Presence Of Inorganic Anions Research Articles

DEGRADATION KINETICS OF TEXTILE AZO DYE REACTIVE ORANGE-16 BY GAMMA IRRADIATION

Gamma radiation have become attention since their high potential for degrading compounds, especially organic pollutants. In this research, gamma radiation was studied for degrading the Reactive Orange-16 (RO-16) dye, a toxic and carcinogenic pollutant. The radiolytic degradation process was studied in a batch reactor with a gamma-ray dose rate of 2.930 kGy/h. The effect of experimental variable such as initial peroxide concentration, initial pH, initial dye concentration, and addition of inorganic anion were studied. The highest degradation rates were achieved at a peroxide concentration ranging from 2 to 4 mM. In contrast, the higher peroxide concentration indicated the slower degradation process caused by the scavenging effect of the peroxide. Degradation of 88% RO-16 dye with 0.1 mM initial concentration, was achieved at 2.0 kGy irradiation dose and 97.4% degradation in the presence of 4 mM peroxide. The dose constant (d) for those degradation processes was 1.0657 kGy-1 and 1.8420 kGy-1 respectively. The degradation was more efficient in acid pH. The degradation process increased with lower initial dye concentrations. The degradation of RO-16 dye by gamma-ray was inhibited by the presence of inorganic anions in the following sequence: NO3-→ CO32− → HCO3− → CH3COO-→ Cl-.

Cobalt-Modified Biochar from Rape Straw as Persulfate Activator for Degradation of Antibiotic Metronidazole

A cobalt-loaded magnetic biochar (Co-MBC) catalyst was synthesized to enhance the removal of metronidazole (MNZ). Study explored the performance and mechanism of MNZ degradation by Co-MBC activated permonosulfate (PMS). Results showed that cobalt oxides were effectively deposited onto the biochar surface, new oxygen functional groups were added to the modified biochar, and the presence of the metallic element Co enhanced the efficiency of PMS activation in the composite. More than 90% of MNZ was removed after 60 min with a catalyst dosage of 0.2 g/L and a PS concentration of 1 mM. After four reuses, Co-MBC still showed excellent catalytic performance to degrade over 75% of MNZ. The reaction system performed well even in the presence of inorganic anions and organic macromolecules. However, the degradation rate was inhibited under alkaline conditions. The quenching experiment indicated that •SO4−, •OH, 1O2, and •O2− synergistically degraded MNZ, and that•SO4− played a dominant role. LC-MS was applied to assess intermediate degradation products, in which CO2, H2O, and NO3− were the final degradation products, and potential degradation pathways were suggested. In conclusion, Co-MBC was an efficient and stable catalytic material, and its ability to activate PMS was improved to effectively degrade antibiotics, a typical priority pollutant.

Degradation of tetracycline wastewater by Fe-TiO2/Bi2MoO6/PTFE photocatalytic composite membrane

A Fe-TiO2/Bi2MoO6/PTFE photocatalytic composite membrane was innovatively fabricated for TCH wastewater treatment. It was characterized by XRD, SEM-EDS, FT-IR, BET, XPS, UV–vis, water contact angle, membrane flux, and BSA adsorption. The Fe-TiO2/Bi2MoO6 particles were securely adhered to the PTFE membrane, confirmed by repeated tests, exhibiting remarkable stability. The addition of Fe3+ and the incorporation of TiO2 increased the surface area, while the formation of the Fe-TiO2/Bi2MoO6 heterojunction facilitated the efficient separation of photogenerated electron-hole pairs. Furthermore, the doping of Fe3+ simultaneously disperses TiO2 and Bi2MoO6, enhancing their interactions. This leads to a close bonding between TiO2, Bi2MoO6, and Fe3+, further enhancing the hydrophilicity of the composite membrane. Treating TCH wastewater for 2 h with Fe-TiO2/Bi2MoO6/PTFE composite membrane under UV light achieved 87.4 % TCH removal and up to 76.1 % TOC reduction. The presence of inorganic anions (Cl−, CO32−, and NO3−) and humic acid (HA) have an inhibitory effect on the removal of TCH. The free radical trapping experiment identifies ·O2− as the primary reactive species. The E. coli colony assay shows no notable antibacterial activity in the treated effluent. LC-MS analysis reveals possible TCH degradation pathways in wastewater at different times.

Fenton-like water disinfection using fixed-bed reactor filled with a CoFe2O4 catalyst: Mechanisms, the impact of anions, electromagnetic heating, and toxicity evaluation

This work is a pioneering study demonstrating a promising breakthrough in water disinfection using a cobalt ferrite catalyst in a fixed bed. The performance of CoFe2O4 in E. coli inactivation is due to HO• radicals generated in the Fe3+/Fe2+ and Co3+/Co2+ redox cycles. In contrast to existing reports using cobalt ferrite nanoparticles, the bulk cobalt ferrite provides long-lasting catalytic performance in a flow reactor. The positively charged surface of cobalt ferrite attracts negatively charged E. coli membranes, which enhances disinfection. The CoFe2O4 catalyst was synthesized by the flow co-precipitation method, which allows obtaining kilogram quantities needed for industrial applications. The efficiency of E. coli inactivation was studied as a function of H2O2 concentration. For the first time, the reactor with a CoFe2O4 catalyst was additionally boosted by an electromagnetic field to decompose H2O2 and inactivate bacteria. The electromagnetically heated CoFe2O4/H2O2 system provides a significant 6 log bacterial inactivation. Importantly, cobalt ferrite is very stable under operating conditions. Only a negligible leaching of Fe and Co ions was observed. The presence of inorganic anions was beneficial for the bacterial inactivation. Ecotoxicological analysis revealed the absence of the toxicity of the treated water after using CoFe2O4/H2O2 with electromagnetic heating in the presence of bicarbonate ions. The results show that the magnetic cobalt ferrite is a promising, durable, heterogeneous catalyst for large-scale water disinfection.

In-situ growth of Mn-Ni3S2 on nickel foam for catalytic ozonation of p-nitrophenol

In this study, a new catalyst for catalytic ozonation was obtained by in-situ growth of Mn-Ni3S2 nanosheets on the surface of nickel foam (NF). The full degradation of p-nitrophenol (PNP) was accomplished under optimal conditions in 40 min. The effects of material dosage, ozone dosage, pH and the presence of inorganic anions on the degradation efficiency of PNP were investigated. ESR analysis showed that singlet oxygen (1O2) and superoxide radical (O2•-) are the main contributors of PNP degradation. This study offers a new combination of supported catalysts with high efficiency and easy recovery, which provides a new idea for wastewater treatment.

Novel magnetic Carbon@BaBiFe12O19 photocatalyst for efficient pollutants degradation under peroxymonosulfate activation

Mhexaferrite (BaFe12O19) is considered as a potential photocatalyst for PMS activation and water purification. However, as a first report, this study indeed provides a different preparation route in a diverse way to synthesize a novel Carbon@BaBiFe12O19 nanoparticles photocatalyst, which so far has not been reported in literature yet as a main objective of our study. The as-prepared Carbon@BaBiFe12O19 magnetic photocatalyst (NPs) was further used to explore the pollutants removal capacity by triggering peroxymonosulfate (PMS) under visible light irradiation. Methylene Orange (MO) removal capacity of the PMS/NPs/Light system reached 97.2% within 50 min. The enhanced efficacy of MO degradation can be ascribed to the effective generation of exceptionally reactive species, including O2•-, SO4•-, h+ and •OH. The study investigated various experimental parameters, such as the development of novel photocatalysts, PMS, light, pH level of the solution, type of pollutants, generation of active species, presence of inorganic anions, dosage of pollutants, water matrices, stability/recyclability, as well as the reaction mechanism for the NPs/PMS/Light system. Therefore, these findings explain how dopants (Bi-carbon) and faults affect the PMS-based photocatalytic water treatment performance. These intriguing discoveries indeed provide novel insights into the development and application of NPs that exhibit exceptional photocatalytic and chemical stability towards oxidative decontamination process.

Activation of peroxymonosulfate using heterogeneous Fe-doped carbon-based catalyst to generate singlet oxygen for the degradation of sulfamethoxazole

Non-radical catalytic oxidation processes can eliminate refractory pollutants from wastewater containing complex substrates such as dissolved organic matter, but the production of selective non-radicals is challenging during the activation of peroxymonosulfate (PMS). Herein, a novel magnetic carbon-based catalyst (Fe3O4@CD-8, where 8 represents an annealing temperature of 800 ℃) with N and Fe species as catalytic active sites was fabricated to remediate sulfamethoxazole (SMX)-containing water. It showed excellent SMX removal efficiency and facilitated singlet oxygen (1O2) production. The characterization results revealed that Fe3O4@CD-8 had a microscopically hierarchical pore structure and an overall core–shell-like structure. Due to its large specific surface area, N-containing species, and Fe nanoparticles, 0.1 g/L Fe3O4@CD-8 removed almost 100% SMX (24 min) and achieved a 44.1% mineralization (40 min) efficiency in the presence of 0.5 mM PMS. This catalytic system also maintained its removal performance in the presence of inorganic anions and humic acids and over a wide pH range of 3–11, showing good tolerance to various environmental factors. 1O2 was confirmed to be the predominant active species for SMX degradation using the Fe3O4@CD-8/PMS system. Density functional theory (DFT) calculations, intermediate monitoring, and toxicity evaluation demonstrated that SMX was transformed into low-toxicity molecules and completely mineralized into CO2 and H2O. The addition of Fe nanoparticles enhanced PMS adsorption and facilitated the Fe(III)/Fe(II) redox cycle to accelerate the activation of PMS. This study provides new insights and strategies for the controlled production of non-radicals for remediating antibiotic-containing wastewater.

Influence of Inorganic Anions on the Chemical Stability of Molybdenum Disulfide Nanosheets in the Aqueous Environment.

Chemical stability is closely associated with the transformations and bioavailabilities of engineered nanomaterials and is a key factor that governs broader and long-term application. With the growing utilization of molybdenum disulfide (MoS2) nanosheets in water treatment and purification processes, it is crucial to evaluate the stability of MoS2 nanosheets in aquatic environments. Nonetheless, the effects of anionic species on MoS2 remain largely unexplored. Herein, the stability of chemically exfoliated MoS2 nanosheets (ceMoS2) was assessed in the presence of inorganic anions. The results showed that the chemical stability of ceMoS2 was regulated by the nucleophilicities and the resultant charging effects of the anions in aquatic systems. The anions promote the dissolution of ceMoS2 by triggering a shift in the chemical potential of the ceMoS2 surface as a function of the anion nucleophilicity (i.e., charging effect). Fast charging with HCO3- and HPO42-/H2PO4- was validated by a phase transition from 1T to 2H and the emergence of MoV, and it promoted oxidative dissolution of the ceMoS2. Additionally, under sunlight, ceMoS2 dissolution was accelerated by NO3-. These findings provide insight into the ion-induced fate of ceMoS2 and the durability and risks of MoS2 nanosheets in environmental applications.

Effect and mechanism of inorganic anions on the adsorption of Cd2+ on two-dimensional copper-based metal–organic framework

Metal-organic frameworks exhibit strong adsorption performance for Cd2+ in wastewater due to their multi-level pores and easily modified structure. In this paper, a copper based metal–organic framework: [Cu·(HL)·(DMF)]n (1) (H3L = 5-hydroxy isophthalic acid; DMF = N,N-dimethylformamide), was synthesized by hydrothermal synthesis method. The structural analysis shows that each Cu(II) in 1 is coordinated with four carboxylate O atoms from HL2− and one O atom from DMF. The two carboxylate groups in HL2− take μ2-η1:η1 to bridge two Cu(II) ions formed a two-dimensional structure. The scanning electron microscope (SEM) analysis shows that the nanomaterials prepared by the crushing method have dendritic structures and particle diameters of approximately 100 nm. The experimental results of the nano adsorbent adsorbing Cd2+ show that at an isoelectric point pH = 6, the optimal adsorbent concentration is 0.20 g/L. The maximum adsorption capacity at this time is 75.22 mg/g, which is superior to most MOFs adsorbents. At this optimal adsorbent concentration, as the solution pH increases, the adsorption capacity of the adsorbent for Cd2+ significantly increases. The thermodynamic analysis results of adsorption show that the △G < 0 and △H < 0 of the adsorbent in the range of 20–40 ℃, indicating that the adsorption of Cd2+ by the adsorbent is a spontaneous and exothermic process. The inorganic anions Cl−, HCO3−, NO3−, SO42− inhibit the adsorption of Cd2+ by nano adsorbent at a pH of 6. However, at low pH values (4, 5), it promotes the adsorption of Cd2+. This is mainly because the presence of inorganic anions changes the form of Cd2+ in solution, affecting the adsorption of it by the adsorbent.

Peroxyacetic acid activation by cobalt-doped peanut shell biochar for efficient CBZ degradation: Role of organic radicals, singlet oxygen, and high-valent cobalt species

Peroxyacetic acid (PAA) oxidant has a broad application prospect to be combined with biochar in the treatment of organic pollutants due to its excellent characteristics of eco-friendly and easy activation. In this study, peanut shell biochar-loaded Co nanoparticles (Co-BC-850) catalysts were prepared through pyrolysis to activate PAA for carbamazepine (CBZ) degradation. The pyrolysis temperature significantly affected the CBZ degradation efficiency of the catalysts. The experimental results revealed that the Co-BC-850 catalyst exhibited the highest CBZ degradation efficiency. Within 20 min, a CBZ degradation rate of 99.9% was achieved with Co-BC-850 concentration of 50 mg/L and PAA concentration of 1 mM. The Co-BC-850/PAA system achieved high degradation performance for CBZ at a pH ranging from 5.0 to 9.0, even in the presence of inorganic anions. The analysis of the Co-BC-850/PAA system revealed a complex interplay of reactive species (RSs). Organic radicals (R-O•), singlet oxygen (1O2), and high-valent cobalt species (Co(IV)) collaboratively contributed to CBZ degradation. These findings revealed the intricate mechanism of CBZ degradation via Co-BC-850-activated PAA, thereby elucidating potential degradation pathways. This study demonstrates the promising application of biochar PAA-based AOPs and offers a sustainable and effective solution for the degradation of CBZ and other potential pharmaceutical compounds in water.

Topological defects strengthened nonradical oxidation performance of biochar catalyzed peroxydisulfate system

Nonradical oxidation based on peroxydisulfate (PDS) activation has attracted increasing attention for selective degradation of organic pollutants. Herein, topological defects were introduced into biochar (BC) via removing N atoms in N-doped BC (NBC) in an attempt to improve the nonradical catalytic performance. Compared to the pristine BC and NBC, the introduction of topological defects could achieve up to 36.6- and 8.7-times catalytic activity enhancement, respectively. More importantly, it was found that the catalytic activity was dominated by topological defects, which was verified by the significant positive correlation between the pseudo-first-order rate constants and the content of topological defects. Theoretical calculations suggested that topological defects enhanced the electron-donating ability of BC by reducing the energy gap, which made the electrons transfer to PDS molecules more easily. As a result, holes were generated after the carbon defects lost electrons, and induced a nonradical oxidation process. Benefiting from the merits of nonradical oxidation, the developed BC/PDS system showed superior performance in removing electron-rich contaminants in the presence of inorganic anions and in the actual environments. This study not only provides a potential avenue for designing efficient biochar-based catalysts, but also advances the mechanism understanding of nonradical oxidation process induced by carbon defects.Graphical

Simultaneous hydrodynamic cavitation and glow plasma discharge for the degradation of metronidazole in drinking water

In this study, a novel hydrodynamic cavitation unit combined with a glow plasma discharge system (HC-GPD) was proposed for the degradation of pharmaceutical compounds in drinking water. Metronidazole (MNZ), a commonly used broad-spectrum antibiotic, was selected to demonstrate the potential of the proposed system. Cavitation bubbles generated by hydrodynamic cavitation (HC) can provide a pathway for charge conduction during glow plasma discharge (GPD). The synergistic effect between HC and GPD promotes the production of hydroxyl radicals, emission of UV light, and shock waves for MNZ degradation. Sonochemical dosimetry provided information on the enhanced formation of hydroxyl radicals during glow plasma discharge compared to hydrodynamic cavitation alone. Experimental results showed a MNZ degradation of 14% in 15 min for the HC alone (solution initially containing 300 × 10−6 mol L−1 MNZ). In experiments with the HC-GPD system, MNZ degradation of 90% in 15 min was detected. No significant differences were observed in MNZ degradation in acidic and alkaline solutions. MNZ degradation was also studied in the presence of inorganic anions. Experimental results showed that the system is suitable for the treatment of solutions with conductivity up to 1500 × 10−6 S cm−1. The results of sonochemical dosimetry showed the formation of oxidant species of 0.15 × 10−3 mol H2O2 L−1 in the HC system after 15 min. For the HC-GPD system, the concentration of oxidant species after 15 min reached 13 × 10−3 molH2O2L−1. Based on these results, the potential of combining HC and GPD systems for water treatment was demonstrated. The present work provided useful information on the synergistic effect between hydrodynamic cavitation and glow plasma discharge and their application for the degradation of antibiotics in drinking water.

Acid-washed zero-valent aluminum as a highly efficient persulfate activator for degradation of phenacetin.

Phenacetin (PNT) is one of the most frequently detected nonsteroidal anti-inflammatory drugs in the water ecosystems, which poses a potential risk to environmental aquatic organisms. Acid-washed zero-valent aluminum (ZVAl) as a highly efficient activator for persulfate (PS) process was investigated to degrade PNT from the aqueous solution. The results indicated that acid-washed pretreatment for ZVAl could efficiently increase the degradation efficiency of PNT in the PS treatment. The degradation efficiency of PNT (50 μM) was up to 90% in 4 hours with the addition of 0.2 g/L acid-washed ZVAl and 8 mM PS at pH 6.8 and 25 °C. The PNT degradation followed pseudo-first order kinetics in the present system. High activator dosage, PS concentration, and reaction temperature could enhance the PNT degradation. The presence of inorganic anions (i.e., NO3-, HCO3-) and humic acid (HA) showed inhibitory effects on the PNT degradation. The reuse results illustrated the acid-washed ZVAl material would have continuous and efficient activation performance for PS to degrade thePNT. Radical scavenger experiments and electron paramagnetic resonance indicated that both SO4•- and •OH were major reactive species during the PNT degradation. The possible degradation pathways of PNT mainly included the break of C-N and C-O bonds and further oxidation.

Efficient activation of peroxydisulfate by a novel magnetic nanocomposite lignin hydrogel for contaminant degradation: Radical and nonradical pathways

A novel magnetic nanocomposite lignin hydrogel (MNLH) was synthesized and applied for peroxydisulfate (PDS) activation in this study. Detailed characterization data indicated that the unique 3-dimensional (3D) structure of the lignin hydrogel is beneficial in dispersing magnetic nanoparticles (nZVI/Ni particles), which enhances the maximum exposure of nZVI/Ni particles. The 3D structure of the lignin hydrogel provides more attachment sites for nZVI/Ni, PDS and contaminants, accelerating the electron transfer between nZVI/Ni and PDS and promoting the degradation of contaminant. Notably, the optimized MNLH0.8 catalyst (where the number 0.8 indicates the mass ratio of [Lignin hydrogel]/[nZVI/Ni] = 0.8) exhibits excellent performance for PDS activation. Under the MNLH0.8/PDS system, 5 mg/L bisphenol A (BPA, 40 mL) can be completely degraded within 15 min with 0.05 g/L catalyst and 0.66 mM PDS. Quenching experiments and electron spin resonance (ESR) spectra reveal that both radicals (O2•−) and nonradicals (1O2) are generated in the MNLH0.8/PDS system as the dominant active species for BPA degradation. In addition, the MNLH0.8 catalyst still shows effectiveness for BPA degradation in the presence of inorganic anions and natural organic matter (NOM). UPLC-Q-TOF-MS system was used to identify the BPA degradation products and four possible pathways for BPA degradation were proposed. According to the results of toxicity prediction, BPA can eventually be transformed into nontoxic products. Additionally, the MNLH/PDS system can effectively degrade different contaminants in water, which highlights promising applications for organic wastewater treatment.

Efficient removal of trifluoroacetic acid from water using surface-modified activated carbon and electro-assisted desorption

Trifluoroacetic acid (TFA) is a very persistent, very mobile substance (vPvM) with potential toxicity, and causes increasing environmental concerns worldwide. Conventional wastewater treatment strategies are inefficient for selective TFA removal in the presence of inorganic anions. Here we show that surface defunctionalized activated carbon felt (DeACF) carrying anion exchange sites exhibits an outstanding adsorption efficiency towards TFA thanks to introduced electrostatic attraction and enhanced interactions between hydrophobic carbon surface and CF3 moieties (qmax = 30 mg/g, Kd = (840 ± 80) L/kg at cTFA = 3.4 mg/L in tap water). Flow-cell experiments demonstrated a strongly favored TFA uptake by DeACF from tap water over Cl- and SO42- but a remarkable co-adsorption of the inorganic water contaminant NO3-. Electro-assisted TFA desorption using 10 mM Na2SO4 as electrolyte and oxidized ACF as anode showed high recoveries of ≥ 87% at low cell voltages (< 1.1 V). Despite an initial decrease in TFA adsorption capacity (by 33%) caused by partial surface oxidation of DeACF after the 1st ad-/desorption cycle, the system stability was fully maintained over the next 4 cycles. Such electro-assisted ‘trap&release’ approach for TFA removal can be exploited for on-site regenerable adsorption units and as a pre-concentration step combined with degradation technologies.

Inorganic anions influenced the photoaging kinetics and mechanism of polystyrene microplastic under the simulated sunlight: Role of reactive radical species

The photo-transformation of microplastic (MP) in natural water may involve interactions with various ingredients, but the photoaging kinetics and underlying mechanism are not well understood. This work systematically explored the photoaging process of polystyrene microplastic (PS-MP) in the presence of commonly-found inorganic anions, including NO3−, HCO3−, Br− and Cl−. The addition of these ions led to more obvious changes in the morphology, functional groups and molecular weight of photoaging PS-MP. The evolution of carbonyl index value for the photoaged samples conformed to pseudo-first-order kinetic model, and the photoaging rate constant (k) in the presence of inorganic anions at their environmentally relevant concentrations of 0.6 mM, 1.2 mM, 0.1 M and 0.1 mM was calculated to be kHCO3- = 0.0074 d−1, kNO3- = 0.01001 d−1, kCl- = 0.00783 d−1, and kBr- = 0.00888 d−1, which was higher than that in ultrapure water (k=0.00705 d−1). Electron paramagnetic resonance technique and quenching experiments demonstrated that photo-transformation of PS-MP was mainly mediated by indirect photolysis, i.e., the formation of reactive radical species. The photosensitivity of NO3− promoted more •OH production, thereby accelerated the indirect photoaging of PS-MP. Meanwhile, the presence of halide ions promoted the generation of reactive halogen species, which were also involved in the indirect photoaging of PS-MP. Interestingly, as •OH scavenger, HCO3− had no inhibitory effect on PS-MP photoaging, attributing to the oxidation of CO3•−. This study provides valuable insights into the understanding of photo-transformation of MPs in natural aquatic environments.

Ferric nitrate/dopamine/melamine-derived nitrogen doped carbon material as the activator of peroxymonosulfate to degrade sulfamethoxazole

• Preparation of nitrogen-doped carbon materials from inexpensive raw materials. • Explored the influence of different raw materials on catalyst performance. • Graphitization and nitrogen doping have vital effect on degrading sulfamethoxazole. • Graphite nitrogen and Fe-N x are the main active sites. • Free radicals bound to the catalyst surface are considered to be mainly active oxygen. Nitrogen-doped carbon materials can effectively activate peroxymonosulfate (PMS) to degrade organic pollutants. In this study, one or more of the following raw ingredients, ferric nitrate, dopamine hydrochloride and melamine, were used as raw materials to prepare different carbon-based catalysts. The different effects of each raw ingredient on the performance of the catalyst were studied. Characterization by X-ray diffract grams spectra, Raman spectroscopy and X-ray photoelectron spectroscopy found that Fe(NO 3 ) 3 ·9H 2 O in the catalyst is beneficial to promote the degree of graphitization, and melamine can increase the nitrogen content in the catalyst. The prepared Fe-DA-CN catalyst, prepared with three materials has the highest activity. When the catalyst dose was 50 mg/L and the PMS concentration was 0.25 mM, the removal rate of 5 mg/L sulfamethoxazole (SMX) reached more than 99% after 30 min of reaction; furthermore, the pH, presence of inorganic anions (HPO 4 2- , NO 3 – , CO 3 2– , Cl - ) and presence of humic acid had little effect on the SMX removal rate. Repeated use experiments show that the catalyst has good stability. Through electron paramagnetic resonance and quenching tests, it is found that the main active substances that activate PMS to degrade SMX are free radicals (·OH, SO 4 ·- ) bound on the catalyst surface and a small part of singlet oxygen ( 1 O 2 ).

Peroxymonosulfate/LaCoO3 system for tetracycline degradation: Performance and effects of co-existing inorganic anions and natural organic matter

The activation of peroxymonosulfate (PMS) has been developed as an efficient method for the degradation of antibiotics by generating reactive oxygen species (ROS), where perovskite oxides have been found as effective catalysts. However, the reaction mechanism, degradation pathways, as well as the effects of co-existing inorganic anions and natural organic matter are largely unknown. Therefore, the degradation efficiency and mechanism of tetracycline (TC) through the activation of PMS by LaCoO3 were investigated. Moreover, the effects of common inorganic anions and natural organic matter (e.g., humic acid (HA)) on degradation efficiency were also compared. Without the presence of coexisting substance, TC removal exceeded 90% within 30 min, while 72% mineralization was achieved in 6 h, under optimal reaction conditions at neutral pH. In addition to the traditional free radicals of OH and SO4−, 1O2 and O2− also contributed the degradation process, where the lattice oxygen of LaCoO3 played a significant role in 1O2 production. The degradation of TC followed the pathways including demethylation, hydroxylation and ring-opening reactions. The presence of inorganic anions (i.e., H2PO4−, Cl− and SO42−) and low-concentration of HA promoted the degradation. Among them, H2PO4− and lower concentration of HA showed the most obvious outcome, while the SO42− can regulate the radical formation, minimize the peak radical level, and therefore promote the overall performance of the process. LaCoO3 exhibited stable reusability with minor decrease in TC removal, likely due to the adsorption of intermediate products from previous stages. These obtained results shed light on the application of perovskite oxides for PMS activation on removing antibiotics.

Rapid degradation of tetracycline in aqueous solution by Fe/Cu catalysis enhanced by H2O2 activation

ABSTRACT Tetracycline (TC) is widely detected in the environment because of its abuse and persistence. There is an urgent need to efficiently treat TC due to its potential threat to the ecosystem and human health. In this study, microscale Fe/Cu bimetallic particles’ (mFe/Cu) catalysis enhanced by H2O2 was proposed to remove TC in an aqueous solution. Based on the pre-experiment, the effect of theoretical Cu mass loading (TMLCu) and some key operating parameters on the TC removal efficiency were investigated thoroughly. The degradation rates of TC by mFe/Cu with different TMLCu followed the pseudo-first-order kinetics model, and the optimal TMLCu (0.34 g Cu/g Fe) was obtained. The optimal operating parameters of mFe/Cu dosage, concentration of H2O2, initial concentration of TC, stirring speed and operating temperature were 5 g/L, 50 mM, 50 ppm, 400 r/min, and 55°C, respectively. Compared with the control system, the system of mFe/Cu catalysis enhanced by H2O2 (mFe/Cu-H2O2) presented excellent performance due to its synergistic effect. Also, the fresh and reacted mFe/Cu was characterized by scanning electron microscope, which showed the surface of mFe/Cu was rougher after reaction, indicating mFe/Cu participated in the degradation reaction. Besides, with the presence of inorganic anions, the degradation of TC in mFe/Cu-H2O2 system did not change much. And mFe/Cu presented good stability and recyclability after 10 repeated tests. Therefore, mFe/Cu-H2O2 system had a great potential for cost-effective removal of antibiotics in wastewater.

Photocatalysis of Tris-(2-chloroethyl) phosphate by ultraviolet driven peroxymonosulfate oxidation process: Removal performance, energy evaluation and toxicity on bacterial metabolism network

Tris(2-chloroethyl) phosphate (TCEP) as a typical chlorinated-organophosphate esters (OPEs) are identified to be contaminants of emerging concern owing to its health risk and resistance to conventional biological remediation in water matrix. Although ultraviolet-driven radical-based advanced oxidation processes exhibited a well performance in terms of removing refractory emerging organic pollutants, residual biotoxicity and potential environment risks induced by their intermediates products have become a new concern. A comprehensive assessment regarding TCEP elimination using UV-activated peroxymonosulfate (PMS) was performed, which was attempted to provide detailed information about security and fesibility of UV/PMS technology for OPEs control. Degradation of TCEP can be described by a pseudo-first order kinetics equation with a apparent rate constant (0.1311 min−1) and three steady degradation products including C4H9Cl2O4P (m/z 222.969), C2H6ClO4P (m/z 160.976), C6H11Cl2O6P (m/z 280.974) were generated via hydroxylation and dechlorination reactions. The removal efficiency was inhibited in presence of inorganic anions (Cl−, CO32− and H2PO4−), moreover, the inhibitory effects induced by Cl− was more powerful than the other two. Compared to intact TCEP, metabolic pathways were up-regulated expression associated with carbohydrate metabolism, lipid biosynthesis, vitamin metabolism, pyrimidine and purine metabolism, whereas oxidative phosphorylation metabolism, biotin metabolism, oxidation stress response were down-regulated in Escherichia coli exposed to intermediates mixture. The proteomics results confirmed that detoxification of TCEP was achieved in case of an incomplete mineralization, and UV/PMS will be employed as a promising treatment method for controlling micro-pollutants from aquatic environment.