Photocatalytic Treatment of Pharmaceuticals in Real Hospital Wastewaters for Effluent Quality Amelioration

Photocatalytic systems: reactions, mechanism, and applications

The photocatalytic field revolves around the utilization of photon energy to initiate various chemical reactions using non-adsorbing substrates, through processes such as single electron transfer, energy transfer, or atom transfer. The efficiency of this field depends on the capacity of a light-absorbing metal complex, organic molecule, or substance (commonly referred to as photocatalysts or PCs) to execute these processes. Photoredox techniques utilize photocatalysts, which possess the essential characteristic of functioning as both an oxidizing and a reducing agent upon activation. In addition, it is commonly observed that photocatalysts exhibit optimal performance when irradiated with low-energy light sources, while still retaining their catalytic activity under ambient temperatures. The implementation of photoredox catalysis has resuscitated an array of synthesis realms, including but not limited to radical chemistry and photochemistry, ultimately affording prospects for the development of the reactions. Also, photoredox catalysis is utilized to resolve numerous challenges encountered in medicinal chemistry, as well as natural product synthesis. Moreover, its applications extend across diverse domains encompassing organic chemistry and catalysis. The significance of photoredox catalysts is rooted in their utilization across various fields, including biomedicine, environmental pollution management, and water purification. Of course, recently, research has evaluated photocatalysts in terms of cost, recyclability, and pollution of some photocatalysts and dyes from an environmental point of view. According to these new studies, there is a need for critical studies and reviews on photocatalysts and photocatalytic processes to provide a solution to reduce these limitations. As a future perspective for research on photocatalysts, it is necessary to put the goals of researchers on studies to overcome the limitations of the application and efficiency of photocatalysts to promote their use on a large scale for the development of industrial activities. Given the significant implications of the subject matter, this review seeks to delve into the fundamental tenets of the photocatalyst domain and its associated practical use cases. This review endeavors to demonstrate the prospective of a powerful tool known as photochemical catalysis and elucidate its underlying tenets. Additionally, another goal of this review is to expound upon the various applications of photocatalysts.

Photocatalytic Degradation of Inherent Pharmaceutical Concentration Levels in Real Hospital WWTP Effluents Using g-C3N4 Catalyst on CPC Pilot Scale Reactor

The objective of this work was to evaluate the efficiency of a solar photocatalytic process using g-C₃N₄ as photocatalyst on the degradation of pharmaceutical compounds detected in hospital wastewater treatment plant secondary effluents. A compound parabolic collector pilot plant, established in the secondary effluent stream of the Ioannina city hospital wastewater treatment plant, was used for the photocatalytic experiments. The analysis of the samples before and after the photocatalytic treatment was accomplished using solid phase extraction (SPE), followed by UHPLC-LTQ/Orbitrap HRMS. Initial effluent characterization revealed the presence of ten pharmaceutical compounds. Among these, amisulpride, O-desmethyl venlafaxine, venlafaxine and carbamazepine were detected in all experiments. Initial concentrations ranged from 73 ng L^-1 for citalopram to 2924.53 ng L^-1 for O-desmethyl venlafaxine. The evolution of BOD₅ and COD values were determined before and after the photocatalytic treatment. All detected pharmaceuticals were removed in percentages higher than 54% at an optimum catalyst loading ranging between 200 and 300 mg L^-1. The potential of the catalyst to be reused without any treatment for two consecutive cycles was studied, showing a significant efficiency decrease.

Photocatalytic Degradation of Psychiatric Pharmaceuticals in Hospital WWTP Secondary Effluents Using g-C3N4 and g-C3N4/MoS2 Catalysts in Laboratory-Scale Pilot

Today, the pollution caused by a multitude of pharmaceuticals used by humans has been recognized as a major environmental problem. The objective of this study was to evaluate and compare the photocatalytic degradation of ten target psychiatric drugs in hospital wastewater effluents using g-C3N4 and 1%MoS2/g-C3N4 (1MSCN) as photocatalytic materials. The experiments were performed using real wastewater samples collected from hospital wastewater treatment plant (WWTP) secondary effluent in spiked and inherent pharmaceutical concentration levels. The photocatalytic experiments were performed in a laboratory-scale pilot plant composed of a stainless-steel lamp reactor (46 L) equipped with ten UVA lamps and quartz filters connected in series with a polypropylene recirculation tank (55–100 L). In addition, experiments were carried out in a solar simulator apparatus Atlas Suntest XLS+ at a 500 Wm−2 irradiation intensity. The analysis of the samples was accomplished by solid-phase extraction, followed by liquid chromatography-Orbitrap high-resolution mass spectrometry. Results showed that the photocatalytic degradation of pharmaceutical compounds followed first-order kinetics. In all cases, 1MSCN presented higher photocatalytic performance than g-C3N4. The removal rates of the pharmaceutical compounds were determined above 30% and 54% using g-C3N4 and 1MSCN, respectively. Parallel to kinetic studies, the transformation products (TPs) generated during the treatment were investigated.

Photocatalytic Degradation of Pharmaceutical Amisulpride Using g-C3N4 Catalyst and UV-A Irradiation

In the present study, the photocatalytic degradation of amisulpride using g-C3N4 catalyst under UV-A irradiation was investigated. The photocatalytic process was evaluated in terms of its effectiveness to remove amisulpride from ultrapure and real municipal wastewater. High removal percentages were achieved in both aqueous matrices. However, a slower degradation rate was observed using wastewater as matrix that could be attributed to its complex chemical composition. The transformation products (TPs) were identified with liquid chromatography–mass spectrometry (LC–MS) in both ultrapure and real municipal wastewater. Based on the identified TPs, the photocatalytic degradation pathways of amisulpride are proposed which include mainly oxidation, dealkylation, and cleavage of the methoxy group. Moreover, the contribution of reactive species to the degradation mechanism was studied using well-documented scavengers, and the significant role of h+ and O2•− in the reaction mechanism was proved. The evolution of ecotoxicity was also estimated using microalgae Chlorococcum sp. and Dunaliella tertiolecta. Low toxicity was observed during the overall process without the formation of toxic TPs when ultrapure water was used as matrix. In the case of real municipal wastewater, an increased toxicity was observed at the beginning of the process which is attributed to the composition of the matrix. The application of heterogeneous photocatalysis reduced the toxicity, and almost complete detoxification was achieved at the end of the process. Our results are in accordance with literature data that reported that heterogeneous photocatalysis is effective for the removal of amisulpride from aqueous matrices.

Scale-up of photoreactor with TiO2 thin layer for wastewater treatment

This study is devoted to the scale-up potential of TiO₂/UV photocatalyst for real wastewater treatment including its durability tests. The activity of the prepared TiO₂ layers was first tested in a laboratory reactor on key representative pollutants diclofenac, chloramphenicol and triclosan. A special pilot plant reactor of a two-tube system with 21 stainless steel annulets covered by TiO₂ thin layers and the inner volume of 3.5 L was constructed. Pilot tests were performed with wastewater from the pharmaceutical industry containing danazol and norethisterone with the concentration varying between 4 and 7 mg L^-1 at the flow 18 L h^-1 and municipal wastewater at the output sewage plant for 67,000 inhabitants containing bisphenol A, 4-nonyphenol, estron, ethinylestradiol and triclosan in the concentrations of the individual contaminants varying between 50 and 600 ng L^-1 at the flow 200 L h^-1. After the treatment during the pilot photocatalytic test, the concentration of individual contaminants decreased by 82-100%, while no decrease in the efficiency of the photocatalytic process was recorded during the long-term tests lasting for 3-6 months.

Inactivation of biohazards in healthcare wastewater by E-Beam and Gamma irradiation: a comparative study

The main objective of this study is to evaluate the effect of irradiation by Gamma rays and Electron Beam (E-Beam) on naturally occurring microorganisms shed in healthcare wastewater issued from multi-specialties hospital. We examined the susceptibility of naturally occurring total indicator bacteriophages towards Gamma rays and E-Beam irradiation to evaluate their appropriateness as viral indicators for healthcare wastewater quality control. Results showed that healthcare wastewater is a rich matrix containing bacteriophages surrogates of pathogenic waterborne viruses (4.5 Log10 PFU/100 mL for SOMCPH and 2.3 Log10 PFU/100 mL for FRNAPH), antibiotic resistant bacteria (Mean concentrations from 2.3 to 5.5 Log10 CFU/100 mL), molds and yeasts (2.7 Log10 CFU/100 mL), and spores of Clostridium perfringens (Mean concentration of 3.3 Log10 CFU/100 mL). After E-Beam irradiation, naturally occurring bacteria in healthcare wastewater showed lower resistance patterns (D10 values ranging between 0.21 ± 0.005 and 0.59 ± 0.005) compared to those obtained after Gamma irradiation (D10 values ranging between 0.25 ± 0.015 and 0.70 ± 0.0001). Spores of Clostridium perfringens were the most resistant assayed microbes either after E-Beam (D10 values of 3.74 ± 0.005) or Gamma irradiation (D10 values of 4.77 ± 0.025) of collected samples. According to inactivation patterns, a dose of 10 kGy was sufficient for a complete inactivation of spores. Bacteriophages isolated from healthcare wastewater showed the same resistance patterns as those previously obtained in urban treated sewage and were inactivated using higher doses than waterborne bacteria (D10 values of SOMCPH 1.46 ± 0.057; D10 values of FRNAPH 1.03 ± 0.057). Their resistance to irradiation treatment in such complex matrix corroborates their use to survey the viral quality of healthcare wastewater before their discharge in the urban sanitation network. D10 value analysis showed that bacteria and bacteriophages inactivation by E-Beam irradiation required lower doses than those required for their inactivation using Gamma rays. According to inactivation patterns, a dose of 7 kGy was sufficient for total inactivation of both pathogenic bacteria and viruses. Thus, E-Beam irradiation seems to be an efficient physical pre-treatment process for healthcare wastewater treatment prior to its discharge in urban sanitation system to ensure compliance with environmental standards and protect public health.

Improved Magnetite Nanoparticle Immobilization on a Carbon Felt Cathode in the Heterogeneous Electro-Fenton Degradation of Aspirin in Wastewater

Toward the improvement of the application of heterogeneous electro-Fenton in water treatment, we report a new strategy of enhancing the immobilization of a magnetite nanoparticle catalyst on a carbon felt cathode. Exploiting the intrinsic ferrimagnetic properties of magnetite nanoparticles, magnet bars were used to attach the magnetite into the void spaces of the porous carbon felt (CF) cathode. The magnetite nanoparticles were prepared by coprecipitation with variations in the molar ratios of Fe²⁺/Fe³⁺. The magnetite was characterized, attached onto the CF electrode with magnetic bars, and used in the heterogeneous electro-Fenton (EF) degradation of aspirin. The effects of the following on the degradation were studied: Fe²⁺/Fe³⁺, pH, catalyst loading concentration, and voltage. The heterogeneous EF degradation of aspirin in wastewater improved by 23% when magnetic bars were used to enhance the immobilization of the magnetite catalysts. The 1:4 Fe²⁺/Fe³⁺ ratio resulted in the highest hetero-EF catalytic degradation of aspirin with complete degradation (100%) achieved after 140 min. For a mixture of pharmaceuticals, degradation percentages of 94.3% (aspirin), 88% (ciprofloxacin), and 80% (paracetamol) in 3 h were obtained. The magnetized magnetite on the cathode was reusable for 10 cycles. Thus, the use of magnets shows a promising strategy to avoid the leaching of ferrimagnetic nanoparticle catalysts embedded in the cathode for heterogeneous EF processes.

Performance of TiO2/UV-LED-Based Processes for Degradation of Pharmaceuticals: Effect of Matrix Composition and Process Variables

Ultra-violet light-emitting diode (UV-LED)-based processes for water treatment have shown the potential to surpass the hurdles that prevent the adoption of photocatalysis at a large scale due to UV-LEDs' unique features and design flexibility. In this work, the degradation of five EU Watch List 2020/1161 pharmaceutical compounds was comprehensively investigated. Initially, the UV-A and UV-C photolytic and photocatalytic degradation of individual compounds and their mixtures were explored. A design of experiments (DoE) approach was used to quantify the effects of numerous variables on the compounds' degradation rate constant, total organic carbon abatement, and toxicity. The reaction mechanisms of UV-A photocatalysis were investigated by adding different radical scavengers to the mix. The influence of the initial pH was tested and a second DoE helped evaluate the impact of matrix constituents on degradation rates during UV-A photocatalysis. The results showed that each compound had widely different responses to each treatment/scenario, meaning that the optimized design will depend on matrix composition, target pollutant reactivity, and required effluent standards. Each situation should be analyzed individually with care. The levels of the electrical energy per order are still unfeasible for practical applications, but LEDs of lower wavelengths (UV-C) are now approaching UV-A performance levels.

Green and efficient synthesis of Co-MOF-based/g-C3N4 composite catalysts to activate peroxymonosulfate for degradation of the antidepressant venlafaxine

Based on single metal-organic framework (MOF) composite catalyst ZIF-67/g-C₃N₄ (ZG), the composite catalysts ZIF-67/MOF-74(Ni)/g-C₃N₄ (ZNG) and ZIF-67/MIL-100(Fe)/g-C₃N₄ (ZMG) with double MOFs were synthesized, used to effectively activate peroxymonosulfate (PMS) for degrade venlafaxine (VEN). Various characterization methods (XRD, FT-IR, Raman, SEM, EDS, TEM and TG) showed that ZIF-67 and g-C₃N₄; ZIF-67, MOF-74(Ni) and g-C₃N₄; as well as ZIF-67, MIL-100(Fe) and g-C₃N₄ successfully formed heterostructures. The series of catalytic degradation results showed that within 120 min, the degradation rate of VEN by ZMG achieved 100% and the mineralization rate reached 51.32%. The removal rate of VEN by ZNG was 91.38%, while that by ZG was only 27.75%. Free radical quenching tests and EPR further confirmed the production of OH and SO₄^-, which could be conducive to the degradation of VEN. The mechanism analysis of PMS activation confirmed that the interaction of Fe²⁺/Co³⁺ was stronger than that of Ni²⁺/Co³⁺, and it was an important driving force to significantly enhance the synergistic effect. Finally, Gauss theory calculation and HPLC-MS/MS were used to analyze the intermediate products of VEN. It was verified that the main chemical reactions in the degradation process of VEN were hydroxylation, dehydration, demethylation and tertiary amine substitution.

Predicting the trend and utility of different photocatalysts for degradation of pharmaceutically active compounds: A special emphasis on photocatalytic materials, modifications, and performance comparison

The rapid rise in the healthcare sector has led to an increase in pharmaceutically active compounds (PhACs) in different aqueous bodies. The toxicity of the PhACs and their ability to persist after conventional treatment processes have escalated research in the field of photocatalytic treatment. Although different photocatalysts have been successful in degrading PhACs, their inherent drawbacks have severely limited their application on a large scale. A substantial amount of research has been aimed at overcoming the high cost of the photocatalytic material, low quantum yield, the formation of toxic end products, etc. Hence, to further research in this field, researchers must have a fair idea of the current trends in the application of different photocatalysts. In this article, the trends in the use of various photocatalysts for the removal of different PhACs have been circumscribed. The performance of different groups of photocatalysts to degrade PhACs from synthetic and real wastewater has been addressed. The drawbacks and advantages of these materials have been compared, and their future in the field of PhACs removal has been predicted using S-curve analysis. Zinc and titanium-based photocatalysts were efficient under UV irradiation, while bismuth and graphene-based materials exhibited exemplary performance in visible light. However, iron-based compounds were found to have the most promising future, which may be because of their magnetic properties, easy availability, low bandgap, etc. Different modification techniques, such as morphology modification, doping, heterojunction formation, etc., have also been discussed. This study may help researchers to clarify the current research status in the field of photocatalytic treatment of PhACs and provide valuable information for future research.

Nano-adsorbents an effective candidate for removal of toxic pharmaceutical compounds from aqueous environment: A critical review on emerging trends

Advancements in medical research has resulted in the modernization of healthcare facilities, subsequently leading to a higher level of production and usage of pharmaceuticals to sustain better quality of life. Pharmaceutical active compounds (PhACs) possess high genotoxicity and eco-toxicity thus presenting numerous side effects to living beings on long-term exposure. The fate and toxicity of PhACs were explored in detail, aiming to elucidate their occurrence and transmission in wastewater treatment systems (WWTPs). Adsorption of pharmaceutical compounds using Nano-adsorbents has gained momentum in recent years owing to their low-cost, high surface area and effectiveness. This review has been conducted in order to widen the utilization of Nano adsorbents in the adsorption of pharmaceutical compounds with a focus on the aqueous environment. The synthesis routes and properties of Nano-adsorbents for removal of PhACs were assessed in a comprehensive way. The recovery and reuse ability of nano-adsorbents also forms an integral part of its application in the removal of PhACs and has hence been delineated.

Assessment of multiclass pharmaceutical active compounds (PhACs) in hospital WWTP influent and effluent samples by UHPLC-Orbitrap MS: Temporal variation, removals and environmental risk assessment

Nowadays the occurrence and associated risks of Pharmaceutical Active Compounds (PhACs) in the aquatic environment comprises a major issue. In the present study, a comprehensive survey on contamination profiles, occurrence, removals, temporal variation and ecological risk of multiclass multiresidue PhACs, such as antibiotics, non-steroidal anti-inflammatories, lipid regulators and phsychiatrics, (including past and newly monitored PhACs as well as some of their metabolites) was performed in wastewaters from the WWTP of Ioannina University hospital along one year period on a monthly sampling basis. WWTP influent and effluent samples were analyzed for physicochemical quality parameters and PhACs concentration levels using Ultra High Performance Liquid Chromatography-Orbitrap-Mass Spectrometry (UHPLC-Orbitrap-MS), after Solid Phase Extraction (SPE) through Oasis HLB cartridges. Influent concentrations ranged between < LOQ (Limit of Quantification) for diclofenac and tolfenamic acid and 48586 ng/L for caffeine, while effluent concentrations between < LOQ for tolfenamic acid and simvastatin and 3361 ng/L for caffeine. Removal efficiencies ranged between -132.6% for venlafaxine and 100% for caffeine. Environmental risk assessment by means of Risk Quotient (RQ) for maximum and minimum concentration levels as well as optimized by the frequency of exceeding toxicity threshold values, RQ_f, was applied revealing that up to 12 PhACs posed acute toxicity (clofibric acid, fenofibrate, sulfadiazine, sulfamethoxazole, trimethoprim, amitryptiline, fluoxetine, fluvoxamine, norfluoxetine, sertraline, venlafaxine, caffeine) while up to 4 compounds exerted long-term toxicity (sulfamethoxazole, fluoxetine, sertraline, caffeine) at least for one of the studied organisms. Furthermore, mixture RQ_MEC/PNEC and RQ_STU effect of multiple compounds showed high potential risks of the target groups in some cases, although some contaminants were not included due to lack of available data. Results can be used to prioritization of PhACs and their metabolites for surveillance in receiving water bodies as well as development of knowledge on toxicity and mechanism(s) of action.

Differentiation Between Metronidazole Residues Disposal by Using Adsorption and Photodegradation Processes Onto MgO Nanoparticles

Background

Metronidazole (MNZ) is an antibiotic form that is considered as a dangerous environmental pollutant due to its widespread use as growth promoters in livestock and aquaculture operations along with its therapeutic application for humans.

Purpose

The objective of this work was to conduct a comparative study between the efficiency of the adsorption and photocatalytic degradation of MNZ in an aqueous solution by using magnesium oxide nanoparticles (MgO NP) under different effects, as well as evaluate the performance, reusability and cost study.

Materials and Methods

Several instruments such as XRD, EDX, SEM, and TEM were used to characterize the chemical composition and morphological properties of the synthesized MgO NP, while the GC-MS analysis was used to monitor the degradation pathway of MNZ particles within 180 min. The simple photo-batch reactor was used to investigate the degradation of MNZ under the effect of UV radiation, initial concentration of MNZ, pH, catalyst loading, inorganic salts addition, time, and temperature.

Results

The degradation efficiency is mainly divided into two steps: 35.7% for maximum adsorption and 57.5% for photodegradation. Adsorption isotherm models confirmed that the process nature is chemisorption and appropriate Langmuir model, as well as to be a nonspontaneous and endothermic reaction according to the thermodynamic study. Adsorption constant during dark condition is smaller than typical adsorption equilibrium constant derived from the Langmuir-Hinshelwood kinetic model through photodegradation of MNZ that follows pseudo-first-order kinetics. Toxicity rates were reduced considerably after the photodegradation process to 88.21%, 79.84%, and 67.32% and 57.45%, 51.98%, and 43.87% by heamolytic and brine shrimp assays, respectively, for initial MNZ concentrations (20, 60, and 100 mg/L).

Conclusion

We significantly recommend using MgO NP as a promising catalyst in the photodegradation applications for other organic pollutants in visible light.

Exploring the Efficiency of UHPLC-Orbitrap MS for the Determination of 20 Pharmaceuticals and Acesulfame K in Hospital and Urban Wastewaters with the Aid of FPSE

Aside from the classical residues of persistent organic pollutants (POPs), the occurrence of emerging contaminants (ECs) in the environment has become a subject of increasing concern due to their harmful impact on the aquatic environment. Wastewater treatment plant (WWTP) effluents are major sources of environmental pollution. Therefore, data concerning their existence is required. In this study, twenty compounds representative of different drug groups considered ECs and belonging to antibiotics, antipsychotics, anti-inflammatory drugs plus acesulfame K were selected to be accurately detected and quantified with UHPLC–LTQ-Orbitrap MS in hospital and urban WWTP effluents. Chromatographic parameters (column efficiency, mobile phase, etc.), as well as mass spectrometry conditions concerning ionization mode and Orbitrap analysis (ESI options, mass resolving power, AGC target, tube lens, injection time), were evaluated. Moreover, a novel fabric phase sorptive extraction (FPSE) method based on fiber glass coated with PEG300 was employed as sample preparation process. Experimental parameters affecting extraction and desorption steps such as sample pH, extraction time, ionic strength, elution time and solvent have been optimized. The optimized methodology was validated providing excellent linearity (R2 > 0.99), and low detection and quantification limits up to 3.1 and 9.3 ng/L, for carbamazepine, respectively. Relative recoveries ranged from 81.1% to 114.0%, while a medium matrix effect for most of the target compounds occurred. Applying the above analytical method in effluents of WWTPs from NW Greece, nine compounds were quantified with concentrations that varied from 55.4 to 728.4 ng/L.

Photocatalytic Hydrogen Evolution over Exfoliated Rh-Doped Titanate Nanosheets

Various amounts of Rh-doped titanate nanosheets (Ti₃NS:Rh(x), where x is doped amount) were prepared to develop a new nanostructured photocatalyst based on metal oxide compounds that can split water to produce H₂ under sunlight. Ti₃NS:Rh(x) was obtained by acid exchange, intercalation, and exfoliation of Rh-doped layered sodium titanate compound (Na₂Ti_3-x Rh _x O₇). A new energy gap was found in the diffuse reflection spectrum of the Ti₃NS:Rh(x) colloidal suspension solution; this new energy gap corresponds to electrons in the 4d level of Rh³⁺ or Rh⁴⁺, which are doped in the Ti⁴⁺ site. A photocatalyst activity of Ti₃NS:Rh(x) for H₂ evolution in water with triethylamine (TEA) as an electron donor was investigated. The appropriate amount of Rh doping can improve the photocatalytic activity of Ti₃NS for H₂ evolution from water using triethylamine (TEA) as a sacrifice agent. The reason was related to the rich state of Rh³⁺ or Rh⁴⁺ doped in the Ti⁴⁺ site of Ti₃NS. Doping Rh 1 mol % of Ti, Ti₃NS:Rh(0.03) shows the H₂ evolution rates up to 1040 nmol/h, which is about 25 times larger than that of nondoped Ti₃NS under UV irradiation (>220 nm) and 302 nmol/h under near-UV irradiation (>340 nm). These results show that the development of new nanostructured photocatalyst based on Rh-doped titanate compounds that can produce H₂ under near-UV irradiation present in sunlight was a success.