Versatile magnetic gel from peach gum polysaccharide for efficient adsorption of Pb2+ and Cd2+ ions and catalysis

Polysaccharides in fruits: Biological activities, structures, and structure-activity relationships and influencing factors-A review

Fruits are a rich source of polysaccharides, and an increasing number of studies have shown that polysaccharides from fruits have a wide range of biological functions. Here, we thoroughly review recent advances in the study of the bioactivities, structures, and structure-activity relationships of fruit polysaccharides, especially highlighting the structure-activity influencing factors such as extraction methods and chemical modifications. Different extraction methods cause differences in the primary structures of polysaccharides, which in turn lead to different polysaccharide biological activities. Differences in the degree of modification, molecular weight, substitution position, and chain conformation caused by chemical modification can all affect the biological activities of fruit polysaccharides. Furthermore, we summarize the applications of fruit polysaccharides in the fields of pharmacy and medicine, foods, cosmetics, and materials. The challenges and perspectives for fruit polysaccharide research are also discussed.

Highly efficient and selective removal of anionic dyes from aqueous solutions using polyacrylamide/peach gum polysaccharide/attapulgite composite hydrogels with positively charged hybrid network

To avoid the weakness (lower adsorption rate and selectivity) of peach gum polysaccharide (PGP) and improve the adsorption performance of polyacrylamide (PAAm) hydrogel (lower adsorption capacity), in the present work, the PGP was chemically tailored to afford ammoniated PGP (APGP) and quaternized PGP (QPGP), and attapulgite (ATP) was bi-functionalized with cation groups and carbon‑carbon double bond. Then, PAAm/APGP and PAAm/QPGP/ATP hydrogels were synthesized via redox polymerization. The synthesis procedure and properties of hydrogels were traced by FTIR, SEM, XPS, TGA, TEM, and BET methods, and the dye adsorption performance of the hydrogels was evaluated using the new coccine (NC) and tartrazine (TTZ) aqueous solutions as the model anionic dyes. Effects of initial dye concentration, pH, and ionic strength on the adsorption were investigated. Compared with PAAm/APGP hydrogel, PAAm/APGP/ATP hydrogel exhibits higher adsorption rate, superior adsorption capacity, stability, and selectivity towards anionic dye. The adsorption process of PAAm/QPGP/ATP hydrogel reached equilibrium in about 20 min and followed the pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacities towards NC and TTZ of PAAm/QPGP/ATP hydrogel were calculated as 873.235 and 731.432 mg/g. This hydrogel adsorbent originating from PAAm, PGP, and ATP shows great promise for application in practical water treatment.

Efficient adsorption of selenium (Se(IV) and Se(VI)) from water using Acacia senegal polysaccharide with multiple amine groups: Synthesis and application

In this study, an amine-rich gel (ARAS) was prepared by chemically altering Acacia senegal (AS). ARAS acts as an adsorbent for selenium. Owing to the introduction of amino functional groups and a remarkable specific surface area (91.89 g/m2), ARAS shows maximum adsorption capacities at 75 and 130 mg g-1 for Se(IV) and Se(VI), respectively. The removal efficiency of ARAS is higher (ωSeIV = 98.2 % and ωSeVI = 98.6 %) at lower concentrations (CSeIV = 100 ppm and CSeVI = 95 ppm) and the adsorption equilibrium is achieved within 60 min. The adsorption process of Se (IV) and Se (VI) via ARAS is elucidated using the Quasi-Second-Order kinetic and Langmuir models. The enhanced adsorption capacity of the adsorbent could be attributed to the synergistic effects of electrostatic attraction, hydrogen bonding, and specific physicochemical properties. Thermodynamic studies reveal that the surface adsorption process is spontaneous and exothermic. Notably, ARAS maintains remarkable adsorption stability under a variety of solution conditions, including variable pH (4-11), NaCl concentrations (0-1 M), and the presence of organic solvents. It retains approximately 60 % of its initial adsorption capacity for Se(IV) and Se(VI) after three adsorption cycles. Therefore, ARAS with its cost-effectiveness and exceptional performance shows considerable potential for applications in water treatment.

Multivalent iron-based magnetic porous biochar from peach gum polysaccharide as a heterogeneous Fenton catalyst for degradation of dye pollutants

Water contamination caused by organic dyes has become a significant concern, and catalytic degradation of dye pollutants is an effective solution. However, developing an affordable, easy-to-prepare, high-catalytic-activity, and renewable catalyst has proved challenging. The current study addresses this issue by introducing an efficient heterogeneous Fenton catalyst, known as multivalent iron-based magnetic porous biochar (mFe-MPB). This catalyst comprises multiple iron species, such as Fe3O4, γ-Fe2O3, zero-valent Fe (Fe0), and Fe3C. The mFe-MPB was easily prepared by utilizing a straightforward crosslinking-pyrolysis strategy with natural peach gum polysaccharide (PGP), which has a unique structure and composition that facilitates the creation of multivalent iron species. The mFe-MPB demonstrates high catalytic activity in the degradation of an array of dyes, including cationic dyes such as methylene blue (MB) and methyl violet (MV), as well as anionic new coccine (NC) dye. Its mass standardized rate constant value for catalytic degradation of MB can reach as high as 1.65 L min-1 g-1. Additionally, the catalyst can be easily recovered through magnetic separation and possesses remarkable structural stability, enabling several reuses without compromising its efficiency. Therefore, this study offers a viable strategy to fabricate low-cost, efficient and sustainable Fenton catalyst for removal of dye pollutants from water.

Cross-linked peach gum polysaccharide adhesive by citric acid to produce a fully bio-based wood fiber composite with high strength

As a natural polysaccharide, efficiently converting peach gum (PG) into practical materials remains a significant challenge due to its complex structure and high molecular weight. This study developed a polysaccharide adhesive using PG as the primary raw material and citric acid (CA) as a cross-linking agent to produce a fully bio-based wood fiber composite. The chemical compositions of PG and the synthesis process of PG-CA/55-45 adhesive were mainly discussed. The properties of the composites were explained through a microscopic perspective. The gel permeation chromatography (GPC) analysis revealed that the mean molecular weights of PG and PG-CA/55-45 adhesive were 9.07 × 106 Da and 9.98 × 104 Da, respectively. CA was introduced to depolymerize PG and cross-linked the degraded PG to form macromolecules with higher strength by the esterification reaction. PG-CA/55-45 adhesive demonstrated good mildew resistance and thermal stability. In addition, the composites exhibited excellent mechanical properties and water resistance. This study provided a simple and feasible approach to developing a polysaccharide adhesive for producing higher strength wood fiber composites, which can propose a new strategy for realizing the high-value utilization of PG.

Efficacious Sorption Capacities for Pb(II) from Contaminated Water: A Comparative Study Using Biowaste and Its Activated Carbon as Potential Adsorbents

Heavy-metal pollution is a persevering environmental menace, which demands the necessity of its removal by green and ecofriendly adsorbents. To combat this problem, discarded plant biomass can be used as an efficient substitute. Herein, a comparative study has been highlighted for the removal of Pb²⁺ ions using Euryale ferox Salisbury seed coat and its activated carbon, which is prepared by a first-time-reported activating agent that is a novel and non-hazardous bioresource. The batch investigation revealed a 99.9% removal efficiency of Pb(II) by the activated carbon compared to Euryale ferox Salisbury seed coat, which shows only an 89.5% removal efficiency at neutral pH. The adsorption mechanism is mainly a multilayered process, which involves electrostatic, van der Waals, and hydrogen bonding interactions. The adsorption equilibrium, kinetic, and thermodynamic studies were examined for the biosorbents, which revealed the adsorption process to be feasible, spontaneous, and exothermic with both physisorption and chemisorption adsorption mechanisms. The desorption study asserted the reusability of both the biosorbents to a maximum of three cycles.

Magnetic MXene-NH2 decorated with persimmon tannin for highly efficient elimination of U(VI) and Cr(VI) from aquatic environment

Herein, a magnetic MXenes based composite (Fe₃O₄@Ti₃C₂-NH₂-PT) was constructed by loading Fe₃O₄ nano-particles into the interlamellar spacing of persimmon tannin-functionalized Ti₃C₂-NH₂. The structure, morphology and physicochemical properties of the as-prepared adsorbents were probed by advanced spectroscopy techniques, while the impact of various experimental conditions like pH values, amount of adsorbent and contact time on the removal trend were examined by batch experiments. The elimination results revealed that Fe₃O₄@Ti₃C₂-NH₂-PT could be applied in a wide range of initial concentrations, and exhibited outstanding removal efficiency for U(VI) (104.9 mg/g, pH = 5.0) and Cr(VI) (83.8 mg/g, pH = 2.0). Meanwhile, the adsorption process was described well with the Langmuir isotherm and Pseudo-second-order kinetics models, which indicated that the monolayer chemical adsorption occurred during elimination of the two contaminants. The spectral analysis results manifested that elimination of U(VI) followed an inner-sphere configuration, whereas uptake of Cr(VI) was determined by electrostatic interaction and adsorption-reduction process. This work opened a new opportunity in designing MXenes based adsorbents in the application for environmental remediation.

Three-dimensional acanthosphere-like hierarchical Co@graphitic carbon for dispersive magnetic solid-phase extraction of nitroimidazole

Herein, a magnetic three-dimensional acanthosphere-like hierarchical Co@graphitic carbon (3D Co@GC) is introduced as an efficient adsorbent for extraction of three nitroimidazoles (NMZs: metronidazole (MNZ), ornidazole (ONZ) and tinidazole (TNZ)) from environmental water and food samples. The proposed 3D Co@GC was synthesized by a simple template-free method, which consisted of plentiful freely arranged one-dimensional nanowires. The adsorption properties of 3D Co@GC for three NMZs were investigated systematically by adsorption kinetic and isotherm studies. 3D Co@GC exhibits good adsorption capacity and fast adsorption kinetics toward three NMZs by virtue of its unique hierarchical structure. In addition, it was also found that a bit of methanol can effectively elute the adsorbed NMZs, eliminating the need for other dangerous strong acid or base solutions. Thus, 3D Co@GC as adsorbent to extraction three trace NMZs followed by direct quantification detection of targets with high-performance liquid chromatography with ultraviolet-visible detector (HPLC-UV) was developed. The parameters of dispersed magnetic solid-phase extraction (d-MSPE) were optimized by univariate and multivariate methods (Box-Behnken design). This established method revealed wide linear range and low limits of detection. Furthermore, the satisfactory recoveries of NMZs (86.7-106.7%) were acquired in spiked river water, honey, milk, and muscle samples. This study might provide a potential strategy for the efficient extraction and sensitive analysis of trace NMZs in river water, honey, milk, and muscle samples.

In situ growth of ZIF-8 on carboxymethyl chitosan beads for improved adsorption of lead ion from aqueous solutions

In this study, a method for the in situ growth of zeolitic imidazolate framework-8 (ZIF-8) on carboxymethyl chitosan beads (BCMC) to produce a composite adsorbent (BCMC@ZIF-8) for the removal of Pb²⁺ from water is proposed. The results revealed that the utilization of the BCMC as a framework enhanced the stability of ZIF-8, and the presence of the latter in the composite improved the removal efficiency of Pb²⁺ from water. Data from X-ray photoelectron spectroscopy analysis and adsorption kinetics revealed that the adsorption mechanism included diffusion and the sharing/transfer of electrons between BCMC@ZIF-8 and Pb²⁺. The maximum adsorption capacity of BCMC@ZIF-8 fitted using the Langmuir model was 566.09 mg/g. Results of the experiments on the regeneration of the adsorbent and its stability in water further indicated that BCMC improved the stability of ZIF-8. This study demonstrated that the stability of metal-organic framework (MOF) materials, which exhibited high efficiencies for the removal of heavy metals in water can be improved through fixation of the polymer skeleton. Thus, the present study offers practical and theoretical guidance for the application of MOF materials in water treatment.

Sequestration of Anionic and Cationic Dyes through Thermally Activated Slate and Their Kinetics and Thermodynamic Characteristics

Adsorption is one of the most common and most robust techniques for the decontamination approach of effluents, owing to its design flexibility, simplicity, cost effectiveness, and high efficiency. However, its application is limited on a large scale due to its cost. The current study investigates the use of low-cost, ecofriendly, and ubiquitous thermally activated clay material. Thermally treated clay was used for the adsorption of crystal violet (CV), Congo red (CR), and malachite green (MG) organic dyes from aqueous solutions. Characterization of slate was carried out with Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy, X-ray diffraction, N₂ physisorption, and XRF spectrometry. The adsorption process was studied as a function of concentration, time, pH, and temperature. Using the batch adsorption technique, the experimentally obtained adsorption data were fitted to both Langmuir and Freundlich isotherms. The adsorption data followed the pseudo-second-order kinetics, and the adsorption capacity was recorded as 360.12 mg/g for CV, 409.23 mg/g for CR, and 390.14 mg/g for MG. The good uptake is the outcome of a greater surface area (24.751 m²/g) for the slate activated at 873 K. The thermodynamic studies showed that the adsorption process remained endothermic and spontaneous. Thermally activated slate proved itself to be an efficient adsorbent and can effectively be used for the removal of textile dyes from the contaminated water, and it is evident from the good uptake of the adsorbate by the adsorbent.

A review on peach gum polysaccharide: Hydrolysis, structure, properties and applications

To achieve sustainable development, increasing attention has been paid to the utilization of renewable polysaccharides extracted from plant gum instead of synthetic materials. Peach gum polysaccharide (PGP) is a typical polysaccharide, which can be readily obtained by hydrolysis of peach gum, one of the abundant plant gums in the world. In the past decade, the research on the hydrolysis, structure, properties and applications of PGP has aroused great interest. The PGP with highly branched macromolecular structure shows remarkable merits of numerous functional groups, excellent water solubility, good biocompatibility, favorable emulsifying property, fine antioxidant and antibacterial activity, and low cost. The application of PGP has expanded from the pharmaceutical field to the fields of food, adsorbents, functional carbon materials, binders and gel materials. This review systematically introduces the research progress of PGP, as well as the opportunities and challenges faced by PGP in scientific research and practical application.

Facile synthesis of amine-crosslinked starch as an efficient biosorbent for adsorptive removal of anionic organic pollutants from water

Developing applicable biosorbents for adsorptive removal of organic pollutants from water is highly demanded. However, most biosorbents suffer poor adsorption capability for anionic organic pollutants due to their negatively charged surface. Herein, we present a facile method to synthesize amine-crosslinked starch (ACS) biosorbent for removing anionic organic pollutants. The adsorption properties of ACS were thoroughly evaluated by selecting anionic brilliant blue (BB), amaranth (ART), diclofenac sodium (DS) as representatives. The results show that the ACS can selectively adsorb anionic molecules with large adsorption capacity and fast removal rate. The adsorption kinetic and isotherm behaviors can be well described by the pseudo-second-order and Langmuir models, respectively. The maximum uptake capacity of ACS for BB, ART and DS is as high as 1287.7, 724.6 and 595.2 mg g^-1, respectively. Moreover, the ACS can be easily regenerated and still exhibits favorable adsorption performance even after reusing for five times.

Designed new magnetic functional three-dimensional hierarchical flowerlike micro-nano structure of N-Co@C/NiCo-layered double oxides for highly efficient co-adsorption of multiple environmental pollutants

In order to eliminate multiple coexisting pollutants in environmental wastewater, a magnetic three-dimensional hierarchical porous flower-like N, Co-doped graphitic carbon nano-polyhedra decorated NiCo-layered double oxides (N-Co@C/NiCo-LDOs) adsorption material was synthesized, which consisted of two-dimensional LDOs nanosheets with functionalized surfaces (N, Co-doped graphitic carbon loaded on both sides of NiCo-LDOs nanosheets). The adsorption properties of N-Co@C/NiCo-LDOs for five types of typical pollutants (cationic dyes: rhodamine b, methylene blue; pesticides: ethofenprox, bifenthrin; anionic dyes: methyl orange, congo red; inorganic cations: Cr²⁺, Cd²⁺, Pb²⁺, Zn²⁺, inorganic anions: Cr₂O₇^2-, AsO₃^3-) were investigated systematically in single and coexisting systems. Combined with the results of FTIR and zeta potential, the adsorption mechanism was discussed. By virtue of its hierarchical porous architecture and the combined effect of functionalized surfaces and LODs supporter, the as-prepared N-Co@C/NiCo-LDOs demonstrates excellent adsorption performance towards five types of typical pollutants with fast adsorption rate, high adsorption capacity and good co-adsorption performance. More importantly, the N-Co@C/NiCo-LDOs showed satisfactory removal efficiency, stability and reusability in model wastewater. The broad-spectrum, rapid, easily separable, and reusable adsorption properties make N-Co@C/NiCo-LDOs promising for highly efficient wastewater treatments. This work also provides a feasible way for the preparation of adsorption materials for the treatment of complex wastewater systems.

Super and Selective Adsorption of Cationic Dyes onto Carboxylate-Modified Passion Fruit Peel Biosorbent

The carboxylate-functionalized passion fruit peel (PFPCS) was an efficient and rapid biosorbent for wastewater treatment. The PFPCS exhibited excellent selectivity to the cationic dyes, where the maximum adsorption capacities for methylene blue (MB) and methyl violet (MV) were 1,775.76 mg g-1 and 3,756.33 mg g-1, respectively. And the adsorption process of MB and MV on PFPCS reached equilibrium within 20 min. Moreover, the adsorption conditions and mechanisms were investigated. The adsorption process was in good agreement with the pseudo-second-order and Langmuir isotherm models. The adsorption mechanism was also proposed to be electrostatic interaction and hydrogen bond. After six cycles of desorption-adsorption, the removal efficient of MB and MV could be kept above 95%. Thus, PFPCS was considered as a highly efficient absorbent for removing cationic dyes from polluted water due to excellent adsorption characteristics, low cost and environmental friendliness.

An environmental-friendly magnetic bio-adsorbent for high-efficiency Pb(Ⅱ) removal: Preparation, characterization and its adsorption performance

In this paper, environmental friendly magnetic composite adsorbent (MSAL), exhibited excellent adsorption capacity for lead ions in the solution, was successfully prepared using two non-biologically toxic materials including L-cysteine and sodium alginate. Batch experiments were carried out to discuss the influences of different parameters like pH, adsorbent dosing, initial concentration and contact time on adsorption performance. Results showed sorption process followed by pseudo-second-order kinetic model and Langmuir isotherm model, which suggested the adsorption was limited by the chemical process dominated by the molecular layer. Based on Langmuir isotherm model, the maximum Pb(Ⅱ) adsorption capacity was about 330 mg/g, which was better than a large amount of other lead adsorbents. Various analytical methods, such as SEM-EDS, FTIR, VSM, TGA, XPS and Zeta potential, were applied to characterize the performance of this adsorbent as well as exploring the adsorption mechanism. Characterization results found this adsorbent exhibited a large contact area, good thermal stability, sufficient adsorption sites and excellent magnetic responsiveness. It also has been found that the adsorption mechanism mainly included ion exchange and chelation between amino, carboxyl and lead ions. After 5 cycles, the adsorption capacity decreased from 98.04% to 87.40% and still maintained at high level. The average iron ions concentration in the adsorbed solution sample or in the regeneration solution were 0.34 mg/L and 0.15 mg/L. Overall, all above results imply that MSAL is a promising reusable adsorbent for removing Pb(Ⅱ) in solution.

Facile synthesis of amphiphilic peach gum polysaccharide as a robust host for efficient encapsulation of methylene blue and methyl orange dyes from water

Despite impressive progress of macromolecular encapsulation technique based on hyperbranched polymer (HP), the use of natural HP for guest encapsulation has rarely been reported. Herein, we present the simple synthesis of amphiphilic PGP-DC from natural peach gum polysaccharide (PGP) and demonstrate that the PGP-DC can be utilized as a robust host for encapsulation of dye molecules from water. The influences of initial dye concentration, dosage of PGP-DC, pH, ionic strength, and encapsulation mode on the encapsulation were systematically studied. The PGP-DC simultaneously exhibited fast encapsulation rate and superior encapsulation capability. Under optimal conditions, the encapsulation capacity of PGP-DC towards methylene blue (MB) (1 mM) can reach as high as 182.67 mg/g, which compares favorably to other separation techniques. Moreover, the MB-encapsulated PGP-DC could be well regenerated in acidic solution. Based on its simple synthetic process, excellent encapsulation performance and fine reusability, the PGP-DC holds great promise for using as a host for practical encapsulation applications.

Granular reduced graphene oxide/Fe3O4 hydrogel for efficient adsorption and catalytic oxidation of p-perfluorous nonenoxybenzene sulfonate

The catalytic performance of Fe₃O₄/reduced graphene oxide (Fe₃O₄/rGO) nanocomposite makes it attractive for the removal of emerging pollutants from water, but the combination of its efficient adsorption and degradation of per- and polyfluoroalkyl substances has not been studied. Here we report the optimal granular Fe₃O₄/rGO with high thermal and acid resistance stability through controlling its self-assembly for the adsorption and degradation of sodium p-perfluorous nonenoxybenzene sulfonate (OBS) from water. The maximum adsorption capacity for OBS was calculated to be 362.4 μmol/g according to Langmuir fitting. Electrostatic, π-π and hydrogen bonding interactions were involved in OBS adsorption, and the quaternary N in Fe₃O₄/rGO was a key adsorption site. The efficiency of the utilization of free radicals generated in Fenton-like and persulfate (PS) systems increased with the increase of OBS adsorbed onto the Fe₃O₄/rGO, while the increase of OBS amount adsorbed on Fe₃O₄/rGO would casue a slow OBS removal in the adsorption-degradation process due to the slow adsorption process. The Fenton-like oxidation was more efficient for OBS removal than PS oxidation. The spent Fe₃O₄/rGO was able to be reused in the Fenton-like system at least ten times, while the OBS removal in the PS reaction system was reduced to 47.8 % after six reuse cycles.

Preparation of Polyaniline/Emulsion Microsphere Composite for Efficient Adsorption of Organic Dyes

Surface-functionalized polymeric microspheres have wide applications in various areas. Herein, monodisperse poly(styrene-methyl methacrylate-acrylic acid) (PSMA) microspheres were prepared via emulsion polymerization. Polyaniline (PANI) was then coated on the PSMA surface via in situ polymerization, and a three-dimensional (3D) structured reticulate PANI/PSMA composite was, thus, obtained. The adsorption performance of the composite for organic dyes under different circumstances and the adsorption mechanism were studied. The obtained PANI/PSMA composite exhibited a high adsorption rate and adsorption capacity, as well as good adsorption selectivity toward methyl orange (MO). The adsorption process followed pseudo-second-order kinetics and the Langmuir isotherm. The maximum adsorption capacity for MO was 147.93 mg/g. After five cycles of adsorption-desorption, the removal rate remained higher than 90%, which indicated that the adsorbent has great recyclability. The adsorbent materials presented herein would be highly valuable for the removal of organic dyes from wastewater.

Facile synthesis of amino-functional large-size mesoporous silica sphere and its application for Pb2+ removal

Amino-functional large-size mesoporous silica spheres (LMS-AP) were successfully synthesized through a one-step method with (3-aminopropyl) triethoxysilane (APTES) addition during the pseudomorphic transformation process. LMS-AP were characterized using thermogravimetry-differential thermal analysis, Nitrogen adsorption-desorption measurement, infrared spectroscopy, and X-ray photoelectron spectroscopy. The study found that -NH₂ was grafted into LMS, and the LMS-AP had a better thermal stability than other samples. The Pb²⁺ removal properties of LMS-AP were investigated using the static and dynamic experiments in simulated and real wastewater solutions. The kinetic and equilibrium experiments indicated that the adsorption process of LMS-AP fitted the Langmuir adsorption model and the pseudo-second-order kinetics model (R² > 0.98), respectively. The maximum Q_e (mg/g) was about 100 mg/g in the static adsorption condition. The adsorption mechanism of removal of Pb²⁺ was also investigated. In fix bed column experiments, LMS-AP exhibited excellent Pb²⁺ adsorption ability for simulated wastewater, with the maximum q_e (mg/g) of 48.7 mg/g for particle size under 1-3 mm. Meanwhile in actual industrial wastewater treatment process, LMS-AP had a better Pb²⁺, Zn²⁺ and Cr (VI) removal efficiency of 80% and As (V) of 30-40% removal efficiency at initial pH 4, suggesting selective adsorption property for different heavy metal ions.

Facile Functionalization of Natural Peach Gum Polysaccharide with Multiple Amine Groups for Highly Efficient Removal of Toxic Hexavalent Chromium (Cr(VI)) Ions from Water

The development of low-cost adsorbent with excellent adsorption property remains a big challenge. Herein, the functionalization of natural peach gum polysaccharide (PGP) with multiple amine groups for the removal of toxic Cr(VI) ions from water was studied. The obtained PGP-NH₂ gel exhibited high-removal efficiency (>99.5%) toward Cr(VI) ions, especially with relatively low initial concentration of Cr(VI) ions (≤250 mg/L). The influences of pH, ionic strength, contact time, initial concentration, and temperature on the adsorption of Cr(VI) ions were systematically investigated. The PGP-NH₂ gel showed rapid adsorption rate and could reach adsorption equilibrium within about 40 min. The Cr(VI) ion uptake process could be described by pseudo-second-order kinetic and Langmuir isotherm models. The maximum adsorption capacity of PGP-NH₂ gel could reach 188.32 mg/g. Thermodynamic investigation results indicated the spontaneous and exothermic characteristic of the uptake process. Moreover, the PGP-NH₂ gel also exhibited favorable reusability, and 135.52 mg/g of adsorption capacity was retained even after being reused for five times. Considering its low cost and superior uptake property, the PGP-NH₂ gel holds a great promise for employing as an adsorbent to treat Cr(VI) ion-containing wastewater.

Efficient Adsorption of Pb(II) from Aqueous Solutions by Metal Organic Framework (Zn-BDC) Coated Magnetic Montmorillonite

Composite adsorption materials combine the advantages of various adsorptive materials and compensate for the defects of single adsorbents. Magnetic montmorillonite (MMMT) shows good adsorption properties for Pb(II). In order to further improve the adsorption properties of MMMT, in this work, Zn-BDC, a kind of metal⁻organic framework (MOF), was modified onto the surface of MMMT by in situ polymerization. The composite material MMMT@Zn-BDC was characterized by Zetasizer, SEM, TEM, FTIR, XRD, VSM, and XPS. The influence of adsorption conditions on the adsorption capacity of MMMT@Zn-BDC for Pb(II) was examined, including the adsorbent dosage, pH of Pb(II) solution, initial concentration of Pb(II), and the temperature and adsorption time. Also, the adsorption mechanism was studied. The results of this study show that MMMT@Zn-BDC adsorbs Pb(II) via chemisorption. In addition, MMMT@Zn-BDC exhibits good potential for adsorbing Pb(II), including its high adsorption capacity (724.64 mg/g) and good recyclability.

Magnetogels: Prospects and Main Challenges in Biomedical Applications

Drug delivery nanosystems have been thriving in recent years as a promising application in therapeutics, seeking to solve the lack of specificity of conventional chemotherapy targeting and add further features such as enhanced magnetic resonance imaging, biosensing and hyperthermia. The combination of magnetic nanoparticles and hydrogels introduces a new generation of nanosystems, the magnetogels, which combine the advantages of both nanomaterials, apart from showing interesting properties unobtainable when both systems are separated. The presence of magnetic nanoparticles allows the control and targeting of the nanosystem to a specific location by an externally applied magnetic field gradient. Moreover, the application of an alternating magnetic field (AMF) not only allows therapy through hyperthermia, but also enhances drug delivery and chemotherapeutic desired effects, which combined with the hydrogel specificity, confer a high therapeutic efficiency. Therefore, the present review summarizes the magnetogels properties and critically discusses their current and recent biomedical applications, apart from an outlook on future goals and perspectives.

Superior amine-rich gel adsorbent from peach gum polysaccharide for highly efficient removal of anionic dyes

Herein, we demonstrated the potential of peach gum polysaccharide-based amine-rich gel (ARG) as an efficient adsorbent for removal of anionic dyes from water. The adsorption performance of ARG was systematically studied by choosing methyl orange (MO) and amaranth (ART) as representative anionic dyes. The effects of various parameters such as pH, ionic strength, temperature, initial dye concentration and contact time on the adsorption were investigated. The ARG exhibited superior adsorption selectivity and stable adsorption behaviors against variation of pH and ionic strength for anionic dyes. Adsorption process reached equilibrium within 10 min and showed good correlation with pseudo-second-order kinetic model and Langmuir isotherm. The adsorption capacity of ARG for MO and ART can reach 1949.5 and 1082.2 mg g^-1, respectively. Based on its sustainable characteristic, low cost and excellent adsorption property, the ARG holds great promise for utilizing as an adsorbent for practical water treatment applications.