SYNTHESIS AND CHARACTERIZATION OF MONTMORILLONITE-SUPPORTED TiO 2 COMPOSITES FOR ENHANCED UV ABSORPTION
- PDF / 6,907,572 Bytes
- 11 Pages / 547.087 x 737.008 pts Page_size
- 35 Downloads / 171 Views
SYNTHESIS AND CHARACTERIZATION OF MONTMORILLONITE-SUPPORTED TiO2 COMPOSITES FOR ENHANCED UV ABSORPTION DAEYOUNG KIM1,2, DANIEL KIM2, JAEHWAN KIM2, CHANGYUN PARK2, KI-MIN ROH1,2, IL-MO KANG2, AND SUNG MAN SEO2 * 1 Department of Nanomaterials Science and Engineering, University of Science and Technology, Daejeon 34113, Korea Advanced Geo-materials R&D Department, Pohang Branch, Korea Institute of Geoscience and Mineral Resources, Pohang 37559, Korea
2
Abstract—Titanium dioxide (TiO2, rutile) nanoparticles, inorganic ultraviolet absorbers, are used extensively in sunscreen cosmetics as an inorganic ultraviolet (UV) absorber to prevent skin damage; because of their nanotoxicity, use in combination with a support, such as montmorillonite (Mnt), rather than alone, is suggested. Mnt-supported TiO2 composites (Mnt-TiO2) for sunscreens are most suitable when the particles are spherical and of relatively uniform size, which are normally accomplished by spray drying, but this is difficult to achieve because of the naturally layered structure of Mnt. The objective of the present study was, therefore, to find the ideal characteristics of spray-drying nozzles to produce the desired spherical shape and size distribution of the Mnt-TiO2 composite particles. The starting Mnt was extracted from natural bentonite by particle-size separation. An ultrasonic nozzle in the spray dryer was selected for use in the synthesis of Mnt-TiO2 composites based on the particle-size distribution (PSD) of Mnt prepared using a two-fluid nozzle and an ultrasonic nozzle at 453 K. The incorporation of TiO2 in the final Mnt-TiO2 composites was examined by X-ray powder diffraction (XRD) and elemental analysis. With increasing TiO2 concentration, the TiO2 content and average particle size of the Mnt-TiO2 composites increased. Scanning electron microscopy (SEM) images showed that all samples prepared had uniform and nearly spherical shapes. Absorbance of UV by Mnt-TiO2 (5:1) composites was greater than that by either purified Mnts or pure TiO2. The present study demonstrated a simple method, using a spray dryer with an ultrasonic nozzle, to synthesize Mnt-TiO2 composites of uniform size and shape suitable for cosmetic application. Keywords—Bentonite . Composite . Montmorillonite . Spray dryer . Titanium dioxide . UV absorption INTRODUCTION Sunscreens consist mainly of various organic and/or inorganic UV filters and are used worldwide because UV radiation is classified as a group 1 carcinogen for humans by the International Agency for Research on Cancer (Armstrong et al. 2012). Numerous laboratory, clinical, and case studies have shown that topically applied organic UV filters, such as avobenzone, oxybenzone, octocrylene, octyl methoxycinnamate, and amiloxate increase plasma concentrations, trigger endocrine disruption, and cause allergic reactions (Schlumpf et al. 2001; Collaris and Frank 2008; Janjua et al. 2008; Burnett and Wang 2011; Gilbert et al. 2013; Kim and Choi 2014; Matta et al. 2019; Adler and DeLeo 2020). While effective inorganic alternatives,
Data Loading...
