Heterogeneous catalytic system of photocatalytic persulfate activation by novel Bi2WO6 coupled magnetic biochar for degradation of ciprofloxacin

Visible light photocatalytic degradation of oxytetracycline hydrochloride using chitosan-loaded Z-scheme heterostructured material BiOCOOH/O-gC3N4

In this work, a Z-scheme heterostructured BiOCOOH/O-gC3N4 material was synthesized and immobilized on chitosan (CTS) to obtain the BiOCOOH/O-gC3N4/CTS photocatalytic material for photocatalytic degradation of oxytetracycline hydrochloride (CTC).Our findings indicate that the composite material BiOCOOH/O-gC3N4, as well as the BiOCOOH/O-gC3N4/CTS composite membrane, displayed a significantly higher efficiency in photocatalytic degradation of CTC compared to BiOCOOH alone, owing to the synergistic effect of adsorption and photocatalysis. Following four cycles of use, the composite material retained around 96 % of its initial photocatalytic degradation activity. The addition of CTS in the photocatalytic material resolved issues such as aggregation and difficult recovery commonly encountered with powder materials, thereby facilitating effective collision between the photocatalytic active sites and CTC. Experimental and theoretical calculations provided confirmation that the combination of BiOCOOH and O-gC3N4 effectively enhanced the light absorption capacity and photocatalytic performance. Furthermore, we investigated the influence of environmental factors such as pH value and anions on the photocatalytic degradation experiment, which offers valuable insights for the application of composite catalysts in wastewater treatment.

Solar photocatalytic degradation of ciprofloxacin using biochar supported zinc oxide- tungsten oxide photocatalyst

Ciprofloxacin (CIP) is an antibiotic used to treat bacterial infections. It is not completely broken down during conventional wastewater treatment processes and can persist in the environment, leading to the development of antibiotic-resistant bacteria. This study focuses on the solar photocatalytic degradation CIP using biochar-supported photocatalysts. The photocatalysts developed by combining ZnO and WO3 in different ratios (1:2, 1:1, 2:1) were supported on hemp herd biochar. The photocatalyst made with a ratio of 2:1:1 of ZnO:WO3:biochar (Z2W1H) reported the highest CIP degradation efficiency of 87.3% and TOC removal efficiency of 43.1% at a catalyst dosage of 2 g/L, initial CIP concentration of 3 mg/L, and treatment time of 150 min. Subsequently, the effects of operating parameters on CIP degradation were investigated using central composite design (CCD). About 85.4% degradation efficiency of CIP was obtained at optimum conditions (pH ∼8.4, initial CIP concentration ∼4.4 mg/L, catalytic dosage ∼3.4 g/L) within 90 min. A quadradic model was developed to interpret the linear and interactive effect of operating parameters on the CIP degradation efficiency with 2.24-4.59% error. The adsorption-desorption study showed around 42.21% of adsorbed CIP was desorbed from Z2W1H. Scavenger studies demonstrated that the CIP breakdown was notably done by the superoxide radical (O2•-). The mechanism of CIP degradation was adsorption on biochar and subsequent degradation by photocatalyst. The prevalent degradation reactions such as C-N bond cleavage, decarboxylation, decarbonylation, defluorination, and ring opening lead to formation of various intermediates. The Z2W1H reusability test showed ~ 4.2% decrease in CIP removal efficiency after three cycles.

The performance of a visible light-responsive material Fe3O4/Bi2WO6 cooperating with peroxymonosulfate to degrade bisphenol A

In this study, the visible light-responsive catalysts Fe3O4/Bi2WO6 were prepared and characterized by BET, SEM, EDS, XRD, XPS, and MPMS. The performances of five catalysts (0.05 Fe/Bi, 0.13 Fe/Bi, 0.17 Fe/Bi, 0.21 Fe/Bi, and 0.30 Fe/Bi) for photocatalytic degradation of bisphenol A under visible light (300-W Xe lamp) were compared. Among five catalysts, 0.17 Fe/Bi (the molar ratio of Fe3O4 to Bi2WO6 was 0.17) acquired the highest BPA photocatalytic removal of 90.2% at 120 min. With the synergistic effect between Vis/0.17 Fe/Bi and peroxymonosulfate (PMS), the BPA removal obtained was as high as 100% at 90 min ([BPA] = 100 mg/L, [0.17 Fe/Bi] = 1.25 g/L, [PMS] = 2.0 g/L, and T = 25 °C). After five times reused of 0.17 Fe/Bi, its removal of BPA dropped by 13.4% in presence of PMS, which demonstrated 0.17 Fe/Bi possessed relatively stable performance. High BPA degradation was attributed to the attacking effects of various oxide species (SO4•-, •OH, h+, O2•-) generated in the Fe3O4/Bi2WO6/PMS system under the cooperation of photocatalyst Fe3O4/Bi2WO6 and oxidizing agent PMS.

A Review on N-Doped Biochar for Oxidative Degradation of Organic Contaminants in Wastewater by Persulfate Activation

The Persulfate-based advanced oxidation process is the most efficient and commonly used technology to remove organic contaminants in wastewater. Due to the large surface area, unique electronic properties, abundant N functional groups, cost-effectiveness, and environmental friendliness, N-doped biochars (NBCs) are widely used as catalysts for persulfate activation. This review focuses on the NBC for oxidative degradation of organics-contaminated wastewater. Firstly, the preparation and modification methods of NBCs were reviewed. Then the catalytic performance of NBCs and modified NBCs on the oxidation degradation of organic contaminants were discussed with an emphasis on the degradation mechanism. We further summarized the detection technologies of activation mechanisms and the structures of NBCs affecting the PS activation, followed by the specific role of the N configuration of the NBC on its catalytic capacity. Finally, several challenges in the treatment of organics-contaminated wastewater by a persulfate-based advanced oxidation process were put forward and the recommendations for future research were proposed for further understanding of the advanced oxidation process activated by the NBC.