Environmentally friendly starch/alginate aerogels for copper adsorption from aqueous media. A microstructural and kinetic study

Abstract

This work investigated the synthesis and characterization of alginate/starch porous materials and their application as copper ions adsorbents from aqueous media. Initially, pregel aqueous solutions with different biopolymer concentrations (1, 3, and 5% w/w) and alginate contents (25, 50, and 75% w/w) were prepared. Hydrogel formation was performed by internal and external gelation methods. Finally, the drying step was done via CO₂^sc leading to aerogels and via freeze-drying leading to cryogels. Process parameters influence on the final properties of materials was evaluated by BET isotherms, SEM, EDS, and TGA. Regardless the gelation method applied, interesting materials with meso- and macro-pore structure were prepared from pregel mixtures with 3% w/w biopolymer concentration and an alginate content of only 25% w/w. Low alginate content reduces the final cost of the materials. Concerning copper removal, the adsorption data were well fitted to the pseudo-second order kinetic model for aerogels and cryogels, showing aerogels the highest adsorption capacity (40 mg/g) and removal efficiency (∼ 92%). Materials demonstrated excellent reusability throughout five consecutive adsorption/desorption cycles. Hence, environmentally friendly materials with a high practical value as low-cost bioadsorbents were synthesized, having great performance in the removal of copper ions from aqueous solution.

Keywords:

• Alginate and starch composite materials
• polysaccharides
• aerogels and cryogels
• supercritical drying
• freeze-drying
• metal cations adsorption
• reusable adsorbents
• remediation
• contaminant
• heavy metals

Disclosure statement

The authors declare no conflicts of interest associated with this publication and that the financial support for this work has not influenced the results and/or discussion reported in this paper. Moreover, all the material is original and owned by the authors and no permissions are required.

Availability of data and materials

The supporting data of this study are available from the corresponding author upon reasonable request.

Additional information

Funding

The authors would like to thank the Universidad Nacional del Sur (UNS) (PGI 24/M154 and 24/M177) and the Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) for their financial support.