Enhancing photo-degradation of ciprofloxacin using simultaneous usage of eaq- and OH over UV/ZnO/I- process: Efficiency, kinetics, pathways, and mechanisms

Alien emergent aquatic plants develop better ciprofloxacin tolerance and metabolic capacity than one native submerged species

Antibiotic pollution and biological invasion pose significant risks to freshwater biodiversity and ecosystem health. However, few studies have compared the ecological adaptability and ciprofloxacin (CIPR) degradation potential between alien and native macrophytes. We examined growth, physiological response, and CIPR accumulation, translocation and metabolic abilities of two alien plants (Eichhornia crassipes and Myriophyllum aquaticum) and one native submerged species (Vallisneria natans) exposed to CIPR at 0, 1 and 10 mg/L. We found that E. crassipes and M. aquaticum's growth were unaffected by CIPR while V. natans was significantly hindered under the 10 mg/L treatment. CIPR significantly decreased the maximal quantum yield of PSII, actual quantum yield of PSII and relative electron transfer rate in E. crassipes and V. natans but didn't impact these photosynthetic characteristics in M. aquaticum. All the plants can accumulate, translocate and metabolize CIPR. M. aquaticum and E. crassipes in the 10 mg/L treatment group showed greater CIPR accumulation potential than V. natans indicated by higher CIPR contents in their roots. The oxidative cleavage of the piperazine ring acts as a key pathway for these aquatic plants to metabolize CIPR and the metabolites mainly distributed in plant roots. M. aquaticum and E. crassipes showed a higher production of CIPR metabolites compared to V. natans, with M. aquaticum exhibiting the strongest CIPR metabolic ability, as indicated by the most extensive structural breakdown of CIPR and the largest number of potential metabolic pathways. Taken together, alien species outperformed the native species in ecological adaptability, CIPR accumulation and metabolic capacity. These findings may shed light on the successful invasion mechanisms of alien aquatic species under antibiotic pressure and highlight the potential ecological impacts of alien species, particularly M. aquaticum. Additionally, the interaction of antibiotic contamination and invasion might further challenge the native submerged macrophytes and pose greater risks to freshwater ecosystems.

Positive profile of natural small molecule organic matters on emerging antivirus pharmaceutical elimination in advance reduction process: A deep dive into the photosensitive mechanism of triplet excited state compounds

Natural small molecular organic matter (NSOM), ubiquitous in natural waters and distinct from humic acid or fulvic acid, is a special type of dissolved organic matter (DOM) which is characterized as strong photosensitivity and simple molecular structure. However, little study had been directed on the role of NSOM in eliminating emerging contaminants in advanced reduction process (ARP). This study took three small molecular isomeric organic acids (p-hydroxybenzoic acid, pHBA; salicylic acid, SA; m-hydroxybenzoic acid, mHBA) as the representative substances of NSOM to explore these mechanisms on promoting Ribavirin (RBV, an anti COVID-19 medicine) degradation in ultraviolet activated sulfite (UV/Sulfite) process. The results demonstrated that the observed degradation rate constant of RBV (kobs-RBV) was 7.56 × 10-6 s-1 in UV/Sulfite process, indicating that hydrated electron (eaq-) from UV/Sulfite process could not effectively degrade RBV, while it increased by 178 and 38 times when pHBA and SA were introduced into UV/Sulfite process respectively, suggesting that pHBA and SA strongly promoted RBV degradation while mHBA had no promotion on RBV abatement in UV/Sulfite process. Transient absorption spectra and reactive intermediates scavenging experiment indicated that the triplet excited state pHBA and SA (3pHBA* and 3SA*) contributed to the degradation of RBV through non-radical process. Notably, eaq- played the role of key initiator in transforming pHBA and SA into their triplet states. The difference of kobs-RBV in UV/Sulfite/pHBA and UV/Sulfite/SA process was attributed to different generation pathways of 3pHBA* and 3SA* (high molar absorptivity at the wavelength of 254 nm and photosensitive cycle, respectively) and their second order rate constants towards RBV (kRBV-3pHBA* = 8.60 × 108 M-1 s-1 and kRBV-3SA* = 6.81 × 107 M-1 s-1). mHBA could not degrade RBV for its lack of intramolecular hydrogen bond and low molar absorptivity at 254 nm to abundantly transform into its triplet state. kobs-RBV increased as pH increased from 5.0 to 11.0 in UV/Sulfite/SA process, due to the high yield of eaq- in alkaline condition which promoted the generation of 3SA* and the stable of the absorbance of SA at 254 nm. By contrast, kobs-RBV underwent a process of first increasing and then decreasing in UV/Sulfite/pHBA process as the increase of pH, and its highest value achieved in a neutral condition. This lied in the exposure of eaq- increased as the increase of pH which promoted the generation of 3pHBA*, while the molar absorptivity of pHBA at 254 nm decreased as the increase of pH in an alkaline condition which inhibited the yield of 3pHBA*. The RBV degradation pathways and products toxicity assessment indicated that UV/Sulfite/pHBA had better detoxification performance on RBV than UV/Sulfite/SA process. This study disclosed a novel mechanism of emerging contaminants abatement through non-radical process in NSOM mediated ARP, and provide a wide insight into positive profile of DOM in water treatment process, instead of only taking DOM as a quencher of reactive intermediates.

Predicting environmental risks of pharmaceutical residues by wastewater surveillance: An analysis based on pharmaceutical sales and their excretion data

Pharmaceutical residues are increasingly becoming a significant source of environmental water pollution and ecological risk. This study, leveraging official national pharmaceutical sales statistics, predicts the environmental concentrations of 33 typical pharmaceuticals in the Tianjin area. The results show that 52 % of the drugs have a PEC/MEC (Predicted Environmental Concentration/Measured Environmental Concentration) ratio within the acceptable range of 0.5-2, including atenolol (1.21), carbamazepine (1.22), and sulfamethoxazole (0.91). Among the selected drugs, tetracycline, ciprofloxacin, and acetaminophen had the highest predicted concentrations. The EPI (Estimation Programs Interface) biodegradation model, a tool from the US Environmental Protection Agency, is used to predict the removal efficiency of compounds in wastewater treatment plants. The results indicate that the EPI predictions are acceptable for macrolide antibiotics and β-blockers, with removal rates of roxithromycin, spiramycin, acetaminophen, and carbamazepine being 14.1 %, 61.2 %, 75.1 %, and 44.5 %, respectively. However, the model proved to be less effective for fluoroquinolone antibiotics. The ECOSAR (Ecological Structure-Activity Relationships) model was used to supplement the assessment of the potential impacts of drugs on aquatic ecosystems, further refining the analysis of pharmaceutical environmental risks. By combining the concentration and detection frequency of pharmaceutical wastewater, this study identified 9 drugs with significant toxicological risks and marked another 24 drugs as substances of potential concern. Additionally, this study provides data support for addressing pharmaceutical residues of priority concern in subsequent research.

Optimizing physico-chemical properties of hierarchical ZnO/TiO2 nano-film by the novel heating method for photocatalytic degradation of antibiotics and dye

The design of semiconductor catalysts with excellent photocatalytic properties, stability, recyclability, and good separation for the treatment of polluted water is still challenging. In this paper, the ZnO/TiO2 nano-thin films were fabricated using the magnetron sputtering technique and then heating the underlying ZnO layer and the upper TiO2 layer for their respective optimal heating time, i. e. heating ZnO for 3 h and heating TiO2 for 2 h. The as-prepared films were characterized. The results show that the preferred growth of TiO2 grains along the [001] axis, relatively large specific surface area, and increased amounts of surface oxygen vacancies (OVs) were induced to the heterojunction catalysts through this optimized heating strategy, which boosts the photocatalytic activity of ZnO/TiO2 nano-film. The degradation experiment inndicates that the ciprofloxacin (CIP) removal efficiency can reach 97.3% in 2 h duration, which was higher than that of the samples annealed for the same periods. Meanwhile, the prepared ZnO/TiO2 photocatalytic film exhibited favorable stability of 95.5% degradation efficiency after the fourth run and general applicability for the photodegradation of various contantains, whih removed 99.5% of ofloxacin (OFX) and 77.6% of tetracycline (TC) in 2 h and 94.1% of Rhodamine B (RhB) in 1 h. This work is expected to yields a novel insight into the production of heterojunction photocatalysts with excellen ability for photocatalytic degradation of pollutants in the practical industry.

Fabrication of new composite NCuTiO2/CQD for photocatalytic degradation of ciprofloxacin and pharmaceutical wastewater treatment: degradation pathway, toxicity assessment

In this research, the photocatalytic degradation of CIP from aqueous solutions using CQD decorated on N-Cu co-doped titania (NCuTCQD) was made during two synthesis steps by sol-gel and hydrothermal methods. The fabricated catalysts were analyzed using various techniques, including XRD, FT-IR, BET, FESEM, EDX, and DRS. The results showed that N and Cu atoms were doped on TiO2 and CQD was well deposited on NCuT. The investigation of effective operational parameters demonstrated that the complete removal of ciprofloxacin (CIP: 20 mg/L) could be achieved at pH 7.0, NCuTCQD4wt%: 0.8 g/L, and light intensity: 100 mW/cm2 over 60 min reaction time. The O2•- and OH˙ radicals were identified as the primary reactive species during the decontamination process. The synthesized photocatalyst could be recycled after six consecutive cycles of CIP decomposition with an insignificant decrease in performance. Pharmaceutical wastewater was treated through the optimum degradation conditions which showed the photocatalytic degradation eliminated 89% of COD and 75% of TOC within 180 min. In the effluent toxicity evaluation, the EC50 values for treated and untreated pharmaceutical wastewater increased from 62.50% to 140%, indicating that the NCuTCQD4wt%/Vis system can effectively reduce the toxic effects of pharmaceutical wastewater on aquatic environments.

High-performance NiO@Fe3O4 magnetic core-shell nanocomposite for catalytic ozonation degradation of pharmaceutical pollution

Pharmaceuticals that are present in superficial waters and wastewater are becoming an ecological concern. Therefore, it is necessary to provide high-performance methods to limit the harmful ecological effects of these materials to achieve a sustainable environment. In this research, NiO@Fe3O4 nanocomposite was prepared by the co-precipitation method and utilized in the catalytic ozonation process for the degradation of 1-cyclopropyl-6-fluoro-4-oxo-7-piperazin-1-yl-quinoline-3-carboxylic acid (ciprofloxacin antibiotic), for the first time. The influencing parameters in the degradation process were analyzed and optimized via response surface methodology (RSM). The optimal ciprofloxacin removal efficiency (100%) was found at pH = 6.5, using 7.5 mg of the NiO@Fe3O4 nanocatalyst and 0.2 g L-1 h-1 ozone (O3) flow, applied over 20 min. Results showed a significant synergistic effect in the analyzed system, which makes the proposed catalytic ozonation process more efficient than using the catalyst and ozone separately. Also, based on the kinetic analysis data, the catalytic ozonation process followed the pseudo-first-order model. In addition, the nanocatalyst showed high recyclability and stability (88.37%) after five consecutive catalytic ozonation process cycles. In conclusion, the NiO@Fe3O4 nanocatalyst/O3 system can be effectively used for the treatment of pharmaceutical contaminants.

Recent perspective of antibiotics remediation: A review of the principles, mechanisms, and chemistry controlling remediation from aqueous media

Antibiotic pollution is an ever-growing concern that affects the growth of plants and the well-being of animals and humans. Research on antibiotics remediation from aqueous media has grown over the years and previous reviews have highlighted recent advances in antibiotics remediation technologies, perspectives on antibiotics ecotoxicity, and the development of antibiotic-resistant genes. Nevertheless, the relationship between antibiotics solution chemistry, remediation technology, and the interactions between antibiotics and adsorbents at the molecular level is still elusive. Thus, this review summarizes recent literature on antibiotics remediation from aqueous media and the adsorption perspective. The review discusses the principles, mechanisms, and solution chemistry of antibiotics and how they affect remediation and the type of adsorbents used for antibiotic adsorption processes. The literature analysis revealed that: (i) Although antibiotics extraction and detection techniques have evolved from single-substrate-oriented to multi-substrates-oriented detection technologies, antibiotics pollution remains a great danger to the environment due to its trace level; (ii) Some of the most effective antibiotic remediation technologies are still at the laboratory scale. Thus, upscaling these technologies to field level will require funding, which brings in more constraints and doubts patterning to whether the technology will achieve the same performance as in the laboratory; and (iii) Adsorption technologies remain the most affordable for antibiotic remediation. However, the recent trends show more focus on developing high-end adsorbents which are expensive and sometimes less efficient compared to existing adsorbents. Thus, more research needs to focus on developing cheaper and less complex adsorbents from readily available raw materials. This review will be beneficial to stakeholders, researchers, and public health professionals for the efficient management of antibiotics for a refined decision.

Simultaneous Cr (VI) reduction and diazinon oxidation with organometallic sludge formation under photolysis: kinetics, degradation pathways, and mechanism

In this study, simultaneous removal of an organic matter (diazinon, DIZ) and an inorganic substance (chromium, Cr) was used. Breaking down of organic matter by UV irradiation produces various radicals, including sulfides, carboxyl, hydroxyl, hydrated electrons, and various organic radicals that are highly reactive and help us to precipitation inorganic substance (Cr). The optimal condition was 30:1 DIZ:Cr molar ratio, pH 9, and about 100% and 82.3% of DIZ and Cr were obtained in 30 min. Cr deposition was very slow at first. After the destruction of the DIZ structure, Cr deposition began, and various types of sludge with disturbed properties were formed. These sledges were analyzed by FTIR analysis and showed that green sludge could be chromium (III) hydroxide; brown sludge due to chromium (III) hydroxide, tiny green crystals from chromium (III) oxide, red brick from chromium (II) acetate chromium trioxide, as well as black sludge caused by chromium oxide were identified. In UV/DIZ/Cr process, kobs and robs range obtained 0.33-0.15 and 16.8-23.4 $ with both Cr and DIZ concentration increased from 50 to 150 mg L-1. Also, EEO for Cr precipitation was 24.65 to 5.74 and for DIZ 12.54 to 4.73 (kwh m-3). Depending on the amount of energy consumption, TCS was 37.19 to 10.47 for Cr precipitation and 4.46 to 1.25 $. It is important to note that when both pollutants are exposed to ultraviolet light, more energy and cost are generally required from UV/DIZ process and less than of UV/Cr process. But it should be noted that in fact 50 mg L-1 of chromium and 50 mg L-1 of DIZ are being removed at the same time. In UV/DIZ and UV/Cr processes that are exposed to ultraviolet radiation alone, only one of them is removed. Also, when these two pollutants are being removed at the same time, the total amount of energy is much less than the total energy consumption of the pollutants one by one.

Impact of water matrices on oxidation effects and mechanisms of pharmaceuticals by ultraviolet-based advanced oxidation technologies: A review

The binding between water components (dissolved organic matters, anions and cations) and pharmaceuticals influences the migration and transformation of pollutants. Herein, the impact of water matrices on drug degradation, as well as the electrical energy demands during UV, UV/catalysts, UV/O₃, UV/H₂O₂-based, UV/persulfate and UV/chlorine processes were systemically evaluated. The enhancement effects of water constituents are due to the powerful reactive species formation, the recombination reduction of electrons and holes of catalyst and the catalyst regeneration; the inhibition results from the light attenuation, quenching effects of the excited states of target pollutants and reactive species, the stable complexations generation and the catalyst deactivation. The transformation pathways of the same pollutant in various AOPs have high similarities. At the same time, each oxidant also can act as a special nucleophile or electrophile, depending on the functional groups of the target compound. The electrical energy per order (EEO) of drugs degradation may follow the order of EEO_UV > EEO_UV/catalyst > EEO_UV/H2O2 > EEO_UV/PS > EEO_UV/chlorine or EEO_UV/O3. Meanwhile, it is crucial to balance the cost-benefit assessment and toxic by-products formation, and the comparison of the contaminant degradation pathways and productions in the presence of different water matrices is still lacking.

Sunlit expeditious visible light-mediated photo-fenton degradation of ciprofloxacin by exfoliation of NiCo2O4 and Zn0·3Fe2·7O4 over g-C3N4 matrix: A brief insight on degradation mechanism, degraded product toxicity, and genotoxic evaluation in Allium cepa

Pharmaceutical pollutant in the environmental water bodies has become a major concern, which causes adverse effect to aquatic entities. This study provides an incisive insight on the photocatalytic degradation of ciprofloxacin (CIP) and the development of rationally engineered g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite for boosted photocatalytic performance under visible light irradiation. The g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite was synthesized via ultrasonication-assisted hydrothermal method. The characterization of the as-prepared material was evaluated by XPS, SEM, HR-TEM, PL, FT-IR, EIS, ESR, XRD, BET, and UV-Vis DRS techniques. Furthermore, the effect of catalytic dosage, drug dosage, and pH changes was explored, where g-C3N4-NiCo2O4-Zn0.3Fe2·7O4-10% unveiled excellent visible light photo-Fenton degradation of 92% for CIP at 140 min. The hydroxyl radicals (OH.) served as the predominant radical species on the photodegradation of CIP, which was confirmed by performing a radical scavenging test. Furthermore, the degradation efficiency was determined by six consecutive cycle tests, where the nanomaterial exhibited excellent stability with 98.5% reusable efficiency. The degradation of CIP was further scrutinized by GC-MS analysis, where the degraded intermediate products and the possible pathway were elucidated. The degraded product toxicity was determined by ECOSAR program, where the degraded products haven't exhibited any considerable toxic effects. In addition, the genotoxicity of the nanomaterial was determined by treating them with root tips of A. cepa, where it was found to be non-toxic. Here, the prepared g-C3N4-NiCo2O4-Zn0.3Fe2·7O4 nanocomposite (CNZ NCs) shows eco-friendly and excellent photo-Fenton activity for environmental applications.

Fate and transport of pharmaceuticals in water systems: A processes review

Pharmaceuticals are globally consumed by humans and animals to support daily health and to treat disease. Following consumption, they may reach the aquatic environment either directly through the discharge of untreated wastewater to water bodies, or indirectly via treated wastewater as a result of their incomplete removal from wastewater treatment plants. This paper reviews the processes that control the occurrence and fate of pharmaceuticals in water systems, including sorption, photodegradation, hydrolysis and biodegradation. The degree to which these four processes occur is influenced by pharmaceutical types and their chemical structure as well as environmental factors such as sunlight, water depth, organic matter content, water chemistry, sediment properties, and type and abundance of microorganisms. Depending on the complex interactions of these factors, pharmaceutical compounds may be mineralized, partially degraded, or remain intact because they are resistant to degradation. Kinetic rate parameters and the half-life of a variety of pharmaceutical products are provided herein for the above processes under different environmental conditions. Usually, photodegradation and biodegradation represent dominant reaction processes, while hydrolysis only affects some pharmaceuticals, particularly antibiotics. The identified sorption and reaction rate parameters can be incorporated into a concise modeling framework to assess and predict longitudinal concentration profiles of pharmaceutical products in the manmade and natural systems, particularly when large amounts of pharmaceuticals are discharged during abnormal events such as a virus outbreak. Finally, future research is suggested, including the fate of transformed products (intermediates) in water systems.

Efficient reductive and oxidative decomposition of haloacetic acids by the vacuum-ultraviolet/sulfite system

Haloacetic acids (HAAs), as a representative category of halogenated disinfection byproducts, are widely detected in disinfected water. In this work, the vacuum ultraviolet (VUV)/sulfite process under N₂ saturated conditions was proposed to eliminate a series of HAAs (i.e., monochloroacetic acid (MCAA), difluoroacetic acid (DFAA), trifluoroacetic acid (TFAA), dichloroacetic acid (DCAA), etc.). The in situ generated hydrated electron (e_aq^-) demonstrated to be the main species to fulfill the initial degradation and dechlorination of MCAA, while hydroxyl radicals (˙OH) were in charge of the mineralization of MCAA. This means that the VUV/sulfite system is a combination of advanced reduction and oxidation processes (ARPs and AOPs). A significant enhancement of MCAA removal was observed with increasing pH values from 6.0 to 10.0, and surprisingly, k_obs correlated well with the proportion of SO₃^2- as the pH changed. This can be explained by the production of e_aq^- from VUV irradiation of SO₃^2- rather than HSO₃^- and also due to e_aq^- being more stable under alkaline conditions. Increasing the sulfite dosage also elevated the degradation of MCAA. However, the addition of certain anions (i.e., chloride (Cl^-), bicarbonate (HCO₃^-), and nitrate (NO₃^-)) and dissolved organic matter (DOM) inhibited the removal of MCAA to varying degrees. The VUV/sulfite system was effective toward various types of halogenated disinfection byproducts, supporting its broad applicability. Nevertheless, even in real waters, the VUV/sulfite system was also promising for the simultaneous abatement of HAAs and other oxyanions.

Phytoremediation of antibiotic-contaminated wastewater: Insight into the comparison of ciprofloxacin absorption, migration, and transformation process at different growth stages of E. crassipes

The selection of aquatic plants at different growth stages and their absorption, migration, and transformation mechanisms has yet to be clarified. In this study, Eichhornia crassipes at the seedling and mature stages were selected to uptake antibiotics under hydroponic conditions. The results showed that the enrichment of ciprofloxacin (CIP) in roots at the seedling and mature stages were 7.72～2114.39 μg g^-1 and 0.07～3711.33 μg g^-1, respectively. The enrichment of CIP in aerial parts at the seedling and mature stages were 16.38～24.24 μg g^-1 and 9.55～20.13 μg g^-1, respectively. The translocation from roots to aerial parts at the seedling stage was high, as evidenced by the relatively higher transfer factor (TF). In addition, eight and ten major metabolic products were observed in the tissues of seeding and mature stage of E. crassipes, respectively. The metabolic pathway of CIP was short at the maturity stage, and CIP had a strong upward migration ability at the seedling stage, facilitating long-time photodegradation. However, E. crassipes exhibited a poor CIP tolerance at the mature stage and decayed relatively early. Therefore, the seedling stage of E. crassipes was proposed to be applied for phytoremediation, and these findings might improve the ability to phytoremediation of antibiotic-contaminated water.

Construction of direct Z-scheme Bi5O7I/UiO-66-NH2 heterojunction photocatalysts for enhanced degradation of ciprofloxacin: Mechanism insight, pathway analysis and toxicity evaluation

Direct Z-scheme Bi₅O₇I/UiO-66-NH₂ (denoted as BU-x) heterojunction photocatalysts were successfully constructed through ball-milling method. Photocatalytic activities of the as-prepared BU-x samples were determined by using a typical fluoroquinolone antibiotic, ciprofloxacin (CIP). All BU-x heterojunctions exhibited better CIP removal performances than that of pristine Bi₅O₇I and UiO-66-NH₂ upon exposure to white light irradiation. In comparison, the heterojunction with UiO-66-NH₂ content of 50 wt% (BU-5) showed excellent structural stability and the optimal adsorption-photodegradation efficiency for the CIP removal. The removal efficiency of CIP (10 mg/L) over BU-5 (0.75 g/L) achieved 96.1% within 120 min illumination. Meanwhile, the effect of photocatalyst dosage, pH and inorganic anions were systemically explored. Reactive species trapping experiments, electron spin resonance (ESR) signals, Mott-Schottky measurements and density functional theory (DFT) simulation revealed that the photo-generated holes (h⁺), hydroxyl radical (·OH) and superoxide radical (·O₂^-) played crucial roles in CIP degradation. This result can be ascribed to that the unique Z-scheme charge transfer configuration retained the excellent redox capacities of Bi₅O₇I and UiO-66-NH₂. Meanwhile, the CIP degradation pathways and the toxicity of various intermediates were subsequently analyzed. This work provided a feasible idea for removing antibiotics by bismuth-rich bismuth oxyhalide/MOF-based heterostructured photocatalysts.

Reduction of bromate from drinking water by sulfite/ferric ion systems: Efficacy and mechanisms

In this work, we investigate radical-based chemical reduction systems for BrO₃^- reduction. Sulfite/ferric ions [S(IV)/Fe(III)] systems eliminated 85% of 0.1 mM BrO₃^- in 1 min at pH_ini. 7.0, and 2.2 mg/L dissolved oxygen (DO) with rate constants (2.104 ± 0.090 min^-1) orders of magnitude faster than previously published advanced reduction processes. Increasing S(IV) and Fe(III) concentrations and decreasing DO and pH contributed to faster BrO₃^- reduction likely due to enhanced reactive species. Lower anionic levels (0.5 mM) did not hinder BrO₃^- reduction but further increases in the levels to 1.0 mM decreased their reduction. Notably, S(IV)/Fe(III) process reduced 68% of 25.6 μg/L BrO₃^- in 3 min from tap water at pH_ini. 7.0, 0.02 mM Fe(III), and 1.0 mM S(IV), meeting drinking water standard (<10 μg/L). Also, ~99% of irons could be removed after the following activated carbon treatment. Moreover, sulfite radicals formed by S(IV) activation with Fe(III) were significant reactive species in the S(IV)/Fe(III) system. Reduction pathways were proposed accordingly. Collectively, S(IV)/Fe(III) process is a viable technology for reductively decontaminating realistic waters, especially when applied between the ozone-activated carbon process (i.e., the ozone-S(IV)/Fe(III)-activated carbon process).

Efficient photochemical denitrification by UV/sulfite system: Mechanism and applications

Denitrification is an effective strategy to control eutrophication caused by excessive nitrate in water. However, the comparatively low efficiency of nitrate removal and N₂ selectivity remains a challenge in the denitrification process. Herein, this study proposed a novel photochemical denitrification process by introducing hydrated electron (e_aq^-) to reduce nitrate in UV/sulfite system. The results indicated that the optimized UV/sulfite system could effectively reduce nitrate to N₂ with a nearly 100% denitrification efficiency in 90 min. e_aq^- was identified as the mainly reactive species to achieve rapid removal of nitrate and nitrite, and the result was verified by quenching and laser flash photolysis tests. Benefiting from the high dispersion of e_aq^- in water and the rapid reaction rate between e_aq^- and the target, the generated N₂O is susceptible to be reduced, leading to a high selectivity of N₂ that was confirmed by ¹⁵N-isotopic. Besides, thermodynamic results based on the density functional theory (DFT) calculations suggested that the photochemical denitrification process was exothermic process and tend to transform to N₂. Significantly, UV/sulfite system applied in the nickel-plating wastewater showed high denitrification efficiency, demonstrating that the novel photochemical denitrification process is promising for practical wastewater treatment.

Enhanced Photocatalytic Degradation of Ternary Dyes by Copper Sulfide Nanoparticles

We report the effect of thermolysis time on the morphological and optical properties of CuS nanoparticles prepared from Cu(II) dithiocarbamate single-source precursor. The as-prepared copper sulfide nanoparticles were used as photocatalysts for the degradation of crystal violet (CV), methylene blue (MB), rhodamine B (RhB), and a ternary mixture of the three dyes (CV/MB/RhB). Powder XRD patterns confirmed the hexagonal covellite phase for the CuS nanoparticles. At the same time, HRTEM images revealed mixed shapes with a particle size of 31.47 nm for CuS1 prepared at 30 min while CuS2 prepared at 1 h consists of mixtures of hexagonal and nanorods shaped particles with an average size of 21.59 nm. Mixed hexagonal and spherically shaped particles with a size of 17.77 nm were obtained for CuS3 prepared at 2 h. The optical bandgaps of the nanoparticles are 3.00 eV for CuS1, 3.26 eV for CuS2 and 3.13 eV for CuS3. The photocatalytic degradation efficiency showed that CuS3 with the smallest particle size is the most efficient photocatalyst and degraded 85% of CV, 100% of MB, and 81% of RhB. The as-prepared CuS showed good stability and recyclability and also degraded ternary dyes mixture (CV/MB/RhB) effectively. The byproducts of the dye degradation were evaluated using ESI-mass spectrometry.

A review targeting veterinary antibiotics removal from livestock manure management systems and future outlook

Veterinary antibiotics (VAs) contamination has been considered as a worldwide environmental and health concern in recent decades. This paper reviewed the variability of contents of VAs and their release from the animal breeding industry into the surrounding environment along with the performance of the manure treatment technologies. The data collected revealed that VAs were mostly excreted in animal feces and observed in manure, soil, water, and sediment. The findings illustrate the disparity of VAs in excretion rates, consumption, and their residues in the environment with relatively high distribution for tetracyclines, fluoroquinolones, and sulfonamides. Anaerobic digestion has a capacity to remove of 73% VAs while manure composting and constructed wetlands can remove 84.7%, and 90% VAs. Due to the profound effect of antibiotics on the environment, further research and intensive management strategies for livestock manure need to be designed to improve the removal efficiency and manure management technologies.

Degradation of ciprofloxacin using UV-based advanced removal processes: Comparison of persulfate-based advanced oxidation and sulfite-based advanced reduction processes

In this study, the degradation of ciprofloxacin (CIP) in wastewater was investigated using UV-based sulfate radical advanced oxidation processes (SR-AOP) and UV-based advanced reduction processes (ARP). More specifically, a comparison of the UV-based persulfate advanced oxidation process (the UV/PS process) and the UV-based sulfite advanced reduction process (the UV/sulfite process) was made. Considering the UV-based SR-AOPs, the UV/PS process was much more efficient than the UV-based peroxymonosulfate advanced oxidation process (the UV/PMS process), with pseudo first order reaction rate constants (k_obs) of 0.752 and 0.145 min^-1, respectively. For the UV-based ARPs, the UV/sulfite process was the most efficient, compared to the UV/sulfide and the UV/dithionite process (k_obs of 0.269, 0.0157 and 0.0329 min^-1, respectively). The optimal process parameters for both the UV/PS and the UV/sulfite process were determined and the contribution of the produced reactive species were identified. For the UV/PS process, maximal CIP degradation was found at pH 8, and both OH and SO₄^- were responsible for CIP degradation. For the UV/sulfite process, H and e_aq^- were responsible for CIP degradation, with e_aq^- being the predominant radical at pH 8.5. Although CIP degradation was much faster for the UV/PS process, the UV/sulfite process was determined to be much more efficient in the defluorination of CIP.

Adsorption-photocatalytic processes for removal of pentachlorophenol contaminant using FeNi3/SiO2/ZnO magnetic nanocomposite under simulated solar light irradiation

The adsorption followed by photocatalytic degradation process was examined for the pentachlorophenol (PCP) removal from aqueous solution. These processes were accomplished by using FeNi₃/SiO₂/ZnO magnetic nanocomposite as an adsorbent-photocatalytic agent and under the irradiation of solar light. The magnetic nanocomposite used was first synthesized and then was characterized using transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), vibrating-sample magnetometer (VSM), and X-ray diffraction (XRD) spectroscopy. The PCP removal efficiency was tested for various factors, including pH, PCP concentration, and nanocomposite dose at different contact times. The characterization results of TEM, FE-SEM, and VSM analysis showed that the synthesized nanoparticles are amorphous and tend to agglomerate due to their high super-paramagnetic property. In addition, the EDX technique showed that the Zn and O elements had the highest weight percent in the synthesized nanocomposite, respectively. On the other hand, XRD analysis revealed that the crystalline size of the nanoparticles was about 42 nm. The kinetic of PCP degradation followed the pseudo-first-order model with R² = 0.978. According to the results of the isotherm study, the adsorption of PCP onto the nanoparticles followed the Freundlich model. The results of adsorption-photocatalytic degradation experiments showed that 100% removal of PCP was obtained at optimum conditions of pH = 3, nanocomposite dose = 0.5 g/L, contact time = 180 min, and initial PCP concentration of 10 mg/L. Through the results obtained from this study, the adsorption process followed by solar light photocatalytic degradation process using FeNi₃/SiO₂/ZnO magnetic nanocomposite is found to be an efficacious treatment method for the removal of PCP contaminant from water and wastewater.

Degradation of antibiotics by advanced oxidation processes: An overview

Antibiotics are becoming emerging contaminants due to their extensive production and consumption, which have caused hazards to the ecological environment and human health. Various techniques have been studied to remove antibiotics from water and wastewater, including biological, physical and chemical methods. Among them, advanced oxidation processes (AOPs) have received increasing attention due to their fast reaction rate and strong oxidation capability, which are effective for the degradation of antibiotics in aquatic environments. In this review paper, a variety of AOPs, such as Fenton or Fenton-like reaction, ozonation or catalytic ozonation, photocatalytic oxidation, electrochemical oxidation, and ionizing radiation were briefly introduced, including their principles, characteristics, main influencing factors and applications. The current applications of AOPs for the degradation of antibiotics in water and wastewater were analyzed and summarized, the concluding remarks were given and their future perspectives and challenges were discussed.