Insights into the p -nitrophenol adsorption by amidoxime-modified poly(acrylonitrile- co -acrylic acid): characterization, kinetics, isotherm, thermodynamic, regeneration and mechanism study.

This study performs an appraisal of the adsorptive capacity of amidoxime-modified poly(acrylonitrile- co -acrylic acid) or abbreviated as (AO-modified poly(AN- co -AA)) for the p -nitrophenol (PNP) adsorption, from aquatic environments via batch system. The AO-modified poly(AN- co -AA) polymer was developed with redox polymerization, and then altered by using hydroxylamine hydrochloride (HH). Tools used to describe the physicochemical and morphological characteristics of the AO-modified poly(AN- co -AA) were Fourier transform infrared (FTIR) spectroscopy, CHN elemental analysis, X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The adsorption kinetics were examined by pseudo-first order, pseudo-second order, Elovich and intraparticle diffusion kinetic models. Meanwhile, the isotherms were investigated by Langmuir, Freundlich, Temkin and Redlich-Peterson models. It was found that the adsorption was best fitted with pseudo-second order, and agreed with both Langmuir and Freundlich isotherm models. It was described best with the Freundlich isotherm due to highest R 2 (0.999). The maximum adsorption capacity was 143.06 mg g -1 at 298 K, and thermodynamic functions showed that the adsorption process was exothermic. Also, following five regeneration cycles, the adsorbent recorded 71.7% regeneration efficiency. The finding in this study indicates that the AO-modified poly(AN- co -AA) is an effective adsorbent to remove PNP from an aqueous solution.