Fabrication of physically multi-crosslinked sodium alginate/carboxylated-chitosan/montmorillonite-base aerogel modified by polyethyleneimine for the efficient adsorption of organic dye and Cu(II) contaminants

Efficient removal of contaminants, like heavy metal ions and dyes, from wastewater by eco-friendly and low-cost adsorbent is highly desirable. Herein, a green aerogel was prepared using sodium alginate/carboxylated chitosan/montmorillonite (MSC-P) as the basic framework, followed by polyethyleneimine functionalized and Ca2+ post-crosslinking. The multi-crosslinked aerogel exhibited the excellent adsorption capacity towards methylene blue (MB), Congo red (CR) and Cu(II), with the qm being 723.97 mg/g, 1573.21 mg/g and 203.99 mg/g, respectively. The mathematical model suggested that the adsorption process for MB fitted pseudo-first-order kinetics model better, whereas the CR and Cu (II)'s adsorption process were conformed to pseudo-second-order kinetics model. Moreover, the adsorption isotherm for three contaminants could be well described by Langmuir model, suggesting that the adsorption process was spontaneous and mainly controlled by monolayer coverage. Moreover, MSC-P aerogel exhibited good reusability as the removal efficiencies for MB and Cu(II) were 85.16 % and 51.4 % after ten cycles of adsorption–desorption, respectively. Importantly, it possessed considerable simultaneous removal ability for binary system mixed dyes. In combination of FTIR analyses, it was found that electrostatic attraction, hydrogen bonding, coordination and cation exchange were the main adsorption mechanisms involved. Therefore, the as-prepared aerogel can be considered as a promising adsorbent for the treatment of wastewater.