The Radiation Degradation of Neutral Red Solution by γ-Ray

Xiu-Hua Liu, Yi Yi Deng, Yin-Hang Zhou, Liang Xia, Lan-Lan Ding, Yu-Chuan Zhang

China Academy of Engineering Physics, Mianyang, China.

DOI: 10.4236/wjnst.2012.24019                

Abstract

Neutral red is kind of biologic colourant and acidity-basicity indicator. Radiation degradation of neutral red in aqueous solution was done by γ-Ray. The removal rate of chemical oxygen demand, total organic carbon, chroma and the changing of pH value were studied under various conditions. With the increase of absorbed doses, the chemical oxygen demand and chroma decreased conspicuously. The absorbed dose rate has little effect on the degradation of neutral red. When the absorbed doses are the same, the chemical oxygen demand and chroma decreased more obviously with the increase of neutral red concentration. Weak basic condition and proper H₂O₂ addiation are propitious to removal of chemical oxygen demand of neutral red.

Keywords

γ-Ray; Irradiation; Neutral Red; Degradation

1. Introduction

For the rapid development of dyestuff industry, the dyeing wastewater is recognized as one of the intractable industrial organic wastewater for its large amount discharge, complex composition with toxicity and deep color [1]. Neutral red is an important coloring agent for its aqueous solution in deep red. Neutral red is often used as linsey-woolsey coloring agent, biological stain and acid-base indicator. Therefore, neutral red is also an important composition in dyeing wastewater.

Ionizing radiation seems to be an effective technology for the degradation of organic pollutants. Relative researches show that irradiation can achieve the effective treatment of organophosphorus compounds, halogenated hydrocarbon, carboxymethylcellulose, etc. [2-8]. Radiation degradation can be performed at ambient temperature and for large-scale treatment. Since the γ-ray has higher penetration, radiation degradation of neutral red in aqueous solution was done by γ-ray. The removal rate of COD, TOC, Chroma and the changing of pH value were studied under various conditions. The effect of absorbed dose rate, absorbed dose and H₂O₂ content on degradation efficiency of neutral red has been obtained.

2. Experiment Method

2.1. Irradiation Method of γ-Ray

The radiation degradation of neutral red was done by a ⁶⁰Co-γ-source with an activity of 230 kCi (average energy of 1.25 MeV). Neutral red solution was irradiated in 100 mL colorimetric glass vessels at certain dose rates. Absorbed dose was controlled by irradiated time. Every colorimetric vessel contained 55 mL neutral red solution. The absorption dose was calibrated by silver dichromate stoichiometric method (Chinese National Standard: JJG 1028-91). All experiments were performed at ambient temperatures.

2.2. Analytical Method

Several main indices of neutral red solution were quantitatively measured before and after irradiation. Chemical oxygen demand (COD) was measured by bichromate method (Chinese National Standard: GB 11914-89). Chroma was determined by diluted multiple method (Chinese National Standard: GB 11903-89). Total organic carbon (Chinese National Standard: TOC) and total inorganic carbon (TIC) were measured by OI Analytical 1030 C Aurora Combustion Total Organic Carbon Analyzer according to nondispersive infrared absorption method (Chinese National Standard: HJ 501-2009). The pH value was determined by Mettler Toledo SG2 pH meter according to glass electrode method (Chinese National Standard: GB 6920-86). UV-Vis spectra of neutral red solution was carried out by a PE Lamda 12 UV-Vis spectrophotometer.

3. Result and Discussion

3.1. The Effect of Absorbed Dose

Neutral red solutions with concentration at 10 mg/L, 28.9 mg/L, 60 mg/L were irradiated for different doses from 0 to 20 kGy at 74.68 Gy/min, in accordance with different concentrations. A little precipitation produced after radiation. The evolution of pH values, COD contents and Chroma of superstratum limpid liquid are showed in Figure 1. After irradiation, COD and pH value decreased rapidly. pH value decreased more obviously with the increase of absorbed doses, indicating that there is at least an acidic compound produced during the radiation degradation of neutral red.

COD of neutral red solutions decreased gradually with the increase of absorbed dose. For the solutions with the concentrations at 10 mg/L, 28.9 mg/L, 60 mg/L, the COD decreased more than 57.6% at a dose of 5 kGy. When the absorbed doses are the same, the COD and

(a)(b)(c)

Figure 1. pH values (a), COD contents (b) and chroma (c) of the neutral red solutions under different absorbed doses.

chroma of the neutral red solutions decreased more obviously with concentration increase. The chroma of neutral red solution decreased dramatically after irradiation. The color removed completely with an initial neutral red concentration of 10 mg/L at a dose of 1 kGy, an initial neutral red concentration of 28.9 mg/L at a dose of 5 kGy, an initial neutral red concentration of 60mg/L at a dose of 10 kGy.

Figure 2 is the UV-Vis spectra of neutral red solutions. The absorbency data are normalized to the highest peak of 0 kGy spectrum. The UV-Vis spectra illustrate that the main characteristic absorption peaks both at 266 nm and

Conflicts of Interest

The authors declare no conflicts of interest.

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