Search

The research in biopolymer-based superabsorbents is gaining importance in the green chemistry field thanks to their environmentally friendly properties. In this study, a biopolymer-based superabsorbent made of calcium ion crosslinked alginate/carboxymethyl cellulose composite was prepared by a new quasi-cryogelation process, where the complete ionic gelation takes place before the freezing step, in contrast to the conventional cryogelation technique in which gelation occurs under semi-frozen conditions. Thanks to the facile quasi-cryogelation method, the morphology of the gels changed and a significant increase in water absorption properties has been achieved. The swelling properties of the material were investigated in distilled water and different physiological fluids. Results show that the proposed material shows good water absorption property where a water absorption of 2343% was reached and even after five cycles this value was 1200%. As a result, this study reports a biopolymer-based sustainable superabsorbent which is appropriate for various applications such as the removal of pollutants from water or diaper production. [ABSTRACT FROM AUTHOR]

Cerium oxide nanoparticles were synthesized by thermal decomposition of cerium alginate biopolymer gel at 450 °C, where alginate both acts as a precursor and a template. The synthesis is a green, facile and one-step method and the resulting nanoparticles have functionalized surface. The resulted material were characterized using X-ray diffraction for confirmation of cerium oxide, crystallite size analysis and grain size distribution. Transmission electron microscopy was used for the particle size determination, hydrodynamic size estimation was studied by dynamic light scattering and surface characteristics were analyzed using zeta potential measurements. Results show the presence of spherical particles with a size of < 5 nm. Having only a negative surface charge in such a wide pH range will ensure that the behavior of obtained nanoparticles in different environments is predictable. Isoelectric point of the synthesized material is significantly different from non-functionalized cerium oxide, and indicates the surface functionality, which is an important property for biocompatibility. [ABSTRACT FROM AUTHOR]

Uncontrolled pollution of surfactants to the environment is an important problem nowadays. In this study, anionic charged surfactant sodium dodecyl benzene sulfonate (SDBS) was chosen as a model surfactant for removal studies. Biopolymer based, crosslinked chitosan films were used for the aqueous removal of SDBS. Sodium sulfate was selected as the crosslinker. Batch adsorption studies show that positively charged chitosan has an affinity towards negatively charged surfactant SDBS. Adsorption parameters such as the effect of contact time, pH, crosslinker concentration, and adsorbent dose were investigated during experimental studies. The maximum amount of adsorbed SDBS was reached at pH 2 and at 180 min. Experimental data were modeled using kinetic and isothermal models, and the system was found to be following pseudo-second order kinetics. Significantly high adsorption capacity of films (qm) for SDBS was found as 714 mg/g. This study suggests a potential use of crosslinked chitosan films for the removal of anionic surfactants from aquatic media. [ABSTRACT FROM AUTHOR]

A novel alginate-montmorillonite biopolymer-clay composite bead formulation for water defluoridation was developed in this study. Montmorillonite was dispersed alginate solution, and the mixture was cross-linked in an aqueous solution of aluminum(III). The resulting cross-linked beads were characterized using FTIR, SEM, and mechanical measurements. In order to reveal the defluoridation capacity of the beads, batch adsorption experiments were carried out. Optimum conditions and effect of competing ions were investigated. Experimental data were modeled using several isothermal, kinetic, and thermodynamic models. Maximum Langmuir adsorption capacity was reached as 31.0 mg g at 25 °C. It is also found that the adsorption is physical in nature and follows the Elovich kinetic model, and the fluoride removal efficiency is not affected by the presence of most competing anions. The results show that aluminum alginate-montmorillonite composite beads can be used as effective and natural sorbents for fluoride removal from water. [ABSTRACT FROM AUTHOR]

In this study, spherical alginate beads containing pyranine ( P) as a fluorescence probe were prepared by ionotropic gelation of a sodium alginate solution. The steady state fluorescence technique was used to study pyranine release from the alginate beads crosslinked with calcium, barium and aluminum ions, respectively. The slow release of P was observed with the time drive mode of the spectrophotometer at 512 nm. Fluorescence emission intensity ( I) from P was monitored during the release process, and the encapsulation efficiency (EE) of pyranine from the alginate beads was calculated. The Fickian Diffusion model was used to measure the release coefficients, D. It was seen that the slow release coefficients of pyranine from the alginate beads crosslinked with Ca, Ba, and Al ions increased in the following order: D (Al)> D (Ca)> D (Ba). In contrast, the initial amount of pyranine and EE into the beads showed the reverse behavior. [ABSTRACT FROM AUTHOR]

Quasi-cryogelation technique is a simple yet effective technique for improving the adsorptive efficiency of biopolymer-based adsorbent materials. In this work, a biopolymer-based adsorbent material, graphene oxide alginate quasi-cryogel beads are reported. Alginate biopolymer was crosslinked and frozen at − 21 °C in order to obtain a gel with cryogel-like microstructure. Graphene oxide was included in the bead formulation in order to enhance the adsorptive characteristics. Beads were characterized using Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and swelling experiments. Removal of the model cationic dye, methylene blue, was studied by batch adsorption method. It is found that the adsorption follows the Freundlich isotherm model and pseudo-first order kinetics with reaching an adsorption capacity of 122.26 mg/g in 60 min. Results indicate that the physisorption might be due to the π-π interactions between graphene oxide and methylene blue, in addition to electrostatic interactions. Moreover, quasi-cryogelation technique significantly improved the dye removal properties. [ABSTRACT FROM AUTHOR]