In-situ growth of MOF-199 on multiple crosslinked sodium alginate aerogels with high efficiency and selective adsorption performance

Abstract

The design and preparation of environmentally-friendly and efficient adsorbents are of crucial importance in the treatment of dyes-containing wastewater. In this study, to improve the water stability of alginate (SA) aerogel, the multi-crosslinking strategy was put forward, where Ca²⁺, polyaniline (PANI) and chitosan (CTS) acted as the “crosslinkers” to connect, reinforce and stabilize the network of the adsorbents through multiple interactions. And then metal organic framework (MOF) material MOF-199 was in-situ grown onto the aerogel adsorbents by the layer-by-layer method to solve the problems of MOF material applied alone in the adsorption field of dispersion and collection after use. The prepared aerogel adsorbents were characterized and applied to enrich cationic dye methylene blue (MB) from aqueous solution. The results showed that the adsorption process conformed to pseudo-second-order kinetics and Langmuir isotherm. The aerogel adsorbents could selectively enrich cationic dyes like MB in the presence of anionic dyes, and adsorption efficiencies all remained above 94% after five adsorption-desorption cycles. Adsorption mechanism included electrostatic attraction, π-π stacking, p-π coordination and hydrogen bonding in the adsorption process, which were characterized by FTIR and XPS spectra before and after adsorption. The aerogel adsorbents with special properties of facile preparation, excellent regeneration ability, high adsorption efficiency and adsorption selectivity for cationic dye, offered a valuable reference for the efficient removal of cationic dyes from wastewater.