title: Quantitative methylene blue decolourisation assays as rapid screening tools for assessing the efficiency of catalytic reactions.
abstract: Identifying the most efficient oxidation process to achieve maximum removal of a target pollutant compound forms the subject of much research. There exists a need to develop rapid screening tools to support research in this area. In this work we report on the development of a quantitative assay as a means for identifying catalysts capable of decolourising methylene blue through the generation of oxidising species from hydrogen peroxide. Here, a previously described methylene blue test strip method was repurposed as a quantitative, aqueous-based spectrophotometric assay. From amongst a selection of metal salts and metallophthalocyanine complexes, monitoring of the decolourisation of the cationic dye methylene blue (via Fenton-like and non-Fenton oxidation reactions) by the assay identified the following to be suitable oxidation catalysts: CuSO4(a Fenton-like catalyst), iron(II)phthalocyanine (a non-Fenton oxidation catalyst), as well as manganese(II) phthalocyanine. The applicability of the method was examined for the removal of bisphenol A (BPA), as measured by HPLC, during parallel oxidation experiments. The order of catalytic activity was identified as FePc > MnPc > CuSO4for both BPA and MB. The quantitative MB decolourisation assay may offer a rapid method for screening a wide range of potential catalysts for oxidation processes.
authors.affiliation: Biotechnology Innovation Centre, Rhodes University, Grahamstown, 6140, South Africa.
authors.forename: Jan
authors.initials: J
authors.lastname: Kruid
authors.affiliation: Biotechnology Innovation Centre, Rhodes University, Grahamstown, 6140, South Africa. Electronic address: r.fogel@ru.ac.za.
authors.forename: Ronen
authors.initials: R
authors.lastname: Fogel
authors.affiliation: Biotechnology Innovation Centre, Rhodes University, Grahamstown, 6140, South Africa.
authors.forename: Janice Leigh
authors.initials: JL
authors.lastname: Limson
mesh_terms: D001559:Benzhydryl Compounds / Q000737:chemistry; D002384:Catalysis; D003116:Color; D019327:Copper Sulfate / Q000737:chemistry; D005296:Ferrous Compounds / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D007211:Indoles / Q000737:chemistry; D008345:Manganese / Q000737:chemistry; D008751:Methylene Blue / Q000737:chemistry*; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D019327:Copper Sulfate; D005296:Ferrous Compounds; D006861:Hydrogen Peroxide; D007211:Indoles; D008345:Manganese; D008751:Methylene Blue; D010636:Phenols; D014874:Water Pollutants, Chemical; C493990:iron phthalocyanine; C006780:bisphenol A; D000098826:Bisphenol A Compounds
keywords: Catalyst screening; Metallophthalocyanine; Methylene blue; Oxidation reaction