Ozone pre-oxidation to the degradation technology research of MC-LR

Abstract

Ozone pre-oxidation can effectively degrade MC-LR, 2mg / L ozone for MC-LR removal efficiency of 65.28%. 2mg / L ozone for MC-LR removal efficiency reach to 65.28%. Ozone also has a better removal effect for turbidity and UV254 , 4mg / L ozone for UV254 and turbidity removal efficiency are 50% and 59.38%. But ozone removal efficiency of TOC and CODMn was poor, 3mg / L ozone for TOC and CODMn removal rate are only 15.06% and 14.29%. Introduction Algal toxins is a cyclic heptapeptide substance, there is a strong heat resistance and can withstand extreme pH, natural degradation speed is very slow.Microcystin isomers are about more than 60 kinds, which the widely distributed and the representative of microcystin (Microcystin, namely MC). Especially MC-LR, the widely distributed, and the strongest toxicity .World Health Organization (WHO) recommended the algal toxins in drinking water standard for MC-LR should be less than 1. 0μg/L. Our country provides MC-LR limit of 1 μg/L in drinking Water Standards 2012. The study found that ozone on algal toxin has good removal effect Hengfeng Miao [4] and other analysts believe,in the O3: MC is 6, MC LR removal efficiency can reach 92%,the study found that Kejia Zhang, etc, the degradation of ozone in MC LR pseudo-first-order reaction kinetics,the ozone dosing quantity increased from 0.31 mg/L to 0.31 mg/L,MC LR degradation rate increased by 0.0103 min 1 to 0.0407 min .The experiment mainly to study the ozone removal of MC-LR. Materials and Methods Experimental Materials Experiments with water taken from a water source of raw water of the north, through the cultivation of algae.MC-LR standard solution (20ug / L) was purchased from scientific testing by the Environmental Protection Department of Agriculture. Trifluoroacetic acid (purity > 99%) was purchased from Scharlau Company, methanol and other agents were of analytical grade. Experimental apparatus and method Using high performance liquid chromatography (HPLC) of Agilent 1200C for MC-LR was measured, measurement parameters: the injection volume was 20uL; UV-visible detector wavelength 238nm; column temperature was 25 °C ; mobile phase 0.05% TFA aqueous solution/Methanol is 45/55; the flow rate was 1.0ml / min.Application of ozone generator (3S-A3), through iodometric method to measure the concentration of ozone, Control the ozone dosing quantity is 1 mg/L, 2 mg/L, 3 mg/L, 4 mg/L, 5 mg/L, the reaction time was 30min, the reaction temperature using room temperature is 25°C, and observe the response to the phenomenon. Determination of MC LR containing algae water quality concentration is 5.3 ug/l. The TOC VCPN total organic carbon analyzer of island ferry company to measure the TOC, measurement of turbidity using HACH 2100N turbidity analyzers,UV254 measured using CV-1700 UV-visible spectrophotometer. Water containing algae water quality characteristics are shown in table 1. International Conference on Materials Engineering and Information Technology Applications (MEITA 2015) © 2015. The authors Published by Atlantis Press 809 Table 1 raw water quality characteristics turbidity (NTU) TOC (mg/L) UV254 (cm) CODMn (mg/L) MC-LR (ug/L) 3.2 7.57 0.16 5.6 5.3 Results and Analysis The ozone pre-oxidation for MC LR removal Figure 1 shows that, ozone has good removal effect on MC – LR, with the increase of ozone dosing quantity, removal rate of MC LR gradually strengthened. Ozone dosing 1 mg/L, MC LR removal rate was 8.11%, at this point, the chroma of the water significantly reduce than raw water, analysis of the reasons may be due to ozone make the algal cells rupture and break down , resulting in decreased chroma. But the removal rate of MC LR is low , possible reason is due to the bursting of the algal cells make intracellular toxin is released more [6, , lead to the removal rate of MC LR is not obvious. Ozone dosing 2 mg/L, MC LR removal rate reached 65.28%, removal rate significantly increased. 3 mg/L ozone for MC LR removal rate reached 85.66%, relative to 2 mg/L ozone, removal rate increased by 20%, visible, ozone dosage exceeds 2mg / L, the removal efficiency of MC-LR showed a decreasing trend. Ozone can effectively remove the MC LR is due MC LR molecule contains plenty of unsaturated bond, ozone destroys the MC-LR unsaturated bonds, so as to be oxidized to become saturated small organic molecules. Fig. 1 Ozone pre-oxidation removal of MC-LR The impact on other water quality characteristics of ozone pre – oxidation The removal of turbidity and UV254 The figure 2 shows, with the increase of ozone dosing quantity, ozone pre-oxidation for UV254 and turbidity removal rate gradually enhanced, dosing 4mg / L of ozone, turbidity and UV254 removal rate were 50% and 59.38%,continue adding ozone, the growth rate of removal rate is slow. Experiments show that ozone has a certain removal capability to turbidity and UV254 , but there are certain limits .