Synthesis of montmorillonite/chitosan/ammonium acrylate composite and its potential application in river water flocculation

Abstract

Composites based on montmorillonite/chitosan-grafted-ammonium polyacrylate (MMT/CS-g-APA) were synthesized by gamma irradiation (3–7 kGy) induced polymerization. The composites were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric analysis (TGA), dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). FTIR results revealed the emergence of vibrational bands in the range of 1622 to 1606 cm−1 in the composites spectra indicating the grafting of APA to CS. The shift in the MMT band at 1030 cm−1 to lower wavenumber indicated a strong interchelation interaction in the composite. XRD results showed a shift in the MMT diffraction peak from 2θ = 7° to 5.3° with an increased interplanar spacing from 13.36 Å to 16.61 Å, which indicated the interchelated-exfoliated nanostructure of MMT by CS-APA chains. The thermal stability of the composite increased at lower irradiation dose and higher content of APA. TEM images indicated that MMT particles were completely covered with CS-g-APA matrix and the DLS revealed the swelling of the composite particles. SEM showed the imperfect microsphere morphology of the composite due to the soft nature of CS-g-APA. The flocculation performance of the composites on river water was tested by jar test and compared with alum. The composite prepared with equal ratios of CS and APA and irradiated at 3 kGy approached the flocculation efficiency of alum with a remaining turbidity % of 9 and 8% for the composite and alum respectively. Furthermore, the composite was used for the removal of methylene blue (MB) from water. A dose of 20 mg/50 ml of the composite was sufficient to completely remove MB from a solution with an initial concentration of 50 mg/l.