Oxidation-coagulation of β-blockers by K2FeVIO4 in hospital wastewater: assessment of degradation products and biodegradability

Transformation of metoprolol in UV/PDS process: Role and mechanisms of degradation and polymerization

Advanced oxidation processes for the treatment of organic pollutants in wastewater suffer from difficulties in mineralization, potential risks of dissolved residues, and high oxidant consumption. In this study, radical-initiated polymerization is dominated in an UV/peroxydisulfate (PDS) process to eliminate organic pollutant of pharmaceutical metoprolol (MTP). Compared with an ideal degradation-based UV/PDS process, the present process can save four fifths of PDS consumption at the same dissolved organic carbon removal of 47.3%. Simultaneously, organic carbon can be recovered from aqueous solution by separating solid polymers at a ratio of 50% of the initial chemical oxygen demand. The chemical structure of products was analyzed to infer the transformation pathways of MTP. Unlike previous studies on simple organic pollutants that the polymerization can occur independently, the polymerization of MTP is dependent on the partial degradation of MTP, and the main monomer in polymerization is a dominant degradation product (4-(2-methoxyethyl)-phenol, denoted as DP151). The separated solid polymers are formed by repeated oxidation and coupling of DP151 or its derivatives through a series of intermediate oligomers. This proof-of-concept study demonstrates the advantage of polymerization-dominated mechanism on dealing with large organic molecules with complex structures, as well as the potential of UV/PDS process for simultaneous organic pollution reduction and organic carbon recovery from aqueous solution.

Ferrate(VI)/Periodate System: Synergistic and Rapid Oxidation of Micropollutants via Periodate/Iodate-Modulated Fe(IV)/Fe(V) Intermediates

The presence of organic micropollutants in water sources worldwide has created a need for the development of effective and selective oxidation methods in complex water matrices. This study is the first report of the combination of ferrate(VI) (Fe(VI)) and periodate (PI) for synergistic, rapid, and selective elimination of multiple micropollutants. This combined system was found to outperform other Fe(VI)/oxidant systems (e.g., H₂O₂, peroxydisulfate, and peroxymonosulfate) in rapid water decontamination. Scavenging, probing, and electron spin resonance experiments showed that high-valent Fe(IV)/Fe(V) intermediates, rather than hydroxyl radicals, superoxide radicals, singlet oxygen, and iodyl radicals, played a dominant role in the process. Further, the generation of Fe(IV)/Fe(V) was evidenced directly by the ⁵⁷Fe Mössbauer spectroscopic test. Surprisingly, the reactivity of PI toward Fe(VI) is rather low (0.8223 M^-1 s^-1) at pH 8.0, implying that PI was not acting as an activator. Besides, as the only iodine sink of PI, iodate also played an enhanced role in micropollutant abatement by Fe(VI) oxidation. Further experiments proved that PI and/or iodate might function as the Fe(IV)/Fe(V) ligands, causing the utilization efficiency of Fe(IV)/Fe(V) intermediates for pollutant oxidation to outcompete their auto-decomposition. Finally, the oxidized products and plausible transformation pathways of three different micropollutants by single Fe(VI) and Fe(VI)/PI oxidation were characterized and elucidated. Overall, this study proposed a novel selective oxidation strategy (i.e., Fe(VI)/PI system) that could efficiently eliminate water micropollutants and clarified the unexpected interactions between PI/iodate and Fe(VI) for accelerated oxidation.

Fate of selected pharmaceuticals in hospital and municipal wastewater effluent: occurrence, removal, and environmental risk assessment

The concentrations and distribution of β-blockers, lipid regulators, and psychiatric and cancer drugs in the influent and effluent of the municipal wastewater treatment plant (WWTP) and the effluent of 16 hospitals that discharge into the wastewater treatment plant mentioned in this study at two sampling dates in summer and winter were examined. The pharmaceutical contribution of hospitals to municipal wastewater was determined. The removal of target pharmaceuticals was evaluated in a WWTP consisting of conventional biological treatment using activated sludge. Additionally, the potential environmental risk for the aquatic receiving environments (salt lake) was assessed. Beta-blockers and psychiatric drugs were detected in high concentrations in the wastewater samples. Atenolol (919 ng/L) from β-blockers and carbamazepine (7008 ng/L) from psychiatric pharmaceuticals were detected at the highest concentrations in hospital wastewater. The total pharmaceutical concentration determined at the WWTP influent and effluent was between 335 and 737 ng/L in summer and between 174 and 226 ng/L in winter. The concentrations detected in hospital effluents are higher than the concentrations detected in WWTP. The total pharmaceutical contributions from hospitals to the WWTP in summer and winter were determined to be 2% and 4%, respectively. Total pharmaceutical removal in the WWTP ranged from 23 to 54%. According to the risk ratios, atenolol could pose a high risk (risk quotient > 10) for fish in summer and winter. There are different reasons for the increase in pharmaceutical consumption in recent years. One of these reasons is the COVID-19 pandemic, which has been going on for 2 years. In particular, hospitals were operated at full capacity during the pandemic, and the occurrence and concentration of pharmaceuticals used for the therapy of COVID-19 patients has increased in hospital effluent. Pandemic conditions have increased the tendency of people to use psychiatric drugs. It is thought that beta-blocker consumption has increased due to cardiovascular diseases caused by COVID-19. Therefore, the environmental risk of pharmaceuticals for aquatic organisms in hospital effluent should be monitored and evaluated.

Removal of microorganic pollutants in aquatic environment: The utilization of Fe(VI)

Microorganic pollutants (MOPs) in aquatic environment with low levels but high toxicity are harmful to ecosystem and human health. Fe(VI) has a dual-functional role in oxidation and coagulation, and can effectively remove MOPs, heavy metal, phosphate, particulates and colloids. Moreover, Fe(VI) can combine with traditional coagulants, or use as a pretreatment for membrane treatment because of its characters to generate nanoparticles by degradation in water. Based on the relevant toxicity experiments, Fe(VI) had been proved to be safe for the efficient treatment of MOPs. For better utilization of Fe(VI), its oxidation and coagulation mechanisms are summarized, and the knowledge about the control parameters, utilization methods, and toxicity effect for Fe(VI) application are reviewed in this paper. pH, different valences of iron, environmental substances, and other parameters are summarized in this study to clarify the important factors in the treatment of MOPs with Fe(VI). In the future study, aiming at cost reduction in Fe(VI) preparation, transportation and storage, enhancement of oxidation in the intermediate state, and better understanding the mechanism between interface and Fe(VI) oxidation will help promote the application of Fe(VI) in the removal of MOPs. This study offers guidelines for the application and development of Fe(VI) for the treatment of MOPs in aquatic environment.

Degradation of ofloxacin by potassium ferrate: kinetics and degradation pathways

Drug residues, including various antibiotics, are being increasingly detected in aqueous environments. Ofloxacin (OFX) is one such antibiotic that is widely used in the treatment of several bacterial infections; however, chronic exposure to this antibiotic can have adverse impacts on human health. Hence, the identification of an effective OFX degradation method is essential. Thus, in this study, the degradation performance of OFX using potassium ferrate (Fe(VI)) under the influence of different initial concentrations, pH, temperature, and common ions in water was investigated. OFX degradation by Fe(VI) was directly proportional to the concentration of Fe(VI) and temperature and inversely proportional to the pH. Among the common ions in water, Fe³⁺ and NH₄⁺ could significantly promote the degradation of OFX by Fe(IV), while humic acid (HA) significantly inhibited it. Under the conditions of [Fe(VI)]:[OFX] = 15:1, T = 25℃, and pH = 7.0, the removal efficiency of 8 μM OFX reached more than 90% in 4 min. Seven intermediates were identified by quadrupole time-of-flight tandem ultra-performance liquid chromatography mass spectrometry (Q-TOF LC/MS), and two possible pathways for the degradation of OFX by Fe(VI) were proposed. Overall, the results suggest that advanced oxidation technology using Fe(VI) is effective for treating wastewater containing OFX.

An Update on the Use of Molecularly Imprinted Polymers in Beta-Blocker Drug Analysis as a Selective Separation Method in Biological and Environmental Analysis

Beta-blockers are antihypertensive drugs and can be abused by athletes in some sport competitions; it is therefore necessary to monitor beta-blocker levels in biological samples. In addition, beta-blocker levels in environmental samples need to be monitored to determine whether there are contaminants from the activities of the pharmaceutical industry. Several extraction methods have been developed to separate beta-blocker drugs in a sample, one of which is molecularly imprinted polymer solid-phase extraction (MIP-SPE). MIPs have some advantages, including good selectivity, high affinity, ease of synthesis, and low cost. This review provides an overview of the polymerization methods for synthesizing MIPs of beta-blocker groups. The methods that are still widely used to synthesize MIPs for beta-blockers are the bulk polymerization method and the precipitation polymerization method. MIPs for beta-blockers still need further development, especially since many types of beta-blockers have not been used as templates in the MIP synthesis process and modification of the MIP sorbent is required, to obtain high throughput analysis.

Sustainable ferrate oxidation: Reaction chemistry, mechanisms and removal of pollutants in wastewater

This review is intended to evaluate the use of ferrate (Fe(VI)), being a green coagulant, sustainable and reactive oxidant, to remove micro pollutants especially pharmaceutical pollutants in contaminated water. After a brief description of advanced oxidation processes, fundamental dimensions regarding the nature, reactivity, and chemistry of this oxidant are summarized. The degradation of contaminants by Fe(VI) involves several mechanisms and reactive agents which are critically evaluated. The efficiency and chemistry of Fe(VI) oxidation differs according to the reaction conditions and activation agent, such as soluble Fe(VI) processes, which involve Fe(VI), UV light, and electro-Fe(VI) oxidation. Fe(VI) application methods (including single dose, multiple doses, chitosan coating etc), and Fe(VI) with activating agents (including sulfite, thiosulfate, and UV) are also described to degrade the micro pollutants. Besides, application of Fe(VI) to remove pharmaceuticals in wastewater are intensely studied. Electrochemical prepared Fe(VI) has more wide application than wet oxidation method. Meanwhile, we elaborated Fe(VI) performance, limitations, and proposed innovative aspects to improve its stability, such as the generation of Fe(III), synergetic effects, nanopores entrapment, and nanopores capsules. This study provides conclusive direction for synergetic oxidative technique to degrade the micro pollutants.

Exploring the phototransformation and assessing the in vitro and in silico toxicity of a mixture of pharmaceuticals susceptible to photolysis

The present study comprehensively investigates the phototransformation and ecotoxicity of a mixture of twelve pharmaceutically active compounds (PhACs) susceptible to photolysis. Namely, three antibiotics (ciprofloxacin, levofloxacin, moxifloxacin), three antidepressants (bupropion, duloxetine, olanzapine), three anti-inflammatory drugs (diclofenac, ketoprofen, nimesulide), two beta-blockers (propranolol, timolol) and the antihistamine ranitidine were treated under simulated solar irradiation in ultra-pure and river water. A total of 166 different transformation products (TPs) were identified by ultra-high performance liquid chromatography coupled with Orbitrap high resolution mass spectrometry (UHPLC-Orbitrap HRMS), revealing the formation of twelve novel TPs and forty-nine not previously described in photolytic studies. The kinetic profiles of the major TPs resulting from a series of chemical reactions involving hydroxylation, cleavage and oxidation, dehalogenation, decarboxylation, dealkylation and photo substitution have been investigated and the transformation pathways have been suggested. Additionally, an in vitro approach to the toxicity assessment of daphnids was contrasted with ecotoxicity data based on the Ecological Structure Activity Relationships (ECOSAR) software comprising the in silico tool to determine the adverse effects of the whole mixture of photolabile parent compounds and TPs. The results demonstrated that photolysis of the target mixture leads to a decrease of the observed toxicity.

Efficient degradation of typical pharmaceuticals in water using a novel TiO2/ONLH nano-photocatalyst under natural sunlight

Photocatalytic degradation of typical pharmaceuticals in natural sunlight and in actual water is of great significance. In this study, the oxygen or nitrogen linked heptazine-base polymer (ONLH) was successfully incorporated with TiO₂ nanoparticles and formed a TiO₂/ONLH nanocomposite which was responded to the natural sunlight. Under natural sunlight, the TiO₂/ONLH can effectively degrade ten types of pharmaceuticals. In particular, fluoroquinolone containing N-piperazinyl, and cardiovascular drugs containing long aromatic side chains were easily degraded. The half-life of the best degradation performance of propranolol was less than 5 min. The rate constants of propranolol using the TiO₂/ONLH were approximately six- and eight-fold higher than those of pristine TiO₂ and ONLH, respectively. Two reactive species (OH and O₂^-) facilitated the rapid degradation of propranolol, which occurred primarily through the hydroxyl radical addition, ring-opening, and ipso substitution reactions. An acute toxicity test using luminescent bacteria indicated that the toxicity of the propranolol reaction solution gradually decreased with lower total organic carbon (TOC). According to the toxicity evaluation of monomer products, the TiO₂/ONLH also reduced the generation of toxic transformation products. The effects of actual water/wastewater have further shown the TiO₂/ONLH might be applied for the removal of pharmaceuticals in wastewater.

Effect of Metal Ions on Oxidation of Micropollutants by Ferrate(VI): Enhancing Role of FeIV Species

This paper investigated the oxidation of recalcitrant micropollutants [i.e., atenolol (ATL), flumequine, aspartame, and diatrizoic acid] by combining ferrate(VI) (Fe^VIO₄^2-, Fe^VI) with a series of metal ions [i.e., Fe(III), Ca(II), Al(III), Sc(III), Co(II), and Ni(II)]. An addition of Fe(III) to Fe^VI enhanced the oxidation of micropollutants compared solely to Fe^VI. The enhanced oxidation of studied micropollutants increased with increasing [Fe(III)]/[Fe^VI] to 2.0. The complete conversion of phenyl methyl sulfoxide (PMSO), as a probe agent, to phenyl methyl sulfone (PMSO₂) by the Fe^VI-Fe(III) system suggested that the highly reactive intermediate Fe^IV/Fe^V species causes the increased oxidation of all four micropollutants. A kinetic modeling of the oxidation of ATL demonstrated that the major species causing the increase in ATL removal was Fe^IV, which had an estimated rate constant as (6.3 ± 0.2) × 10⁴ M^-1 s^-1, much higher than that of Fe^VI [(5.0 ± 0.4) × 10^-1 M^-1 s^-1]. Mechanisms of the formed oxidation products of ATL by Fe^IV, which included aromatic and/or benzylic oxidation, are delineated. The presence of natural organic matter significantly inhibited the removal of four pollutants by the Fe^VI-Fe(III) system. The enhanced effect of the Fe^VI-Fe(III) system was also seen in the oxidation of the micropollutants in river water and lake water.

Comparative evaluation of metoprolol degradation by UV/chlorine and UV/H2O2 processes

The degradation of metoprolol (MTP), a β-blocker commonly used for cardiovascular diseases, by UV/chlorine and UV/H₂O₂ processes was comparatively evaluated. MTP direct photolysis at 254 nm could be neglected, but remarkable MTP degradation was observed in both the UV/chlorine and UV/H₂O₂ systems. Compared with UV/H₂O₂, UV/chlorine has a more pronounced MTP degradation efficiency. In addition to primary radicals (OH and Cl), secondary radicals (ClO and Cl₂^-) played a pivotal role in degrading MTP by UV/chlorine process. The relative contributions of hydroxyl radicals (OH) and reactive chlorine species (RCS) in the UV/chlorine system varied at different solution pH values (i.e., the contribution of RCS increased from 57.7% to 75.1% as the pH increased from 6 to 8). The degradation rate rose as the oxidant dosage increased in the UV/chlorine and UV/H₂O₂ processes. The presence of Cl^- slightly affected MTP degradation in both processes, while the existence of HCO₃^- and HA inhibited MTP degradation to different extents in both processes. In terms of the overall cost of electrical energy, UV/chlorine is more cost efficient than UV/H₂O₂. The degradation products during the two processes were identified and compared, and the degradation pathways were proposed accordingly. Compared with the direct chlorination of MTP, pre-oxidation with UV/chlorine and UV/H₂O₂ significantly enhanced the formation of commonly known DBPs. Therefore, when using UV/chlorine and UV/H₂O₂ in real waters to remove organic pollutants, the possible risk of enhanced DBP formation resulting from the degradation of certain pollutants during post-chlorination should be carefully considered.

Degradation of propranolol by UV-activated persulfate oxidation: Reaction kinetics, mechanisms, reactive sites, transformation pathways and Gaussian calculation

Contamination with β-blockers such as propranolol (PRO) poses a potential threat to human health and ecological system. The present study investigated the kinetics and mechanisms of PRO degradation by UV-activated persulfate (UV/PS) oxidation. Here, the experimental results showed that the degradation of PRO followed pseudo-first-order reaction kinetics, the degradation rate constant (k_obs) was increased dramatically with increasing PS dosage or decreasing initial PRO concentration. And increasing the initial solution pH could also enhance the degradation efficiency of PRO. Radical scavenging experiments demonstrated that the main radical species was sulfate radicals (SO₄^•-), with hydroxyl radicals (HO·) playing a less important role. Meanwhile, the second-order rate constants of PRO degradation with SO₄^•- and HO· were determined to be 1.94 × 10¹⁰ M^-1 s^-1 and 6.77 × 10⁹ M^-1 s^-1, respectively. In addition, the presence of natural organic matter (NOM) and nitrate anion (NO₃^-) showed inhibitory effect on PRO degradation, whereas bicarbonate anion (HCO₃^-) and chlorine anion (Cl^-) greatly enhanced the degradation of PRO. Moreover, the transformation products of PRO were identified by applying ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC/Q-TOF-MS) technique. Molecular orbital calculations were used to estimate the reaction site of PRO with radicals, simultaneously. Hence, the transformation pathways including hydroxylation, dehydration, naphthalene ring opening, and the cleavage of aldehyde groups were proposed. This work enriches the mechanism of PRO degradation under UV/PS system on the basis of results obtained by experimental characterization and Gaussian theoretical calculation.

Binuclear cobalt phthalocyanine supported on manganese octahedral molecular sieve: High-efficiency catalyzer of peroxymonosulfate decomposition for degrading propranolol

Propranolol (PRO) is widely detected in the aquatic environment and proved to be detrimental to multifarious aquatic organisms. In view of some virtues of sulfate radicals than hydroxyl radicals, advanced oxidation technologies that involve the activation of peroxymonosulfate (PMS) have stimulated wide-ranging research on the PRO removal. In this paper, a composite (C₂NOMS-2) of amino-functionalized manganese octahedral molecular sieve (NOMS-2) and binuclear cobalt phthalocyanine (Co₂CPc) was synthesized easily, and utilized as a catalyzer for PMS to degrade PRO in water. The apparent rate constants of PRO degradation by PMS with C₂NOMS-2 as a catalyst was found to be higher than with NOMS-2, Co₂CPc and the composite of uninuclear cobalt phthalocyanine (CoCPc) and NOMS-2. The catalytic ability of C₂NOMS-2 was investigated under various reaction conditions: catalyst dosages (0.5-2.0 g/L), PMS doses (50-500 mg/L), initial pH (5-11), reaction temperature (20-35 °C), and natural water constituents (Cl^-, HCO₃^-, and sodium huminate). Radical scavenging tests and electron paramagnetic resonance spectroscopy showed that ¹O₂ was the most critical reactive oxygen species, and conceivable mechanisms of PMS activation with C₂NOMS-2 were proposed established on the curve estimation of high-resolution XPS spectra, revealing that the generation of reactive oxygen species was mainly resulted from the cycles of Mn³⁺/Mn⁴⁺, Co³⁺/Co²⁺ and surface lattice oxygen/surface adsorbed oxygen. The intermediate products of propranolol degradation were identified by LC-MS/MS. Cycling experiments and ion dissolution detection suggested that C₂NOMS-2 could maintain satisfactory stability in an aqueous system.

Advanced coagulation using in-situ generated liquid ferrate, Fe (VI), for enhanced pretreatment in seawater RO desalination during algal blooms

Harmful algal blooms (HABs) are considered a major threat for seawater reverse osmosis (SWRO) plants. The presence of HABs in the raw feed water can cause increase of chemical consumption within the desalination plant, increase membrane fouling rate and might lead to plant shutdown. The removal of Algal Organic Matters (AOMs) during the pretreatment will help in increasing the membrane lifetime, reduce operation cost and increase the plant reliability. In this study, the efficiency of liquid ferrate and ferric chloride during coagulation on the removal of AOMs was investigated. The liquid ferrate was generated in-situ by wet oxidation of ferric iron using hypochlorite in a caustic medium. Two seawater models were employed, the first one contains 10 mg c/L of sodium alginate and the second one contains also 10 mg c/L of Chaetoceros affinis algae (CA). During the advanced coagulation, liquid ferrate proved to be more effective in removing AOM than ferric chloride, with an overall DOC removal of 90%, enabling 100% algal removal and the inactivation of 99.99% of the microorganisms. The results presented in this study highlights the efficiency of liquid ferrate as seawater pretreatment during the HABs events.

Droplet flow-assisted heterogeneous electro-Fenton reactor for degradation of beta-blockers: response surface optimization, and mechanism elucidation

In this study, we report an effective degradation method for trace level beta-blockers (propranolol and acebutolol) in hospital wastewater using a new droplet flow-assisted heterogeneous electro-Fenton reactor (DFEF) system. Biogenic iron-carbon nanocomposites (RHS/C-x% Fe) as eco-friendly and low-cost heterogeneous Fenton catalysts were synthesized from rice husk via hydrolytic sol-gel routes. Here, we demonstrate the use of natural air as a nebulizing agent for fast and continuous catholyte air saturation and Fenton catalyst transfer to the cathode electrode. The effects of key operational parameters were evaluated and optimized using central composite design. Results clearly indicated that enhanced beta-blocker degradation was mainly dependent on the interactive effects of electrolysis time, current density, and catalyst dosage. Fast degradation efficiencies (≥ 99.9%) was recorded at neutral pH conditions. The decay followed pseudo-first-order kinetics with degradation rates of up to 2.72 × 10^-2 and 2.54 × 10^-2 min^-1 for acebutolol and propranolol, respectively. The synergistic contribution of ^•OH_bulk attributable to DFEF process and ^•OH_adsorbed for anodic oxidation (AO) at the anode electrode significantly enhanced the degradation process. Compared to AO, the conventional flow-assisted electro-Fenton (FEF), and the batch electro-Fenton (BEF), DFEF degradation efficiency followed a decreasing order: DFEF ˃ FEF ˃ BEF˃ AO. This trend in performance was mainly due to the fast and continuous cathodic electro-generation of H₂O₂ and Fe²⁺ regeneration. Additionally, in order to elucidate degradation mechanism, we used a combination of DFEF approach with liquid chromatography-tandem mass spectrometry analysis. This approach demonstrates a simple, cleaner, and highly efficient degradation approach for trace level recalcitrant pollutants in a complex aquatic matrix, without the need for external chemical addition and pH adjustment.

Enhanced degradation of organic contaminants by zero-valent iron/sulfite process under simulated sunlight irradiation

Degradation of propranolol (PrP) by a combined zero-valent iron and sulfite system under simulated sunlight irradiation (ZVI/sulfite/photo) was investigated. Simulated sunlight irradiation enhanced the degradation of PrP by accelerating the decomposition of ferric sulfite complex as a result to producing sulfite radical (SO₃^•-). As bubbles would block the transport of photons in the reaction solution, mechanical aeration rather than purging air was suggested to sustain the essential dissolved oxygen. The degradation of PrP increased with the elevation of initial ZVI concentration from 0.05 to 0.5 mM, but decreased a little with further increasing ZVI concentration to 1.0 mM. The degradation of PrP raised from 68.5% to 98.7% while sulfite dose increased from 0.1 to 2.0 mM. High removal efficiencies were always achieved when the initial PrP concentration ranged from 10 to 40 μM. As HSO₃^- which can efficiently complex Fe(II) and transfer Fe(III) to Fe(II) is the dominant species of sulfite at pH 4.0-6.0, the highest removal of PrP was achieved at pH 4.0-6.0. The presence of bicarbonate and humic acid significantly retarded the removal of PrP, while chloride ions could promote the removal of PrP to some extent. SO₄^•-, HO^• and SO₅^•- were suggested to account for PrP removal, while SO₄^•- was evidenced to be the dominant radicals. Good reuse of ZVI in the system was also achieved as the removal of PrP kept higher than 80% after repeatedly used for 5 times. Possible degradation pathways of PrP in the ZVI/sulfite/photo system were accordingly proposed based on LC-MS and density functional theory calculation. The removal of amitriptyline, nitrobenzene, imipramine and methylparaben in the ZVI/sulfite/photo system was also evaluated. As a reducing agent, sulfite is expected to consume the possible formed bromine-containing intermediates as a result to inhibiting the formation of bromate, which is better than the activated persulfate system.

Kinetic and mechanistic investigations of the degradation of propranolol in heat activated persulfate process

This study investigated the heat activated persulfate (heat/PS) process in the degradation of propranolol from water. Various factors (e.g., temperature, persulfate dose, initial pH and natural water constituent) on PRO degradation kinetics have been investigated. The results showed that the PRO degradation followed a pseudo-first-order kinetics pattern. As temperature rises, the pseudo-first-order rate constant (k obs) was improved significantly, and the k obs determined at 40-70 °C satisfied the Arrhenius equation, yielding an activation energy of 99.0 kJ mol-1. The radical scavenging experiments and the EPR tests revealed that both SO4˙- and ·OH participated in degrading PRO, with SO4˙- playing a dominant role. Higher PS concentration and neutral pH favored PRO degradation. The impact of Cl- and HCO3 - were concentration-dependent. A lower concentration of Cl- and HCO3 - could accelerate PRO degradation, while the presence of HA showed inhibitory effects. Seven degradation products were recognized through LC/MS/MS analysis. Cleavage of ether bond, hydroxylation, and ring-opening of naphthol moiety are involved in the PRO's degradation pathway. Finally, the formation of disinfection byproducts (DBPs) before and after pre-treated by heat/PS was also evaluated. Compared with direct chlorination of PRO, the heat/PS pre-oxidation greatly impacted the DBPs formation. The higher PRO removal efficiency in natural water indicated the heat/PS process might be capable of treating PRO-containing water samples, however, its impacts on the downstream effect on DBPs formation should be also considered.

Ultrasound-assisted heterogeneous activation of persulfate by nano zero-valent iron (nZVI) for the propranolol degradation in water

This study investigated the degradation of propranolol (PRO), a beta (β)-blockers, by nano zero-valent iron (nZVI) activated persulfate (PS) under ultrasonic irradiation. Effects of several critical factors were evaluated, inclusive of PS concentration, nZVI dosage, ultrasound power, initial pH, common anions, and chelating agent on PRO degradation kinetics. Higher PS concentration, nZVI dosage and ultrasound power as well as acidic pH favored the PRO degradation. Conversely, anions and chelating agent took on the inhibitory effect towards PRO degradation to different extents. Furthermore, the variations of morphology and surface composition of nZVI before and after the reaction were characterized by TEM, XRD and XPS. Finally, on the basis of identified degradation intermediates by LC/MS/MS analysis, this work tentatively proposed the degradation pathways. These encouraging results suggest that US/nZVI/PS process is a promising strategy for the treatment of PRO-induced water pollutant.

Fe(VI)-Mediated Single-Electron Coupling Processes for the Removal of Chlorophene: A Combined Experimental and Computational Study

Potassium ferrate [Fe(VI)] is a promising oxidant widely used in water treatment for the elimination of organic pollutants. In this work, the reaction kinetics, products, and mechanisms of the antimicrobial agent chlorophene (CP) undergoing Fe(VI) oxidation in aqueous solutions were investigated. CP is very readily degraded by Fe(VI), with the apparent second-order rate constant, k, being 423.2 M^-1 s^-1 at pH 8.0. A total of 22 oxidation products were identified using liquid chromatography-quadrupole time-of-flight-mass spectrometry , and their structures were further elucidated using tandem mass spectrometry. According to the extracted peak areas in mass spectra, the main reaction products were the coupling products (dimers, trimers, and tetramers) that formed via single-electron coupling. Theoretical calculations demonstrated that hydrogen abstraction should easily occur at the hydroxyl group to produce reactive CP· radicals for subsequent polymerization. Cleavage of the C-C bridge bond, electrophilic substitution, hydroxylation, ring opening, and decarboxylation were also observed during the Fe(VI) oxidation process. In addition, the degradation of CP by Fe(VI) was also effective in real waters, which provides a basis for potential applications.

Removal of selected pharmaceuticals and personal care products in reclaimed water during simulated managed aquifer recharge

This study investigated the removal of selected pharmaceuticals and personal care products (PPCPs) in a simulated managed aquifer recharge (MAR) system. The PPCPs included antibiotic, antiepileptic, antihypertensive, anti-inflammatory, and antilipidemic drugs, contrast media, herbicides, and stimulants. We first monitored the occurrence and fate of 22 PPCPs at a water reclamation facility (WRF) in Korea, and found carbamazepine and primidone were not readily removed (below 25% removal in average) by the WRF. This reclaimed water passed through a laboratory-scale soil column set-up at 0.5 m/d over one year, simulating MAR system. Atenolol, propranolol, and trimethoprim exhibited higher removal rates (>80%) than other PPCPs through the simulated MAR, while atrazine, carbamazepine, lincomycin, primidone, and sulfamethazine were not readily removed, exhibiting removal rates below 20%. It can be efficient to monitor and manage these recalcitrant compounds at MAR systems to improve water quality.

The effects and the toxicity increases caused by bicarbonate, chloride, and other water components during the UV/TiO2 degradation of oxazaphosphorine drugs

The influences of HCO₃^-, Cl^-, and other components on the UV/TiO₂ degradation of the antineoplastic agents ifosfamide (IFO) and cyclophosphamide (CP) were studied in this work. The results indicated that the presence of HCO₃^-, Cl^-, NO₃^-, and SO₄^2- in water bodies resulted in lower degradation efficiencies. The half-lives of IFO and CP were 1.2 and 1.1 min and increased 2.3-7.3 and 3.2-6.3 times, respectively, in the presence of the four anions (initial compound concentration = 100 μg/L, TiO₂ loading =100 mg/L, anion concentration = 1000 mg/L, and pH = 8). Although the presence of HCO₃^- in the UV/TiO₂/HCO₃^- system resulted in a lower degradation rate and less byproduct formation for IFO and CP, two newly identified byproducts, P11 (M.W. = 197) and P12 (M.W. = 101), were formed and detected, suggesting that additional pathways occurred during the reaction of •CO₃^- in the system. The results also showed that •CO₃^- likely induces a preferred ketonization pathway. Besides the inorganic anions HCO₃^-, Cl^-, NO₃^-, and SO₄^2-, the existence of dissolved organic matter in the water has a significant effect and inhibits CP degradation. Toxicity tests showed that higher toxicity occurred in the presence of HCO₃^- or Cl^- during UV/TiO₂ treatment and within 6 h of reaction time, implying that the effects of these two anions should not be ignored when photocatalytic treatment is applied to treat real wastewater.

Identification and characterization of photodegradation products of metoprolol in the presence of natural fulvic acid by HPLC-UV-MSn

Metoprolol is a β-blocker highly prescribed for the treatment of heart diseases. It is not efficiently removed in wastewater treatment plants and it has been detected not only in the treated effluents, but also in natural waters. Thus, the knowledge of its fate in the environment is an important issue, and photodegradation is an important degradation pathway. While direct photodegradation of metoprolol by solar light is not relevant, there is evidence in the literature that it suffers indirect photodegradation and a few studies have been published showing the important role of dissolved humic matter as photo-sensitizer. However, the identification of the photoproducts formed in the presence of humic matter is very poor, since only 2 photoproducts had been identified. This study investigated the degradation of metoprolol under simulated solar radiation and in the presence of fulvic acids (FA) extracted from a river. During the photodegradation experiments we observed the formation of new compounds which were separated and tentatively identified by HPLC-UV-ESI-MSⁿ. At least 16 compounds were tentatively identified, including the 2 compounds previously identified in the literature and 4 new compounds which had not been detected by other authors as degradation products of metoprolol, even when submitted to artificial degradation processes.

Evaluation of a sequencing batch reactor sewage treatment rig for investigating the fate of radioactively labelled pharmaceuticals: Case study of propranolol

Pharmaceuticals are frequently detected in the aquatic environment, and have potentially damaging effects. Effluents from sewage treatment plants (STPs) are major sources of these substances. The use of sequencing batch reactor (SBR) STPs, involving cycling between aerobic and anoxic conditions to promote nitrification and denitrification, is increasing but these have yet to be understood in terms of removal of pharmaceutical residues. This study reports on the development of a laboratory rig to simulate a SBR. The rig was used to investigate the fate of radiolabelled propranolol. This is a commonly prescribed beta blocker, but with unresolved fate in STPs. The SBR rig (4.5 L) was operated on an 8 h batch cycle with settled sewage. Effective treatment was demonstrated, with clearly distinct treatment phases and evidence of nitrogen removal. Radiolabelled (14)C-propranolol was dosed into both single (closed) and continuous (flow-through) simulations over 13 SBR cycles. Radioactivity in CO2 off-gas, biomass and liquid was monitored, along with the characteristics of the sewage. This allowed apparent rate constants and coefficients for biodegradation and solid:water partitioning to be determined. Extrapolation from off-gas radioactivity measurements in the single dose 4-d study suggested that propranolol fell outside the definitions of being readily biodegradable (DegT50 = 9.1 d; 60% biodegradation at 12.0 d). During continuous dosing, 63-72% of propranolol was removed in the rig, but less than 4% of dose recovered as (14)CO2, suggesting that biodegradation was a minor process (Kbiol(M) L kg d(-1) = 22-49) and that adsorption onto solids dominated, giving rise to accumulations within biomass during the 17 d solid retention time in the SBR. Estimations of adsorption isotherm coefficients were different depending on which of three generally accepted denominators representing sorption sites was used (mixed liquor suspended solids, reactor COD or mass of waste activated sludge). With further development and evaluation, the rig developed for simulating SBR processes has potential to be used for informing better environmental risk assessments for those pharmaceuticals showing ambiguous results in field fate studies.

Re-Designing of Existing Pharmaceuticals for Environmental Biodegradability: A Tiered Approach with β-Blocker Propranolol as an Example

Worldwide, contamination of aquatic systems with micropollutants, including pharmaceuticals, is one of the challenges for sustainable management of water resources. Although micropollutants are present at low concentrations, many of them raise considerable toxicological concerns, particularly when present as components of complex mixtures. Recent research has shown that this problem cannot be sustainably solved with advanced effluent treatment. Therefore, an alternative that might overcome these environmental problems is the design of new pharmaceutical molecules or the redesign of existing pharmaceutical molecules that present the functionality needed for their application and have improved environmental biodegradability. Such redesigning can be performed by small molecular changes in the drug molecule with intact drug moiety which could incorporate the additional attribute such as biodegradability while retaining its pharmacological potency. This proof of concept study provides an approach for the rational redesign of a given pharmaceutical (Propranolol as an example). New derivatives with small molecular changes as compared to propranolol molecule were generated by a nontargeted photolysis process. Generated derivatives with intact drug moieties (an aromatic ring and a β-ethanolamine moiety) were further screened for aerobic biodegradability and pharmacological potency. The feasibility of the approach of redesigning an existing pharmaceutical through nontargeted generation of new derivatives with intact drug moiety and through subsequent screening was demonstrated in this study. Application of such approaches in turn might contribute to the protection of water resources in a truly sustainable manner.

A sustainable chemistry solution to the presence of pharmaceuticals and chemicals in the aquatic environment – the example of re-designing β-blocker Atenolol

Generation of new biodegradable, drug-like molecules through re-designing certain moieties from known drug molecules while preserving their pharmacophore.

Beta-blockers in the environment: part I. Mobility and hydrolysis study

Beta-blockers (BB) are one of the most widely used pharmaceuticals whose presence in different environmental compartments has already been proven in concentrations of even up to a few μg L(-1). However, our knowledge of their fate in the environment is still scarce. To obtain a better understanding on the environmental behavior of three selected BB comprehensive laboratory experiments assessing their mobility and hydrolytic stability has been conducted. Propranolol, metoprolol and nadolol--the most commonly consumed and detected in environmental samples--were selected as representatives of this group of pharmaceuticals. The objectives of our research were: (i) evaluation of the sorption potential and an explanation of the sorption mechanisms of these compounds onto soil and clay mineral (kaolinite); and (ii) investigation of the hydrolytic stability of these BB according to OECD 111. This comprehensive study supports the Environmental Risk Assessment of these pharmaceuticals.

Beta-blockers in the environment: part II. Ecotoxicity study

The increasing consumption of beta-blockers (BB) has caused their presence in the environment to become more noticeable. Even though BB are safe for human and veterinary usage, ecosystems may be exposed to these substances. In this study, three selected BB: propranolol, metoprolol and nadolol were subjected to ecotoxicity study. Ecotoxicity evaluation was based on a flexible ecotoxicological test battery including organisms, representing different trophic levels and complexity: marine bacteria (Vibrio fischeri), soil/sediment bacteria (Arthrobacter globiformis), green algae (Scenedesmus vacuolatus) and duckweed (Lemna minor). All the ecotoxicological studies were supported by instrumental analysis to measure deviation between nominal and real test concentrations. Based on toxicological data from the green algae test (S. vacuolatus) propranolol and metoprolol can be considered to be harmful to aquatic organisms. However, sorption explicitly inhibits the hazardous effects of BB, therefore the risks posed by these compounds for the environment are of minor importance.

Designing green derivatives of β-blocker Metoprolol: a tiered approach for green and sustainable pharmacy and chemistry

The presences of micro-pollutants (active pharmaceutical ingredients, APIs) are increasingly seen as a challenge of the sustainable management of water resources worldwide due to ineffective effluent treatment and other measures for their input prevention. Therefore, novel approaches are needed like designing greener pharmaceuticals, i.e. better biodegradability in the environment. This study addresses a tiered approach of implementing green and sustainable chemistry principles for theoretically designing better biodegradable and pharmacologically improved pharmaceuticals. Photodegradation process coupled with LC-MS(n) analysis and in silico tools such as quantitative structure-activity relationships (QSAR) analysis and molecular docking proved to be a very significant approach for the preliminary stages of designing chemical structures that would fit into the "benign by design" concept in the direction of green and sustainable pharmacy. Metoprolol (MTL) was used as an example, which itself is not readily biodegradable under conditions found in sewage treatment and the aquatic environment. The study provides the theoretical design of new derivatives of MTL which might have the same or improved pharmacological activity and are more degradable in the environment than MTL. However, the in silico toxicity prediction by QSAR of those photo-TPs indicated few of them might be possibly mutagenic and require further testing. This novel approach of theoretically designing 'green' pharmaceuticals can be considered as a step forward towards the green and sustainable pharmacy field. However, more knowledge and further experience have to be collected on the full scope, opportunities and limitations of this approach.

Degradation of β-blockers in hospital wastewater by means of ozonation and Fe2+/ozonation

This study investigates the degradation of the β-blockers in hospital wastewater by direct ozonation and Fe2+/ozonation with a focus on measurements at different initial pHs and Fe2+ concentrations, and the determination of kinetic constants. The results showed that these 'emerging contaminants' were completely degraded, when the removal rate of organic matter reached 30.6% and 49.1% for ozonation and Fe2+/ozonation, respectively. Likewise, the aromaticity removal rates were 63.4% and 77.9% for ozonation and Fe2+/ozonation, respectively. The experimental design showed that pH was the variable which had the greatest effect on the Fe2+/ozonation. The kinetic constants of atenolol, metoprolol and propranolol degradation by direct ozonation complied with pseudo-first-order conditions, while Fe2+/ozonation was suited to a biphasic degradation model. The k obs tended to rise when the pH increases; propranolol showed high k obs, which can be attributed to the naphthalene group (an electron-rich moiety). The identification of degradation products was carried out in aqueous solution using HPLC-MS2, followed by a suggestion of degradation pathways by means of ozonation. The degradation products proved to be dependent on the initial pH, and followed pathways that are based on direct ozonolysis and free radicals.