Constructing carboxylated cellulose nanofibers/chitosan aerogel loading with CdS/UiO-66-NH2 for wastewater treatment: Synergistic adsorption and visible light photocatalytic degradation

Abstract

The discharge of industrial effluents containing heavy metal ions and organic dyes has laid heavy burdens on ecosystem, meanwhile, drawing extensive scientific attention globally. In this work, CdS/UiO-66-NH₂ heterojunction was uniformly loading on the aerogel skeleton composed of cellulose (CNF), chitosan (CS) and montmorillonite (MMT). The fabricated composite aerogel noted as CUN-CCMA was equipped with light density, a large specific area and a robust three-dimensional interpenetrating network. The MMT not only reinforced the mechanical stability of the aerogel, but also regulated the distribution of the heterojunction. The CUN-CCMA could adsorb various organic dyes and heavy metal ions, and the maximum adsorption capacities for methylene blue (MB) and Cu²⁺ were 111.5 mg/g and 45.1 mg/g, respectively. The corresponding adsorption processes were in better consistence with the pseudo-second-order kinetic model and the Freundlich isotherm. The hydrogen bonding, electrostatic interaction, π-π stacking and chelating effect might be attributed to the adsorption mechanism. Most importantly, the removal efficiency of MB with a high concentration of 300 mg/L could reach 94 % when synergistic effect of adsorption and visible light photocatalytic degradation was exerted. The active species that played vital roles during the photodegradation process were recognized as ·OH and $·O_2^{-}$. Furthermore, the CUN-CCMA demonstrated an excellent reusability. These outstanding characteristics of CUN-CCMA broadened its application prospects in complicated sewage treatment.