Efficient degradation of tetracycline by heterogeneous cobalt oxide/cerium oxide composites mediated with persulfate

Cerium oxide /Co-Co Prussian blue analogue composite catalyst for enhanced peroxymonosulfate activation for effective removal of tetracycline hydrochloride from water

In this paper, a novel CeO2/Co3[Co(CN)6]2 (CeO2/PBACo-Co) composite was prepared with co-precipitation and utilized to activate peroxymonosulfate (PMS) to eliminate tetracycline hydrochloride (TCH). Catalyst screening showed that the composite with a CeO2:PBACo-Co mass ratio of 1:5 (namely, 0.2-CeO2/PBACo-Co) had the best performance. The degradation efficiency of TCH in 0.2-CeO2/PBACo-Co/Oxone system was investigated. The experimental results illustrated that 98% of 50 mg/L TCH and 48.5% of TOC were degraded by 50 mg/L 0.2-CeO2/PBACo-Co and 400 mg/L Oxone within 120 min at 25 °C and initial pH 5.3. Recycling studies showed that the elimination rate of TCH can still achieve 85.8% after five cycles, suggesting that 0.2-CeO2/PBACo-Co composite processes good reusability. Trapping experiments and EPR tests revealed that the reaction system produced multiple active species (1O2, O2•-, SO4•-, and •OH). We proposed the catalytic mechanism of 0.2-CeO2/PBACo-Co for PMS activation, which mainly involves the promoted Co3+/Co2+ cycle by Ce3+ donated electrons. These results indicate that CeO2/PBACo-Co composite is an effective catalyst for wastewater remediation.

Development of natural attapulgite derived ferromanganese spinel oxides as heterogeneous catalysts for persulfate activation of tetracycline degradation

Ferromanganese spinel oxides (MnFe2O4, MFO) have been proven effective in activating persulfate for pollutants removal. However, their inherent high surface energy often leads to agglomeration, diminishing active sites and consequently restricting catalytic performance. In this study, using Al-MCM-41 (MCM) mesoporous molecular sieves derived from natural attapulgite as a support, the MFO/MCM composite was synthesized through dispersing MnFe2O4 nanoparticles on MCM carrier by a simple hydrothermal method, which can effectively activate persulfate (PS) to degrade Tetracycline (TC). The addition of Al-MCM-41 can effectively improve the specific surface area and adsorption performance of MnFe2O4, but also reduce the leaching amount of metal ions. The MFO/MCM composite exhibited superior catalytic reactivity towards PS and 84.3% removal efficiency and 64.7% mineralization efficiency of TC (20 mg/L) was achieved in 90 min under optimized conditions of 0.05 mg/L catalyst dosage, 5 mM PS concentration, room temperature and no adjustment of initial pH. The effects of various stoichiometric MFO/MCM ratio, catalyst dosage, PS concentration, initial pH value and co-existing ions on the catalytic performance were investigated in detail. Moreover, the possible reaction mechanism in MFO-MCM/PS system was proposed based on the results of quenching tests, electron paramagnetic resonance (EPR) and XPS analyses. Finally, major degradation intermediates of TC were detected by liquid chromatography mass spectrometry technologies (LC-MS) and four possible degradation pathways were proposed. This study enhances the design approach for developing highly efficient, environmentally friendly and low-cost catalysts for the advanced treatment process of antibiotic wastewater.

Heterostructured Co/CeO2-Decorating N-Doped Porous Carbon Nanocubes as Efficient Sulfur Hosts with Enhanced Rate Capability and Cycling Durability toward Room-Temperature Na-S Batteries

Room-temperature sodium-sulfur (RT Na-S) batteries have gained significant interest thanks to their satisfactory energy density and abundant earth resources. Nevertheless, practical implementations of RT Na-S batteries are still impeded by serious shuttle effects of sodium polysulfide (NaPS) intermediates, sluggish redox kinetics of cathodes, and poor electronic conductivity from S-species. To solve these problems, heterostructured Co/CeO2-decorating N-doped porous carbon nanocubes (Co/CeO2-NPC) are constructed as a S support, which integrates the strong adsorption and fast conversion of NaPSs, together with superior electronic conductivity. Consequently, the as-synthesized S@Co/CeO2-NPC cathode for RT Na-S batteries exhibits improved rate performance (1275, 561.1, and 485 mAh g-1 at 0.1, 5, and 10 C, respectively) and superior cyclic durability (capacity degeneration of 0.027% per cycle after 1000 cycles at 5 C). Such a S cathode combining a heterostructure interface, hierarchical porous carbon nanocubes, and polar compositions can considerably increase electronic conductivity and promote NaPS adsorption and conversion, achieving superior performance toward RT Na-S batteries.

Z-Type Heterojunction MnO2@g-C3N4 Photocatalyst-Activated Peroxymonosulfate for the Removal of Tetracycline Hydrochloride in Water

A Z-type heterojunction MnO2@g-C3N4 photocatalyst with excellent performance was synthesized by an easy high-temperature thermal polymerization approach and combined with peroxymonosulfate (PMS) oxidation technology for highly efficient degrading of tetracycline hydrochloride (TC). Analysis of the morphological structural and photoelectric properties of the catalysts was achieved through different characterization approaches, showing that the addition of MnO2 heightened visible light absorption by g-C3N4. The Mn1-CN1/PMS system showed the best degradation of TC wastewater, with a TC degradation efficiency of 96.97% following 180 min of treatment. This was an approximate 38.65% increase over the g-C3N4/PMS system. Additionally, the Mn1-CN1 catalyst exhibited excellent stability and reusability. The active species trapping experiment indicated •OH and SO4•- remained the primary active species to degrade TC in the combined system. TC degradation pathways and intermediate products were determined. The Three-Dimensional Excitation-Emission Matrix (3DEEM) was employed for analyzing changes in the molecular structure in TC photocatalytic degradation. The biological toxicity of TC and its degradation intermediates were investigated via the Toxicity Estimation Software Test (T.E.S.T.). The research offers fresh thinking for water environment pollution treatment.

Underwater bubbling plasma assisted with persulfate activation for the synergistic degradation of tetracycline hydrochloride

The performance and mechanism of persulfate consisting of peroxymonosulfate (PMS) and peroxydisulfate (PDS) activation by underwater bubbling plasma (UBP) for the synergistic removal of tetracycline hydrochloride (TCH) were comparatively investigated. Both PMS and PDS addition significantly promoted the removal of TCH in UBP system, indicating persulfate exhibited highly synergistic effect with UBP. Furthermore, enhancing the persulfate dosage, peak voltage and pulse frequency, as well as reducing initial TCH concentration were favorable for the elimination of TCH. Compared with neutral condition, acidic and alkaline condition were advantageous to TCH removal. The presence of coexisting substances including Cl-, SO42- and humic acid (HA) had an adverse effect on TCH degradation, while Fe2+ could improve the removal of TCH. The degradation of ciprofloxacin and metronidazole proved the applicability for other antibiotics degradation of the reaction system. SO4-·, ·OH, ·O2-, hydrated electrons, O3 and H2O2 were the active substances responsible for TCH removal. The reduction of aqueous O3 concentration and enhancement of H2O2 concentration were observed after persulfate addition. UV-vis spectra and TOC analysis illustrated the addition of PMS or PDS facilitated the degradation and mineralization of TCH. 3D-EEMF spectra visually displayed the degradation process of TCH. Plausible degradation routes were deduced based on LC-MS and the toxicities of TCH and its intermediates were evaluated by Toxicity Estimation Software Tool.

Acid-modified red mud biochar for the degradation of tetracycline: Synergistic effect of adsorption and nonradical activation

In this study, a novel acid-modified red mud biochar catalyst (MMBC) was synthesized by industrial waste red mud (RM) and peanut shell (PSL) to activate peroxodisulfate (PDS) for the degradation of TC. Meanwhile, MMBC exhibited remarkable adsorption capacity, reaching a 60% removal ratio of TC within 60 min (equilibrium adsorption capacity = 12 mg/g). After adding PDS, MMBC/PDS system achieved a 93.8% removal ratio of TC within 60 min. Quenching experiments and electron paramagnetic resonance (EPR) results showed that 1O2 played a dominant role in the degradation of TC and O2•- was the mainly precursor for the production of 1O2 in the MMBC/PDS system. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) analysis showed that the surface Fe(II), -OH and -COOH provided the active sites for the activation of PDS by MMBC. In addition, acid modification optimised the surface structure of the catalyst and enhanced the conversion of Fe (mainly Fe(III) to Fe(II)), thereby improving the adsorption and catalytic efficiency of MMBC. This study confirmed that modified red mud biochar is an efficient composite with both adsorption and catalysis, providing new ideas for the practical treatment of antibiotic wastewater and the resource utilization of red mud.

Fabrication of chitosan-MnO2‑iridium/nanoceria supported nanoparticles: Catalytic and anti-radical activities

Chitosan capped MnO₂‑iridium nanoparticles supported on nanoceria (Ch-MnO₂-Ir/CeO₂) were fabricated by using combination of colloidal solution and metal displacement galvanic methods. The oxidative degradation of acid orange 7 in aqueous solution by activated persulfate with the as-prepared nanoparticles was studied. The resulting Ch-MnO₂-Ir/CeO₂ with S₂O₈^2-, 80 % degraded 70.06 mg/L of acid orange 7 within 100 min, while at the same time, Ch-Ir, Ch-MnO₂, and Ch-Ir-MnO₂ remained inactive. CeO₂ increased the surface of the catalyst, and also improved the reactive oxygen species site of Ch-Ir-MnO₂ through the activation of S₂O₈^2- with CeO₂. The reversible redox cycle reaction, Ce (III) ↔ Ce (IV) and strong synergistic effect of MnO₂-Ir are responsible for the remarkable catalytic performance of Ch-MnO₂-Ir/CeO₂/S₂O₈^2- system. The degradation of acid orange 7 could be significantly retarded with inorganic (NO₃^- < Cl^- < SO₄^2- < H₂PO₄^- < HCO₃^-) and organic scavengers (ethanol < tertiary butanol < benzoquinone < phenol). Ch-MnO₂-Ir/CeO₂ exhibited excellent stability and reusability. Anti-radical activity of chitosan and Ch-MnO₂-Ir/CeO₂ was evaluated with 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical. The free radical properties increase with concentration of chitosan and Ch-MnO₂-Ir/CeO₂.

Ball milling and acetic acid co-modified sludge biochar enhanced by electrochemistry to activate peroxymonosulfate for sustainable degradation of environmental concentration neonicotinoids

Neonicotinoids pose potential serious risks to human health even at environmental concentration and their removal from water is considered as a great challenge. A novel ball milling and acetic acid co-modified sludge biochar (BASBC) was the first time synthesized, which performed superior physicochemical characteristics including larger surface area, more defect structures and functional groups (e.g., CO and -OH). Electrochemistry was introduced to enhance BASBC for peroxymonosulfate (PMS) activation (E/BASBC/PMS) to degrade environmental concentration neonicotinoids (e.g., imidacloprid (IMI)). The degradation efficiency of IMI was 95.2% within 60 min (C₀ (PMS)= 1 mM, E= 25 V, m (BASBC)= 10 mg). Solution pH and anionic species/concentrations were critical affecting factors. The scavenging and electron paramagnetic resonance experiments suggested that ^•OH and ¹O₂ were the dominant reactive oxygen species contributing to IMI degradation. Three degradation pathways were proposed and pathway Ⅲ was the main one. 86.1% of IMI were mineralized into non-toxic CO₂ and H₂O, and others were converted into less toxic intermediates. Also, E/BASBC/PMS system achieved the sustainable degradation of IMI in the cycle experiments. Additionally, it exhibited excellent degradation performance for other three typical neonicotinoids (96.6% of thiacloprid (THI), 96.5% of thiamethoxam (THX) and 82.6% of clothianidin (CLO)) with high mineralization efficiencies (87.8% of THI, 90.5% of THX and 75.4% of CLO).

Sulfate radicals-based advanced oxidation processes for the degradation of pharmaceuticals and personal care products: A review on relevant activation mechanisms, performance, and perspectives

Owing to the rapid development of modern industry, a greater number of organic pollutants are discharged into the water matrices. In recent decades, research efforts have focused on developing more effective technologies for the remediation of water containing pharmaceuticals and personal care products (PPCPs). Recently, sulfate radicals-based advanced oxidation processes (SR-AOPs) have been extensively used due to their high oxidizing potential, and effectiveness compared with other AOPs in PPCPs remediation. The present review provides a comprehensive assessment of the different methods such as heat, ultraviolet (UV) light, photo-generated electrons, ultrasound (US), electrochemical, carbon nanomaterials, homogeneous, and heterogeneous catalysts for activating peroxymonosulfate (PMS) and peroxydisulfate (PDS). In addition, possible activation mechanisms from the point of radical and non-radical pathways are discussed. Then, biodegradability enhancement and toxicity reduction are highlighted. Comparison with other AOPs and treatment of PPCPs by the integrated process are evaluated as well. Lastly, conclusions and future perspectives on this research topic are elaborated.

Catalytic ozonation mechanisms of Norfloxacin using Cu-CuFe2O4

As an easily recoverable, environmentally friendly and cost-effective catalyst, CuFe₂O₄ is a promising candidate for the catalytic ozonation of antibiotics in wastewater. However, its catalytic activity is restricted due to its limited active sites and low electron transfer efficiency. In this study, cetyl trimethyl ammonium bromide (CTAB) and Cu⁰ were doped with CuFe₂O₄ to introduce more O_V, providing more active sites and improving electron transfer efficiency. Experimental results show that the optimum removal efficiency of the catalytic ozonation of Norfloxacin (NOR, a widely used antibiotic) using CTAB doped with Cu-CuFe₂O₄ as the catalyst is 81.58% with a first-order reaction kinetics constant of 0.03967 min^-1. The associated O₃ and catalyst dosages are 2.72 mg·L^-1 and 0.1 g·L^-1, respectively, which are 1.63 times and 2.22 times higher than those in an equivalent O₃ system. O_V can provide generation sites for surface hydroxyl groups and trigger ·O₂^- and ¹O₂ as the main active oxygen species. The synergistic redox cycles of Fe²⁺/Fe³⁺ and Cu⁰/Cu²⁺ accelerate electron transfer efficiency. The possible degradation pathways of NOR are identified as defluorination, naphthyridine ring-opening and piperazine ring-opening. In summary, this work proposes a new strategy for the modification of CuFe₂O₄ catalysts and provides new insights into the catalytic ozonation mechanisms for NOR removal.

A Review of Persulfate Activation by Magnetic Catalysts to Degrade Organic Contaminants: Mechanisms and Applications

All kinds of refractory organic pollutants in environmental water pose a serious threat to human health and ecosystems. In recent decades, sulfate radical-based advanced oxidation processes (SR-AOPs) have attracted extensive attention in the removal of these organic pollutants due to their high redox potential and unique selectivity. This review first introduces persulfate activation by magnetic catalysts to degrade organic contaminants. We present the advances and classifications in the generation of sulfate radicals using magnetic catalysts. Subsequently, the degradation mechanisms in magnetic catalysts activated persulfate system are summarized and discussed. After an integrated presentation of magnetic catalysts in SR-AOPs, we discuss the application of persulfate activation by magnetic catalysts in the treatment of wastewater, landfill leachate, biological waste sludge, and soil containing organic pollutants. Finally, the current challenges and perspectives of magnetic catalysts that activated persulfate systems are summarized and put forward.

Fe/Co redox and surficial hydroxyl potentiation in the FeCo2O4 enhanced Co3O4/persulfate process for TC degradation

A magnetic FeCo₂O₄/Co₃O₄ nanocomposite was successfully synthesized by a facile hydrothermal method as an efficient activator for persulfate (PS) activation to degrade tetracycline (TC) in an aqueous solution. TC removal and mineralization efficiencies reached up to 91.63% and 43.57% in 120 min in the FCC-3/PS system, respectively. The mixed-valence of Fe/Co in the nanocomposite catalyst was beneficial for electrons transfer between Co and Fe elements and enhanced the redox circulation of Fe and Co in between divalent and trivalent. Surficial analysis and phosphate adsorption test confirmed the existence of -OH groups on the surfaces of FeCo₂O₄/Co₃O₄ nanocomposite. Fe/Co redox and surficial hydroxyl in the catalyst played significant roles in the TC potentiation degradation, which was contributed by the plenty of adsorbed -OH groups and excellent dispersity of FeCo₂O₄ in the FeCo₂O₄/Co₃O₄ composite. The sulfate radicals were major species followed by the hydroxyl radicals, and the surficial adsorbed hydroxyl made great contributions to radical generation. The cycling test and intermediate toxicity analysis indicated that the nanocomposite was considered stable and practicable in water treatment. This work demonstrated that the FeCo₂O₄/Co₃O₄ nanocomposite was an effective and environ-friendly catalyst towards PS activation for removing organic pollutants from water.

PMS activation by magnetic cobalt-N-doped carbon composite for ultra-efficient degradation of refractory organic pollutant: Mechanisms and identification of intermediates

Refractory organic pollutant effluent has led to severe water pollution. In this study, magnetic Co-N-doped carbon hybrid catalysts (Co-NC-x) were fabricated using a facile cation exchange combined pyrolysis and self-reduction technique to activate peroxymonosulfate (PMS) for rehabilitation of the water environment. Factors affecting the catalytic activity of the Co-NC-850 were comprehensively examined. 100% of RhB degradation efficiency within 20 min was achieved in the Co-NC-850/PMS system at the optimum conditions (C₀ = 80 mg L^-1, catalyst loading 0.025 g L^-1, PMS concentration 0.8 mM, native pH and 25 °C). The electron paramagnetic resonance measurements and competitive quenching tests demonstrated that a sulfate radical (SO₄•^-) and singlet oxygen (¹O₂) account for RhB degradation in the Co-NC-850/PMS system, and ¹O₂ contributed ~86.2% to RhB removal. The synergistic effect of Co⁰ nanoparticles (NPs) and NC on Co-NC-850 might induce a predominant non-radical route to trigger PMS activation for RhB degradation. Direct oxidation of O₂•^- by a hydroxyl radical (•OH) might be the crucial process for forming ¹O₂. Magnetic response and successive cycles verified that Co-NC-850 has superior separable performance and reusability. This innovative magnetic Co-NC-850 hybrid catalyst for PMS activation delivered vast potential for disintegration of refractory organic contaminants.

Persulfate assisted photocatalytic degradation of tetracycline by bismuth titanate under visible light irradiation

Tetracycline is a commonly used broad-spectrum antibiotic to prevent and cure the bacterial infections. However, the incompletely metabolic tetracycline molecules by organisms discharged into aquatic environment increase the ecological toxicity....

The removal of tetracycline with biogenic CeO2 nanoparticles in combination with US/PMS process from aqueous solutions: kinetics and mechanism

Antibiotics have received great attention because of their abuse and potential hazards to the human health and environment. In the current work, peroxymonosulfate (PMS) was added to a cerium oxide (CeO₂)/ultrasonic (US) system for tetracycline (TC) degradation. CeO₂ nanoparticles (NPs) were synthesized by a simple and cost-effective method using Stevia rebaudiana leaf extract and cerium nitrate as precursors. The as-synthesized CeO₂ NPs were characterized by X-ray diffraction, field emission scanning electron microscopy, and Fourier-transform infrared spectroscopy analysis. The effects of catalyst dosage, PMS concentration, US power, initial antibiotic concentration, and pH on TC removal were investigated. The results confirmed the formation of CeO₂ NPs with a fluorite structure, spherical shape, and average particle size of 29 nm. The removal efficiency of TC was 92.6% in the optimum oxidation conditions ([TC] = 15 mg/L, [PMS] = 50 mM, [CeO₂] = 0.6 g/L, pH = 6, and US = 70 W) and followed the zero-order kinetics. Experiment scavenger demonstrated both sulfate and hydroxyl radicals (SO₄^•-, ^•OH) were responsible for degrading antibiotics. Biogenic CeO₂ NPs and ultrasound waves-activated PMS is a promising technology for water pollution caused by contaminants such as pharmaceuticals.

Magnetic Fe3O4-N-doped carbon sphere composite for tetracycline degradation by enhancing catalytic activity for peroxymonosulfate: A dominant non-radical mechanism

The design of sustainable, effective and recyclable hybrid catalysts for advanced oxidation processes is highly significant for remediation of the water environment. In this study, we synthesized magnetic Fe₃O₄-N-doped carbon sphere composite catalysts (Fe₃O₄-NCS-x) for efficient removal of tetracycline by activating peroxymonosulfate (PMS). The Fe₃O₄-NCS-x composite was obtained by facile hydrothermal treatment of chitosan-iron complexes followed by pyrolysis. The unique structure of N-doped carbon spheres embedded in Fe₃O₄ nanoparticles intensified the electron transport, consequently improving the catalytic activity via a synergistic effect. Factors influencing the catalytic activity of the Fe₃O₄-NCS-2 were systematically investigated. High degradation efficiency of TC-97.1% within 1 h-was achieved in this Fe₃O₄-NCS-2/PMS system under the optimum conditions (C₀ = 20 mg L^-1, catalyst dosage 0.2 g L^-1, PMS concentration 2.4 mM, native pH and 25 °C). The inhibitory effect of anions in the water matrix decreased in the order Cl^- > NO₃^- > SO₄^2- > CH₃COO^- > HCO₃^-. The obtained results from the competitive quenching tests and electron paramagnetic resonance measurements demonstrated that singlet oxygen (¹O₂), a non-radical species, plays a major role in TC degradation. It is estimated that ¹O₂ and hydroxyl radicals (·OH) contributed ∼65.2% and ∼24.2% to TC degradation in the Fe₃O₄-NCS-2/PMS system, respectively. The M-H hysteresis loop of Fe₃O₄-NCS-2 revealed that its saturation moment is 56 emu g^-1. Magnetic responsive behavior and consecutive runs confirmed that Fe₃O₄-NCS-2 possesses remarkable separation performance and desirable reusability. This novel magnetic Fe₃O₄-NCS-2 composite activator for PMS promises great potential in TC degradation.

Tetracycline Removal by Activating Persulfate with Diatomite Loading of Fe and Ce

Persulfate (PS)-based oxidation technology is efficient in removing refractory organics from water. A novel diatomite (DIA) support Fe and Ce composite (Fe-Ce/DIA) was prepared for activating persulfate to degrade tetracycline in water. The Fe and Ce were uniformly loaded on DIA, and the total pore size of Fe-Ce/DIA was 6.99 × 10⁻² cm³/g, and the average pore size was 12.06 nm. Fe-Ce/DIA presented a good catalytic activity and 80% tetracycline was removed under the persulfate system. The Fe-Ce/DIA also had photocatalytic activity, and the corresponding tetracycline removal efficiency was 86% under UV irradiation. Fe-Ce/DIA exhibited less iron dissolution rate compared with Fe-DIA. The tetracycline degradation rate was enhanced when the temperature increased. The optimal tetracycline removal efficiency was obtained when the conditions were of persulfate 10 mM, Fe-Ce/DIA dosage 0.02 g/L, and tetracycline concentration 50 mg/L. In addition, Fe-Ce/DIA showed a wide pH application and good reusability and stability.

Ce-based catalysts used in advanced oxidation processes for organic wastewater treatment: A review

Refractory organic pollutants in water threaten human health and environmental safety, and advanced oxidation processes (AOPs) are effective for the degradation of these pollutants. Catalysts play vital role in AOPs, and Ce-based catalysts have exhibited excellent performance. Recently, the development and application of Ce-based catalysts in various AOPs have been reported. Our study conducts the first review in this rapid growing field. This paper clarifies the variety and properties of Ce-based catalysts. Their applications in different AOP systems (catalytic ozonation, photodegradation, Fenton-like reactions, sulfate radical-based AOPs, and catalytic sonochemistry) are discussed. Different Ce-based catalysts suit different reaction systems and produce different active radicals. Finally, future research directions of Ce-based catalysts in AOP systems are suggested.

Rhodamine B dye is efficiently degraded by polypropylene-based cerium wet catalytic materials

Polypropylene-based cerium wet catalytic materials (Ce/PPNW-g-PAA) were prepared through ultraviolet grafting and ion exchange technology. They were used as effective and reusable heterogeneous catalysts for rhodamine B (RhB) degradation. The physicochemical properties of Ce/PPNW-g-PAA were characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), specific surface area measurements (BET), and X-ray photoelectron spectroscopy (XPS). The catalytic capacity of the Ce/PPNW-g-PAA–H₂O₂ system for the removal of RhB was tested in comparison with several other systems, which demonstrated that Ce/PPNW-g-PAA effectively promoted the oxidation and degradation of RhB by catalytic wet H₂O₂ oxidation. The results of the RhB degradation showed that Ce/PPNW-g-PAA exhibited excellent degradation performance by achieving a high removal rate for RhB (97.5%) at an initial RhB concentration of 100 mg L⁻¹, H₂O₂ dosage of 5.0 mmol, Ce/PPNW-g-PAA dosage of 0.15 g L⁻¹, and initial pH of 5.0 at 298 K. The degradation of RhB by Ce/PPNW-g-PAA conformed to the first-order kinetic reaction model. Consecutive experiments performed with the Ce/PPNW-g-PAA sample showed little activity decay, further confirming the high stability of the catalyst. In addition, the possible degradation mechanism of RhB was also investigated by XPS and electron paramagnetic resonance. The results suggested that Ce³⁺ and hydroxyl radical played important roles during the RhB degradation process.

Polypropylene non-woven fabric grafted with polyacrylic acid enriched with cerium ions was used for the degradation of RhB.

Shuttle-like CeO2/g-C3N4 composite combined with persulfate for the enhanced photocatalytic degradation of norfloxacin under visible light

In this work, the shuttle-like CeO₂ modified g-C₃N₄ composite was synthesized and was combined with persulfate (PS) for the efficient photocatalytic degradation of norfloxacin (NOR) under visible light. Scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), UV-vis diffuse reflectance spectroscopy (DRS) and photoluminescence (PL) emission spectra were used to characterize the structural and optical properties of the as-prepared catalysts. Active species trapping experiments demonstrated that additional sulfate radicals (·SO₄^-) formed upon the addition of PS which could cooperate with superoxide radicals (O₂^-), holes (h⁺) and hydroxyl radicals (OH) to decompose NOR. Singlet oxygen (¹O₂) was also formed during the reaction and acted as an important active species. The degradation products of NOR were also identified and analyzed by using LC-MS technology, and the possible degradation mechanism and pathways were proposed and discussed. This work indicated that the shuttle-like CeO₂ modified g-C₃N₄ coupled with PS displayed promising applications in the field of pharmaceutical wastewater purification.

Amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposites as water-dispersible adsorbents for the removal of the oxytetracycline antibiotic from aqueous solutions: adsorption performance, effects of coexisting ions, and natural organic matter

The amino-functionalized mesoporous silica-magnetic graphene oxide nanocomposite (A-mGO-Si) was synthesized and used for oxytetracycline (OTC) removal from water. Various factors like the effects of initial concentration, contact time, and influence of pH were investigated. Selective adsorption experiments in connection with coexisting ions and dissolved organic matter (DOM) were also investigated. In this study, humic acid (HA) and tannic acid (TA) were representative of both hydrophobic and hydrophilic DOM, respectively. Results indicated that A-mGO-Si had an adsorption ability for OTC that was relatively greater than that of virgin magnetic graphene oxide (mGO), graphene oxide (GO), Fe₃O₄ particles, and SBA-15 mesoporous silica and also showed a better uptake removal capacity for OTC at low initial concentration in comparison with the other adsorbents. The adsorption behavior of OTC onto A-mGO-Si could be described by the pseudo-second-order kinetic model and the Freundlich isotherm model. The electrostatic interaction has no influence on the OTC absorbed when the OTC is in an aqueous medium in its zwitterion form (3.22 < pH < 7.46). At high pH, the weak π-π EDA interactions and hydrogen bonding may manifest themselves, hence causing a lower adsorption capacity. The main adsorption mechanisms were plausibly activated by H-bonding, and π-π EDA interactions, while the electrostatic interaction (cation-π interaction) might be the minor adsorption mechanism. Addition of individually exogenous ions (Na⁺, Mg²⁺, NO^-, and CO₃^2-) resulted in a decrease of OTC adsorption due to the emergence of a competitive effect. Considering the presence of HA and TA in mixed solute systems, the DOM was likely to form a stronger interaction system with mGO-Si, thereby resulting in an adsorption level which was more competitive in the process at low aqueous phase concentration of OTC. In contrast to the high aqueous phase, the coexistence of DOM could promote OTC adsorption. The phenomenon may reflect the result that a surface complexation mechanism could achieve in adsorptions.

Batch interaction of emerging tetracycline contaminant with novel phosphoric acid activated corn straw porous carbon: Adsorption rate and nature of mechanism

In this work, corn straw (CS) based porous carbon was prepared by one-step phosphoric acid (H₃PO₄) low temperature activation. The impregnation ratios (H₃PO₄/CS, g/g) played an important role in the pore development. ACS_300-1 engineered at 300 °C and the impregnation ratio of 1.0 showed the maximal specific surface area of 463.89 m²/g with total pore volume of 0.387 cm³/g, attaining a high tetracycline (TC) uptake of 227.3 mg/g. The adsorption of TC onto ACS_300-1 was found tolerant with wide pH (2.0-10.0) and high ionic strength (0 - 0.5 M). The adsorption data can be fitted well by the pseudo-second order kinetic model and Langmuir isotherm model. The endothermic and spontaneous properties of the adsorption system was implied by Thermodynamic study. The findings of the current work conclude that one-step H₃PO₄ activation is a green and promising method for corn straw based porous carbon that may be found with great potentials in antibiotic containing wastewater treatment.