CaltechAUTHORS
  A Caltech Library Service

TiO_2-Photocatalyzed As(III) Oxidation in Aqueous Suspensions: Reaction Kinetics and Effects of Adsorption

Ferguson, Megan A. and Hoffmann, Michael R. and Hering, Janet G. (2005) TiO_2-Photocatalyzed As(III) Oxidation in Aqueous Suspensions: Reaction Kinetics and Effects of Adsorption. Environmental Science and Technology, 39 (6). pp. 1880-1886. ISSN 0013-936X. https://resolver.caltech.edu/CaltechAUTHORS:20150806-062700415

Full text is not posted in this repository. Consult Related URLs below.

Use this Persistent URL to link to this item: https://resolver.caltech.edu/CaltechAUTHORS:20150806-062700415

Abstract

Oxidation of arsenite, As(III), to arsenate, As(V), is required for the efficient removal of arsenic by many water treatment technologies. The photocatalyzed oxidation of As(III) on titanium dioxide, TiO_2, offers an environmentally benign method for this unit operation. In this study, we explore the efficacy and mechanism of TiO_2-photocatalyzed As(III) oxidation at circumneutral pH and over a range of As(III) concentrations approaching those typically encountered in water treatment systems. We focus on the effect of As adsorption on observed rates of photooxidation. Adsorption (in the dark) of both As(III) and As(V) on Degussa P25 TiO_2 was examined at pH 6.3 over a range in dissolved arsenic concentrations, [As]_(diss), of 0.10−89 μM and 0.2 or 0.05 g L^(-1) TiO_2 for As(III) and As(V), respectively. Adsorption isotherms generally followed the Langmuir−Hinshelwood model with As(III) exhibiting an adsorption maxima of 32 μmol g^(-1). As(V) adsorption did not reach a plateau under the experimental conditions examined; the maximum adsorbed concentration observed was 130 μmol g^(-1). The extent of As(III) and As(V) adsorption observed at the beginning and end of the kinetic studies was consistent with that observed in the adsorption isotherms. Kinetic studies were performed in batch systems at pH 6.3 with 0.8−42 μM As(III) and 0.05 g L^(-1) TiO_2; complete oxidation of As(III) was observed within 10−60 min of irradiation at 365 nm. The observed effect of As(III) concentration on reaction kinetics was consistent with surface saturation at higher concentrations. Addition of phosphate at 0.5−10 μM had little effect on either As(III) sorption or its photooxidation rate but did inhibit adsorption of the product As(V). The selective use of hydroxyl radical quenchers and superoxide dismutase demonstrated that superoxide, O_2^(•-), plays a major role in the oxidation of As(III) to As(V).


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1021/es048795nDOIArticle
http://pubs.acs.org/doi/full/10.1021/es048795nPublisherArticle
ORCID:
AuthorORCID
Hoffmann, Michael R.0000-0001-6495-1946
Additional Information:© 2005 American Chemical Society. Received for review August 2, 2004. Revised manuscript received December 6, 2004. Accepted December 16, 2004. Publication Date (Web): February 1, 2005. We thank Dr. A. J. Colussi for helpful discussions and suggestions concerning this work. Financial support from the U.S. Environmental Protection Agency’s Science to Achieve Results program (91596201-0) is gratefully acknowledged.
Funders:
Funding AgencyGrant Number
Environmental Protection Agency (EPA)91596201-0
Issue or Number:6
Record Number:CaltechAUTHORS:20150806-062700415
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20150806-062700415
Official Citation:TiO2-Photocatalyzed As(III) Oxidation in Aqueous Suspensions:  Reaction Kinetics and Effects of Adsorption Megan A. Ferguson, Michael R. Hoffmann, and Janet G. Hering Environmental Science & Technology 2005 39 (6), 1880-1886 DOI: 10.1021/es048795n
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:59259
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:06 Aug 2015 16:32
Last Modified:03 Mar 2020 13:01

Repository Staff Only: item control page