Photocatalytic removal of organic phosphate esters by TiO2: Effect of inorganic ions and humic acid

Ting Tang; Guining Lu; Wenjing Wang; Rui Wang; Kaibo Huang; Zhiyuan Qiu; Xueqin Tao; Zhi Dang

doi:10.1016/j.chemosphere.2018.04.161

Photocatalytic removal of organic phosphate esters by TiO₂: Effect of inorganic ions and humic acid

Chemosphere. 2018 Sep:206:26-32. doi: 10.1016/j.chemosphere.2018.04.161. Epub 2018 Apr 30.

Authors

Ting Tang¹, Guining Lu², Wenjing Wang¹, Rui Wang¹, Kaibo Huang¹, Zhiyuan Qiu³, Xueqin Tao³, Zhi Dang⁴

Affiliations

¹ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China.
² School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; Guangdong Provincial Engineering and Technology Research Center for Environmental Risk Prevention and Emergency Disposal, Guangzhou 510006, China. Electronic address: gnlu@foxmail.com.
³ School of Environmental Science and Engineering, Zhongkai University of Agriculture and Engineering, Guangzhou 510225, China.
⁴ School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; The Key Lab of Pollution Control and Ecosystem Restoration in Industry Clusters, Ministry of Education, Guangzhou 510006, China.

PMID: 29723749
DOI: 10.1016/j.chemosphere.2018.04.161

Abstract

In this study, the TiO₂-mediated photocatalytic removal of organic phosphate esters (OPEs) under UV irradiation was investigated. In addition, the effects of selected inorganic ions and humic acid (HA) were examined. TCEP, TCPP, and TDCPP hardly undergo degradation via photolysis, and TiO₂-mediated photocatalysis was confirmed to be effective for removing OPEs present in a water matrix. Inorganic ions (e.g., PO₄^3-, SO₄^2-, Cl^-, and NO₃^-) and HA inhibited the degradation of OPEs. Among these selected ions, PO₄^3- exhibited the strongest inhibition ability, followed by SO₄^2- and then Cl^- and NO₃^-, and the inhibition effect increased with the ion concentration. The inhibition effect was caused by two main reasons: (1) Inorganic ions or HA served as ·OH scavengers and competed with OPEs for ·OH. (2) On account of the adsorption of inorganic ions and HA on TiO₂, the available surface-active sites for OPEs decreased, followed by their oxidation with surface-bound ·OH. The ·OH concentrations were measured by electron spin resonance and the probe method, and it was positively correlated to the degradation rate of OPEs. This study emphasized the importance of inorganic species and HA on the photocatalytic degradation of OPEs and clarified the inhibition mechanism for the degradation of OPEs by the inorganic species or HA.

Keywords: Humic acid; Hydroxyl radical; Ions species; Kinetic; Organic phosphate esters; TiO(2).

MeSH terms

Esters / chemistry*
Humic Substances / analysis*
Photolysis*
Titanium / chemistry*

Substances

Esters
Humic Substances
titanium dioxide
Titanium