A new magnetic β-cyclodextrin polyurethane nanocomposite for the removal of organic pollutants in wastewater

Abstract

Herein, we report the synthesis of a new thermally stable magnetic polyurethane nanocomposite (MPUNc) (14) containing azobenzene moiety and β-cyclodextrin (β-CD) and its application in removing some organic pollutants from water. First, 4,4′-azodibenzene dicarboxylic acid (2) was synthesized and then it was converted to 4,4′-azodibenzene diacyl azide (3). MPUNc (14) was synthesized by grafting magnetic nanoparticles (MNPs) (11) onto β-CD-AzoPU (10). The properties of the MPUNc (14) were characterized by FTIR, 1H NMR, XRD, SEM, EDX, VSM, and TGA. By adding MPUNc (14) to PVA, the stress–strain curves of the resulting blend showed a ductile fracture due to the digressing toughness of PVA. The magnetic saturation (Ms) values demonstrated that the magnetic property of Fe3O4 was reduced when coated by SiO2. The TGA thermogram of MPUNc (14) showed a 10% weight loss below 300 °C. In addition, the weight loss of about 33% between 350 and 750 °C was due to the chemical decomposition of β-CD-AzoPU (10) and EPO moieties. Thus, the results showed that the grafted β-CD-AzoPUs (10) to MNPs (11) had a density of about 18%. The MPUNc (14) was used as a new absorbent to remove 4-chlorophenol (4-CP) and 4-nitrophenol (4-NP) from water. Besides, the effects of pH, time, temperature, and the absorbent dosage on the adsorption ability were studied. The results showed that the pH and the adsorbent dosage had a key role in removing 94% of the 4-NP and 91.3% of 4-CP at the optimized pH of 3 using 50 mg of the sorbent.