Self-cleaning and multi-active sites amphoteric composite sponges: Efficient removal, selective adsorption and photocatalyst substrates of dyes

To address the complex dyeing wastewater containing oil pollution and bacterial microorganisms in practical environments, in this work, amphoteric (CHI/ALG) C/A composite sponges with self-cleaning and multi-active sites were prepared by composite chitosan (CHI) and alginate (ALG) using urea/alkali composite solutions. The C/A composite sponges have good water wettability and demonstrated underwater anti-oil and anti-bacterial microbial adhesion. The adsorption process was spontaneous entropy-increasing and could be accurately described using the Pseudo-First-Order and Langmuir models. Notably, the adsorption capacity of C/A composite sponges for methylene blue and acid blue dye reached 656.33 mg/g and 502.49 mg/g, respectively. The amphoteric C/A composite sponges can selectively adsorb both anionic and cationic dyes. Additionally, epichlorohydrin (ECH) cross-linking and intermolecular self-assembly molding enabled the C/A composite sponges to form a three-dimensional network structure with nanofiber weaving and a specific surface area of 67.63 m2/g. Interestingly, this endowed the C/A composite sponges with the potential to serve as dyes photocatalyst substrates, and the photocatalytic degradation of dyes was successfully achieved by loading TiO2 on the C/A composite sponges. More importantly, the C/A composite sponge remained self-cleaning after loading TiO2. The amphoteric C/A composite sponges have great potential in complex dyeing wastewater treatment containing oil and bacterial microbes.