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1.
Carbohydr Polym ; 257: 117624, 2021 Apr 01.
Article in English | MEDLINE | ID: mdl-33541651

ABSTRACT

Stable gellan gum (GG)/graphene oxide (GO) aerogels were prepared by freeze-drying a mixture of GG and GO. On introduction of GO, the GG/GO aerogels had different level pore structures due to the different freezing temperatures. The volume per gram (1/ρ) of GG/GO aerogels ranges from 76.80 ± 1.54-158.30 ± 2.30 cm3/g. The porosity of GG/GO-3 (-80 °C) and GG/GO-6 (-20 °C) was 45.53 % and 61.30 %, respectively. The resulting three-dimensional GG/GO aerogels exhibited excellent performance in methylene blue (MB) adsorption. The pseudo-first-order and Freundlich isotherm models produced the best fits for the adsorption kinetics and adsorption equilibrium, respectively. The Gibbs free energy, enthalpy, and entropy of adsorption indicated that the adsorption was a spontaneous, exothermic, and entropy-increasing process. It is illustrated that the GG/GO aerogels exhibited faster adsorption kinetics and adsorption capacity. These GG/GO aerogels can remove MB from aqueous solutions.

2.
Int J Biol Macromol ; 153: 573-582, 2020 Jun 15.
Article in English | MEDLINE | ID: mdl-32145230

ABSTRACT

A poly(gellan gum-co-acrylamide-co-acrylic acid) (GGDA) hydrogel was synthesized by modifying gellan gum (GG) with partly neutralized acrylic acid (AAc) and acrylamide (AAm) under the crosslinking agent trimethylolpropane triglycidyl ether. With the introduction of carboxyl and amino groups by the AAc and AAm, the GGDA showed better regularity than GG, leading to a more porous structure and higher thermal stability. Methylene blue (MB) was used as a model organic dye to evaluate the adsorption capacity of the GGDA. The GGDA exhibited excellent MB adsorption abilities and pH sensitivity. The pseudo-second-order and Freundlich isotherm models produced the best fits for the adsorption kinetics and adsorption equilibrium, respectively. The Gibbs free energy, enthalpy, and entropy of adsorption indicated that the adsorption was a spontaneous, exothermic, and entropy-decreasing process. The maximum equilibrium adsorption capacity of MB was 423.46 ± 13.60 mg/g. This pH-sensitive hydrogel is a potential alternative absorbent for organic dye removal in aqueous solutions.


Subject(s)
Acrylamide/chemistry , Acrylates/chemistry , Hydrogels/chemistry , Methylene Blue/chemistry , Polysaccharides, Bacterial/chemistry
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