Dual cross-linked alginate/lignosulfonate—based aerogel with robust flame retardancy and antibacterial property

In modern society, with the rapid increase in energy consumption, there is a growing interest in the effective utilization of bio-resources. Biomass aerogels have considerable academic research value due to their eco-friendly attributes and renewable nature. In this work, sodium alginate (SA) and sodium lignosulfonate (SLS) are employed as the matrix, which are dually cross-linked with Ca²⁺ and bis[tetrakis(hydroxymethyl)phosphonium] sulfate (THPS). Subsequently, a well-formed aerogel (CA-SP) is obtained through the lyophilization process. The formed dual crosslinking network and the “egg-box” structure endow the CA-SP aerogel with superior flame retardancy and thermal insulation properties, as evidenced by a limiting oxygen index value of 40.8%, achievement of the UL94 V-0 rating and low total heat release (1.35 MJ·m⁻²). Moreover, the THPS simultaneously endows the SA-SP aerogel with excellent flame retardancy and antimicrobial effect. The exceptional flame retardancy, smoke suppression capabilities, and antimicrobial effects of the CA-SP aerogel expand its prospects for application.