Adsorption of estrone, 17β-estradiol, and 17α-ethinylestradiol from water onto modified multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon.

Danijela Prokić,Marija Vukčević,Marina Maletić,Ana Kalijadis,Angelina Mitrović,Tatjana Đurkić,Ivona Janković-Častvan

doi:10.1007/s11356-021-15970-4

Abstract

Carbon materials of different structural and textural properties (multi-walled carbon nanotubes, carbon cryogel, and carbonized hydrothermal carbon) were used as adsorbents for the removal of estrone, 17β-estradiol, and 17α-ethinylestradiol from aqueous solutions. Chemical modification and/or activation were applied to alter surface characteristics and to increase the adsorption and desorption efficiency of carbon materials. Surfaces of treated and untreated carbon materials were characterized through the examination of the textural properties, the nature of surface functional groups, and surface acidity. It was found that the adsorption capacity of tested carbon materials is not directly proportional to the specific surface area and the content of surface oxygen groups. However, a high ratio of surface mesoporosity affected the adsorption process most prominently, by increasing adsorption capacity and the rate of the adsorption process. Adsorption of estrone, 17β-estradiol, and 17α-ethinylestradiol followed pseudo-second-order kinetic model, while the equilibrium adsorption data were best fitted with the Langmuir isotherm model. Calculated mean adsorption energy values, along with the thermodynamic parameters, indicated that removal of selected hormones was dominated by the physisorption mechanism. High values of adsorption efficiency (88-100 %) and Langmuir adsorption capacities (29.45-194.7 mg/g) imply that examined materials, especially mesoporous carbon cryogel and multi-walled carbon nanotubes, can be used as powerful adsorbents for relatively fast removal of estrogen hormones from water.

Highlights

Hormones, both naturally secreted or of synthetic origin, are trace pollutants of major concerns due to their potential of disrupting the endocrine activities of living organisms (Auriol et al 2006)
This paper aimed to examine the efficiency of different carbon materials for adsorption and desorption of estrone, 17β-estradiol, and 17α-ethinylestradiol, and to reveal which features of materials surface affect the adsorption process most prominently
At high P/P0, adsorption isotherm obtained for carbonized hydrothermal carbon (CHTC) does not exhibit any limiting adsorption, which is related to the non-rigid aggregates of plate-like particles and slit-shaped pores (Lowell et al 2004)

Summary

Introduction

Both naturally secreted or of synthetic origin, are trace pollutants of major concerns due to their potential of disrupting the endocrine activities of living organisms (Auriol et al 2006). Present at very low concentrations (the order of magnitude ng/L) (Auriol et al 2008), these compounds still can cause serious adverse effects on aquatic organisms (Snyder et al 2003) and domestic animals (Gao et al 2019) Many pathological phenomena, such as carcinogenicity, disorders in reproductive function, decreased fertility in fish, infertility, the feminization of male fish, are induced by the presence of steroid estrogens in the environment (Vilela et al 2018; Khanal et al 2006; Bilal and Iqbal 2019). These hormones are not removed from sewage in wastewater-treatment plants completely, so their effluents contain a significant concentration of these substances (Vilela et al 2018) These substances may pose a risk to humans and animals indirectly, via food contamination (Hartmann et al 1998). The removal of estrogens from water has become a very important issue worldwide

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