Chitosan-tripolyphosphate-tannic acid cryogels as a biocompatible adsorbent for the removal of Cu2+ ions

A chitosan (CH) cryogel is a supermacropore material that can be used as an adsorbent. However, its utilization as a metal adsorbent is limited due to its low stability in acidic conditions. A CH cryogel has been modified using tripolyphosphate (TPP) and tannic acid (TA) as biocompatible cross-linke...

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Main Authors: Jaya Hardi, Tristan Tijsseling, Hayato Takase, Masahiro Yoshida, Koichiro Shiomori, Hideki Matsune
Format: Article
Language:English
Published: The Royal Society 2025-08-01
Series:Royal Society Open Science
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Online Access:https://royalsocietypublishing.org/doi/10.1098/rsos.242274
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Summary:A chitosan (CH) cryogel is a supermacropore material that can be used as an adsorbent. However, its utilization as a metal adsorbent is limited due to its low stability in acidic conditions. A CH cryogel has been modified using tripolyphosphate (TPP) and tannic acid (TA) as biocompatible cross-linkers. TPP increases the stability of the cryogels in acidic solutions, and TA increases their mechanical properties. CH-TPP, CH-TPP2.5-TA, CH-TPP5-TA and CH-TPP7.5-TA cryogels were applied for the adsorption of Cu2+ ions. The CH-TPP-TA cryogels reached optimum conditions at pH 5.0 with a removal efficiency of 91–96%. The adsorption of Cu2+ ions by CH-TPP-TA cryogels fits the nonlinear Freundlich isotherm, or Cu2+ is adsorbed on the heterogeneous cryogels’ surfaces. CH-TPP5-TA has an adsorption capacity up to 109 mg g−1 at an initial Cu2+ concentration of 500 mg l−1. The adsorption kinetics of Cu2+ ions follows pseudo-second order. It is interpreted that the adsorption mechanism is generally through chemical interactions. Copper elements are proven to be adsorbed by the cryogel, which is detected by energy-dispersive X-ray analysis. The photographic results show that Cu2+ ions can be adsorbed into the inner layer of the cryogel. Finally, the CH-TPP-TA cryogel is promising to be used as a biocompatible adsorbent for copper.
ISSN:2054-5703