Catalysis of organic pollutant photodegradation by metal phthalocyanines immobilized on TiO2@SiO2

Abstract

A TiO 2 @SiO 2 hybrid support was prepared by the sol-precipitation method using n-octylamine as a template. The photocatalyst manganese phthalocyanine tetrasulfonic acid (MnPcS) was immobilized on the support to form MnPcS-TiO 2 @SiO 2 . X-ray diffraction (XRD) and UV-Visible diffuse reflectance spectra (UV-Vis DRS) were employed to characterize the catalyst. The photocatalytic degradation of rhodamine B (RhB) and the catalytic oxidation of o-phenylenediamine (OPDA) under visible light irradiation were used as probe reactions. The mineralization efficiency and the degradation mechanism were evaluated using chemical oxygen demand (COD Cr ) assays and electron spin resonance (ESR), respectively. RhB was efficiently degraded by immobilized MnPcS-TiO 2 @SiO 2 under visible light irradiation. Complete decolorization of RhB occurred after 240 min of irradiation and 64.02% COD Cr removal occurred after 24 h of irradiation. ESR results indicated that the oxidation process was dominated by the hydroxyl radical (·OH) and superoxide radical (O 2 −· ) generated in the system.

Synthesis and characterization of novel unsymmetrical phthalocyanine/TiO 2 composites and their evaluation as photocatalysts for degradation of 4-chlorophenol under visible light

“…10−12 Metallophthalocyanines (MPcs) are able to absorb in visible light or sunlight, and have attracted high * Correspondence: sevim@itu.edu.tr interest for visible light-employing catalytic photodegradation of toxic industrial wastes. 13 The photoactivity of phthalocyanines comes from their ability to produce very reactive species such as hydroxyl radical (• OH) and singlet oxygen species ( 1 O 2 ) by photon flux absorption in the ultraviolet or visible part of the spectrum. In particular, in polar solvents, phthalocyanines show a tendency to form π -aggregates and the photocatalytic activity is reduced greatly, because aggregated metallophthalocyanines' excited energetic states are offset by nonexcited states.…”

“…Aggregation inhibits ordering crystalline packing and localization of internal spaces. 13 Under these conditions, MPcs are dispersed and their photocatalytic activity is very effective.…”

Photocatalytic Behavior of Water-Based Styrene-Acrylic Coatings Containing TiO2 Sensitized with Metal-Phthalocyanine Tetracarboxylic Acids

“…Phthalocyanines can be one of the most efficient and stable class of photosensitizers for TiO 2 photocatalysts operating under visible light irradiation, as some studies have already reported [20][21][22][23][24][25][26][27][28][29], but the anchoring groups that could bind them on the nanoparticles surface [30] decisively determine the overall efficiency. Studies related to the stability of several coupling functionalities, such as carboxyl, phosphate, sulfonate, acetyl, silyl, hydroxyl, or amino reveal that carboxyl groups exhibit a very good stability during photocatalytic processes [31].…”

Degradation of organic pollutants by a Co3O4-graphite composite electrode in an electro-Fenton-like system

“…They tend to be lipid soluble and undergo food chain amplification and, if toxic, threaten human health. Advanced oxidation processes (AOPs) are among the best advanced treatment technologies because of their ability to mineralize organic pollutants [1,2].…”

“…H 2 O 2 generated in situ is consumed prior to decomposition to H 2 O and O 2 , giving higher yields and selectivity for the targeted reactions. Although the classic Fenton reactions (Fe 2+ /H 2 O 2 ) have been widely used for the treatment of POPs, they have three main drawbacks: the high cost of H 2 O 2 , the large production of ferric hydroxide sludge and the narrow working pH range [2]. As iron ions precipitates as a hydroxide at higher pH values.…”