Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Preparation and characterization of organofunctionalized bentonite clay bearing aminophosphonic groups in heavy metal uptake Liudmyla Kostenko a , Olena Artiushenko b , Tatiana Kovalchuk a , Iryna Tomashchuk c , Vladimir Zaitsev b, ⁎ a Department of Chemistry, Taras Shevchenko National University of Kyiv, Lva Tolstoho Street 12, 01033 Kyiv, Ukraine b Department of Chemistry, Pontifcal Catholic University of Rio de Janeiro, Rua Marques de Sao Vicente, 225-Gavea, 22451-900 Rio de Janeiro, Brazil c Laboratoire Interdisciplinaire Carnot de Bourgogne, UMR 6303 CNRS/Université de Bourgogne - Franche Comté, 12 rue de la Fonderie, 71200 Le Creusot, France ARTICLEINFO Keywords: Bentonite Covalent immobilization Aminophosphonic acid Adsorption Water purifcation ABSTRACT Bentonite (Bnt) with covalently immobilized N-propylaminodi(methylenephosphonic) groups (Bnt-ADPA) was obtained through a two-step synthesis including aminosilanization and phosphorylation of resulting amino- bentonitethroughMoedritzer-Iranireaction.Thegraftingofanaminosilanelayerintheinterplanarspaceofthe bentonite was investigated by XRD, and the presence of N and P-containing groups was confrmed by FTIR, 31 P and 29 Si MAS NMR. The immobilization of the organic functional groups increased the interplanar distance in bentonite matrix at 52% that essentially improved fltration properties compared to raw bentonite. The number of surface acid groups was evaluated to 0.8mmol g −1 . The obtained adsorbent showed high afnity for heavy metalionsaccordingto pH 1/2 sequenceFe(III)(2.3)<Pb(II)(4.6)<Zn(II)(5.3)≈Cu(II)(5.8)<Cd(II)(6.7). The adsorption/desorption process on Bnt-ADPA is completely reversible and allows multiple uses of the ad- sorbent for water purifcation. The Bnt-ADPA was tested for the purifcation of water samples from the Lybid River(Kyiv,Ukraine).ItwasdemonstratedthatfltrationofwatersamplesthroughBnt-ADPA flterresultedina complete(>97%)eliminationofPb(II)andasignifcant(59–65%)decreaseoftheamountofCu(II)andZn(II). AccordingtotheX-rayfuorescenceanalysisofthe flter,Bnt-ADPAalsoretainedCa(II),Mn(II)andSr(II)ions. 1. Introduction Water quality is a vitally important issue in today’s world [1]. Heavy metal ions became one of the major water contamination pro- blems due to their high toxicity, non-biodegradable behavior, and ac- cumulation capacity. Many adsorbents have been developed for metal removal, however, the high cost of synthetic adsorbents is the main reason for a continuous search of new efective and afordable systems for selective water purifcation [2,3]. Among them, clay materials have been evaluated as environmentally compatible and inexpensive mate- rials, which can be easily obtained and regenerated [4–6]. Montmor- illonite(2:1layeredaluminosilicate)isoneofthemostinvestigatedclay and promising minerals in the feld of adsorption because of its high swelling capacity, hydrophilicity and easy tailoring [7]. The use of natural clay minerals for the uptake of metal ions in water purifcation has several limitations. Most importantly, the small particle size of natural clays can cause some difculties in water fl- tration [8]. Another limitation of the clays is their low adsorption se- lectivity. Ion-exchange mechanism of cations uptake on naturals clays cannot provide sufcient selectivity towards toxic metals [9]. Non- covalent immobilization of organic molecules enhances selectivity and elimination efciency towards toxic metals, making them suitable fora variety of environmental remediation applications [5,10–12]. Never- theless, the fxation of chemical modifers through the physical ad- sorption alone is associated with risk to pollute the treated water with leaching molecules of modifer. Covalent grafting of functional groups enables stable immobilization of organic layer and allows multiple re- generations. The previous studies on covalent modifcation of clays using various aminosilanes demonstrated efcient silanization (1.1- 1.5mmol g −1 of groups) associated with the crucial increase of the basal space [13–15]. These organoclays had higher selectivity and ad- sorption capacity for metal ions: Sr (II) [16], Hg (II) [17], Pb (II) [17,18], Cr (VI) [19], Cu (II) and Cd (II) [17,20]. Grafting of 3-mer- captopropyltrimethoxysilane allowed efcient removal of Ni (II) from industrial efuents [21]. The covalent modifcation of montmorillonite and kaolinite with EDTA-containing silane allowed efcient uptake of heavy metal cations from individual and mixed solutions [22]. Bi- functional organoclay with -SO 3 H and –NH 2 groups was used as a https://doi.org/10.1016/j.jece.2019.103434 Received 3 July 2019; Received in revised form 30 August 2019; Accepted 22 September 2019 ⁎ Corresponding author. E-mail address: vnzaitsev@puc-rio.br (V. Zaitsev). Journal of Environmental Chemical Engineering 7 (2019) 103434 Available online 24 September 2019 2213-3437/ © 2019 Elsevier Ltd. All rights reserved. T