Enhanced malachite green photolysis at the colloidal-aqueous interface. (January 2022)

• Record Type: Journal Article
• Authors: Kaylor, Lukas; Skelly, Paul; Alsarrani, Mansour; Subir, Mahamud
• Is Part Of: Chemosphere. Volume 287:Part 1(2022)
• Publication Date: 2022-01
• Subjects: Colloidal interface -- Microplastics -- Natural particulate matter -- Emerging contaminants -- Surface photolysis -- Second harmonic generation; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2021.131953
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Colloids, such as natural particulate matter and microplastics, can play a significant role in the fate and transport of organic contaminants. Specifically, these small nano-to micron-sized particles provide large surface area; thus, particle-aqueous interfacial chemistry becomes significant. In this work, we present an experimental investigation of interfacial photokinetics of malachite green cation ( MG + ) adsorbed at the surface of polystyrene carboxyl (PSC) microspheres suspended in aqueous solution. Second harmonic generation (SHG), an interfacial selective laser spectroscopic tool, has been used to probe the buried interface. It is revealed that relative to the bulk, photoinduced degradation of MG + is accelerated by approximately 10-fold at this noncatalytic particle surface. By measuring the SHG-based surface electronic spectra, we have also demonstrated that N -demethylated intermediates of MG + remain at the interface until they are further decomposed. MG + exhibits a bathochromic shift at the interface. Together with strong binding affinity and faster initial rate of photodegradation of MG + at the interface, this work highlights that adsorption and surface photolysis are important pathways by which organic compounds can be transformed within the aquatic environment. Moreover, this research also stimulates further questions on the enrichment of reactive species at the colloidal-aqueous interface and their influence on facilitating decompositions of organic pollutants. Graphical abstract: Image 1 Highlights: Photodegradation of cationic malachite green ( MG + ), an organic pollutant, is enhanced at the colloidal/aqueous interface. MG + exhibits a bathochromic shift at the surface of a non-catalytic polystyrene carboxylate (PSC) microparticle. N -demethylated photoinduced products of MG + remain adsorbed at the PSC particle surface. Use of second harmonic generation to probe photokinetic and spectral properties of MG + at a colloidal interface demonstrated.