Research Article Adsorption of Malachite Green Dye from Liquid Phase Using Hydrophilic Thiourea-Modified Poly(acrylonitrile-co-acrylic acid): Kinetic and Isotherm Studies Abel A. Adeyi , 1,2 Siti N. A. M. Jamil , 3 Luqman C. Abdullah , 1 and Thomas S. Y. Choong 1 1 Department of Chemical and Environmental Engineering, Faculty of Engineering, Universiti Putra Malaysia (UPM), Serdang 43400, Malaysia 2 Department of Chemical and Petroleum Engineering, College of Engineering, Afe Babalola University Ado-Ekiti (ABUAD), PMB 5454, Ekiti State, Nigeria 3 Department of Chemistry, Faculty of Science, Universiti Putra Malaysia (UPM), Serdang 43400, Malaysia Correspondence should be addressed to Siti N. A. M. Jamil; ctnurulain@upm.edu.my Received 3 September 2018; Accepted 19 December 2018; Published 3 February 2019 Academic Editor: Frederic Dumur Copyright © 2019 Abel A. Adeyi et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. iourea-modiﬁed poly(acrylonitrile-co-acrylic acid) (TU-poly(AN-co-AA)) adsorbent was a surface modiﬁcation of poly(- acrylonitrile-co-acrylic acid) synthesized by facile redox polymerization. Surface functionalization with thiourea was carried out to provide hydrophilicity on the surface of a polymeric adsorbent. Fourier transform infrared (FTIR) spectrometer, scanning electron microscope (SEM), and Zetasizer characterized the morphology and structures of TU-poly(AN-co-AA). Co- polymerization of poly(acrylonitrile-co-acrylic acid) and its successful incorporation of the thioamide group was conﬁrmed by the FTIR spectra. e SEM micrographs depicted uniform and porous surface morphologies of polymeric particles. e average diameter of modiﬁed and unmodiﬁed poly(acrylonitrile-co-acrylic acid) was 289 nm and 279 nm, respectively. Zeta potentials of TU-poly(AN-co-AA) revealed the negatively charged surface of the prepared polymer. Adsorption capacities of hydrophilic TU- poly(AN-co-AA) were investigated using malachite green (MG) as an adsorbate by varying experimental conditions (pH, initial concentration, and temperature). Results showed that the pseudo-second-order reaction model best described the adsorption process with chemisorption being the rate-limiting step. Furthermore, Elovich and intraparticle diﬀusions play a signiﬁcant role in adsorption kinetics. e equilibrium isotherm has its ﬁtness in the following order: Freundlich model > Temkin mod- el > Langmuir model. ermodynamic analysis indicates that the sorption process is spontaneous and exothermic in nature. e reusability results suggested potential applications of the TU-poly(AN-co-AA) polymer in adsorption and separation of cationic malachite green dye from wastewater. 1. Introduction e treatment of dye bearing industrial wastewater is a global environmental challenge faced by government agencies and scientiﬁc community. is is due to adverse eﬀects on environment and human beings [1, 2]. Presence of dyes in waterbodies pollute natural habitat and constitute health problems because they are not biodegradable and complex by nature [3, 4]. Malachite green (MG) dye is not only used in textile, paper, rubber, and leather industries for product colouring but equally used as antiprotozoan, fungicide in ﬁshery, and medical disinfectant. Research however showed that MG is harmful to freshwater animals in acute and chronic exposure [5]. It is highly toxic to mammalian cells and organs like liver, kidney, lung, spleen, and skin [6, 7]. erefore, it is imperative to eliminate dyestuﬀ from coloured wastewater for environmental safety and health beneﬁts. Adsorption [8], photocatalytic degradation [9], bio- degradation [10], and chemical oxidation [11] are devel- oped physical and chemical treatment/puriﬁcation methods to remove dye from wastewater. Adsorption stands out Hindawi Journal of Chemistry Volume 2019, Article ID 4321475, 14 pages https://doi.org/10.1155/2019/4321475