Synergistic degradation of tetracycline by BiOBr microspheres combined with peroxydisulfate under visible LED light irradiation

Application of BiOX Photocatalyst to Activate Peroxydisulfate Ion-Investigation of a Combined Process for the Removal of Organic Pollutants from Water

The persulfate-based advanced oxidation processes employing heterogeneous photocatalysts to generate sulfate radicals (SO4•−) from peroxydisulfate ion (PDS, S2O82−) have been extensively investigated to remove organic pollutants. In this work, BiOX (X = Cl, Br, and I) photocatalysts were investigated to activate PDS and enhance the transformation rate of various organic substances under UV (398 nm) and Vis (400–700 nm) radiation. For BiOCl and BiOBr, in addition to excitability, the light-induced oxygen vacancies are decisive in the activity. Although without organic substances, the BiOI efficiency highly exceeds that of BiOBr and BiOCl for PDS activation (for BiOI, 15–20%, while for BiOBr and BiOCl, only 3–4% of the PDS transformed); each BiOX catalyst showed enhanced activity for 1,4-hydroquinone (HQ) transformation due to the semiquinone radical-initiated PDS activation. For sulfamethoxypyridazine (SMP), the transformation is driven by direct charge transfer, and the effect of PDS was less manifested. BiOI proved efficient for transforming various organic substances even under Vis radiation. The efficiency was enhanced by PDS addition (HQ is wholly transformed within 20 min, and SMP conversion increased from 40% to 90%) without damaging the catalyst; its activity did change over three consecutive cycles. Results related to the well-adsorbed trimethoprim (TRIM) and application of biologically treated domestic wastewater as a matrix highlighted the limiting factors of the method and visible light active photocatalyst, BiOI.

Morphological and elemental tuning of BiOCl/BiVO4 heterostructure for uric acid electrochemical sensor and antibiotic photocatalytic degradation

Deep eutectic solvents (DES) consisting of EG-(ChCl: C₂H₆O₂) and TU-(ChCl: CH₄N₂S) assisted synthesized BiOCl/BiVO₄ heterostructured catalyst studied for electrochemical uric acid (UA) sensor and tetracycline photocatalytic degradation. The chemical composition of the BiOCl/BiVO₄ catalyst was analyzed by X-ray photoelectron spectroscopy (XPS). UV-vis spectroscopy reveals increased absorption of visible light till the near-infrared region, which results in a narrowing of band gap energy from 2.3 eV to 2.2 eV for BiOCl/BiVO₄-TU. Morphology of catalyst analyzed using field-emission scanning electron microscope (FE-SEM) and Transmission electron microscope (TEM) technique. Time-Resolved photoluminescence (TRPL) confirms an increased lifetime of e^-/h⁺ pair after heterostructure formation. The catalyst-modified glassy carbon electrode shows selectivity toward the detection of uric acid (UA). The limit of detection (LOD) is estimated to be 0.04688 μM for UA; also, interference and stability of catalyst were studied. Photocatalytic activity of the synthesized catalyst was investigated by degrading tetracycline (TC) antibiotic pollutants, and their intermediate product was analyzed by ion trap mass spectrometry (MS).

Facile synthesis of magnetic ZnFe2O4/AC composite to activate peroxydisulfate for dye degradation under visible light irradiation

Heterogeneous photocatalysis/persulfate oxidation process has been considered as a promising technology for dye contaminants removal. The magnetic ZnFe₂O₄/active carbon (AC) composites were hydrothermally synthesized and firstly used to activate peroxydisulfate (PDS) for rhodamine B (RhB) degradation under visible LED light irradiation. The optimized Vis-ZnFe₂O₄/AC(4/1)-PDS system can enhance the RhB degradation efficiency by 32.01% and 13.87% compared with Vis-ZnFe₂O₄-PDS and Vis-AC-PDS systems, respectively. The influence of operational parameters such as catalyst dosage (0.2 - 0.4 g L^-1), PDS concentration (1.0 - 2.0 g L^-1), temperature (25 - 45 °C), solution pH (2.7 - 10.9), and coexisting inorganic ions (Cl^-, NO₃^-, HCO₃^-, PO₄^3-, Cu²⁺, Fe³⁺, and Ca²⁺) on RhB degradation was studied, and 100% of RhB (20 mg L^-1) was degraded after 80 min at operational condition: 0.30 g L^-1 of ZnFe₂O₄/AC(4/1) and 1.5 g L^-1 of PDS, solution pH of 2.74, reaction temperature of 25 °C. The quenching experiments, EPR test, and XPS analysis were employed to reveal the proposed mechanism, which demonstrated that ¹O₂ played a more important role than other reactive species (SO₄^•-, •OH, O₂^•-, and h⁺) in RhB degradation. The generation of ¹O₂ via the two routes was as follows: (i) the in situ formed active oxygen (O^*) reacted with HSO₅^- to produce ¹O₂; (ii) O₂^•- was oxidized by h⁺ to form ¹O₂. After five consecutive cycles, the photodegradation efficiency of RhB by ZnFe₂O₄/AC(4/1) catalyst slightly decreased from 88.52 to 83.92%, indicating the excellent reusability of ZnFe₂O₄/AC(4/1) photocatalyst. As designed, Vis-ZnFe₂O₄/AC-PDS oxidation system can effectively remove RhB from the different real water matrices, and the degradation efficiency of RhB in tap water, river water, and secondary effluent was 78.24%, 79.55%, and 74.53% after 80 min of reaction, respectively.

Generation of singlet oxygen over CeO2/K, Na-codoped g-C3N4 for tetracycline hydrochloride degradation in a wide pH range

Singlet oxygen (1O2) were widely studied for catalytic oxidation and photo dynamic therapy (PDT) and so on due to its unique properties, such as its long lifetime, wide pH tolerance,...