Synthesis of magnetic carboxymethyl chitosan-g-poly(acrylamide)/laponite RD nanocomposites with enhanced dye adsorption capacity

Abstract

This investigation reports the synthesis of magnetic nanocomposite hydrogels based on carboxymethyl chitosan-g-poly(acrylamide) (CMC-g-PAAm). The magnetic nanoparticles were prepared via in situ co-precipitation of iron salts in the presence of laponite RD nanoclay. Different contents of magnetic nanoclay were utilized to prepare magnetic CMC-g-PAAm nanocomposites. The structure of nanocomposite hydrogels was characterized by transmittance electron microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and vibrating sample magnetometer techniques. The obtained magnetic nanocomposites were examined to remove crystal violet (CV) cationic dye from aqueous solutions. By introducing magnetic laponite RD, the nanocomposites showed an enhanced adsorption capacity for CV dye. Equilibrium adsorption data were modeled according to Langmuir and Freundlich isotherm models. The following experimental isotherm data from models was affected by the content of magnetic laponite RD. The maximum adsorption of crystal violet on magnetic nanocomposite hydrogels was 169 mg g -1 . In addition to high adsorption capacity of magnetic nanocomposites for CV, the regeneration of obtained adsorbents was effective and the corresponding nanocomposites may be considered as new candidate in the treatment of colored water.

Synthesis and characterization of magnetic amidoximated chitosan-g poly(polyacrylonitrile)/laponite RD nanocomposites with enhanced adsorption capacity for Cu$^{2+}$

“…The vibration stretching of Mg-O and the O-H bending vibration due to the adsorbed water in laponite can be confirmed by the bands at 465 cm −1 and 645 cm −1 , respectively. 23 The characteristic absorption band of laponite RD appeared in the magnetic laponite RD with slight absorption band shifting to lower frequencies. Due to over- lapping by the characteristic absorption band of nanoclay at around 466 cm −1 , the distinctive absorption bands of Fe-O in Fe 3 O 4 /laponite RD (450 and 470 cm −1 ) are not identifiable.…”

“…The procedure was done according to our previous work. 23 First, 1.5 wt% of laponite RD solution was prepared by dispersing 3 g of laponite RD in 200 mL of double distilled water. In order to disperse the clay homogeneously, the solution was kept under sonication for 10 min (operating frequency used in sonication was 50 kHz).…”

“…Additionally, combination of chitosan with cation exchanger clays such as montmorillonite, bentonite, rectorite, and zeolite can produce good adsorbents with high mechanical properties and high adsorption capacity for metal ions. 8,20−22 Based on the above discussion and our previous work, 23 we endeavored to prepare magnetic and amidoximated chitosan-g-polyacrylonitrile (ChitoPAN) copolymers as new adsorbents for adsorption Cu 2+ ions from aqueous solutions. In our previous work, we demonstrated that introducing magnetic laponite RD in carboxymethyl chitosan nanocomposites had a significant effect on the dye adsorption capacity of nanocomposites for cationic methylene blue dye.…”

“…The dye adsorption capacity of nanocomposites increased with increasing content of magnetic laponite RD. 23 Laponite RD is known as a biocompatible and silicate-based clay, with a high surface area of 370 m 2 /g. Therefore, magnetic nanoparticles were firstly immobilized on laponite RD nanoclay, and graft copolymerization of acrylonitrile on chitosan was performed in the presence of magnetic laponite RD nanoparticles.…”

Preparation of Chitin Composite Hydrogel for Dye-Contaminated Water Treatment

“…To further enhance the adsorption properties of hydrogel, inorganic adsorbents are incorporated into the hydrogel such as laponite [12], sepiolite [13], and halloysite nanotubes [14]. Attapulgite is a kind of hydrated octahedral layered magnesium aluminum silicate whose theoretical formula is (Al 2 Mg 2 ) Si 8 O 20 (OH) 2 (OH 2 ) 4 •4H 2 O. Attapulgite has rod-like morphology with diameter of 20 nm and length of several micrometers [15].…”