Enhanced adsorption of crystal violet from aqueous solution by polyethyleneimine-modified magnetic hydrogel nanocomposites

Magnetic hydrogels have huge potential environmental applications in the elimination of various noxious pollutants from the water system. Polyethyleneimine (PEI)-modified magnetic hydrogel nanocomposites (PEI-mHNCs) with three-dimensional networks were prepared based on poly (acrylamide-co-acrylic acid) and PEI-modified magnetic nanoparticle and used for the removal of crystal violet dye from aqueous solution. XRD results preliminarily confirmed the target structure of PEI-mHNCs without destroying the structure of magnetic nanoparticles during modification and radical polymerization. PEI-mHNCs had rough and uneven surface with many coarse porous and gap structure. PEI-mHNCs had crystal violet adsorption capacity of 198.5, 286.3 and 372.6 mg/g for initial dye concentration of 300, 500 and 700 mg/L, respectively. Dye absorption approached absorption equilibrium at 90 min and PEI-mHNCs had maximum dye absorption capacity at pH = 8. The adsorption isotherms and kinetics conformed to the Langmuir model and pseudo-second-order kinetic model, respectively. Thermodynamic studies revealed that crystal violet adsorption for PEI-mHNCs was a spontaneous, exothermal and decreased entropy process.Besides, PEI-mHNCs had good magnetic responsiveness, desorption and reusability which made it an efficient adsorbent for the removal of cationic dyes from an aqueous solution.

Automated summary

Magnetic hydrogels have great potential in environmental applications for removing pollutants from water. In this study, Polyethyleneimine (PEI)-modified magnetic hydrogel nanocomposites (PEI-mHNCs) were prepared and used for the removal of crystal violet dye from aqueous solution. The results showed that PEI-mHNCs had good adsorption capacity and magnetic responsiveness, making it an efficient adsorbent for cationic dyes in water.