Abstract
The present study examines the photocatalytic properties of silver carbonate (Ag2CO3) for ethyl paraben (EP) degradation under simulated solar irradiation. Ag2CO3 was prepared according to a solution method and its physicochemical characteristics were studied by means of X-ray diffraction (XRD), the Brunauer–Emmett–Teller (BET) method, diffuse reflectance spectroscopy (DRS), and transmission electron microscopy (TEM). Complete EP (0.5 mg/L) removal was achieved after 120 min of irradiation with the use of 750 mg/L Ag2CO3 in ultrapure water (UPW), with EP degradation following pseudo-first-order kinetics. The effect of several experimental parameters was investigated; increasing catalyst concentration from 250 mg/L to 1000 mg/L led to an increase in EP removal, while increasing EP concentration from 0.25 mg/L to 1.00 mg/L slightly lowered kapp from 0.115 min−1 to 0.085 min−1. Experiments carried out with the use of UV or visible cut-off filters showed sufficient EP degradation under visible irradiation. A series of experiments were performed in real water matrices such as bottled water (BW) and wastewater (WW), manifesting Ag2CO3’s equally high photocatalytic activity for EP degradation. To interpret these results different concentrations of inorganic anions (bicarbonate 100–500 mg/L, chloride 100–500 mg/L) present in aqueous media, as well as 10 mg/L organic matter in the form of humic acid (HA), were added sequentially in UPW. Results showed accelerating effects on EP degradation for the lowest concentrations tested in all cases.
Highlights
A walk through the supermarket or pharmacy is enough to observe the phrase “paraben free” that appears today in some self-care mass market products
The main characteristics of water matrices used in the present study are (i) ultrapure water (UPW: 0.059 μS/cm conductivity, pH = 6.0), (ii) commercial bottled water
It is observed that Ag2CO3 has that all diffraction patterns can be indexed to the monoclinic phase of Ag2 CO3 (JCPDS 12-766) without an absorption threshold at ~467 nm that allows to absorb a significant portion of visible light
Summary
A walk through the supermarket or pharmacy is enough to observe the phrase “paraben free” that appears today in some self-care mass market products. Parabens are p-hydroxybenzoates containing alkyl-side chains linked to an ester group that constitute a large group of preservatives capable of prolonging shelf life in many health and beauty products. Common parabens used are methylparaben, ethylparaben, butylparaben, and propylparaben. Their popularity is attributed to the fact that they possess a great number of desirable characteristics, such as broad antimicrobial spectrum, high efficiency, and low cost [1]. People are exposed to parabens through skin absorption or swallowing and are excreted by urination. Despite the fact that removal efficiencies of parabens in wastewater treatment plants exceed 90%, they have still been detected in river water samples at low concentrations of the ng/L range [4], multiplying the
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