Abstract:

Using the self-assembled anionic surfactant sodium n-dodecyl sulfonate (SDS) micelles as porous templates, a novel porous chitosan-graft-poly(acrylic acid)/Na-montmorillonit (CS-g-PAA/Na-MMT) superabsorbent composite was successfully prepared by grafting copolymerization of chitosan (CS), acrylic acid (AA) and Na-montmorillonite(Na-MMT), using ammonium persulfate(APS) as the initiator and N,N'-methylenebisacrylamide (MBA) as the crosslinker. The mechanism for this reaction was proposed. Scanning electron microscope (SEM) analysis demonstrated that the morphologies of the SDS-added sample displays homogeneous and well-defined porous structures. Effect of SDS concentration on the equilibrium swelling ratio and swelling rate of the hydrogels were evaluated. The results show that the equilibrium swelling ratio of the 1.5 mmol/L SDS sample in distilled water and 0.9% mass fraction of NaCl solution are improved to 53.9% and 35.3%, respectively. Compared to the sample without SDS, the initial swelling rate constant, K_is, is also improved from 1.2652 g/(g·s) to 5.1680 g/(g·s). In addition, the porous structure can accelerate the adsorption rate for Pb²⁺, which reaches the 95% saturation adsorption capacity during the initial 10 min, and achieves adsorption equilibrium within 30 min.

Key words: chitosan, Na-montmorillonite, porous superabsorbent composite, swelling properties, Pb²⁺ absorption