Alginate Gelation Method Research Articles

Enhanced adsorption capacity of low-cost magnetic clinoptilolite powders/beads for the effective removal of methylene blue: Adsorption and desorption studies

Clinoptilolite/Fe 3 O 4 (Clin/Fe 3 O 4 ) nanocomposite powders and Alginate/Clinoptilolite/Fe 3 O 4 (Alg/Clin/Fe 3 O 4 ) nanocomposite beads were prepared and used for methylene blue (MB) cationic dye removal from aqueous solution. The properties of the synthesized adsorbents were characterized by XRD, FTIR, SEM-EDX, dot mapping, VSM and BET analyses. Results confirmed that Fe 3 O 4 nanoparticles were successfully placed in the structure of Clin/Fe 3 O 4 nanocomposite powders and sodium alginate gelation method was effectively used to encapsulate the powders to Alg/Clin/Fe 3 O 4 beads. The impacts of various parameters including pH, temperature, contact time, adsorbent dose, and initial MB dye concentration were investigated on the adsorbents’ performance towards MB dye removal. The maximum MB adsorption efficiency using Clin/Fe 3 O 4 (97.57%) and Alg/Clin/Fe 3 O 4 (93.62%) were obtained at an initial pH of 10. The results of the equilibrium study showed that the adsorption of MB using Clin/Fe 3 O 4 and Alg/Clin/Fe 3 O 4 followed the Langmuir isotherm model. The amount of monolayer adsorption capacity (q m ) for Clin/Fe 3 O 4 and Alg/Clin/Fe 3 O 4 were determined as 45.662 mg/g and 12.484 mg/g, respectively. In addition, the values of n, R L , and E parameters derived from isotherm modeling showed that the MB dye adsorption process using both adsorbents was physically desirable. The kinetic data followed a pseudo-second order (PSO) kinetic model indicating that chemical mechanism was also effective in the adsorption process. The thermodynamic results showed that the adsorption process using both types of adsorbents was exothermic and spontaneous. Regeneration experiments performed in ethanol +0.5 M CaCl 2 solution showed that the adsorption capacity of Clin/Fe 3 O 4 and Alg/Clin/Fe 3 O 4 was only decreased 7.92% and 9.76%, respectively after five cycles. This study demonstrated that Alg/Clin/Fe 3 O 4 beads are efficient, very low-cost, environmentally friendly and fairly regenerable adsorbents for the removal of MB dye from the aquatic environment. • Alg/Clin/Fe 3 O 4 was produced by co-precipitation and ionic gelation methods. • The Clin/Fe 3 O 4 and Alg/Clin/Fe 3 O 4 were used to remove methylene blue. • The amount of q m for Clin/Fe 3 O 4 was determined to be 45.662 mg/g. • The amount of q m for Alg/Clin/Fe 3 O 4 was determined to be 12.484 mg/g. • Alg/Clin/Fe 3 O 4 beads are efficient, very low-cost and regenerable adsorbents.

Understanding of vibrational and thermal behavior of bio-based doped alginate@nickel cross-linked beads: A combined experimental and theoretical study

• Sr and in doped nickel-alginate composites were fabricated and studied. • Structural and thermal properties were investigated using several techniques. • Thermal stability of nickel-alginate beads were enhanced by sr and in doping. • Structural behavior of the beads was compared through molecular dynamic simulation. Herein, in-situ doping of Alginate-Nickel (Alg@Ni) beads by strontium (Sr) and indium (In) was realized via alginate gelation method based on metal cation cross-linking. Three gel beads named Alg@Ni, Alg@Ni/Sr and Alg@Ni/In were prepared by alginate cross-linking of Ni 2+ cation, Ni 2+ /Sr 2+ cations and Ni 2+ /In 3+ , then characterized by Fourier transformed spectroscopy (FTIR), thermal gravimetric (TGA) and differential scanning calorimeter analyses (DSC) to exhibit different properties of gel beads. As a result, FTIR confirmed that the presence of Sr or In dopant could affect Alg@Ni vibrations. Moreover, the thermal stabilities of Alg@Ni beads were improved after Sr and In doping. Besides, theoretical studies were employed to gain more insight into experimental results. In this context, Alg@M ( M = Ni 2+ , Sr 2+ and In 3+ ) complexes were studied individually by using density theory functional (DFT) calculations. The electronic and chemical properties of each complex were calculated and discussed. The correlation between the thermal stability and molecular structure of the Alg@Ni, Alg@Sr, and Alg@In was evaluated using ab initio molecular dynamic (MD) simulation.

Mechanical and electromechanical properties of piezoelectric ceramic fibers drawn by the alginate gelation method

AbstractPiezoelectric ceramic fibers are widely used in piezocomposite devices. The various methods that are used to draw ceramic fibers differ in the way the fiber form is obtained, which in return closely affects the density, uniformity and the properties of the fibers that are obtained at the end. In this study, the processing‐property relationship in the piezoceramic fibers drawn using the alginate gelation method is investigated, with a focus on the mechanical and electrical properties of individual fibers. Fibers with a Weibull strength of 65.3 MPa, remanent polarization of 22 μC/cm2 and a total bipolar field induced strain of 0.25% under an electric field of 2.5 kV/mm, piezoelectric coefficient of 300 pm/V and dielectric constant of 3323 were produced. 1‐3 piezocomposite devices prepared from these fibers had a 6 dB higher free‐field voltage sensitivity and a 50% wider bandwidth compared to a solid disk transducer of the same dimensions.

Properties of [Pb(Zn1/3Nb2/3)O3]x- [Pb(Zr0.48Ti0.52)O3](1-x) Ceramics With Low Sintering Temperature and Their 1-3 Piezocomposites.

In this paper, dense ( x )PZN-( 1-x )PZT ceramics were prepared at sintering temperatures as low as 950 °C with PZN ratios of x=0.4 , 0.5, and 0.6. The 0.4PZN-0.6PZT composition was found to crystallize in the perovskite phase at this sintering temperature without the presence of any other secondary phases. Higher electrical and electromechanical properties were obtained from the 0.4PZN-0.6PZT composition compared with the x=0.5 and x=0.6 counterparts. Dielectric constant, piezoelectric charge coefficient, electromechanical coupling coefficient, and mechanical quality factor of 0.4PZN-0.6PZT were found to be 2608, 477 pC/N, 64.4, and 65, respectively. While the Curie temperature was 140 °C for pure PZN, the Curie temperature was measured as 300 °C for x=0.4 composition. Green PZN-PZT fibers with circular cross section were drawn using alginate gelation method from the 0.4PZN-0.6PZT composition. Dense fibers were obtained after the sintering process, and piezocomposites were prepared with 1-3 connectivity using fibers with an average diameter of 600 [Formula: see text]. Composites with volume fraction of 20 vol% were investigated for passive acoustic sensor applications. Electrical properties of piezocomposites were found to be scalable and compatible with the electrical properties of the bulk composition. The dielectric constant, piezoelectric charge coefficient, and maximum strain value of the PZN-PZT 1-3 piezocomposite were measured as 345, 165 pC/N, and 0.13%, respectively.

Fabrication of textured lead-free strontium barium niobate (SBN61) bulk ceramics and their electrical properties

Abstract Sr0.61Ba0.39Nb2O6 (SBN61) ceramic fibers with a high [001] texture were fabricated by a combination of alginate gelation method and templated grain growth process using acicular Ba2NaNb5O15 (BNN) template particles. The rod-like BNN template particles were prepared by molten salt synthesis method with salt/powder ratio of 2 giving the highest aspect ratio. Fibers were drawn from alginate based slurries without or with 10 wt% BNN template particles. Increasing sintering temperature and time were found to increase the texture. Textured SBN61 bulk ceramics with dimensions in cm scale were fabricated by wet packing a limited number of grain oriented green fibers and sintering the green bulk to obtain a dense, textured bulk ceramic through templated grain growth. A maximum texture fraction, f, of 0.91 was obtained, as measured by Lotgering factor. Increased remnant polarization and electromechanical properties were obtained as a result of this preferred grain orientation.

Processing and Properties of Textured Potassium Sodium Niobate [K,Na]NbO3 Ceramic Ribbons by Alginate Gelation Method

Random and <001> textured potassium sodium niobate – [K,Na]NbO3 (KNN) ceramics with 1 mole% CuO sintering aid were fabricated in ribbon form through a combination of novel alginate gelation process and templated grain growth methods using platelike sodium niobate ‐ NaNbO3 (NN) template particles. The platelike NN template particles were prepared by a two‐step molten salt synthesis method. Ribbons were drawn from alginate‐based slurries without or with 10 wt% NN template particles using 50 mm long slit nozzle with a rectangular orifice of 10 mm × 1 mm. Development of crystallographic texture as a result of varying sintering time and temperature was evaluated through the calculation of the degree of orientation as measured by the Lotgering factor (ƒ(001)) and an ƒ(001) of 0.81 was achieved. The electrical properties of textured ribbons were evaluated with polarization and strain versus electric field measurements.

Drawing of Piezoceramic Fibers and Ribbons Using a Novel Alginate Gelation Method and Properties of Fiber and Ribbon-Based Piezodevices

Piezoceramics are usually shaped into three dimensional bulk form using dry pressing or slip casting methods. However, certain applications require piezoceramics to be shaped in one dimensional fiber or two dimensional ribbon form. In this study, piezoceramic fibers and curved piezoceramic ribbons were fabricated using a novel alginate gelation method. Alginate is a natural linear polymer that is obtained from brown kelp. In the presence of multivalent cations, it forms ionic cross-links and gels in a three dimensional network form. In our study, gelation conditions of alginate containing aqueous slips of lead zirconate titanate based piezoelectric ceramic powders were investigated. Piezoelectric ceramic fibers and ceramic ribbons were prepared by sintering of gelled powders for transducer applications. Structural characteristics of these ceramics and electrical characteristics of piezodevices prepared from these ceramics were investigated and reported.

Processing, Structural and Electrical Properties of Textured Potassium Strontium Niobate (Ksr<sub>2</sub>Nb<sub>5</sub>O<sub>15</sub>) Piezoceramic Fibers

Highly [00 textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. Fibers were drawn from alginate based slurries without or with 25 and 100wt% KSN template particles. A texture fraction of 0.90 was obtained in the case of 25 wt% and a single crystal like texture was obtained in the case of 100wt%. Piezocomposites with 1-3 connectivity were prepared from the KSN fibers and their electrical and electromechanical properties were investigated. Dielectric constant of 140, piezoelectric charge coefficient of 45 pC/N, remnant polarization of 16.6 μC/cm2 and electric field induced strain of up to 0.035% were obtained from piezocomposites with textured fibers.

Drawing of Piezoceramic Fibers and Ribbons Using a Novel Alginate Gelation Method and Properties of Fiber and Ribbon-Based Piezodevices

Piezoceramics are usually shaped into three dimensional bulk form using dry pressing or slip casting methods. However, certain applications require piezoceramics to be shaped in one dimensional fiber or two dimensional ribbon form. In this study, piezoceramic fibers and curved piezoceramic ribbons were fabricated using a novel alginate gelation method. Alginate is a natural linear polymer that is obtained from brown kelp. In the presence of multivalent cations, it forms ionic cross-links and gels in a three dimensional network form. In our study, gelation conditions of alginate containing aqueous slips of lead zirconate titanate based piezoelectric ceramic powders were investigated. Piezoelectric ceramic fibers and ceramic ribbons were prepared by sintering of gelled powders for transducer applications. Structural characteristics of these ceramics and electrical characteristics of piezodevices prepared from these ceramics were investigated and reported.

Processing, Structural and Electrical Properties of Textured Potassium Strontium Niobate (Ksr<sub>2</sub>Nb<sub>5</sub>O<sub>15</sub>) Piezoceramic Fibers

Highly [00 textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. Fibers were drawn from alginate based slurries without or with 25 and 100wt% KSN template particles. A texture fraction of 0.90 was obtained in the case of 25 wt% and a single crystal like texture was obtained in the case of 100wt%. Piezocomposites with 1-3 connectivity were prepared from the KSN fibers and their electrical and electromechanical properties were investigated. Dielectric constant of 140, piezoelectric charge coefficient of 45 pC/N, remnant polarization of 16.6 μC/cm2 and electric field induced strain of up to 0.035% were obtained from piezocomposites with textured fibers.

Processing and Properties of Textured Potassium Strontium Niobate (KSr2Nb5O15) Ceramic Fibers – Texture Development

Highly [001] textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. The needle‐like KSN template particles were prepared by molten salt synthesis method with salt/powder ratio of 2 giving the highest aspect ratio. Fibers were extruded into CaCl2 salt solutions from alginate‐based slurries without or with 10 wt% KSN template particles using a nozzle with 2 mm diameter and 80 mm length. Varying sintering temperature from 1300°C to 1450°C and time from 2 to 6 h were found to increase the texture. A maximum degree of orientation, ƒ(00l), of 0.95 was obtained, as measured by Lotgering factor, and a grain orientation distribution, r, of 0.28 was obtained as measured by rocking curve analysis.

Transport of biological molecules in surfactant–alginate composite hydrogels

Obstructed transport of biological molecules can result in improper release of pharmaceuticals or biologics from biomedical devices. Recent studies have shown that nonionic surfactants, such as Pluronic® F68 (F68), positively alter biomaterial properties such as mesh size and microcapsule diameter. To further understand the effect of F68 (incorporated at concentrations well above the critical micelle concentration (CMC)) in traditional biomaterials, the transport properties of BSA and riboflavin were investigated in F68-alginate composite hydrogels, formed by both internal and external cross-linking with divalent cations. Results indicate that small molecule transport (represented by riboflavin) was not significantly hindered by F68 in homogeneously (internally) cross-linked hydrogels (up to an 11% decrease in loading capacity and 14% increase in effective diffusion coefficient, D(eff)), while protein transport in homogeneously cross-linked hydrogels (represented by BSA) was significantly affected (up to a 43% decrease in loading capacity and 40% increase in D(eff)). For inhomogeneously cross-linked hydrogels (externally cross-linked by CaCl(2) or BaCl(2)), the D(eff) increased up to 50 and 83% for small molecules and proteins, respectively. Variation in the alginate gelation method was shown to affect transport through measurable changes in swelling ratio (30% decrease) and observable changes in cross-linking structure as well as up to a 3.6- and 11.8-fold difference in D(eff) for riboflavin and BSA, respectively. Aside from the expected significant changes due to the cross-linking method utilized, protein transport properties were altered due to mesh size restrictions (10-25 nm estimated by mechanical properties) and BSA-F68 interaction (DLS). Taken as a whole, these results show that incorporation of a nonionic surfactant at concentrations above the CMC can affect device functionality by impeding the transport of large biological molecules.

Electrical Properties of 1–3 Piezocomposites Prepared from Textured KSr2Nb5O15 (KSN) Ceramic Fibers

Highly [001] textured KSr2Nb5O15 (KSN) ceramic fibers were fabricated by a combination of novel alginate gelation method and templated grain growth using acicular KSr2Nb5O15 template particles. Fibers were drawn from alginate based slurries without or with 10 wt% KSN template particles. A maximum texture fraction of 0.96 was obtained. Piezocomposites with 1–3 connectivity were prered from the KSN fibers and their electrical and electromechanical properties were investigated. Dielectric constant of 90, piezoelectric charge coefficient of 60 pC/N, remnant polarization of 10 μC/cm2 and electric field induced strain of up to 0.036% were obtained from piezocomposites with textured fibers.

A novel method for immobilization of yeast cells in alginate gels of various shapes by internal liberation of Ca-ions

In situ gelation of alginate, in which Ca-ions are liberated internally in the gel, was used for immobilization of yeast cells. Compared to the traditional alginate gelation method, internal gelling gave immobilized yeast particles of higher strength, without reduction in fermentation rate.