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Strong adhesion and cohesion of chitosan in aqueous solutions.

ABSTRACT: Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0-8.5), achieving a maximum value at pH 3.0 after a contact time of 1 h (Wad ~ 6.4 mJ/m(2)). We also found weak or no cohesion between two opposing chitosan layers on mica in aqueous buffer until the critical contact time for maximum adhesion (chitosan-mica) was reached. Strong cohesion (Wco ~ 8.5 mJ/m(2)) between the films was measured with increasing contact times up to 1 h at pH 3.0, which is equivalent to ~60% of the strongest, previously reported, mussel underwater adhesion. Such time-dependent adhesion properties are most likely related to molecular or molecular group reorientations and interdigitations. At high pH (8.5), the solubility of chitosan changes drastically, causing the chitosan-chitosan (cohesion) interaction to be repulsive at all separation distances and contact times. The strong contact time and pH-dependent chitosan-chitosan cohesion and adhesion properties provide new insight into the development of chitosan-based load-bearing materials.

SUBMITTER: Lee DW

PROVIDER: S-EPMC3888206 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Strong adhesion and cohesion of chitosan in aqueous solutions.

Lee Dong Woog DW Lim Chanoong C Israelachvili Jacob N JN Hwang Dong Soo DS

Langmuir : the ACS journal of surfaces and colloids 20131106 46

Chitosan, a load-bearing biomacromolecule found in the exoskeletons of crustaceans and insects, is a promising biopolymer for the replacement of synthetic plastic compounds. Here, surface interactions mediated by chitosan in aqueous solutions, including the effects of pH and contact time, were investigated using a surface forces apparatus (SFA). Chitosan films showed an adhesion to mica for all tested pH ranges (3.0-8.5), achieving a maximum value at pH 3.0 after a contact time of 1 h (Wad ~ 6.4 ...[more]

PMID: 24138057

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Project description:The excess presence of phosphate(V) ions in the biosphere is one of the most serious problems that negatively affect aqueous biocenosis. Thus, phosphates(V) separation is considered to be important for sustainable development. In the presented study, an original cerium(IV)-modified chitosan-based hydrogel (Ce-CTS) was developed using the chemical co-precipitation method and then used as an adsorbent for efficient removal of phosphate(V) ions from their aqueous solutions. From the scientific point of view, it represents a completely new physicochemical system. It was found that the adsorptive removal of phosphate(V) anions by the Ce-CTS adsorbent exceeded 98% efficiency which is ca. 4-times higher compared with the chitosan-based hydrogel without any modification (non-cross-linked CTS). The best result of the adsorption capacity of phosphates(V) on the Ce-CTS adsorbent, equal to 71.6 mg/g, was a result of adsorption from a solution with an initial phosphate(V) concentration 9.76 mg/dm3 and pH 7, an adsorbent dose of 1 g/dm3, temperature 20 °C. The equilibrium interphase distribution data for the Ce-CTS adsorbent and aqueous solution of phosphates(V) agreed with the theoretical Redlich-Peterson and Hill adsorption isotherm models. From the kinetic point of view, the pseudo-second-order model explained the phosphates(V) adsorption rate for Ce-CTS adsorbent the best. The specific effect of porous structure of adsorbent influencing the diffusional mass transfer resistances was identified using Weber-Morris kinetic model. The thermodynamic study showed that the process was exothermic and the adsorption ran spontaneously. Modification of CTS with cerium(IV) resulted in the significant enhancement of the chitosan properties towards both physical adsorption (an increase of the point of zero charge of adsorbent), and chemical adsorption (through the presence of Ce(IV) that demonstrates a chemical affinity for phosphate(V) anions). The elaborated and experimentally verified highly effective adsorbent can be successfully applied to uptake phosphates(V) from aqueous systems. The Ce-CTS adsorbent is stable in the conditions of the adsorption process, no changes in the adsorbent structure or leaching of the inorganic filling were observed.

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Strong adhesion and cohesion of chitosan in aqueous solutions.

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Strong adhesion and cohesion of chitosan in aqueous solutions.

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