Contents lists available at ScienceDirect Journal of Environmental Chemical Engineering journal homepage: www.elsevier.com/locate/jece Mitigation of clofibric acid pollution by adsorption: A review of recent developments Joshua O. Ighalo a, *, Oluwaseun Jacob Ajala b, *, Great Umenweke c , Samuel Ogunniyi a , Comfort Abidemi Adeyanju a , Chinenye Adaobi Igwegbe d , Adewale George Adeniyi a a Department of Chemical Engineering, University of Ilorin, Ilorin, Nigeria b Department of Industrial Chemistry, University of Ilorin, Ilorin, Nigeria c Department of Chemical Engineering, University of Abuja, Abuja, Nigeria d Department of Chemical Engineering, Nnamdi Azikiwe University, Awka, Nigeria ARTICLE INFO Editor: Teik Thye Lim Keywords: Adsorption Clofibric acid Ecotoxicology Environment Pollution ABSTRACT Clofibric acid (CA) is one of the recalcitrant pharmaceutical compounds observed as a pollutant in the en- vironment in recent times. This paper aimed to evaluate the recent developments in the last decade on the mitigation of CA from aqueous media by adsorption. The adsorbents were classed into carbon-based materials, clay and minerals, and polymer and resins. It was observed that the best class of adsorbents (with adsorption capacity > 300 mg/g) for CA adsorption were carbon-based materials. The highest reported adsorption capacity for CA in the last decade was 994 mg/g by graphene nano-sheets. CA adsorption was mostly best fit to Langmuir or the Freundlich isotherm and kinetics was majorly according to the pseudo-second order model. CA can successfully be desorbed form adsorbent media by suitable eluents and reused. This suggests that adsorption can be economical in an industrial scale for the removal of CA from effluents. For future work, graphene oxide and metal organic frameworks could be modified for higher adsorption capacity. The disposal technique for used adsorbent after CA uptake could be explored. 1. Introduction The global rise in urbanisation and industrialisation has led to a more serious water pollution problem [1,2]. The diversity of pollutants has also increased due to changing consumption patterns of product utilisation [3,4]. In contemporary times, emerging contaminants have become a cause for concern [5,6]. There has been an unprecedented rise in the concentrations and frequencies at which these emerging contaminants are being detected in surface, ground and drinking water [7,8] and even as much as water flowing through cave systems [9]. These emerging contaminants include pharmaceutically active com- pounds (PhACs), endocrine disruption chemicals (EDCs), pesticides and personal care products (PPCPs) [10–12]. Researchers have been able to pinpoint as much as 65 different neutral and acidic PhACs, antibiotics and estrogens at varying concentrations in surface water [13], in- dustrial effluents and groundwater [14]. Pharmaceutical wastewater contains compounds that are hard to biodegrade [15] and can be re- calcitrant in the environment. Clofibric acid (CA) is one of the recalcitrant pharmaceutical com- pounds observed as a pollutant in the environment in recent times [16]. Clofibric acid (CA) is an herbicide [17] and is also a pharmaceutical compound [18]. CA is a metabolite of clofibrate and serves as a lipid regulator [19]. As a drug, it serves as an anti-cholesteremic, antilipemic and an antineoplastic agent. CA is a white to yellow solid with a molar mass of 214.6 g/mol. The basic properties of CA are summarised in Table 1. The essence of research is to ensure the productive continuity of an already existing technique or method(s) of application. As these im- provements proceed, aside from the efficacy of the technicality of the new process, the health and environmental impacts also need to be fully accessed. Clofibrate can be used as a lipid regulator, and its metabolite, Clofibric acid (CA), can be heavily retained in water bodies, both https://doi.org/10.1016/j.jece.2020.104264 Received 16 May 2020; Received in revised form 8 July 2020; Accepted 11 July 2020 Abbreviations: AC, activated carbon; BDD, boron-doped diamond; CA, clofibric acid; DFT, density functional theory; EDCs, endocrine disruption chemicals; HMS, hexagonal mesoporous silica; MIP, molecularly imprinted polymers; MOF, metal organic frameworks; MIEX, magnetic ion-exchange resin; NOEC, no observed effect concentration; NOM, natural organic matter; PhACs, pharmaceutically active compounds; PPCPs, pesticides and personal care products; TSH, thyroid stimulating hormone; UV, ultra-violet; WTP, wastewater treatment plant ⁎ Corresponding authors. E-mail addresses: oshea.ighalo@yahoo.com (J.O. Ighalo), oluwaseun_ajala81@yahoo.com (O.J. Ajala). Journal of Environmental Chemical Engineering 8 (2020) 104264 Available online 15 July 2020 2213-3437/ © 2020 Elsevier Ltd. All rights reserved. T