Abstract
A surfactant-free method was used to synthesize iron oxyhydroxide (akaganeite, β-FeOOH) nanorods and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy combined with energy-dispersive X-ray spectroscopy (SEM-EDS), and transmission electron microscopy (TEM). The synthesized nanoadsorbent was applied for the adsorptive removal of β-estradiol from aqueous solutions. The parameters affecting the adsorption were optimized using a multivariate approach based on the Box–Behnken design with the desirability function. Under the optimum conditions, the equilibrium data were investigated using two and three parameter isotherms, such as the Langmuir, Freundlich, Dubinin–Radushkevich, Redlich–Peterson, and Sips models. The adsorption data were described as Langmuir and Sips isotherm models and the maximum adsorption capacities in Langmuir and Sips of the β-FeOOH nanorods were 97.0 and 103 mg g−1, respectively. The adjusted non-linear adsorption capacities were 102 and 104 mg g−1 for Langmuir and Sips, respectively. The kinetics data were analyzed by five different kinetic models, such as the pseudo-first order, pseudo-second order, intraparticle, as well as Boyd and Elovich models. The method was applied for the removal β-estradiol in spiked recoveries of wastewater, river, and tap water samples, and the removal efficiency ranged from 93–100%. The adsorbent could be reused up to six times after regeneration with acetonitrile without an obvious loss in the removal efficiency (%RE = 95.4 ± 1.9%). Based on the results obtained, it was concluded that the β-FeOOH nanorods proved to be suitable for the efficient removal of β-estradiol from environmental matrices.
Highlights
Water is the most important natural resource for the survival of all organisms [1]
The OH bending band around the 1431 cm−1 region corresponded to the β-FeOOH Fourier transform infrared spectroscopy (FTIR) spectrum reported in the literature [19,26]
According to [26], decreasing the pH of the synthesis media results in more crystalline akageneite, while increasing the pH of the synthesis media results in less crystalline akaganeite nanoparticles, which was a similar case with the present study
Summary
Water is the most important natural resource for the survival of all organisms [1]. Due to the increase in urbanization, climate change, industrial production, and population growth, the quality of water can be negatively affected. Pollutants entering soil or water pose a variety of threats to the Processes 2020, 8, 1197; doi:10.3390/pr8091197 www.mdpi.com/journal/processes. Soil is frequently polluted with polycyclic aromatic hydrocarbons (PAHs), petroleum-related compounds, heavy metals, chlorophenols, organic pollutants, and pesticides [2]. The United States and the European Union in 2002 and 2009 reported that at least 80% of all collected samples were contaminated with organic pollutants, which frequently have endocrine-disrupting properties [4]. The most widely investigated endocrine disruptors include molecules or metabolites derived from personal care products, pharmaceuticals, polybrominated diphenyl ethers (PBDEs), and hormones [5]
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