Microwave-Assisted Soft Method for Synthesis of Poly (Acrylic Acid)/Organo-clay Composites: Application As Superabsorbent For Phenol and Cr (VI)

A series of superabsorbent composites (PAA/HDTMA-MMT) based on poly (acrylic acid) (PAA) and different content of organo-modified natural clay HDTMA-MMT (1,3 and 5 wt.%) were synthesized via in-situ radical polymerization using microwave method. This eco-friendly route was chosen to avoid the use of toxic solvents and reduce polymerization time. In addition, it can be considered an efficient approach for industrial-scale polymer synthesis. The microstructure of the obtained hydrogels was evidenced by Fourier transformation infrared spectroscopy (FTIR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). Thermal stability was examined according to nano-filler content on the matrix. The composite (PAA/HDTMA-MMT) at 3 wt % exhibits an important swelling capacity value (833.33 g g-1). The efficiency of the synthesized hydrogel composites for phenol and Cr (VI) uptakes from aqueous solutions was studied in batch experiments. The main reason for their selection is their remarkable industrial use, despite their high toxicity and persistence in the environment. In order to underline the mechanism of the phenol and Cr (VI) adsorptions on the (PAA/HDTMA-MMT), respectively, the zeta potential of the hydrogel was evaluated. Maximum adsorption capacity values of 170.7 mg g-1 and 197.3 mg g-1 were screened for phenol and Cr(VI), respectively. The adsorption process concurs with pseudo-second-order kinetics and with the Langmuir isotherm equation. A very high adsorption capacity (qmax=225.2 mg g-1) and a correlation coefficient of 0.998 calculated from isotherm equations show the high efficiency of the adsorbent and thus expected to be a good adsorbent candidate for wastewater treatment. The thermodynamic studies evidenced the exothermic character of the adsorption reactions of the studied pollutants. Polyacrylic acid/ organomodified clay composites with different content in inorganics were prepared through microwave-assisted route, using KPS as an initiator and MBA as crosslinker. This eco-friendly and low-cost method leads to a porous composites' morphology, as evidenced by SEM characterizations. The composite PAA/HDTMA-MMT3 exhibits important efficiency to uptake persistent organic pollutants, such as phenol derivatives (Qe=170.7 mg g-1) and heavy metal ions like Chrome (VI) (197.3 mg g-1). The composite exhibits thermal stability, with enhancement of the Cr (VI) uptake by increasing temperature solution.image