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. [ABSTRACT FROM AUTHOR]