Non-radical activation of CaO2 nanoparticles by MgNCN/MgO composites for efficient remediation of organic and heavy metal-contaminated wastewater

Hydroxyl Defects-Mediated Hydrolytic Activation of Peroxydisulfate Under Nanoconfinement: Role of Lewis Basic Sites for Altering the Photosensitized Species and Pathways

Herein, the pivotal mechanism of defect engineering-mediated triazine-based conjugated polymers (TCPs) is comprehensively elucidated for photosensitized activation of peroxydisulfate (PDS) under nanoconfinement by encapsulating the defective polymer framework into the nanochannel of SBA-15 (d-TCPs@SBA-15). The incorporated hydroxyl defects (-OH defects) substantially accelerate the accumulation of electrons at -OH defects, forming the Lewis basic sites. Due to the facilitated elongation of the S─O bond and reduced energy barrier of SO5* generation, the captured PDS undergo prehydrolysis process, oxidized into O2 - and 1O2 by surrounding h+, thereby setting apart from the conventional reductive activation of SO4 -/•OH generation occurred in pristine TCPs (p-TCPs). Crucially, this work represents a pioneering effort in exploring the PDS activation pathway upon the defective polymer under the nanoconfinement to leverage kinetic merits of slow photon effect and reactive oxygen species (ROSs) enrichment, and the novel prehydrolysis activation mechanism involved may catalyze the rational design of photocatalysts featuring Lewis-acid/base centers.

S-Cu Doubly Doped NiFe LDH@Diatomite with Adjustable Surface Characteristics for the Efficient Removal of Tetracycline

Overuse of antibiotics can lead to increased bacterial resistance; therefore, there is a need to develop efficient nanomaterials for removing antibiotics from water. NiFe bimetallic hydroxide nanosheets doped with S-Cu were prepared on diatomite (S-CuNiFe LDH@diatomite) by using a two-step hydrothermal method. The surface of CuNiFe LDH@DE has a layered structure with an increased specific surface area and pore volume. The average pore size of S-CuNiFe LDH@De increases from 13.3 to 24.7 nm, and a more stereoscopic channel structure is obtained. Tetracycline removal experiments were performed on CuNiFe LDH@De and S-CuNiFe LDH@De. It was found that CuNiFe LDH@De had excellent photocatalytic performance and S-CuNiFe LDH@De had excellent adsorption performance. After CuNiFe LDH@De had been in contact with tetracycline (TC) for 2 h, the TC removal rate reached 95.6%. After S-CuNiFe LDH@De had been in contact with TC for 1 h, the adsorption capacity of TC was 145.5 mg/g. The pseudo-first-order kinetics and Sips isotherm model can be used to describe the adsorption process more accurately. The response surface method was used to optimize the adsorption conditions. According to the optimized conditions, a better adsorption performance of 166.9 mg/g was obtained. The two prepared materials showed good performance in the removal of tetracycline. This study provides a way to synthesize low-cost adsorbents and photocatalysts, which has value in the treatment of TC wastewater.

Eco-friendly oxidation of a reactive textile dye by CaO2: effects of specific independent parameters

Textile wastewater containing dyes poses significant risks to the environment. Advanced oxidation processes (AOPs) effectively eliminate dyes by converting them into harmless substances. However, AOPs have drawbacks such as sludge formation, metal toxicity, and high cost. As an alternative to AOPs, calcium peroxide (CaO2) offers an eco-friendly and potent oxidant for dye removal. Unlike certain AOPs that generate sludge, CaO2 can be directly employed without resulting in sludge formation. This study examines the use of CaO2 for oxidizing Reactive Black 5 (RB5) in textile wastewater without any activator. Various independent factors-pH, CaO2 dosage, temperature, and certain anions-were investigated for their influence on the oxidation process. The effects of these factors on dye oxidation were analyzed using the Multiple Linear Regression Method (MLR). CaO2 dosage was determined to be the most influential parameter for RB5 oxidation, while the optimal pH for oxidation with CaO2 was found to be 10. The study determined that 0.5 g of CaO2 achieved approximately 99% efficiency in oxidizing 100 mg/L of RB5. Additionally, the study revealed that the oxidation process is endothermic, with an activation energy (Ea) and standard enthalpy (ΔH°) for RB5 oxidation by CaO2 determined as 31.135 kJ mol-1 and 110.4 kJ mol-1, respectively. The presence of anions decreased RB5 oxidation, with decreasing effectiveness observed in the order of PO43-, SO42-, HCO3-, Cl-, CO32-, and NO3-. Overall, this research highlights CaO2 as an effective, easy-to-use, eco-friendly, and cost-efficient method for removing RB5 from textile wastewater.

A self-circulating electro-fenton-like process over Fe3O4-CaO2 cathode for highly efficient degradation of levofloxacin

Electro-Fenton reaction was limited by the generation of H₂O₂ and the circulation of Fe(Ⅱ)/Fe(Ⅲ). Herein, an efficient electro-Fenton-like process was constructed based on Fe₃O₄-CaO₂ cathode promoted by peroxymonosulfate (PMS). Levofloxacin (LEV) could be efficiently degraded (92.1%) and mineralized with the TOC removal of 74.5% in this self-circulating process. More importantly, the Fe₃O₄-CaO₂ exhibited good stability in the recycles due that CaO₂ was covered by Fe₃O₄, which inhibited the rapid release of H₂O₂. Mechanism analysis indicated that CaO₂ could not only replace H₂O₂ to accelerate the oxidation of Fe(Ⅱ) to Fe(Ⅲ), but also could form complexes with Fe(Ⅲ) and PMS to transfer electrons from ligands to metals, thereby enhancing the reduction of Fe(Ⅲ) to Fe(Ⅱ). As a result, the electrical consumption was significantly reduced, which was only 5.0% of the Fe₃O₄ in electro-Fenton reaction. Meanwhile, the hydrolyzed product of Ca(OH)₂ reacted with Fe(Ⅲ) in the presence of H₂O₂ and converted into CaO₂. Thus, the self-circulation of CaO₂/Ca(OH)₂ and Fe(Ⅲ)/Fe(Ⅱ) was realized, which accelerated the generation of active species, such as, ·OH, O₂·^- and ¹O₂. This work first proposed a self-circulating electro-Fenton-like system and demonstrated the potential application of Fe₃O₄-CaO₂ in the treatment of wastewater.

Improvement of Carbonyl Groups and Surface Defects in Carbon Nanotubes to Activate Peroxydisulfate for Tetracycline Degradation

Carbon nanotubes (CNTs) were considered a promising activator for persulfates due to their high electrical conductivity, large specific surface area and low toxicity. The functional groups and surface defects of CNTs could significantly affect their activation performance. In this study, CNTs with high C=O ratio and defect density (CNT-O-H) were prepared through a facile treatment of raw CNTs with HNO₃ oxidation followed by calcination at 800 °C under an argon atmosphere. X-ray photoelectron spectroscopy (XPS) and Raman results showed that the C=O proportion and defect degree (I_D/I_G) rose to 75% and 1.53, respectively. The obtained CNT-O-H possessed a superior performance towards peroxydisulfate (PDS) activation, and the degradation efficiency of tetracycline (TC) in the CNT-O-H/PDS system was increased to 75.2% from 56.2% of the raw CNTs/PDS system within 40 min. Moreover, the activity of CNT-O-H after use could be easily recovered with re-calcination. In addition, the CNT-O-H/PDS system exhibited high adaptabilities towards wide solution pH (2-10), common coexisting substances and diverse organic pollutants. Singlet oxygen (¹O₂) was confirmed to be the dominant reactive oxygen species (ROS) generated in the CNT-O-H/PDS system. It was inferred that surface C=O groups and defects of CNTs were the key site to activate PDS for TC degradation.

The remediation of di-(2-ethylhexyl) phthalate-contaminated sediments by water hyacinth biochar activation of calcium peroxide and its effect on cytotoxicity

The presence of di-(2-ethylhexyl) phthalate (DEHP) in the aquatic systems, specifically marine sediments has attracted considerable attention worldwide, as it enters the food chain and adversely affects the aquatic environment and subsequently human health. This study reports an efficient carbocatalytic activation of calcium peroxide (CP) using water hyacinth biochar (WHBC) toward the efficient remediation of DEHP-contaminated sediments and offer insights into biochar-mediated cellular cytotoxicity, using a combination of chemical and bioanalytical methods. The pyrolysis temperature (300-900 °C) for WHBC preparation significantly controlled catalytic capacity. Under the experimental conditions studied, the carbocatalyst exhibited 94% of DEHP removal. Singlet oxygen (¹O₂), the major active species in the WHBC/CP system and electron-rich carbonyl functional groups of carbocatalyst, played crucial roles in the non-radical activation of CP. Furthermore, cellular toxicity evaluation indicated lower cytotoxicity in hepatocarcinoma cells (HepG2) after exposure to WHBC (25-1000 μg mL^-1) for 24 h and that WHBC induced cell cycle arrest at the G2/M phase. Findings clearly indicated the feasibility of the WHBC/CP process for the restoration of contaminated sediment and contributing to understanding the mechanisms of cytotoxic effects and apoptotic of carbocatalyst on HepG2.

Fabrication of Nano Iron Oxide–Modified Biochar from Co-Hydrothermal Carbonization of Microalgae and Fe(II) Salt for Efficient Removal of Rhodamine B

Dye adsorption by magnetic modified biochar has now received growing interest due to its excellent adsorption performance and facile separation for recycling. In this study, nano iron oxide–modified biochar was fabricated via the successive hydrothermal-pyrolyzing method using Chlorella vulgaris (Cv) and FeSO₄·7H₂O as raw materials, and its adsorption on Rhodamine B (RhB) in aqueous solution was studied. Multiple techniques such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET), vibrating sample magnetometry (VSM) and X-ray photoelectron spectroscopy (XPS) were employed to comprehensively characterize the structure, morphology and physicochemical properties of the adsorbent. The as-synthesized nano iron oxide–modified biochar (CBC-Fe(II)) exhibited a large surface area (527.6 m²/g) and high magnetic saturation value (13.7 emu/g) to facilitate magnetic separation. Compared with CBC and CBC-Fe(III), CBC-Fe(II) exhibited superior adsorption ability towards RhB in aqueous solution, with a maximum adsorption capacity of 286.4 mg/g. The adsorption process of RhB onto CBC-Fe(II) was well described by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating monolayer chemisorption behaviors for the adsorption system. Facile preparation, great adsorption performance and magnetic recovery properties endow CBC-Fe(II) to be a promising adsorbent for dye removal.