Multilayer films of graphene oxide and polymeric microgels: reusable adsorbents

Graphene oxide (GO) has arisen as an effective adsorbent for water treatment owing to its high removal efficiency for water pollutants. However, separating GO adsorbents from the pollutant solution is difficult after adsorption. The GO adsorbents are unsuitable for various dyes, and can only remove cationic dyes from an aqueous solution. To address these issues, this study utilized a simple and cost-effective layer-by-layer assembly technique to deposit multilayer films onto solid substrates. These films were composed of poly(allylamine hydrochloride)–dextran (PAHD) microgels and GO, and were designed to be highly effective while remaining affordable. The PAHD/GO multilayer films obtained produced an effortless separation process and demonstrated exceptional adsorption capabilities for cationic, anionic and non-ionic dyes. Specifically, the adsorption capacities for carmine and mulberry red were notably high, measuring 337.4 and 417.7 mg g−1, respectively. In addition, the PAHD/GO multilayer films could be regenerated well in sodium chloride solution without obvious compromise of removal efficiency. The adsorption kinetics, isotherms and thermodynamics of dyes on the PAHD/GO multilayer films were also studied. Thanks to the straightforward manufacturing process and outstanding adsorption capabilities of PAHD/GO multilayer films, this study presents a significant opportunity to advance the practical application of GO in water treatment.