Removal of Paracetamol Using Effective Advanced Oxidation Processes

Abstract

Fenton, photo-Fenton, and photo-induced oxidation, were investigated and compared for the treatment of 0.26 mmol L^-1 of paracetamol (PCT) in a deionised water matrix, during a reaction span of 120.0 min. Low and high Fenton reagent loads were studied. Particularly, the initial concentration of Fe²⁺ was varied between 0.09 and 0.18 mmol L^-1 while the initial concentration of H₂O₂ was varied between 2.78 and 11.12 mmol L^-1. The quantitative performance of these treatments was evaluated by: (i) measuring PCT concentration; (ii) measuring and modelling TOC conversion, as a means characterizing sample mineralization; and (iii) measuring cytotoxicity to assess the safe application of each treatment. In all cases, organic matter mineralization was always partial, but PCT concentration fell below the detection limit within 2.5 and 20.0 min. The adopted semi-empirical model revealed that photo induced oxidation is the only treatment attaining total organic matter mineralization ( ξ MAX = 100% in 200.0 min) at the expense of the lowest kinetic constant (k = 0.007 min^-1). Conversely, photo-Fenton treatment using high Fenton reagent loads gave a compromise solution ( ξ MAX = 73% and k = 0.032 min^-1). Finally, cytotoxicity assays proved the safe application of photo-induced oxidation and of photo-Fenton treatments using high concentrations of Fenton reagents.

Keywords: Fenton; by-products; cytotoxicity; hydrogen peroxide dosage; kinetic model; paracetamol; photo-Fenton; photo-induced oxidation.

Figure 1

Evolution of the measured concentration of Fe²⁺ (◊,♦) and total iron (□,■) represented by a continuous line and of the calculated concentration of Fe³⁺ (∆,▲), represented by a dashed line, during (a) Fenton (empty symbols) and (b) photo-Fenton (solid symbols ) experiments performed with high concentrations of the Fenton reagents.

Figure 2

Evolution of the degradation of (a) PCT (normalized values), (b) TOC (normalized values) and (c) H₂O₂ (concentration, mmol L⁻¹) for different process: photo induced advanced oxidation (●); Fenton, using low and high concentrations of Fenton reagents (◊,∆); photo-Fenton using low and high concentrations of Fenton reagents (♦,▲); and photo-Fenton process following a H₂O₂ dosage strategy (■). Figure 2c also shows the profile of the added hydrogen peroxide during the reaction span (concentration values, mmol L⁻¹). The error bars display the standard deviation for the set of three experiments.

Figure 2

Evolution of the degradation of (a) PCT (normalized values), (b) TOC (normalized values) and (c) H₂O₂ (concentration, mmol L⁻¹) for different process: photo induced advanced oxidation (●); Fenton, using low and high concentrations of Fenton reagents (◊,∆); photo-Fenton using low and high concentrations of Fenton reagents (♦,▲); and photo-Fenton process following a H₂O₂ dosage strategy (■). Figure 2c also shows the profile of the added hydrogen peroxide during the reaction span (concentration values, mmol L⁻¹). The error bars display the standard deviation for the set of three experiments.

Figure 3

Reaction rate as a function of the maximum attainable conversion evaluated for photo induced advanced oxidation process (●); Fenton (◊) and photo-Fenton (♦) process without H₂O₂ dosage using low concentrations of the Fenton reagents; Fenton (∆) and photo-Fenton (▲) process without H₂O₂ dosage using high concentrations of the Fenton reagents; and photo-Fenton process following a H₂O₂ dosage strategy (■).

Figure 4

Evolution (HPLC AREA) of the degradation intermediate BZQ (○) during photo induced oxidation process (line and dots), photo-Fenton process using high (dotted line) and low (dashed line) concentrations of the Fenton reactants and without dosing the hydrogen peroxide, and photo-Fenton process following a H₂O₂ dosage strategy (solid line).

Figure 5

Results of the cytotoxicity assays performed using COS-1 (full symbols) and VERO (slashed symbols) and tested on samples taken after 0 (M0), 75 (M75) and 120 (M120) minutes of reaction.