Evaluation of Portable Rhodamine B Analyzer for Monitoring OH Radical Scavenging Demand in Ultraviolet Advanced Oxidation Processes

Sook-Hyun Nam,Tae-Mun Hwang,Jaewuk Koo ,Eunju Kim ,Ju-Won Lee

doi:10.3390/su132313279

Abstract

A portable OH radical scavenging demand analyzer that can be installed and operated on site was developed to measure water quality indicators that influence the generation of OH radicals from UV/hydrogen peroxide reactions to determine the UV dose and the hydrogen peroxide injection concentration. Rhodamine B (RhB) was used as an indicator for the continuous measurement of the OH radical scavenging demand of four samples with different water quality parameters using the rapid, easy, and real-time UV-Vis spectrophotometer method. The results demonstrated that the estimated rate constant for the RhB color decay rate resulting from direct UV photolysis was low enough to verify its suitability as a probe compound. The mean values of the OH radical scavenging demand for target water samples at different organic concentrations were 20,659 s−1 for plant N, 42,346 s−1 for plant C, 32,232 s−1 for plant Y, and 81,669 s−1 for plant B. Variations in the monitoring results for the target water treatment plants suggest that on-site OH radical scavenging demands should be considered to determine the UV dose and the hydrogen peroxide injection concentration for the UV advanced oxidation process.

Highlights

The advanced oxidation process (AOP) is a promising and attractive water treatment technique that reduces organic chemicals to trace levels [1,2]
The results showed that the UV dosesof ofthe thecolor colordecay decayrate rateof ofRhB
The results from monitoring water samples on-site using this analyzer suggest that the OH radical scavenging demand should be measured in the field and used to determine process operating parameters because there are wide deviations in the former depending on the season and site

Summary

Introduction

The advanced oxidation process (AOP) is a promising and attractive water treatment technique that reduces organic chemicals to trace levels [1,2]. The AOP generates OH radicals, the transient species which play a key role in aqueous photochemistry [3]. OH radical, which has strong oxidizing potential and non-selectivity, is a major oxidation species in the AOP [4,5]. The non-selective property of OH radical could result in a significant radical water matrix demand, which negatively impacts the efficiency of AOPs. OH radicals must be analyzed quantitatively to predict the removal rate of the target compound in the AOP process. The primary species known for OH radical scavenging in water are dissolved organic matter (DOM) and carbonate, bicarbonate, nitrite, bromide ions, and halide species [6,7,8]

Methods

Discussion

Conclusion