Comprehensive two-dimensional liquid chromatography with high resolution mass spectrometry to investigate the photoelectrochemical degradation of environmentally relevant pharmaceuticals and their degradation products in water.

The widespread presence of organic micropollutants in the environment reflects the inability of traditional wastewater treatment plants to remove them. In this context, advanced oxidation processes (AOPs) have emerged as promising quaternary wastewater treatment technologies since they efficiently degrade recalcitrant components by generating highly reactive free radicals. Nonetheless, the chemical characterization of potentially harmful byproducts is essential to avoid the contamination of natural water bodies with hazardous substances. Given the complexity of wastewater matrices, the implementation of comprehensive analytical methodologies is required. In this work, the simultaneous photoelectrochemical degradation of seven environmentally relevant pharmaceuticals and one metabolite from the EU Watch List 2020/1161 was examined in ultrapure water and simulated wastewater, achieving excellent removal efficiencies (overall >95%) after 180 min treatment. The reactor unit was linked to an online LC sample manager, allowing for automated sampling every 15 min and near real-time process monitoring. Online comprehensive two-dimensional liquid chromatography (LC × LC) coupled with high resolution mass spectrometry (HRMS) was subsequently used to tentatively identify degradation products after photoelectrochemical degradation. Two reversed-phase liquid chromatography (RPLC) columns were used: an SB-C18 column operated with 5 mM ammonium formate at pH 5.8 (1A) and methanol (1B) as the mobile phases in the first dimension and an SB-Aq column using acidified water at pH 3.1 (2A) and acetonitrile (2B) as the mobile phases in the second dimension. This resulted in a five-fold increase in peak capacity compared to one-dimensional LC while maintaining the same total analysis time of 50 min. The LC x LC method allowed the tentative identification of 12 venlafaxine, 7 trimethoprim and 10 ciprofloxacin intermediates. Subsequent toxicity predictions suggested that some of these byproducts were potentially harmful. This study presents an effective hybrid technology for the simultaneous removal of pharmaceuticals from contaminated wastewater matrices and demonstrates how multidimensional liquid chromatography techniques can be applied to better understand the degradation mechanisms after the treatment of micropollutants with AOPs.

Treatment of antimicrobial azole compounds via photolysis, electrochemical and photoelectrochemical oxidation: Degradation kinetics and transformation products.

The degradation kinetics and transformation products of pharmaceutical azole drugs from Watch List 2020/1161 (fluconazole, FCZ; miconazole, MCZ; clotrimazole, CTZ; and sulfamethoxazole, SMX) are examined individually and as a mixture in Milli-Q water and simulated wastewater (SWW) upon treatment with three different advanced oxidation processes: (i) photolysis (UV), (ii) electrochemical (eAOP), and (iii) photoelectrochemical (eAOP/UV). For individual pollutant degradation, UV was found to be significantly more effective for SMX and CTZ compared to MCZ and FCZ. Whereas when treating the azole drugs mixture, eAOP/UV was determined to be the most effective treatment method. The degradation efficiency was higher in Milli-Q than in SWW because the treatment efficiency depended on the matrix compositions. The degradation products formed under different processes were identified, and the routes of transformation were proposed. The results of this study can assist in the selection of the most suitable treatment technology depending upon the pollutant or matrix.

Anodic oxidation of sulfamethoxazole paired to cathodic hydrogen peroxide production.

A double chamber electrochemical system is developed consisting of a boron-doped diamond (BDD) anode and a graphite cathode, which not only degrades sulfamethoxazole (SMX) but also simultaneously generates hydrogen peroxide (H2O2). The degradation of SMX is carried out by (in)direct oxidation at the BDD anode and H2O2 is produced by two electron oxygen (O2) reduction reaction (ORR) at the cathode. The effect of different parameters on the kinetics of both mechanisms was investigated. The performance of the system at the optimized conditions (pH 3, 0.05 M Na2SO4 as electrolyte, and 10 mA as applied current) showed that after 180 min of electrolysis, SMX was almost fully degraded (95% removal and ∼90% COD reduction) as well as about 535 µM H2O2 was accumulated. With the help of LC-MS, five intermediates formed during SMX electrolysis were properly identified and a degradation pathway was proposed. This study advocates methods for improving the effectiveness of energy use in advanced wastewater treatment.

Recent advances in carbonaceous catalyst design for the in situ production of H2O2 via two-electron oxygen reduction.

The electrochemical oxygen reduction reaction has received increasing attention as a relatively green, safe and sustainable method for in situ hydrogen peroxide (H2O2) production. Recently, significant achievements have been made to explore carbon-based (noble metal-free) low-cost and efficient electrocatalysts for H2O2 electroproduction, which could potentially replace the traditional anthraquinone process. However, to realize industrial-scale implementation, a highly active and selective catalytic material is needed. In this review paper, we first expound on the oxygen reduction reaction (ORR) mechanism, which is the origin of in situ H2O2 production. Then, the recent progress in the development of modified carbon-based catalysts is reviewed and classified, corresponding to their physical or chemical modulation. Furthermore, an overview is provided of the available examples from pilot/large-scale applications. Finally, an outlook on the current challenges and future research prospects to transfer the lab-developed catalysts into pilot or industrial-scale reactors is briefly discussed.

Wastewater in the food industry: Treatment technologies and reuse potential.

Water is the most extensively used raw material in the food and beverage industry. This industrial sector has a negative impact on the environment and economy as a result of rising water demand and wastewater production. With the increasing scarcity of drinking water, the reuse of wastewater streams has become an important economic and ecological concern. Therefore, the optimisation of water consumption and wastewater reuse in the food industry is essential. On the other hand, several countries limit the reuse of wastewater because of legal curtailment, public health and safety concerns. This represents a major challenge for both industries and administrations due to the technical complexity and financial costs involved. The present review aims at addressing the key issues related to water consumption, wastewater generation, treatment and successful implementation cases of water reuse in the food and beverage industry. Moreover, the various case studies of already employed technologies for the food industry wastewater treatment and reuse have been analysed for their performance. Also, this review reveals future research on the application of other innovative technologies such as ultraviolet irradiation and micro electrolysis. However, the successful implementation of reuse strategies is associated with the holistic evaluation of local factors such as governmental incentives, social acceptance and legislation harmonisation related to the cost, risks, and environmental performance.

Recent advances in technologies for removal and recovery of selenium from (waste)water: A systematic review.

Selenium (Se) is distributed into different environmental compartments by natural and anthropogenic activities, and generally discharged in the form of selenate [SeO42-] and selenite [SeO32-], which are both toxic. Physical-chemical and biological treatment processes have been reported to exhibit good treatment efficiencies for Se from aqueous streams, only a few demonstrated to achieve effluent concentrations <5 µg/L. Moreover, there are only a few numbers of studies that describe the progress in technological developments over the last decade. Therefore, to unify the state of knowledge, identify ongoing research trends, and determine the challenges associated with available technologies, this systematic review critically analyses the published research on Se treatment. Specific topics covered in this review include (1) Se chemistry, toxicity, sources and legislation, (2) types of Se treatment technologies, (3) development in Se treatment approaches, (4) Se recovery and circular economy and (5) future prospects. The current research has been found to majorly focused on Se removal via adsorption techniques. However, the key challenges facing Se treatment technologies are related to the presence of competing ions in the solution and the persistence of selenate compared to selenite during their reduction.