Contents lists available at ScienceDirect Environmental Research journal homepage: www.elsevier.com/locate/envres Effect of phosphate concentration, anions, heavy metals, and organic matter on phosphate adsorption from wastewater using anodized iron oxide nanoflakes Muhammad Naveed Afridi, Won-Hee Lee, Jong-Oh Kim ⁎ Department of Civil and Environmental Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea ARTICLE INFO Keywords: Anodization Iron oxide nanoflakes Adsorption Phosphate Coexisting components ABSTRACT Phosphorus is a necessary nutrient for the growth and survival of living beings. Nevertheless, an oversupply of phosphorus in wastewater results in eutrophication. Therefore, its removal from wastewater is important. However, coexisting components, such as anions, heavy metals, and organic matter, might inhibit the phosphate- adsorption mechanism by competing for the active surface sites of the adsorbent. In this study, iron oxide nanoflakes (INFs) were fabricated on iron foil via anodization. The rate of phosphate adsorption from waste- water onto INFs in the presence of three different coexisting components—anions, heavy metals, and organic matter—was evaluated. The morphology of the INFs was analyzed by X-ray diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and Fourier- transform infrared spectroscopy. The phosphate adsorption equilibrium time using INFs was found to be 1 h. The Elovich model (R 2 > 0.99) and the Langmuir model (R 2 > 0.95) respectively provided the best description of the adsorption kinetics and isotherm, suggesting the chemisorption nature of adsorption. The estimated ad- sorption capacity of the INFs was 21.5 mg-P g –1 . The effect of anions (chloride, sulfate, nitrate, and carbonate) and heavy metals (Cd, As, Cr, and Pb) was studied at three different molar ratios (0.5:1, 1:1, and 1.5:1). The effect of different types of organic matter, such as citric acid, humic acid, and oxalic acid at concentrations of 100 and 200 mg L –1 , was also examined. In five regeneration cycles, the total amount of phosphate adsorbed and desorbed, and the recovery percentage were 6.51 mg-P g –1 , 5.16 mg-P g –1 , and 79.24%, respectively. 1. Introduction Phosphorous is a principal nutrient for the development of animals and plants. Therefore, it is used as a fundamental material in the manufacturing of fertilizers and many other industrial products such as polishing agents, food ingredients, semiconductors, chemical products, and detergents (Krüger and Adam, 2017; Logue, 1946). However, in- creased discharge from these industries and agricultural runoff into water bodies increases the phosphate concentration in wastewater, causing eutrophication (Nguyen et al., 2015). Eutrophication begins with an enrichment of water bodies by nutrients that causes harmful algal blooms, deterioration of water quality and depletion of fish spe- cies (Naushad et al., 2018). According to the Environmental Protection Agency (EPA), the permissible limit for phosphate discharge is 0.1 ppm (Nehra et al., 2018). Therefore, the removal of excess phosphate is imperative, considering its hazardous effects on the environment and aquatic organisms (Islam et al., 2014). Lowering the level of phosphate in wastewater streams to a per- missible level (0.1 ppm) requires an effective, efficient, and economical technology. Different methods have already been introduced and practiced for removing phosphate from effluents, including biological processes, chemical precipitation, and physical separation (Liu et al., 2017). Biological methods utilize fungi or microorganisms to adsorb phosphate. However, the efficiency of these techniques is sensitive to fungal or microbial environments; therefore, it is challenging to remove phosphate at a steady rate (Islam et al., 2014). The chemical pre- cipitation method, while being effective, poses problems for sludge treatment and disposal due to the use of a large amount of chemicals (Choi et al., 2016). Further separation and purification are mandatory for the disposal of the generated residual solid waste (Lalley et al., https://doi.org/10.1016/j.envres.2019.01.055 Received 28 September 2018; Received in revised form 26 December 2018; Accepted 30 January 2019 Abbreviations: AAO, anodic aluminum oxide; DI, deionized; EDX, energy-dispersive X-ray spectroscopy; FE-SEM, field emission scanning electron microscopy; INF, iron oxide nanoflake; INT, iron oxide nanotube; TNT, titanium oxide nanotube; XRD, X-ray diffraction; XPS, X-ray photoelectron spectroscopy; FTIR, Fourier- transform infrared spectroscopy ⁎ Corresponding author. E-mail address: jk120@hanyang.ac.kr (J.-O. Kim). Environmental Research 171 (2019) 428–436 Available online 31 January 2019 0013-9351/ © 2019 Published by Elsevier Inc. T