Ultraviolet-Assisted synthesis of polyacrylamide-grafted chitosan nanoparticles and flocculation performance

In the present work, a new flocculant, polyacrylamide-grafted chitosan nanoparticles (NCS-g-PAM), was synthesized by the copolymerization of acrylamide (AM) and chitosan nanoparticle (NCS) under ultraviolet irradiation using 2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone as photo-initiator. The NCS was prepared by the ionic gelation between chitosan and sodium tripolyphosphate. The structure and morphology of NCS-g-PAM were characterized by Fourier Transform Infraredspectroscopy (FT-IR), X-ray diffraction, ¹H-nuclear magnetic resonance spectrometry, scanning electron microscopy, and thermogravimetric analysis. The factors affecting the intrinsic viscosity and the yield of copolymer were studied, which showed that the optimum conditions for the synthesis of NCS-g-PAM were m_AM:m_NCS = 8:1, 0.15 g of initiator dosage, m_CS:m_TPP = 4.5:1, 1 min of ultrasonication time, 4 h of illumination time, and 30 min of stirring time. The NCS-g-PAM was found to be more effective than NC-g-PAM in the flocculation of both kaolin suspension and Cu²⁺ simulated wastewater. With 5 mg/L of polyaluminium chloride (PAC) coordinated and 1 mg/L of NCS-g-PAM it was confirmed to be appropriate for flocculating kaolin suspension.