Investigation of homogeneous photosensitized oxidation activities of palladium and platinum octasubstituted phthalocyanines: Oxidation of 4-nitrophenol

Ball-milled layer double hydroxide as persulfate activator for efficient degradation of organic: Alkaline sites-triggered non-radical mechanism

Considerable efforts have been put into enhancing the activation performance of peroxydisulfate (PDS) by catalysts toward oxidative degradation of organic pollutants, while the oxidative selectivity is somehow overlooked. Here, we reported an enhanced non-radical oxidation pathway of PDS, activated by ball-milled Mg/Al-layered double hydroxide (BM-LDH), to reconcile the selectivity and reactivity. EPR and quenching experiments suggested that 1O2 dominated the oxidative pathway for phenol degradation without generating carcinogenic halide by-products. Multiple interfacial characterizations and density functional theory (DFT) calculations revealed that BM-LDH played dual roles in PDS activation: (1) the interlaminar BM-LDH allowed PDS intercalation to form complexed PDS, resulting in decreases in the activation barrier of PDS; (2) abundant terminal hydroxyls in the layers of BM-LDH acted as alkaline-activation sites that can efficiently activate PDS to generate 1O2 toward phenol degradation. Ball-milling treatment of LDH refined the structural hierarchy of LDH to create pore volumes, which greatly enhanced the diffusion of phenol to the intercalated PDS, resulting in more than twice the reaction rate for phenol degradation. This study provided a promising approach to simultaneously control over the reactivity and selectivity toward PDS activation that are critical for the degradation of organic pollutants particularly in drinking water treatment.

Advances in photocatalytic degradation of organic pollutants in wastewaters: harnessing the power of phthalocyanines and phthalocyanine-containing materials

Access to clean water is increasingly challenging worldwide due to human activities and climate change. Wastewater treatment and utilization offer a promising solution by reducing the reliance on pure underground water. However, it is crucial to develop efficient and sustainable methods for wastewater purification. Among the emerging wastewater treatment strategies, photocatalysis has gained significant attention for decomposing organic pollutants in water, especially when combined with sunlight and a recoverable photocatalyst. Heterogeneous photocatalysts have distinct advantages, as they can be recovered and reused without significant loss of activity over multiple cycles. Phthalocyanine dyes, with their exceptional photophysical properties, are particularly valuable for homogeneous and heterogeneous photocatalysis. By immobilizing these photosensitizers in various supports, hybrid materials extend their light absorption into the visible spectrum, complementing most supports' limited UV light absorption. The novelty and research importance of this review stems from its discussion of the multifaceted approach to treating contaminated wastewater with phthalocyanines and materials containing phthalocyanines. It highlights key aspects of each study, including photocatalytic efficiency, recyclability characteristics, investigation of the generation of oxygen species responsible for degradation, identification of the major degradation byproducts for each pollutant, and others. Moreover, the review includes tables that illustrate and compare the various phthalocyanines and supporting materials employed in each study for pollutant degradation. Additionally, almost all photocatalysts mentioned in this review could degrade at least 5% of the pollutant, and more than 50 photocatalysts showed photocatalytic rates above 50%. When immobilized in some support, the synergistic effect of the phthalocyanine was visible in the photocatalytic rate of the studied pollutant. However, when performing these types of works, it is necessary to understand the degradation products of each pollutant and their relative toxicities. Along with this, recyclability and stability studies are also necessary. Despite the good results presented in this review, some of the works lack those studies. Moreover, none of the works mentions any study in wastewater.

Using BiVO4/CuO-Based Photoelectrocatalyzer for 4-Nitrophenol Degradation

The present work reports the degradation of 4-nitrophenol using BiVO₄/CuO hybrid material synthesized by the precipitation of BiVO₄ in the presence of CuO. Morphological and structural characterizations were performed using X-ray diffraction and scanning electronic microscopy coupled to energy dispersive X-ray spectroscopy. Through the calculation of the Kubelka–Munk function applied to diffuse reflectance spectrophotometry data, the hybrid material presented absorption edge of 1.85 eV. The formation of p-n heterojunction between BiVO₄ and CuO renders the hybrid material suitable for the construction of a photoanode employed in hydroxyl radical generation. UV–vis spectrophotometry and high-performance liquid chromatography experiments were performed in order to monitor the degradation of 4-nitrophenol and the formation of secondary products. Additional information regarding the hybrid material was obtained through ion chromatography and total organic carbon analyses. The application of BiVO₄/CuO-based photocatalyzer led to a 50.2% decrease in total organic carbon after the degradation of 4-nitrophenol. Based on the results obtained in the study, BiVO₄/CuO has proved to be a promising material suitable for the removal of recalcitrant compounds in water treatment plants.

Cross-linked chitosan aerogel modified with Pd(II)/phthalocyanine: Synthesis, characterization, and catalytic application

Palladium(II) phthalocyanine (PdPc) tetrasulfonate was chemically bonded to an amine moiety of chitosan aerogel. The reaction was promoted by the transformation of sulfonic acid groups of PdPc to sulfonyl chloride, which is highly active for amination. The porous composite showed good catalytic activity in the oxidation reaction of some alkylarenes, aliphatic and benzylic alcohols, and cyclohexanol. High conversions and excellent selectivities were obtained for the solvent-free reactions under aerobic conditions at 80 °C during 24 h. While many oxidation reactions have been reported catalysed with palladium phthalocyanine, this is the first reported oxidation of alkylarenes via this catalyst. The organometallic compound is applicable as a heterogeneous catalyst having high chemical stability with recyclability up to six times.

Mesopolymer modified with palladium phthalocyaninesulfonate as a versatile photocatalyst for phenol and bisphenol A degradation under visible light irradiation

A novel versatile photocatalyst, FDU-PdPcS, was prepared by immobilizing palladium phthalocyaninesulfonate (PdPcS) onto the FDU-15 mesopolymer via multi-step chemical modification processes involving chloromethylation of the FDU-15 mesopolymer first with chloromethyl methyl ether, a subsequent amination reaction with ethylenediamine, and finally modification with palladium phthalocyaninesulfonate via ionic interaction. The obtained FDU-PdPcS photocatalyst was characterized by the X-ray diffraction (XRD), UV-Vis spectrosopy and inductively coupled plasma (ICP) techniques. This photocatalyst not only affords a high dispersion of monomeric PdPcS molecules, which may further be stabilized by the pi-electron of benzene rings of FDU-15, but also provides a number of diamino groups inside the mesopores, which could be advantageous for the photodegradation of phenolic pollutants. In photodegradation studies of phenolic pollutants, the FDU-PdPcS catalyst exhibited excellent visible light photocatalytic activity and reusability. The photodegradation products of phenol and bisphenol A were investigated by the gas chromatoghraphy-mass spectrometry (GC-MS) technique. The results showed that the photodegradation products were composed of carboxylic acids and CO2. Isopropanol, sodium azide and benzoquinone were used as hydroxyl radical (OH*), singlet oxygen (1O2) and superoxide radical (O2*-) scavengers, respectively. The results suggested that 1O2 and O2*- were the prominent active species during the photodegradation process. A possible mechanism for the photodegradation of phenol was also discussed.