Activation of persulfate by LaFe1-xCoxO3 perovskite catalysts for the degradation of phenolics: Effect of synthetic method and metal substitution

Insight into the degradation of carbamazepine by electrochemical-pressure UV-activated peroxodisulphate process: kinetics, radicals, and degradation pathway

In this work, to improve the performance of peroxodisulphate-advanced oxidation, an electrochemical oxidation-assisted UV light-activated peroxodisulphate system (E/UV/PDS) was used to degrade carbamazepine. The degradation of carbamazepine by PDS, E/PDS, UV/PDS and E/UV/PDS systems was compared, and their synergistic effects were analysed. The influence of single factors, such as PDS addition, initial pH, DS voltage, target initial concentration, etc., on the degradation of the E/UV/PDS system was discussed, and the optimal degradation process parameters were given. The active substances were determined by free radical inhibition experiments, such as 1O2, SO 4 - ⋅ and ⋅ OH . It was proved that 1O2 contributes much more to the degradation of carbamazepine than SO 4 - ⋅ and ⋅ OH . The degradation pathway of carbamazepine was proposed. Finally, the degradation mechanism of carbamazepine in the E/UV/PDS system was speculated. The results indicate that the electrochemical combined with the E/UV/PDS system is of great potential application value in the removal of antibiotic drug pollution and environmental purification.

Synthesis, characterization, and application of Cu-substituted LaNiO3 perovskites as photocatalysts and/or catalysts for persulfate activation towards pollutant removal

The presence of emerging contaminants in environmental aqueous matrices is an ever-growing problem, since conventional wastewater treatment methods fail to adequately remove them. Therefore, the application of non-conventional methodologies such as advanced oxidation processes is of great importance to tackle this modern problem. Photocatalysis as well as catalytic activation of persulfates are promising techniques in this field as they are capable of eliminating various emerging contaminants, and current research aims to develop new materials that can be utilized for both processes. In this light, the present study focused on the use of a simple sol-gel-combustion methodology to synthesize Cu-substituted LaNiO3 perovskite materials in an attempt to improve the photocatalytic and catalytic performance of pure LaNiO3, using molar ratios of Cu:Ni that have not been previously reported in the literature. The morphological, structural, and optical features of the synthesized materials were characterized by a series of analytical techniques (e.g., X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy, etc.). Also, their performance as photocatalysts, persulfate anion activators and simultaneously as photocatalysts/persulfate anion activators (hybrid) was evaluated by conducting laboratory-scale experiments using phenol (phenolics) as a model emerging contaminant. Interestingly, the results revealed that LaCu0.25Ni0.75O3 exhibited the best efficiency in all the applied processes, which was mainly attributed to the introduction of oxygen vacancies in the structure of the substituted material. The contribution of selected reactive species in the hybrid photocatalytic/catalytic experiments utilizing LaCu0.25Ni0.75O3 as a (photo)catalyst was investigated using appropriate scavengers, and the results suggested that singlet oxygen is the most dominant. Additionally, the stability of all synthesized perovskites was assessed by monitoring the concentration of the leached Cu and/or Ni cations at the end of every applied process. Finally, the reusability of LaCu0.25Ni0.75O3 was evaluated in three consecutive catalytic cycles using the hybrid experiment methodology, as this process demonstrated the best efficiency in terms of phenolics removal, and the results were rather promising.

Highly Efficient Copper Doping LaFeO3 Perovskite for Bisphenol A Removal by Activating Peroxymonosulfate

A series of copper doping LaFeO3 perovskite (LaCuxFe1−xO3, LCFO, x = 0.1, 0.4, 0.5, 0.6, 0.9) are successfully synthesized by the sol-gel method under mild conditions. In this study, it is applied for the activation of peroxymonosulfate (PMS) for bisphenol A (BPA) removal. More than 92.6% of BPA was degraded within 30 min at 0.7 g/L of LCFO and 10.0 mM of PMS over a wide pH range with limited leaching of copper and iron ions. The physical–chemical properties of the catalysts were demonstrated by using X-ray diffraction (XRD), N2 adsorption–desorption isotherms, scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS). Furthermore, the effects of catalyst dosage, PMS concentration, initial pH value, and inorganic anions on the LCFO/PMS system were fully investigated. Quenching experiments were performed to verify the formation of reactive oxidant species, which showed that the radical reaction and mechanisms play a great role in the catalytic degradation of BPA. The perovskite LCFO is considered a stable, easy to synthesize, and efficient catalyst for the activation of PMS for wastewater treatment.

La2CoO4+δ perovskite-mediated peroxymonosulfate activation for the efficient degradation of bisphenol A

Sulfate radical-based technology has been considered as an efficient technology to remove pharmaceuticals and personal care products (PPCPs) with heterogeneous metal-mediated catalysts for the activation of peroxymonosulfate (PMS). In this study, La₂CoO_4+δ perovskite with Ruddlesden-Popper type structure was synthesised by the sol-gel method, which was employed in PMS activation. Different characteriazation technologies were applied for the characterization of La₂CoO_4+δ , such as SEM-EDX, XRD, and XPS technologies. A common organic compound, bisphenol A (BPA), is used as a target contaminant, and the effect impactors were fully investigated and explained. The results showed that when the dosage of La₂CoO_4+δ was 0.5 g L^-1 and the concentration of PMS was 1.0 mM in neutral pH solution, about 91.1% degradation efficiency was achieved within 25 minutes. Quenching experiments were introduced in the system to verify the catalytic mechanism of PMS for the BPA degradation, proving the existence of superoxide, hydroxyl radicals and sulfate radicals, which are responsible for the catalytic degradation of BPA. Moreover, the reusability and stability of the catalyst were also conducted which showed good stability during the reaction. This work would improve the applications of A₂BO₄-type perovskites for activating PMS to degrade BPA.

Photocatalytic Degradation of Methylene Blue and Ortho-Toluidine Blue: Activity of Lanthanum Composites LaxMOy (M: Fe, Co, Ni)

Lanthanum (La) nanocomposites LaFeO3, LaNiO3, and LaCoO3 were synthesized using a sol-gel method, and different La to-metal (Fe, Ni, or Co) ratios were attained using various concentrations of salts. The resulting composites were calcined at 540 °C and characterized by XRD, SEM-EDX, FT-IR spectroscopy, XPS, thermogravimetric analysis (TGA), and PL spectroscopy. The activity of the lanthanum composites (LaFeO3, LaNiO3, and LaCoO3) was studied using the photocatalytic degradation of methylene blue (MB) and ortho-toluidine blue (o-TB) under visible light with a wavelength below 420 nm. The change in the concentration of dyes was monitored by using the UV-Vis spectroscopy technique. All composites appeared to have some degree of photocatalytic activity, with composites possessing an orthorhombic crystal structure having higher photocatalytic activity. The LaCoO3 composite is more efficient compared with LaFeO3 and LaNiO3 for both dyes. High degradation percentages were observed for the La composites with a 1:1 metal ratio.