To Degrade Water-polluting Pharmaceutical Compounds
Qatar University (QU) researchers lead an international research team to publish a research article in the high impact factor reputable scientific journal, named Chemical Engineering Journal, published by Elsevier.
This research work presented as an efficient sustainable degradation process of the hydroxychloroquine (HCQ) in aqueous solutions by electrochemical advanced oxidation processes including electrochemical oxidation (EO) using boron doped diamond (BDD) and its combination with UV irradiation (photo-assisted electrochemical oxidation, PEO) and sonication (sono-assisted electrochemical oxidation, SEO).
The research team was headed by Prof. Nasr Bensalah, Professor of Chemistry, Department of Chemistry and Earth Sciences, College of Arts and Sciences at Qatar University. The research team included Dr. Mohammad Ibrahim, Research Associate, Central Laboratories Unit, Research and Graduate Studies Sector (VPRGS), Qatar University, Prof. Ahmed Bedoui, Department of Chemistry, Faculty of Sciences, University of Gabes, Tunisia, and Sondos Midassi (PhD student), Department of Chemistry, Faculty of Sciences, University of Gabes, Tunisia.
Prof. Bensalah mentioned that the past studies indicated that the Hydroxychloroquine (HCQ) is widely used as a drug for the treatment of rheumatologically, dermatological diseases and pre-scribed as an antimalarial drug.
Recently, national and international medical organizations globally, allowed using of chloroquine and hydroxychloroquine in the treatment protocols of COVID-19 for certain hospitalized patients. Dr. Mohammad Ibrahim announced that a huge amount of HCQ is needed for the treatment of different diseases over the world, which certainly results in the discharge of large quantities of wastewaters contaminated with HCQ into the environment.
Due to its chemical and biological properties, HCQ has high potential to persist, bioaccumulation, and transfer to living organisms in intensified toxic forms. The literature -as mentioned in the study- indicated that, HCQ can also contaminate air (ozone depleting substance), soil (bioaccumation in vegetation), and groundwater (persistent substance). The high risks of natural water contamination due to the large production and utilization of HCQ, necessitates more attention to limit its hazardous effects on human health and environment.
The research team pointed out in the article that the results offer significant information needed in the future to depollute large quantities of wastewaters contaminated with HCQ drug and its metabolites as it was especially adopted as the first treatment of COVID-19 by many health organizations. HCQ degradation was monitored by UV/VIS spectrophotometry and total organic carbon (TOC) analysis. The analysis of organic and inorganic intermediates was conducted using high performance liquid chromatography (HPLC) and ion chromatography (IC).
The experimental setup used in all electrochemical experiments comprises a single compartment electrochemical flow cell working in batch-operation mode (Figure 1.a). The electrolyte stored in a glass tank was circulated through the electrolytic cell by a centrifugal pump at a constant flow rate. A thermostatic bath/heat exchanger was used to maintain the temperature at 25°C during all the experiments. The same electrochemical flow cell was used in SEO and PEO experiments. In SEO experiments, an ultrasonic generator equipped with a sonication probe that is immersed in the glass tank was used. In PEO experiments, a UV lamp mercury medium pressure located in an axial position submerged in a vertical immersion tube contained in a vertical quartz cooling tube and immersed in glass tank was used. (Figure 1.b)
Figure 1. (a) Electrochemical setup, (b) Electrochemical reactor, and (c) Combined processes setup.
EO using BDD anode achieved complete depletion of HCQ from aqueous solutions regardless of the HCQ concentration, current density, and initial pH value. The decay of HCQ was more rapid than total organic carbon (TOC) indicating that the degradation of HCQ by EO using BDD anode involves successive steps leading to the formation of organic intermediates that end to mineralize (Figure 2.a). Furthermore, the results demonstrated the release of chloride (Cl−) ions at the first stages of HCQ degradation. In addition, the organic nitrogen was converted mainly into NO3− and NH4+ and small amounts of volatile nitrogen species (NH3 and NOx). The chromatographic analysis confirmed the formation of 7-chloro-4-quinolinamine (CQLA), oxamic and oxalic acids as intermediates of HCQ degradation by EO, using BDD anode (Figure 2.b).
Figure 2. (a) Changes in HCQ, TOC with time and intermediates with the specific electrical charge during EO, SEO and PEO of HCQ in aqueous solution using BDD anode. Operating conditions: 0.05 M Na2SO4, [HCQ] = 250 mg/L; j = 20 mA/cm2; initial pH = 7.1; T = 25°C, (b) Simple mechanism of HCQ degradation by electro-generated oxidants using BDD anodes.
The research report revealed that the combination of EO with UV irradiation or sonication enhances the kinetics and the efficacy of HCQ oxidation. PEO requires the lowest energy consumption (EC) of 63 kWh/m3 demonstrating its cost-effectiveness compared to the other EAOPs. PEO has the potential to be an excellent alternative method for the treatment of wastewaters contaminated with HCQ drug and its derivatives.
Dr. Mohammad Ibrahim stated that PEO method utilizes only electrons and photons as reagents without the addition of other hazardous chemicals confirming its sustainability. This method is easy to be scaled in large water treatment plants and can be integrated with renewable resources (i.e. solar energy).