Cascaded uptake of toxic metal ions and catalytic hydrogenation of dyes on a superabsorbent soy protein isolate/polyacrylamide aerogel

Developing advanced materials with excellent metal binding and mechanical properties is invariably challenging but of enormous significance in environmental remediation applications. Herein, aiming to achieve metal chelator-like coordination property with excellent mechanical robustness in a novel adsorbent, we developed a soy protein isolate (SPI)/polyacrylamide (PAM) aerogel via a facile synthetic strategy for efficient uptake of lead (Pb²⁺) and copper (Cu²⁺) from sewages. The grafting of PAM on the SPI network facilitated multiple surface-active sites, porous structure, and high strength, which eventually resulted in enhanced Pb²⁺ and Cu²⁺ uptake capacity. The maximum Pb²⁺ and Cu²⁺ uptake values of the SPI/PAM were ∼277.7 and ∼232.5 mg/g, respectively, which could be modelled using the Langmuir isotherm and pseudo-second-order rate equation. The in-depth binding mechanism interpretation disclosed that chelation and electrostatic attractions predominated the efficient metal ions uptake. Furthermore, cascaded reduction of complexed Cu²⁺ with SPI/PAM yielded Cu nanoparticles (NPs)-embedded aerogel which revealed ultra-rapid catalytic performance for the hydrogenation of organic dyes, i.e., Rhodamine B, methylene blue, and methyl orange (rate constant values: 0.54, 0.33, and 0.80 min⁻¹, respectively). The green and facile synthetic approach, excellent cascaded metal ions uptake and catalytic dyes reduction properties (with high-performance reusability up to four cycles) show great promise to the SPI/PAM aerogel in appealing application concept for the remediation of complex wastewater.