Adsorption of Rare Earths(Ⅲ) Using an Efficient Sodium Alginate Hydrogel Cross-Linked with Poly-γ-Glutamate

With the exploitation of rare earth ore, more and more REEs came into groundwater. This was a waste of resources and could be harmful to the organisms. This study aimed to find an efficient adsorption material to mitigate the above issue. Through doping sodium alginate (SA) with poly-γ-glutamate (PGA), an immobilized gel particle material was produced. The composite exhibited excellent capacity for adsorbing rare earth elements (REEs). The amount of La³⁺ adsorbed on the SA-PGA gel particles reached approximately 163.93 mg/g compared to the 81.97 mg/g adsorbed on SA alone. The factors that potentially affected the adsorption efficiency of the SA-PGA composite, including the initial concentration of REEs, the adsorbent dosage, and the pH of the solution, were investigated. 15 types of REEs in single and mixed aqueous solutions were used to explore the selective adsorption of REEs on gel particles. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy analyses of the SA and SA-PGA gel beads suggested that the carboxyl groups in the composite might play a key role in the adsorption process and the morphology of SA-PGA changed from the compact structure of SA to a porous structure after doping PGA. The kinetics and thermodynamics of the adsorption of REEs were well fit with the pseudo-second-order equation and the Langmuir adsorption isotherm model, respectively. It appears that SA-PGA is useful for recycling REEs from wastewater.     

明胶/海藻酸钠/沙蒿胶复合水凝胶的制备及表征

为探究明胶（G）、海藻酸钠（SA）,沙蒿胶（ASKG）对复合水凝胶的力学性能、溶胀和保湿性能的影响,采用共混-离子交联法制备海藻酸钠/明胶/沙蒿胶复合水凝胶,并对制得的水凝胶进行结构表征和溶血率测试。结果表明:当G质量分数为2.5%,SA为1.5%,ASKG为0.7%时,复合水凝胶压缩强度达到427.2 kPa,拉伸强度达到563.449 kPa,断裂伸长率为117%,溶胀率为744%,且具有较好的保湿性能。红外光谱表明,由于沙蒿胶中存在大量羟基,因此加入沙蒿胶后在3 300 cm^-1～3 600 cm^-1羟基峰形变宽。G/SA/ASKG复合水凝胶溶血率低于5%,具有较好的网络孔结构和血液相容性,为复合水凝胶在医用敷料方面的应用提供一定的参考价值。     

Synthesis of CarAlg/MMt nanocomposite hydrogels and adsorption of cationic crystal violet

CarAlg/MMt nanocomposite hydrogels composed of kappa-carrageenan (Car) and sodium alginate (Alg) biopolymers were synthesized by incorporation of sodium montmorillonite (Na-MMt) nanoclay. Acrylamide (AAm), methylenebisacrylamide (MBA), and ammonium persulfate (APS) were used as monomer, crosslinker, and initiator, respectively. The structure and morphology of nanocomposites were characterized by XRD, SEM, and TEM techniques. The XRD results showed exfoliated MMt nanoclay and exfoliation of MMt was confirmed by TEM graph. The resulting nanocomposites were evaluated to remove cationic crystal violet (CV) dye from water. According to data, the adsorption capacity of nanocomposites was enhanced as the clay content was increased. The experimental data were analyzed according to both Langmuir and Freundlich models and experimental maximum adsorption capacity was obtained 88.8 mg g⁻¹. By studying the effect of pH on the dye adsorption capacity of nanocomposites, it was revealed that the adsorption capacity of nanocomposites was enhanced at acidic pHs as the Na-MMt nanoclay and kappa-carrageenan components were increased.     

Synthesis and characterization of carboxymethyl potato starch and its application in reactive dye printing

Carboxymethyl potato starch (CMPS) was synthesized with a simple dry and multi-step method as a product of the reaction of native potato starch and monochloroacetic acid in the presence of sodium hydroxide. The influence of the molar ratio of sodium hydroxide to anhydroglucose unit, the volume of 95% (v/v) ethanol, the rotation rate of motor driven stirrer and the reaction time for degree of substitution (DS) were evaluated. The product was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray diffractometry (XRD). FTIR spectrometry showed new bonds at 1618 and 1424cm(-1) when native starch underwent carboxymethylation. SEM pictures showed that the smooth surface of native starch particles was mostly ruptured. XRD revealed that starch crystallinity was reduced after carboxymethylation. The viscosity of the mixture paste of carboxymethyl starch and sodium alginate (SA) was measured using a rotational viscometer. In addition, the applied effect of mixed paste in reactive dye printing was examined by assessing the fabric stiffness, color yield and sharp edge to the printed image in comparison with SA. And the results indicated that the mixed paste could partially replace SA as thickener in reactive dye printing. The study also showed that the method was low cost and eco-friendly and the product would have an extensive application in reactive dye printing.     

Radiation synthesis, characterization and dye adsorption of alginate-organophilic montmorillonite nanocomposite

In this paper, the preparation, characterization and dye adsorption properties of nanocomposite (calcium alginate/organophilic montmorillonite) (CA/OMMT) were investigated. A new nanocomposite consisting of alginate and OMMT was prepared by polymerization using γ-rays irradiation as initiator. Physical characteristics of CA/OMMT were studied using X-ray diffraction (XRD), infrared spectrophotometery (IR), thermal gravimetric analysis (TGA), transmission electron microscopy (TEM) and the corresponding selected area electron diffraction (SAED). Two textile dyes, acid green B and direct pink 3B, were used as model anionic dye. Factors affecting dye sorption, such as pH, sorbent concentration and temperature of each dye solution were extensively investigated. It was found from the study that the sorption of dyes by the nanocomposite is pH-dependent and maximum sorption was obtained at pH 2. The thermodynamic data showed that dye adsorption onto alginate was spontaneous, exothermic, and a physisorption reaction. On the basis of the data of the present investigation, one could conclude that the as-prepared adsorbents exhibited excellent affinity for the dye, and can be applied to treat wastewater containing anionic dyes.     

Fabrication of distilled water-soluble chitosan/alginate functional multilayer composite microspheres

Polysaccharides-based functional microspheres were fabricated under mild conditions. Firstly, magnetic alginate microspheres were prepared by emulsification/internal gelation and acted as substrates. Then the multilayer composite microspheres (MCM) were obtained through the layer-by-layer assembly of the distilled water-soluble chitosan and alginate. The components, morphology, and size distribution of the microspheres were characterized by element analysis (EA), X-ray photoelectron spectroscopy (XPS), scanning electron microscope (SEM) and laser particle size analyzer (LPSA). Both EA and XPS analysis results indicated that alternate immersion was an effective method for preparing MCM. Vibrating sample magnetometer, SEM and LPSA results showed that the microspheres had good dispersion, uniform particle size and were superparamagnetic. In addition, in vitro drug release behaviors of the microspheres were investigated by using hemoglobin (HB) and Coomassie brilliant blue G250 (CBB) as model drugs. It was found that the release rates of both HB and CBB from the composite microspheres were slower than those from the substrates.     

Research on the adsorption property of supported ionic liquids for ferulic acid, caffeic acid and salicylic acid

In this paper, the preparation of new supported ionic liquids (SILs) composed of the N-methylimidazolium cation and the quinoline cation is described. They have been confirmed and evaluated by infrared spectroscopy, elemental analysis and thermogravimetric analysis. Six kinds of different SILs included SiO(2)·Im(+)·Cl(-), SiO(2)·Im(+)·BF(4)(-), SiO(2)·Im(+)·PF(6)(-), SiO(2)·Qu(+)·Cl(-), SiO(2)·Qu(+)·BF(4)(-) and SiO(2)·Qu(+)·PF(6)(-). The adsorption characteristics of ferulic acid (FA), caffeic acid (CA) and salicylic acid (SA) on SILs were investigated by static adsorption experiments. It was found that SiO(2)·Qu(+)·Cl(-) had excellent adsorption and desorption capacity to three tested phenolic compounds. The dynamic adsorption characteristics of FA, CA and SA on SiO(2)·Qu(+)·Cl(-) were also studied. The saturated adsorption capacity of FA, CA and SA using SiO(2)·Qu(+)·Cl(-) as adsorbent was 64.6 mg/g, 53.2 mg/g and 72.2 mg/g respectively. Using 70% ethanol as eluent, the saturated desorption efficiencies of FA, CA and SA were 97.2%, 90.3% and 96.5% respectively. Thus, SiO(2)·Qu(+)·Cl(-) had strong adsorption and separation capacity for FA, CA and SA.     

Preparation and characterization of a novel pH-sensitive chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate composite hydrogel bead for controlled release of diclofenac sodium

A series of pH-sensitive composite hydrogel beads composed of chitosan-g-poly (acrylic acid)/attapulgite/sodium alginate (CTS-g-PAA/APT/SA) was prepared as drug delivery matrices crosslinked by Ca²⁺ owing to the ionic gelation of SA. The structure and surface morphology of the composite hydrogel beads were characterized by FTIR and SEM, respectively. pH-sensitivity of these composite hydrogels beads and the release behaviors of drug from them were investigated. The results showed that the composite hydrogel beads had good pH-sensitivity. The cumulative release ratios of diclofenac sodium (DS) from the composite hydrogel beads were 3.76% in pH 2.1 solution and 100% in pH 6.8 solutions within 24 h, respectively. However, the cumulative release ratio of DS in pH 7.4 solution reached 100% within 2 h. The DS cumulative release ratio reduced with increasing APT content from 0 to 50 wt%. The drug release was swelling-controlled at pH 6.8.     

Sodium alginate/poly(vinyl alcohol)/nano ZnO composite nanofibers for antibacterial wound dressings

Sodium alginate (SA)/poly (vinyl alcohol) (PVA) fibrous mats were prepared by electrospinning technique. ZnO nanoparticles of size ∼160 nm was synthesized and characterized by UV spectroscopy, dynamic light scattering (DLS), XRD and infrared spectroscopy (IR). SA/PVA electrospinning was further carried out with ZnO with different concentrations (0.5, 1, 2 and 5%) to get SA/PVA/ZnO composite nanofibers. The prepared composite nanofibers were characterized using FT-IR, XRD, TGA and SEM studies. Cytotoxicity studies performed to examine the cytocompatibility of bare and composite SA/PVA fibers indicate that those with 0.5 and 1% ZnO concentrations are less toxic where as those with higher concentrations of ZnO is toxic in nature. Cell adhesion potential of this mats were further proved by studying with L929 cells for different time intervals. Antibacterial activity of SA/PVA/ZnO mats were examined with two different bacteria strains; Staphylococcus aureus and Escherichia coli, and found that SA/PVA/ZnO mats shows antibacterial activity due to the presence of ZnO. Our results suggest that this could be an ideal biomaterial for wound dressing applications once the optimal concentration of ZnO which will give least toxicity while providing maximum antibacterial activity is identified.f     

Synthesis of interpenetrating network hydrogel from poly(acrylic acid-co-hydroxyethyl methacrylate) and sodium alginate: Modeling and kinetics study for removal of synthetic dyes from water

Several interpenetrating network (IPN) hydrogels were made by free radical in situ crosslink copolymerization of acrylic acid (AA) and hydroxy ethyl methacrylate in aqueous solution of sodium alginate. N,N′-methylenebisacrylamide (MBA) was used as comonomer crosslinker for making these crosslink hydrogels. All of these hydrogels were characterized by carboxylic content, FTIR, SEM, XRD, DTA–TGA and mechanical properties. Swelling, diffusion and network parameters of the hydrogels were studied. These hydrogels were used for adsorption of two important synthetic dyes, i.e. Congo red and methyl violet from water. Isotherms, kinetics and thermodynamics of dye adsorption by these hydrogels were also studied.     

Biosorption of mercury by the inactivated cells of pseudomonas aeruginosa PU21 (Rip64)

Biomass of a mercury-resistant strain Pseudomonas aeruginosa PU21 (Rip64) and hydrogen-form cation exchange resin (AG 50W-X8) were investigated for their ability to adsorb mercury. The maximum adsorption capacity was approximately 180 mg Hg/g dry cell in deionized water and 400 mg Hg/g dry cell in sodium phosphate solution at pH 7.4, higher than the maximum mercury uptake capacity in the cation exchange resin (100 mg Hg/g dry resin in deionized water). The mercury selectivity of the biomass over sodium ions was evaluated when 50 mM and 150 mM of Na(+) were present. Biosorption of mercury was also examined in sodium phosphate solution andphosphate-buffered saline solution (pH 7.0), containing 50mM and 150 mM of Na(+), respectively. It was found that the presence of Na(+) did not severely affect the biosorption of Hg(2+), indicating a high mercury selectivity ofthe biomass over sodium ions. In contrast, the mercury uptake by the ion exchange resin was strongly inhibited by high sodium concentrations. The mercury biosorption was most favorable in sodium phosphate solution (pH 7.4), with a more than twofold increase in the maximum mercury uptake capacity. The pH was found to affect the adsorption of Hg(2+)bythe biomass and the optimal pH value was approximately 7.4. The adsorption of mercury on the biomass and the ion exchange resin appeared to follow theLangmuir or Freundlich adsorption isotherms. (c) 1994 John Wiley & Sons, Inc.     

Synthesis and characterization of MMA–NaAlg/hydroxyapatite composite and the interface analyse with molecular dynamics

A novel composite of α-methyl methacrylate (MMA) grafted sodium alginate (NaAlg) and hydroxyapatite (HA) was prepared in this study. The compositions and chemical groups of materials were investigated by infrared spectra (IR), X-ray diffraction (XRD) and nuclear magnetic resonance (NMR). The results showed that MMA has been successfully grafted with the hydroxyl group of sodium alginate. Moreover many chemical bonds existed in the composite, including the “egg-box” structure and hydrogen bonding. Meanwhile, the chemical bondings between MMA and sodium alginate partly replaced the intermolecular hydrogen bonding or the intramolecular hydrogen bonding in sodium alginate. The composite had better water contact angle than sodium alginate, indicating the strong hydrophilic character of pure sodium alginate was improved. The molecular dynamics (MD) method was used to simulate and evaluate the interaction energies based on the theoretics, which suggested that the copolymer whose every monomer grafted with one MMA had a more stable structure.     

Biocompatible alginate/nano bioactive glass ceramic composite scaffolds for periodontal tissue regeneration

Periodontal regeneration is of utmost importance in the field of dentistry which essentially reconstitutes and replaces the lost tooth supporting structures. For this purpose, nano bioactive glass ceramic particle (nBGC) incorporated alginate composite scaffold was fabricated and characterized using SEM, EDAX, AFM, FTIR, XRD and other methods. The swelling ability, in vitro degradation, biomineralization and cytocompatibility of the scaffold were also evaluated. The results indicated reduced swelling and degradation and enhanced biomineralization and protein adsorption. In addition, the human periodontal ligament fibroblast (hPDLF) and osteosarcoma (MG-63) cells were viable, adhered and proliferated well on the alginate/bioglass composite scaffolds in comparison to the control alginate scaffolds. The presence of nBGC enhanced the alkaline phosphatase (ALP) activity of the hPDLF cells cultured on the composite scaffolds. Thus results suggest that these biocompatible composite scaffolds can be useful for periodontal tissue regeneration.     

Formulation,Characterisation and Stabilisation of Buccal Films for Paediatric Drug Delivery of Omeprazole

This study aimed to develop films for potential delivery of omeprazole (OME) via the buccal mucosa of paediatric patients. Films were prepared using hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), sodium alginate (SA), carrageenan (CA) and metolose (MET) with polyethylene glycol (PEG 400) as plasticiser, OME (model drug) and L-arg (stabiliser). Gels (1% w/w) were prepared at 40°C using water and ethanol with PEG 400 (0–1% w/w) and dried in an oven (40°C). Optimised formulations containing OME and L-arg (1:1, 1:2 and 1:3) were prepared to investigate the stabilisation of the drug. Tensile properties (Texture analysis, TA), physical form (differential scanning calorimetry, DSC; X-ray diffraction, XRD; thermogravimetric analysis, TGA) and surface topography (scanning electron microscopy, SEM) were investigated. Based on the TA results, SA and MET films were chosen for OME loading and stabilisation studies as they showed a good balance between flexibility and toughness. Plasticised MET films were uniform and smooth whilst unplasticised films demonstrated rough lumpy surfaces. SA films prepared from aqueous gels showed some lumps on the surface, whereas SA films prepared from ethanolic gels were smooth and uniform. Drug-loaded gels showed that OME was unstable and therefore required addition of L-arg. The DSC and XRD suggested molecular dispersion of drug within the polymeric matrix. Plasticised (0.5% w/w PEG 400) MET films prepared from ethanolic (20% v/v) gels and containing OME: L-arg 1:2 showed the most ideal characteristics (transparency, ease of peeling and flexibility) and was selected for further investigation.KEY WORDS: buccal drug delivery, omeprazole, oral films, paediatric, plasticiser     

Electrospun sodium alginate/poly(ethylene oxide) core-shell nanofibers scaffolds potential for tissue engineering applications

Core-shell structure nanofibers of sodium alginate/poly(ethylene oxide) were prepared via electrospinning their dispersions in water solution. The core-shell structure morphology of the obtained nanofibers was viewed under scanning electron microscope (SEM) and transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS) analysis was used to further quantify the chemical composition of the core-shell composite SA/PEO nanofibers surface in detail. Furthermore, one-step cross-linking method through being immersed in CaCl₂ solution was investigated to improve the anti-water property of the electrospun nanofibers mats in order to facilitate their practical applications as tissue engineering scaffolds, and the changes of the structural of nanofibers before and after cross-linking was characterized by Fourier transform infrared (FT-IR). Indirect cytotoxicity assessment indicated that SA/PEO nanofibers membrane was nontoxic to the fibroblasts cells, and cell culture suggested that SA/PEO nanofibers tended to promote fibroblasts cells attachment and proliferation. It was assumed that the nanofibers membrane of electrospun SA/PEO could be used for tissue engineering scaffolds.     

Composites with alginate beads: A novel design of nano-adsorbents impregnation for large-scale continuous flow wastewater treatment pilots

The sorption capacity of cadmium (Cd (II)) on three new generated nanocomposite beads sodium alginate (SA) based; SA-Clay (SA-C) beads, SA-Phosphate (SA-P) beads, and SA- Activated Charcoal (SA-Ch) beads was investigated in a batch scale, then a continuous flow reactor.The highest adsorption capacity (137 mg/g) was obtained for SA-Ch using 1000 mg/L of initial Cd (II). The isotherm results showed that the adsorption equilibrium is compatible with the Langmuir isotherm and the sorption capacity of SA-Nano-adsorbent beads is very high. The models used for representing kinetic data was given that the removal of Cd (II) be well-fitted by second-order reaction kinetics. For the fixed bed column treatment, the maximum breakthrough times were 30, 38, and 48  h respectively for the SA-C, SA-P, and SA-Ch.According to the obtained results, it was concluded that SA-Nano-adsorbent bead is an excellent designed material as a nanocomposite for cadmium elimination from wastewater in a continuous treatment process.     

Preparation, characterization and properties of superabsorbent nanocomposites based on natural guar gum and modified rectorite

Novel guar gum-g-poly(sodium acrylate)/rectorite (GG-g-PNaA/REC) superabsorbent nanocomposites were prepared in aqueous solution using guar gum (GG), partially neutralized acrylic acid (NaA), acidified rectorite (H⁺-REC) and organified rectorite (CTA⁺-REC) by cetyltrimethylammonium bromide (CTAB) as raw materials, ammonium persulfate (APS) as initiator and N,N′-methylenebisacrylamide (MBA) as crosslinker. FTIR spectra confirmed that NaA had been grafted onto GG chains and the OH groups of REC participated in polymerization reaction. Exfoliated nanocomposite was obtained for H⁺-REC and intercalated structure was formed for CTA⁺-REC as shown by XRD results. SEM observations show REC has been uniformly dispersed in polymeric matrix. Effects of HCl concentration, organification degree of CTA⁺-REC and content of REC on swelling capabilities were investigated and the swelling kinetics of nanocomposites was evaluated. Results indicate that modifying REC by acidification and organification can improve swelling properties of the resultant nanocomposites, and GG-g-PNaA/CTA⁺-REC exhibited higher swelling capability and swelling rate contrast to GG-g-PNaA/H⁺-REC.     

Formation and oral administration of alginate microspheres loaded with pDNA coding for lymphocystis disease virus (LCDV) to Japanese flounder

Oral delivery of plasmid DNA (pDNA) is a desirable approach for fish immunization in intensive culture. However, its effectiveness is limited because of possible degradation of pDNA in the fish's digestive system. In this report, alginate microspheres loaded with pDNA coding for fish lymphocystis disease virus (LCDV) and green fluorescent protein were prepared with a modified oil containing water (W/O) emulsification method. Yield, loading percent and encapsulation efficiency of alginate microspheres were 90.5%, 1.8% and 92.7%, respectively. The alginate microspheres had diameters of less than 10 microm, and their shape was spherical. As compared to sodium alginate, a remarkable increase of DNA-phosphodiester and DNA-phosphomonoester bonds was observed for alginate microspheres loaded with pDNA by Fourier transform infrared (FTIR) spectroscopic analysis. Agarose gel electrophoresis showed a little supercoiled pDNA was transformed to open circular and linear pDNA during encapsulation. The cumulative release of pDNA in alginate microspheres was or=0.3) for anti-LCDV antibody from week 3 to week 16 for fish orally vaccinated with alginate microspheres loaded with pDNA, in comparison with fish orally vaccinated with naked pDNA. Our results display that alginate microspheres obtained by W/O emulsification are promising carriers for oral delivery of pDNA. This encapsulation technique has the potential for DNA vaccine delivery applications due to its ease of operation, low cost and significant immune effect.     

Fabrication of curcumin-loaded zein nanoparticles stabilized by sodium caseinate/sodium alginate: Curcumin solubility,thermal properties,rheology, and stability

Curcumin is a polyphenol with multiple biological activities, but its extremely poor water solubility severely limits its application in the food industry. The purposes of this work were to study the effect of nano-encapsulation on the water solubility of curcumin (C), the interaction of curcumin with zein (Z), the thermal properties, rheological properties, and the stability under different environmental pressures of the nanoparticles. The results of particle size, zeta potential, and surface hydrophobicity (H₀) indicated that the combination of coating materials including sodium caseinate (SC) and sodium alginate (SA) with zein nanoparticles by electrostatic interaction led to a gradual increase in the particle size of composite nanoparticles and a decrease in surface hydrophobicity. The nano-encapsulation significantly improved the water solubility of curcumin and causing its crystal structure to change to an amorphous state. Fourier transform infrared spectroscopy confirmed that curcumin bound to zein through hydrogen bonding. Rheological test results showed that the coating materials combined with zein led to an increase in the apparent viscosity of the nanoparticles. The stability analysis results indicated that the composite nanoparticles with a sodium alginate coating have excellent stability of pH, salt solution and storage, and excellent anti-gastrointestinal fluids digestion characteristics when compared to pure protein nanoparticles.     

Preparation,characterization, bioactive and metal uptake studies of alginate/phosphorylated chitin blend films

Alginate/phosphorylated chitin (P-chitin) blend films were prepared by mixing of 2% of alginate and P-chitin in water and then cross-linked with 4% CaCl₂ solution. The blended films were characterized by FT-IR. Then, the bioactivity of blend films was studied by biomimetic method in simulated body fluid solution (SBF) for 7, 14 and 21 days. After 7, 14 and 21 days and films were characterized by FT-IR and SEM studies. The SEM and FT-IR studies showed that the hydroxyapatite was formed on the surface of the blend films after 7, 14 and 21 days in the SBF solution. These studies confirmed that the alginate/P-chitin blend films are bioactive. Furthermore, the adsorption of Ni²⁺, Zn²⁺and Cu²⁺onto alginate/P-chitin blend films has been investigated. The parameters studied include the pH, contact time, and initial metal ion concentrations. The maximum adsorption capacity of alginate/P-chitin blend films for Ni²⁺, Zn²⁺and Cu²⁺ at pH 5.0 was found to be 5.67, 2.85 and 11.7 mg/g, respectively. These results suggest that alginate/P-chitin blend films-based technologies may be developed for water purification and metal ions separation and enrichment.