Bio-based 3D dendritic silica nanosphere: A green superior adsorbent

The method of extracting silica from herbal resources is a new environmentally friendly approach to the preparation of nanoporous silica materials that involves lower costs compared to the conventional industrial method of extracting from natural quartz. Sedge (Carex riparia) is a widespread agricultural waste that grows naturally in many parts of the world. The extractable herbal amorphous silica in Sedge can makes it a good candidate as an alternative for current industrial resources of silica. Accordingly, for the first time, a novel kind of bio-based three-dimensional dendritic multi-organo-functionalized (amine, thiol, and carboxyl) silica nanospheres (denoted as 3D DMF-SNSs) with hierarchical bimodal micro-mesoporous channel structure and uniform monodispersed morphology has been successfully synthesized via an environmentally friendly approach. Due to their unique structural and morphological properties such as large surface area (601 m2 g-1), high pore volume (0.99 cm3 g-1), abundant active functional groups, and dendritic bimodal micro-mesoporous channels, 3D DMF-SNS nanoparticles show great potential for use as an adsorbent. Accordingly, in this work, systematic adsorption studies toward the simultaneous removal of chrysoidine G and thallium (I) by the 3D DMF-SNS from aqueous solutions were carried out. Isotherm, kinetic, thermodynamic, and adsorption-desorption investigations were performed and the calculated Langmuir maximum adsorption capacity of chrysoidine G and thallium (I) were calculated to be 880.6 mg g-1 and 806.7 mg g-1, respectively, under optimal conditions (pH = 7.0, adsorbent dose = 0.05 g L-1, contact time = 14 min for chrysoidine G and 20 min for thallium (I), solution temperature = 293 K). Regeneration studies were carried out in ten consecutive adsorption-desorption cycles at 293 K and it was found that the experimental adsorption capacities for chrysoidine G and thallium (I) were decreased to 745 and 660 mg g-1, respectively, indicating the stability of the adsorbent and its excellent adsorption performance even after using it in ten consecutive cycles for simultaneous adsorption of the adsorbates.