title: Metachromasy as an indicator of photostabilization of methylene blue adsorbed to clays and minerals.
abstract: The influence of methylene blue adsorption to different clays on its photodegradation was studied. Methylene blue in solution was decomposed by sunlight in a zero-order process. Adsorption to some clay minerals (sepiolite and vermiculite) and a zeolite (clinoptilolite) accelerated the degradation process, and converted it to a first-order reaction. On the other hand, adsorption to other clay minerals (palygorskite and montmorillonite) stabilized the dye and prevented its degradation. Interestingly, in the clay-dye complexes that exhibited stability, clear metachromasy of the adsorbed methylene blue occurred, whereas the effect was not observed in the clay-dye complexes that underwent photodegradation.
authors.affiliation: Tel Hai College, Sidney Warren Science Education Center for Youth, Upper Galilee, Israel.
authors.forename: Maya
authors.initials: M
authors.lastname: Samuels
authors.forename: Omer
authors.initials: O
authors.lastname: Mor
authors.forename: Giora
authors.initials: G
authors.lastname: Rytwo
mesh_terms: D000327:Adsorption; D000538:Aluminum Silicates / Q000737:chemistry* / Q000378:metabolism; D002863:Chromogenic Compounds / Q000737:chemistry* / Q000378:metabolism; D000077215:Clay; D004355:Drug Stability; D008751:Methylene Blue / Q000737:chemistry* / Q000378:metabolism / Q000528:radiation effects; D010782:Photolysis
chemical_list: D000538:Aluminum Silicates; D002863:Chromogenic Compounds; D000077215:Clay; D008751:Methylene Blue