Frontal polymerization synthesizing super-absorbent cellulose nanocrystal-reinforced hydrogel towards dye adsorption...

Amid the continuously increasing global demand for environmental protection, the development of high-efficiency adsorbents for the removal of organic dyes from wastewater has drawn significant scientific and industrial attention. Herein, a novel cellulose nanocrystal (CNC) reinforced poly(2-methacryloyloxyethyl-trimethyl ammonium chloride-co-acrylamide) (poly(DMC-co-AM)) hydrogel adsorbent is synthesized by frontal polymerization (FP) technique in a rapid, environmentally friendly and controllable manner. The FP process parameters, along with the microstructure and macroscopic performance of the fabricated adsorbents, are comprehensively investigated. The adsorbent with a typical porous structure presents adequate mechanical strength (230 kPa), mechanical stability, superb swelling ability (11622%) and adsorption properties. Notably, the addition of CNC improves all the aforementioned performances. Additionally, the alizarin red is employed as a model anionic dye to verify the adsorption capability of adsorbent. Adsorption parameters, adsorption isotherms, adsorption kinetics, adsorption thermodynamics are thoroughly researched to optimize the adsorption conditions and clarify the underlying adsorption mechanism. It is worth noting that the adsorption displayed high effectiveness over a broad pH range from 1 to 10. The addition of CNC significantly enhanced the adsorption efficiency, especially in an alkaline environment. The maximum adsorption capacity determined by the Langmuir isotherm model is 835.7 mg/g (298 K). The adsorption process is well characterized by pseudo-second-order kinetic model. Thermodynamic evaluation reveals that the adsorption proceeds spontaneously and exothermically. This study offers a cost-effective, high-efficiency, environmentally friendly, and highly feasible approach for dealing with industrial wastewater and protecting the environment.