Chlamydomonas angulosa (green alga) and Nostoc commune (blue-green alga) microalgae-cellulose composite aerogel beads: Manufacture, physicochemical characterization, and Cd (II) adsorption

This study presents composite aerogel beads prepared by mixing dissolved cellulose with Chlamydomonas angulosa and Nostoc commune cells, respectively, at 0.1, 0.3, and 0.5% (w/w). The manufactured composites (termed regenerated cellulose (RC)), with C. angulosa (RCCA-(1, 3, and 5)), and with N. commune (RCNC-(1, 3, and 5)) were analyzed. Both RCCA-5 and RCNC-5 showed the high specific surface area to be about 261.3 and 332.8 m²·g^-1. In the microstructure analysis, network structures were observed in the cross-sections of RC, RCCA-5, and RCNC-5. The pyrolysis temperature of the RCCA-5 and RCNC-5 composite aerogel beads was rapidly increased about 250 °C during the mixing of cellulose with C. angulosa and N. commune. The chemical analysis of RC, RCCA-5, and RCNC-5 showed peaks corresponding to various functional groups, such as amide, carboxyl, and hydroxyl groups from protein, lipid, and carbohydrate. RCNC-5 at pH 6 demonstrated highest Cd²⁺ removal rate about 90.3%, 82.1%, and 63.1% at 10, 25, and 50 ppm Cd²⁺, respectively. At pH 6, Cd²⁺ adsorption rates per unit weight of the RCNC-5 were about 0.9025, 2.0514, and 3.1547 mg/g at 10, 25, and 50 ppm, respectively. The peaks assigned to the amide, carboxyl, and hydroxyl groups in RCCA-5, RCNC-5, and RC were shifted or disappeared immediately after adsorption of Cd²⁺. The specific surface area, total pore volume, and mean pore diameter of composites was decreased due to adsorption of Cd²⁺ on the developed materials. As can be seen in the X-ray powder diffraction (XRD) spectrum, significant changes in the molecular structure of the composite aerogel beads were not observed even after adsorption of Cd²⁺.