture hazardous heavy metal ions. This modified fluorescent dendrimer (FCD) was complexed with Group 12 metal ions (Zn2+, Cd2+, and Hg2+) at a 2:1 (metal: FCD) ratio. Electronic absorption, fluorescence emission, Infra-red (IR), and nuclear magnetic resonance (1H NMR) spectroscopies, conductivity, CHN elemental, thermogravimetry, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analyses were used to characterize the resulting metal complexes. These assays revealed that the synthesized complexes were yellow-colored, thermally stable, nanoscale-sized, and composed of [M2FCD]·4Cl2. Considerable spectral shifts were observed in the emission and absorption spectra of the FCD molecule after binding the Zn2+ ions, which can be used to differentiate the Zn2+ complex from the other two complexes. This work provides basic data to facilitate the detection, quantification, and removal of environmentally hazardous heavy metal ions through complexation with a fluorescent dendrimer.

Magnetic nanostructures functionalized with a derived lysine coating applied to simultaneously remove heavy metal pollutants from environmental systems

The pollution of environmental systems with heavy metals is becoming a serious problem worldwide. These contaminants are one of the main issues in sludge (which is considered waste) and can even have harmful effects if the sludge is not treated properly. Thus, the development of a novel functional magnetic nanoadsorbent based on a derived lysine is reported here, which can be efficiently applied for metal removal from sludge. Magnetic nanoparticles were coated with silica layer and further modified by covalent bonding of derived lysine. The morphology of the nanomaterial, its nano-size and the silica layer thickness were analyzed by transmission electron microscopy. The successful silanization of the lysine derivative to the silica-coated magnetic nanostructures was investigated by several physicochemical characterization techniques, while the magnetic properties were measured with a vibrating sample magnetometer. The synthesized nanostructures were used as adsorbents for simultaneous removal of most critical heavy metals (Cr, Zn, Cu) from real complex sludge suspensions. The main practical adsorption parameters, pH of the native stabilized sludge, adsorbent amount, time, and adsorbent regeneration were investigated. The results show promising adsorption properties among currently available adsorbents (the total equilibrium adsorption capacity was 24.5 mg/g) from the sludge with satisfactory nanoadsorbent reusability and its rapid removal. The stability of the nanoadsorbent in the sludge, an important but often neglected practical parameter for efficient removal, was verified. This work opens up new possibilities for the development of high-quality magnetic nanoadsorbents for metal pollutants applied in various complicated environmental fields and enables waste recovery.

Selective removal of anionic and cationic dyes by magnetic Fe3O4-loaded amine-modified hydrochar

Fe₃O₄-loaded protonated amine-modified hydrochar (Fe₃O₄-PAMH) was successfully prepared and characterized by scan electron microscopy equipped with energy-dispersion X-ray spectroscopy, zeta potential analysis, vibration sample magnetometry, Fourier transform infrared and X-ray photoelectron spectroscopies, Brunauer-Emmett-Teller measurement, and X-ray diffraction. Adsorption properties of Fe₃O₄-PAMH to negatively-charged methyl orange (MO) or positively-charged methylene blue (MB) in one- or two-component systems were evaluated. The Fe₃O₄-PAMH selectively adsorbed MO and MB at pH 5 and 11, respectively. The maximum MO and MB uptake capacities of Fe₃O₄-AMHC were 202.02 mg/g (pH 5.0) and 148.84 mg/g (pH 11) respectively. The Fe₃O₄-PAMH can be reused with simple pH management in adsorption-desorption cycles. The MB and MO adsorption abilities on Fe₃O₄-PAMH were maintained above 99% and 75% for five consecutive recycles, respectively. Thus, Fe₃O₄-PAMH shows powerful potential in efficiently and selectively adsorbing anionic or cationic dyes from mixed wastewater.

Facile synthesis of chitosan membranes for visible-light-driven photocatalytic degradation of tetracycline hydrochloride

Due to the film-forming ability of polymers, a variety of photocatalytic membranes (PMs) based on polymers easily being separated and reused have been constructed for wastewater contaminant treatment. During their construction processes, chitosan (CS) as a bio-polymer with its distinct merits of abundant resources, low-cost and environmental-friendliness, as well as formability and ease of modification, has attracted great attention. However, the role of CS was mostly believed to be just a support or an adsorbent for fixing or dispersing photocatalysts. Whether CS possessed photocatalytic activity or not still remained vague. Herein, in this work, CS membranes (CSM) were facilely prepared for photocatalytic degradation of tetracycline hydrochloride (TC, a model organic pollutant) in aqueous solution, and its photocatalytic performance was investigated and compared with that of CSP (CS powder) and TiO2-P25 (a commercially used photocatalyst). The results showed that the single-phased CSM exhibited a better visible light photocatalytic activity. After visible light irradiation for 60 minutes, the degradation efficiency of TC can reach above 90% when the CSM was used as a photocatalyst, while with the same irradiation time interval, less TC could be degraded over both CSP and TiO2-P25. Through radical scavenging and EPR experiments, ˙O2 - and h+ were found to be the main active oxygen species generated in the reaction system for TC degradation. After being washed with 2 wt% NaOH solution, the CSM revealed a good recyclability implying its potential for practical applications. This study would provide a certain theoretical and data basis for the future development of CS-based PMs and photocatalysts.

Amphoteric Soy Protein-Rich Fibers for Rapid and Selective Adsorption and Desorption of Ionic Dyes

Uniquely amphoteric soy protein (SP)-rich ultra-fine fibers (231 nm average diameter) have been facilely electrospun from aq. colloids and rendered water-insoluble by heating (150 °C, 12 h) to be highly stable over 14 d (pH 7) as well as under extremely acidic to basic (pH 0-10, 2 d) or at boil (2 h) conditions. The SP-rich fibrous membranes are easily tuned to be charged either negatively by deprotonation above or positively by protonation below the 4.5 PI of SPs. This pH-responsive amphoterism has been demonstrated for rapid adsorption of either cationic or anionic dyes, selective adsorption of either dye from their mixtures, and repetitive adsorption/desorption to recover and reuse both dyes and membranes. Chemisorption and heterogeneous adsorption of ionic dyes was confirmed by close fitting to the pseudo-second-order kinetic model (R 2 = 0.9977-0.9999) and Freundlich adsorption isotherm (R 2 = 0.9879). This is the first report of water-resilient and pH-robust ultrafine fibrous membranes fabricated from aqueous colloids of neat globular SPs, the major byproducts of under-utilized edible oil and biodiesel. The natural polyampholyte origin, amphoterism, and green processing make these fibrous materials unique and versatile for many potential applications involving both anionic and cationic species.

pH Responsive Carboxymethyl Chitosan/Poly(amidoamine) Molecular Gate Membrane for CO2/N2 Separation

Efficient carbon dioxide separation is an emerging field of interest in the era of energy scarcity and environmental calamity. The present study focuses on the versatile aspects of carboxymethyl chitosan and dendrimer in terms of CO₂ separation. A comprehensive study has been accomplished to inspect the physicochemical properties of the prepared membrane. The mixed gas (CO₂/N₂) separation performances have been measured varying the temperature (60-110 °C) and sweep/feedwater flow ratio (0.33-3). The blend membrane containing 10 weight (wt.)% dendrimer presented highest CO₂ permeance of ∼100 GPU and CO₂/N₂ selectivity ∼149 on maintenance of sweep/feedwater flow ratio 2.33 and 1.67, respectively, at an operating temperature of 90 °C. The remarkable performance displayed by the membrane has been explained with reference to the dendrimer molecular gate mechanism and the salting out effect offered by carboxymethyl chitosan matrix.

Utilization of Waste Leather Powders for Highly Effective Removal of Dyes from Water

As a natural polymer, leather and its associated industries are known to be the leading economic sector in many countries. However, the huge amounts of leather waste generated from the leather industry causes severe environmental pollution. Herein, cow leather (CL) powders were prepared using a homemade machine and used as a low-cost adsorbent for the effective removal of reactive dyes from wastewater. The as-prepared CL powders exhibited dot-like, rod-like, and fiber-like morphologies. A Fourier transform infrared analysis and an x-ray diffraction analysis demonstrated that the CL powders retained the main structure of the protein contained in it. In addition, an improvement in thermal stability was also observed for the CL powders. Dye adsorption experiments indicate that the CL powders showed the highly effective removal of C.I. Reactive Red 120 (RR120), C.I. Reactive Yellow 127 (RY127), and C.I. Reactive Blue 222 (RB222) with the adsorption capacity of 167.0, 178.9, and 129.6 mg·g⁻¹, respectively. The Langmuir, pseudo-second order, and intraparticle diffusion models could well depict the adsorption equilibrium and kinetics of CL powders toward the investigated reactive dyes. The as-prepared CL powders can be used as a potential adsorbent in the treatment of dye contaminated wastewater. Future studies will mainly focus on the application of the adsorbed CL powders for the pigment printing of textile materials.

Chitosan cross-linked with κ-carrageenan to remove cadmium from water and soil systems

In this study, magnetic bio-adsorbent based on chitosan with high molecular weight was prepared. To stabilize under acidic condition, the synthesized magnetic chitosan was cross-linked with κ-carrageenan (mChitoCar). The magnetic bio-adsorbent was characterized by scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The results indicated that mChitoCar had desirable magnetic-sorption properties, and magnetic/bio-adsorbent was successfully synthesized and cross-linked. The present nanocomposite was applied to remove and immobilize Cd2+ from water and soil systems. Adsorption and desorption of cadmium by the chitosan bio-adsorbent were investigated using batch experiments. Isotherm data were described by using Freundlich, Langmuir, Dubinin-Radushkevich, and Temkin models, and better fitting was introduced by Freundlich model in both water and soil systems. The maximum adsorption capacity (b) of cadmium onto mChitoCar appeared to increase from the water system to the soil system, from 750.2 to 992.7 μmol/g, respectively. The adsorption mechanism with the help of potential theory indicates the adsorption of cadmium onto the mChitoCar surface is following chemical adsorption type. To evaluate the efficiency of the modified chitosan as a good bio-adsorbent in water and soil system, the difference between adsorption and desorption amounts, Δq, was calculated. By comparing the amounts of Δq, the bio-adsorbent is not economically feasible at high initial concentrations in the water system. But, the bio-adsorbent used can be relatively economic as a soil modifier.

Agglomeration of 10 nm amine-functionalized nano-magnetite does not hinder its efficiency as an environmental adsorbent

Amine-functionalized magnetite (nFe₃O₄-NH₂) of two different sizes, 10 nm and 250 nm, were compared as environmental adsorbents. They were synthesized by co-precipitation (10 nm-nFe₃O₄-NH₂) and solvothermal (250 nm-nFe₃O₄-NH₂) methods, respectively. The prepared amine-functionalized magnetite was characterized by scanning electron microscope, transmission electron microscope, X-ray diffraction, vibrating sample magnetometer, Fourier transform infrared spectroscopy, size distribution analysis and surface area analysis to compare the properties of different sizes of nFe₃O₄-NH₂. Both nFe₃O₄-NH₂ contained cubic Fe₃O₄ crystalline structure. The 250 nm-nFe₃O₄-NH₂ exhibited higher magnetic saturation value than the 10 nm-nFe₃O₄-NH₂, but both could be separated from an aqueous solution using an external magnet. The surface area and pore volume of the smaller-sized 10 nm-nFe₃O₄-NH₂ was larger than that of 250 nm-nFe₃O₄-NH₂, but stronger aggregation was observed in the 10 nm-nFe₃O₄-NH₂. Batch adsorption of lead indicated that the 10 nm-nFe₃O₄-NH₂ was a better adsorbent than the 250 nm-nFe₃O₄-NH₂. The maximum adsorption capacity of lead for the 10 nm-nFe₃O₄-NH₂ and the 250 nm-nFe₃O₄-NH₂ were 74.48 mg g^-1 and 54.54 mg g^-1, respectively. The stronger aggregation of nanoparticles with a smaller particle size did not affect the superior performance of the 10 nm-nFe₃O₄-NH₂ as an environmental adsorbent.

Simultaneous cationic Cu (II)‒anionic Sb (III) removal by NH2-Fe3O4-NTA core-shell magnetic nanoparticle sorbents synthesized via a facile one-pot approach

In this study, a regenerable magnetic core-shell nanoparticles NH₂-Fe₃O₄-NTA which include 3-aminopropyltriethoxysilane (APTES) and nitrilotriacetic acid (NTA) crosslinked to Fe₃O₄ was developed by one-pot method for simultaneous removal of cationic and anionic metals. Another nanocomposite NH₂-Fe₃O₄-NTA_II was prepared by multi-step method for comparison. NH₂-Fe₃O₄-NTA had positive zeta potential values of 35.1-0.8 mV at pH 1.8-11.0, with the saturation magnetization and surface area up to 40.56 emu/g and 56.94 m²/g, respectively. The maximum sorption capacities of NH₂-Fe₃O₄-NTA for cationic Cu (II) and anionic Sb (III) were 55.56 and 51.07 mg/L, respectively, which were superior to that of NH₂-Fe₃O₄-NTA_II. Based on screening in terms of characterization and metal sorption capacity, NH₂-Fe₃O₄-NTA with a feasible synthesis scheme was chosen for further evaluation. The Cu (II) removal by NH₂-Fe₃O₄-NTA was favored with increasing pH, while the Sb (III) removal preferred low pH (2-3). Simultaneous sorption of Cu (II) and Sb (III) exhibited same removal performance with the sole sorption under high dosage (>1 g/L). In real wastewater applications of NH₂-Fe₃O₄-NTA, multiple metals in actual wastewater could be removed to well below the regulation levels. Nonspecific electrostatic interactions, inner-sphere complexation, ligand exchange, chelation and coordination complexation were responsible for Cu (II) and Sb (III) removal.

Synthesis of novel modified magnetic chitosan particles and their adsorption performance toward Cr(VI)

Novel adsorbents, poly([2-(methacryloxy)ethyl]trimethylammonium chloride) modified magnetic chitosan particles (DMCPs), were synthesized via free radical polymerization and applied to adsorb Cr(VI) from aqueous solution. The effects of pH (2-11), Cr(VI) concentration (10-200 mg/L) and contact time (0-420 min) on the adsorption performance were evaluated. The results showed that the adsorption capacity of DMCPs was much larger than that of magnetic chitosan particles (MCPs) in the examined pH range and decreased with Cl^- concentration increasing, indicating that electrostatic interaction and ion exchange are the governing mechanisms of Cr(VI) adsorption by DMCPs. The Langmuir isotherm model and pseudo-second-order kinetic model fitted the experimental data well. The maximum adsorption capacity of DMCPs is 153.85 mg/g. Besides, Cr(VI)-loaded DMCPs could be easily separated and efficiently regenerated. Therefore, DMCPs are promising candidates for Cr(VI) adsorption owing to their excellent performance in a wide pH range, easy separation and good reusability.

Computational calculation identified optimal binding sites in nano-sized magnetic-cored dendrimer

Magnetic-cored dendrimers (MDs) with amino groups were prepared with the formation of poly(amidoamine) dendrimer on the surface of magnetite nanoparticles (MNPs). The experiment involved the binding of four different heavy metal ions including Pb (II), Cu (II), Zn (II), and Cr (VI). Density functional theory (DFT) calculation was applied to the experimental results to determine the optimal configurations between the heavy metal species and generation 1 amino (NH₂) functionalized MD (G1-NH₂-MD). Different binding configurations among the possible binding positions of inner and outer G1-NH₂-MD were determined with the ionic radius and coordination number of each heavy metal ion. Although Pb²⁺ and Zn²⁺ were stable in the terminal positions, Cu²⁺ was the most stable in the internal position. The oxygen and hydrogen atoms of HCrO₄^- formed a hydrogen bond with the NH₂ groups, and thus dipole-nonpolar molecular interaction occurred with the CH₂ groups of G1-NH₂-MD. Specific binding positions and energies of different heavy metal species were identified through the DFT calculation in the study. The DFT calculation results also contributed to an understanding of the binding priority of each metal ions in the mixed solution. Furthermore, Pb²⁺ was preferably adsorbed in the mixed solution of Pb²⁺, Cu²⁺, and Zn²⁺.