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ZIF-8, a metal–organic framework that has significant benefits such as a substantial specific surface area, abundant active sites, and high porosity, has extensive application in environmental remediation. However, ZIF-8 is powdery and easily agglomerated, making it difficult to separate ZIF-8 from aqueous solutions and thus limiting its practical application in wastewater treatment. In this work, sodium alginate was chosen as a gel matrix, and CaCl2 as a cross-linking agent to form a calcium cross-linked MOF gel material (ZIF-8/SA). The batch adsorption investigations demonstrated that the saturated adsorption capacities of ZIF-8/SA in single Mn2+ pollution solution and Mn–Cu–Cd composite pollution solution are 179.86 mg g−1 and 101.86 mg g−1, respectively. Specifically, the adsorption of Mn2+ followed the Langmuir model and exhibited monomolecular layer adsorption. Furthermore, the adsorption of Cu2+ and Cd2+ followed the quasi-first-order kinetic model, which is primarily physical adsorption. The adsorption order of ZIF-8/SA for contaminants in the adsorption process is as follows: Cu2+ > Cd2+ > Mn2+. The SEM-EDS, FT-IR, and XPS studies revealed that the adsorption mechanism of ZIF-8/SA mostly involves ion exchange, coordination of carboxyl/hydroxyl/amino groups, and electrostatic attraction. To summarize, the experimental findings of this study demonstrate that the synthetic ZIF-8/SA hydrogel has promising applications for practical pollution treatment. [ABSTRACT FROM AUTHOR]

Solar-driven interfacial evaporation is increasingly used in desalination due to its excellent evaporation performance. The continuous evaporation of water would lead to an increase in the salinity of the evaporator, which has been often neglected and rarely exploited. In this work, a calcium alginate hydrogel and nickel foam composited membrane (CHN) was proposed as a new platform for constructing solar-powered hybrid systems with the function of synchronous desalination and salinity power generation. The calcium alginate hydrogels can reduce the enthalpy of water evaporation and convert the salinity gradient between the evaporator and seawater into electrical energy. The evaporation rate of the mixed system (CHN-CB) with carbon black (CB) as the solar absorber is greater than 2.1 kg m−2 h−1. Additionally, under 1 sun, the system achieved a maximum short-circuit current of 20.3 mA m−2 and generated an extra electrical power of 5.3 mW m−2. As a universal multi-energy conversion platform, the CHN membranes can combine different photothermal materials for synchronous evaporation and salinity gradient power generation. These results open new paths for the combination of desalination and power generation, demonstrating the potential for diversified use of blue energy. [ABSTRACT FROM AUTHOR]

For much of the Caribbean region, plastic pollution and the persistence of the great Atlantic Sargassum belt lead to significant regional loss in biodiversity, employment and tourism. Yet, seaweeds such as Sargassum possess all the characteristics for bioplastic production. This study presents a new process on the production of biodegradable calcium alginate (Ca(Alg)2) composite bioplastic, and evaluates its economic feasibility and environmental impact in the Caribbean, compared to bio-based polylactic acid (PLA) and synthetic plastics (PET). Our cradle-to-gate life cycle impact assessment (LCIA) shows normalized (kg CO2eq per kg plastic) greenhouse gas (GHG) impacts 3 to 7 times higher for the baseline alginate composite process over those of PLA and PET films – linked mainly to chemical consumption. However, through the integration of abundant bioenergy from the local paper industry and the nascent E-methanol (E-MeOH) supply chains, GHG impact reduces by 79% – illustrating a pathway to a sustainable bioplastic production flowsheet. More attractively, the alginate bioplastic outperforms in providing ultra-low oxygen barrier packaging properties – with a required mass of plastic material producing a total carbon footprint (kg CO2eq) 64–978 times lower than PLA and PET respectively, and overall packaging costs 280 times less than current synthetic plastic. Techno-economics illustrate that a total annualized cost (TAC) for alginate bioplastic of $US 4.56 per kg is possible, ensuring high economic feasibility, comparable to current commercial bio-based alternatives. Moreover, sensitivity analysis highlights that variability in TAC was mainly associated with sodium alginate utilization in the manufacture process – contributing up to 67% to the overall cost. In light of this, the integration of sound policies aligned to improved consumer awareness and reduced plastic waste can help to drive greater economic feasibility of the alginate bioplastic industry. Ultimately, our study illustrates a viable and sustainable alginate bioplastic alternative, promoting and informing on packaging innovation while achieving low carbon operations within the Caribbean plastic sector. [ABSTRACT FROM AUTHOR]

The excessive utilization of syringic acid (SA) has caused severe environmental pollution and economic waste. Herein, from an eco-friendly perspective, a magnetic nanomaterial (Fe–Zn/ZIF) was prepared by a one-step method at room temperature. Based on the 3Rs (pollutant reduction, resource recycling, and resource reuse) concept, this carrier exhibits great potential in the adsorption and release of SA. The adsorption process of SA over Fe–Zn/ZIF can reach equilibrium at ∼360 min with a high adsorption capacity of 450.6 mg g−1, superior to those of reported adsorbents, which can be ascribed to synergistic effects of strong electrostatic attraction, H-bonding interaction, and π–π interaction. To overcome the burst release of SA–Fe–Zn/ZIF in the weak acid phenomenon, calcium alginate (CA) was selected as an encapsulation material. As expected, CA@SA–Fe–Zn/ZIF only released 30.6% of SA in the first 180 minutes at pH = 5.8, a decrease of 14.8% compared to SA–Fe–Zn/ZIF. Therefore, the magnetic carrier obtained in this work may realize deep removal and controlled release of SA. [ABSTRACT FROM AUTHOR]

The traditional extraction technique for hemp fibers results in high energy consumption, serious pollution, excessive degumming and strength loss. Herein, a cleaning and reusable biochemical degumming method is provided, which combines calcium alginate microspheres loaded with pectinase lyase (CA-PL) and a small number of chemical auxiliaries. This biochemical degumming method has a shorter reaction time and lower reaction temperature and is environmentally friendly. Complete degumming can be achieved by repeating this method two to three times. The effect of the number of uses of the biochemical degumming solution on the composition, mechanical properties and strength of the resulting hemp fibers was studied. The biochemical degumming solution could be reused three times; the extraction rates of cellulose after each degumming treatment were 77.09%, 76.94% and 70.61%, and the breaking strength was 64.3 cN dtex−1, 62.1 cN dtex−1 and 59.7 cN dtex−1, respectively. The results of repeated degumming treatment showed that the optimal number of recycles of the biochemical degumming solution was two; the degumming efficiency was higher and the cellulose extraction degree was better. [ABSTRACT FROM AUTHOR]

In the present study we provide the sorption properties of four 8-connected Zr4+ MOFs with the general formula H16[Zr6O16(RNH-BDC)4]·solvent (RNH-BDC2− = 2-alkyl-amine-terephthalate; R = ethyl-, ET-MOF; R = propyl-, PROP-MOF; R = isobutyl-, SBUT-MOF; R = n-butyl, BUT-MOF) towards toxic Cr(VI) and radionuclide-related ReO4− oxoanions. These MOFs represent superior sorbents for the removal of oxoanionic species, in terms of kinetics, sorption isotherms, selectivity and regeneration/reusability. The excellent sorption capability of the MOFs is due to a combination of surface and intra-framework sorption phenomena. The latter process proceeds via replacement of terminal water/hydroxyl ligands from the Zr6 clusters and subsequent binding of oxonanions to the Zr4+ centers, a fact that was proved via Rietveld PXRD analysis for the anion-loaded BUT-MOF. Importantly, BUT-MOF demonstrated an exceptional sorption capacity for Cr2O72− (505 mg g−1) and was further utilized in a sorption column in the form of MOF/calcium alginate beads, displaying remarkable removal efficiency towards industrial (chrome-plating) wastewater. Furthermore, the luminescence Cr(VI) sensing properties of BUT-MOF were explored in detail, presenting high sensitivity (detection limits as low as 9 ppb) and selectivity for these species against various competitive anions. [ABSTRACT FROM AUTHOR]

In order to enhance the mechanical properties of a hydrogel film and broaden its applications in the medical field, polydopamine (PDA) was used as the "medium" to construct a dynamically united calcium alginate/carboxymethyl chitosan (CA/CMCS) dual network structure using the Michael addition reaction in this study. A high-strength and high-toughness medical film with a united dual network was prepared by a flow-casting/solvent evaporation method. When the content of sodium alginate (SA)–PDA was 2 wt%, the mechanical properties of the prepared film were the best. The tensile strength and elongation at break were 68.81 Mpa and 3.31%, which increased by 231.61% and 47.77% compared with the CA film. The best comprehensive performance for the medical film could be achieved at the same time. The water absorption rate, maximum swelling rate, water vapor transmission rate, contact angle and degradation rate of the film were 417%, 455%, 1000.45 g m−2 d−1, 55° and 13.13%, respectively. The united dual network structure film had potential applications in the medical field. [ABSTRACT FROM AUTHOR]

Micron-sized alginate hydrogel beads are extensively employed as an encapsulation medium for biochemical and biomedical applications. Here we report on the microfluidic assisted fabrication of calcium alginate (Ca-alginate) beads by on-chip picoinjection of aqueous calcium chloride (CaCl2) in emulsified aqueous sodium alginate (Na-alginate) droplets or by picoinjection of Na-alginate solution in emulsified aqueous CaCl2 droplets. There is no added chelator to reduce the Ca activity in either of the two strategies. The two fabrication strategies are implemented using a flow-focusing and picoinjection modules in a single PDMS chip. Aqueous alginate solution was emulsified and infused with CaCl2 solution as the squeezed droplet pass the picoinjection channel; consequently, monodisperse, spherical, and structurally homogeneous Ca-alginate beads were obtained. Monodisperse alginate microgel populations with a mean diameter in the range of 8 to 28 μm and standard deviation less than 1 μm were successfully generated using microfluidic channels with various dimensions and controlling the flow parameters. Monodisperse but also non-spherical particles with diameters 6 to 15 μm were also fabricated when picoinjecting Na-alginate solution in emulsified aqueous CaCl2 droplets. The Ca-alginate microbeads fabricated with tailormade size in the range from sub-cellular and upwards were in both strategies realized without any use of chelators or change in pH conditions, which is considered a significant advantage for further exploitation as encapsulation process for improved enzymatic activity and cell viability. [ABSTRACT FROM AUTHOR]

In this experiment, calcium alginate (CA)/polyethylene glycol diacrylate (PEGDA)/polyvinyl alcohol (PVA) composite fiber containing PVA microcrystalline cross-linking point and PEGDA/CA double network structure was prepared by "one pot method", freeze–thaw cycle and dynamic molding method. PEGDA was used as the chemical crosslinking component, sodium alginate (SA) was the ionic crosslinking component, and PVA was the microcrystalline crosslinking component. The breaking strength and breaking elongation of the microcrystalline cross-linking synergistically with the double network composite fiber were 3.18 cN per dtex and 11.75%, respectively, which were 30.33% and 74.07% higher than that of the regenerated CA fiber. The rheological properties of the SA/PEGDA/PVA solution, mechanical properties and morphology of the CA/PEGDA/PVA fiber were also studied. This experiment was also focused on analyzing the mechanism and influencing factors of improving the mechanical properties of composite fibers. [ABSTRACT FROM AUTHOR]

Effectively guiding and accurately controlling cell adhesion and growth on the surfaces of specific morphological materials are key issues and hot research topics for optimizing biomaterials. Herein, novel polymorphic alginate microfibers formed through microfluidic spinning technology in a single microchip are presented. Through programming the flow and reaction kinetics in microchannels, other than self-modified micromorphic channel geometry, polymorphic microfibers with precisely tuned curvature-adjustable morphology can be obtained. Finite element (FE) simulations of the flow field (unidirectional fluid–solid coupling) proved the efficacy of the proposed control strategy. Moreover, the specific disordered–ordered cell arrangements showed a linear relationship between bioinspired alginate microfibers with different curvatures and the orientation angle of L929 cells, and diversified growth morphologies, including oblate ellipse, star, tree and strip shapes, occurred on the customizable interface curvature of the calcium alginate microfibers, providing a paradigm for using specific structured natural biomedical materials for cell regulation. This work represents a new design concept for manufacturing polymorphic fibrous biomedical materials through a unique marriage of the fields of green chemistry, hydromechanics, and biomaterials, which should be very useful for guiding the controllable construction of alginate materials for use in structural materials for biomedical and engineering purposes. [ABSTRACT FROM AUTHOR]

Bipolar electrochemistry has attracted great interest for applications based on sensing, electrografting, and electrodeposition, because the technique enables electrochemical reactions to be induced at multiple bipolar electrodes (BPEs) with only a single power supply. However, there are only a few reports on the biofabrication of hydrogels using BPEs. In this study, we applied bipolar electrochemistry to achieve the electrodeposition of calcium-alginate hydrogels at specified target areas, which is possible because of the use of water electrolysis to obtain acidification at the anodic pole. This scheme was used to successfully fabricate an array of hydrogel deposits at a BPE array. In addition, hydrogels were successfully fabricated either at only the target BPEs or only the target areas of BPEs by repositioning the driving electrodes. Furthermore, a hydrogel was drawn on a large BPE as a canvas by using small driving electrodes. As a demonstration of the electrodeposited hydrogels for bioapplications, mammal cells were cultured in the hydrogels. Because the amount and shape of the hydrogel deposits can be controlled by using the bipolar system, the system we developed can be used for biosensors and cell culture platforms. [ABSTRACT FROM AUTHOR]

To investigate the formation mechanism of a physically cross-linked double-network hydrogel and its application as a framework for nanomaterial, in this work, calcium alginate and polyvinyl alcohol (PVA) were selected as hydrogel-forming polymers to form a double-network hydrogel utilized as a framework for graphene oxide (GO). The results showed that completely physically cross-linked double-network hydrogels were obtained with good shape-recovery and self-healing properties. Moreover, the first network had a significant influence on the properties of double networks: when calcium alginate acts as the first network, the hydrogels have denser structures, a lower swelling ratio and higher mechanical properties. The GO/double-network composite hydrogel shows a 3D porous network structure with no obvious aggregation of GO nanosheets and an excellent removal rate for methylene blue. The results indicate the potential of the polymer double network utilized as a nanomaterial framework in biomedical and environmental areas. [ABSTRACT FROM AUTHOR]

Tough swelling nanocomposite hydrogels have been fabricated via introducing graphene oxide (GO) and in situ synthesis. Upon addition of GO, the swelling properties of a calcium alginate/polyacrylamide (CA/PAAm) double network (DN) are considerably suppressed. Moreover, the mechanical properties of CA/PAAm DN gels and GO reinforced DN gels in swelling and as-prepared states have been systematically explored. The results affirm that the swelling largely damages the mechanical properties of gels, due to the osmotic pressure introducing solvents into the gaps between polymer chains and cross-linkers, thereby leading to weak spots in the gels. GO demonstrates the ability to improve the mechanical properties of pristine DN gels in both swelling and as-prepared states by offering large numbers of physical interpenetrations and chemical bindings between long polymeric chains and GO nanosheets, and building a Ca2+ coordination-induced GO network. The toughness of swelling nanocomposite gels is around 106 kJ m−3 that is comparable to that of cartilage in large animal joints. Furthermore, the consecutive loading–unloading tests and cytotoxicity tests show that the swelling nanocomposite gels, respectively, obtain superior fatigue resistance and high biocompatibility. Therefore, these swelling nanocomposite gels are promising as substitutes for load-bearing tissues. [ABSTRACT FROM AUTHOR]

A novel material, “calcium-alginate–silica microsphere” (Cal-Alg–SM) beads, was developed by impregnating silica microspheres in calcium alginate. These beads were highly efficient in the removal of TiO2 nanoparticles from aquatic bodies without disturbing their physicochemical characteristics. The optimum composition of the beads was 10% loading of silica microspheres into a 4% Ca-alginate matrix. They were formed by the controlled addition of a homogenised mixture of SMs and Na-alginate solution into 0.4 M CaCl2 solution. Cal-Alg–SM beads were characterized by measuring zeta potential, recording Fourier Transform infrared spectra and scanning electron microscopy coupled with energy dispersive spectrometry mapping both before and after the uptake. Uptake studies carried out in batch mode showed that Cal-Alg–SM beads are very effective for the removal of TiO2 nanoparticles in the pH range of 3–5 and the sorption was more than 90% in the concentration range of 10–500 μg mL−1. Beads were successfully tested with lake and groundwater samples spiked with TiO2 nanoparticles. The sorption isotherm was seen to follow the Langmuir model and the uptake capacity evaluated was 29.9 mg g−1. The mechanism of sorption was proposed based on the zeta potential values of SMs and TiO2 nanoparticles at different pH values. [ABSTRACT FROM AUTHOR]

Amino acids (AA's) are interesting materials as feedstocks for the chemical industry as they contain chemical functionalities similar to conventional petrochemicals. This offers the possibility to circumvent process steps, energy and reagents. AA's can be obtained by the hydrolysis of potentially inexpensive voluminous protein streams derived from biofuel production. However, isolation of the preferred AA is required in order to carry out further transformation into the desired product. Theoretically separation may be achieved using electrodialysis. To increase efficiency, specific modification to a product of industrial interest and removes charged groups of AA's with similar isoelectric points is required. Here, the reaction of l-lysine decarboxylase (LDC) was studied as a means to specifically convert l-lysine (Lys) to 1,5-pentanediamine (PDA) in the presence of l-arginine (Arg) to produce products with different charge thus allowing isolation of products by electrodialysis. Immobilization of LDC in calcium alginate enhanced the operational stability and conversion in mixtures of amino acids was highly specific. At 30 °C the presence of Arg had little effect on the activity of the enzyme although inhibition by the product PDA could be observed. Volumetric productivity was calculated and raw material and transformation costs were estimated for a potential process using a mixture of Arg and Lys. [ABSTRACT FROM AUTHOR]