Electrochemical mineralization of norfloxacin using distinct boron-doped diamond anodes in a filter-press reactor, with investigations of toxicity and oxidation by-products

Abstract

The contamination of water bodies by antibiotics is a cause of concern due to chronic toxic effects and the possible development of resistance to them by microorganisms, which can lead to serious health problems to humans. Thus, in this work, for the first time the degradation of norfloxacin (100 mg L À1 NOR in 0.1 mol L À1 Na 2 SO 4) is carried out electrochemically, using a filter-press flow reactor with boron-doped diamond (BDD) anodes of distinct characteristics. The investigated variables (and their ranges) were solution pH (3, 7, 10, and without specific control), current density (10, 20, and 30 mA cm À2), temperature (10, 25, and 40 C), and boron content-sp 2 /sp 3 carbon ratio of the BDD anode (100 ppm-215, 500 ppm-325, and 2500 ppm-284). The NOR electrodegradation performance of the distinct anodes was assessed by monitoring the degradation by-products (aromatic compounds and carboxylic acids), NOR concentration and total organic carbon concentration of the electrolyzed solutions, as well as their toxicity to Escherichia coli (i.e. growth inhibition). For the complete removal of NOR, the best condition (not pH dependent) was attained at 10 mA cm À2 and 40 C, when the system is under mass transfer limitations. Concerning NOR oxidation and mineralization rates, mineralization current efficiency, energy consumption, and degradation products, similar results (including the complete detoxification of the electrolyzed solution) were attained for all tested BDD anodes under mass or charge transfer controlled processes. Clearly, the oxidation power of the tested BDD anodes is not affected by the values of their boron content-sp 2 /sp 3 carbon ratio.

Recent Trends in Removal Pharmaceuticals and Personal Care Products by Electrochemical Oxidation and Combined Systems

“…Moreover, the complete removal of norfloxacin is dependent on pH. However, the removal increased with the temperature at 10°C, 25°C, and 40°C may result from a gradual increase in the diffusion coefficient and the oxidation of byproducts under temperature conditions [100]. Interestingly, DEET degradation increased with increasing current density but was moderately affected by temperature (25-75 °C) [52].…”

On the performance of HOCl/Fe2+, HOCl/Fe2+/UVA, and HOCl/UVC processes using in situ electrogenerated active chlorine to mineralize the herbicide picloram

“…After optimization of the electrochemical and photochemical process using the UVC lamp (HOCl/UVC process), its performance towards degradation of PCL (concerning removal of the dissolved organic matter and electrical energy efficiency) were compared to the electrochemical method using a BDD anode and similar hydrodynamic parameters concerning the surface to volume ratio (24 cm 2 of geometric area) and flow velocity (0.3 m s −1 : see [10] for more details of the electrochemical cell setup). The BDD electrode (boron content of 500 ppm in the BDD film, deposited on a Si substrate) was purchased from NeoCoat SA (Switzerland).…”

“…The TOC content was analyzed by subtraction of the measured values of inorganic and total carbon, in terms of generated CO 2 . More experimental details can be found in previous works of our group [10,30].…”

“…These studies have shown that SOC, such as herbicides, antibiotics, personal care products, and so on [4,5], can be found in natural surface water even after treatment at conventional municipal wastewater treatment plants [6,7]. Despite a significant number of studies that show the impact of the acute toxicity of some SOC on microorganisms [8,9], including the relationship between toxicity and structural modifications [10][11][12], few of these studies investigated the effect of a long term exposure of SOC in microorganisms or even in humans. Consequently, and based on the potential harmful effect of SOC to aquatic and human lives [13], there is the necessity to adequately eliminate these pollutants presented on effluents, using distinct methods or their combination [14], before disposal in the environment.…”

“…Among the available methods to treat effluents contaminated with SOC, the ones based on generation of the non selective hydroxyl radicals (HO%) are usually the choice, such as Fenton based [15] and electrochemical processes [16] as well as their combination [17], due to the high oxidation power of HO% and production of less toxic byproducts [10]. The necessity to use acidic solutions and recovery of Fe 2+ ions are the main drawback of the Fenton based processes.…”