Cationic hydrogel with carbon quantum dots: synthesis and methyl orange adsorption capacity

Methyl orange is one of the most commonly used acidic/anionic dyes, and its removal from wastewater is imperative to ensure environmental sustainability. This study developed a novel cationic CQDs/AM/DMC hydrogel using acrylamide (AM) and methylacryloxyethyl trimethyl ammonium chloride (DMC) as main materials, incorporating carbon quantum dots (CQDs). The hydrogel was comprehensively characterized for morphological features, chemical composition and fluorescence characteristics using FTIR, TEM, SEM, PL and XRD analyses. Moreover, as an adsorbent, the hydrogel effectively removed methyl orange (MO) dye from aqueous solutions. Notably, the CQDs/AM/DMC hydrogel exhibited a maximum adsorption capacity of 298.93 mg/g within 30 min, surpassing that of AM/DMC hydrogel (268.29 mg/g within 50 min) in 50 mg/L MO solution. The Langmuir isotherm and pseudo-second-order models had the best agreement with the experimental data, highlighting monolayer and chemical adsorption as the predominant mechanism governing dye uptake. This study contributes valuable insights into the development of an efficient adsorbent for the removal of hazardous materials from wastewater.