Green synthesis of porous polyvinyl alcohol membranes functionalized with L-arginine and their application in the removal of 4-nitrophenol from aqueous solution Thanitporn Narkkun, 1 Patharawadee Boonying, 1 Chalad Yuenyao, 2,3 Sittipong Amnuaypanich 1,2 1 Applied Chemistry Division, Department of Chemistry and Center of Excellence for Innovation in Chemistry, (PERCH-CIC), Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand 2 Materials Chemistry Research Center, Faculty of Science, Khon Kaen University, Khon Kaen 40002, Thailand 3 Department of Physics, Faculty of Science and Technology, Phetchabun Rajabhat University, Phetchabun 67000, Thailand Correspondence to: S. Amnuaypanich (E-mail: asitti@kku.ac.th) ABSTRACT: Green and single-step synthesis of porous poly(vinyl alcohol) membrane functionalized with L-arginine (PVA-g-Arg) is pres- ented. Crosslinking, L-arginine functionalization and pore forming occurred simultaneously by a thermally induced process without using a crosslinker or an initiator. As-synthesized PVA-g-Arg membranes possessed a porous structure with an average pore size of 32–56 μm depending on the amount of L-arginine. The PVA-g-Arg were utilized as adsorbent membranes for the removal of 4-nitrophenol (4-NP) from aqueous solutions and demonstrated higher adsorption capacity than that of the unmodified PVA porous membrane. The pseudo-second-order described satisfactorily the kinetic adsorption of 4-NP by the membranes while the isotherms followed both the Langmuir and Freundlich models. The negative values of ΔG  and thermodynamic parameters confirmed that the adsorption of 4-NP by the PVA-g-Arg membranes was spontaneous and exothermic. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47835. KEYWORDS: adsorption; L-arginine; membranes; nitrophenols; polyvinyl alcohol Received 10 October 2018; accepted 28 March 2019 DOI: 10.1002/app.47835 INTRODUCTION 4-Nitrophenol is one of nitrophenolic compounds used mostly in the pharmaceutical and pesticides industries. 1,2 Since 4-NP is water soluble and toxic, once contaminated into an effluent, it can easily spread, pollute natural water resources and harm marine lifes. 3 4-NP has been listed as the priority pollutants by the U.S. Environmental Protection Agency because of high toxic- ity to humans, animals, and wildlife even at low concentrations. 4 The release and transfer of this chemical from the industries are, therefore, controlled by the code of federal regulation that allows a maximum of 576 μgL -1 for daily 4-NP discharge. 5 A simple and cost-effective for a removal of nitrophenols from contami- nated water is adsorption. Carbonaceous adsorbents such as acti- vated carbon, carbon fibers, and carbon nanotubes have been widely utilized due to their ability to remove aromatic compounds in water and wastewater. 6–8 However, the syntheses of these carbo- naceous adsorbents involve a multistep and energy-intensive pro- cess under harsh conditions. 9,10 Alternatively, adsorbents for nitrophenols adsorption have been developed from polymers which possess a vast variety of functional groups leading to a tai- loring of the adsorbent properties. Moreover, polymer-based adsorbents provide an easy processability into different forms all- owing convenient handling and an ease of regeneration. 11,12 Polymers with hydrophilic property such as polyacrylonitrile, starch, cellulose, and poly(vinyl alcohol) (PVA) have been effec- tively applied for the removal of nitrophenols from aqueous solutions. 13–16 PVA is of particular interest owing to its excellent hydrophilicity, nontoxicity, and high chemical stability. 17–19 PVA can easily be crosslinked via chemical or physical routes resulting in a network-structure gel capable of absorbing a large amount of water, usually more than a 100% of its dry weight. 20,21 Crosslinked PVA, therefore, is suitably utilized for remediation of polluted water. Unfortunately, PVA contains mostly the hydroxyl group thus pro- viding only weak interaction with nitrophenols. To enhance an adsorption capacity of nitrophenols, PVA is essentially modified with nitrophenol-attractive functional groups. Amine is effective functional group offering strong interactions with nitrophenols via H-bonding 22,23 and can be incorporated with PVA by various © 2019 Wiley Periodicals, Inc. 47835 (1 of 11) J. APPL. POLYM. SCI. 2019, DOI: 10.1002/APP.47835