The degradation and removal of nonylphenol polyethoxylates (NPnEO/NP) by photodegradation and electrokinetic remediation in environmental matrices

• Main Authors: Kun-cho Chen, 陳琨焯
• Other Authors: Ching Yuan
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/36623857309663553036

碩士 === 國立高雄大學 === 土木與環境工程學系碩士班 === 96 === Photocatalysis and electrokinetic (EK) process for the remediation were applied of nonylphenol polyethoxylates (NP-9) in aqueous phase and nonylphenol (NP) in soil phase, respectively. Several process parameters were investigated for their degradation efficiency during the aqueous phase photocatalytic process. These process parameters included the aqueous pH environment, types and amounts of composite photocatalyst, addition of enhancing reagent (H2O2) and initial concentration of NP-9. Besides, the degradation pathway of nonylphenol polyethoxylates (NPnEO) was analyzed. Additional parameters affecting the EK process included the processing fluid, potential gradient, processing time and initial concentration of NP were investigated in this research. The removal mechanism of NP using the EK process was also investigated. 　　The absorption behavior of NP-9 in aqueous phase on the carbon nanotube (CNT) was investigated. The absorption capacity was enhanced as pH decreased. The maximum absorption capacity was up to 188.8 mg/g at pH 2.0. The isothermal absorption of NP-9 on the carbon nanotube was conformed to the Freundlich’s absorption formula. Additionally, it was considered as a physical absorption and spontaneous exothermic reaction. 　　During the photodegradation process of NP-9 treated with the composite catalyst, the long-chain NPnEO was gradually broken down to medium-chain fragments, short-chain fragments and NP. CNT was added to titanium dioxide (TiO2) for the formation of nano composite photocatalyst. CNT was capable of storing the electrons released by TiO2 during the photocatalysis, which would hinder the rebinding of electrons and electron-hole pairs. The degradation efficiency was more effective than degradation with only TiO2 alone. During the photodegradation of NP-9, the photodegradation efficiency was enhanced with decreasing pH for the pH environment within the range of 3-11. When H2O2 was added to the photocatalytic system, the average degradation efficiency was above 91.1%. The addition of H2O2 would assist in the formation of hydroxyl radicals and caused significant improvement in the degradation efficiency. 　　For the experiment of removing NP in soil phase using the EK process, the suitable potential gradient was shown at 1.0V/cm. As the current was more stable, the electroosmotic flow rate was more efficient. During the EK process, the total removal rate for the extension of treatment periods to 8-15 days was respectively 1.14-1.34 times as compared to the total removal rate on day 5. The extension of processing time had effectively enhanced the removal rate of NP. The experiments with different processing fluids generated the following sequence for the NP removal rate: Methanol (52.8-68.8%) >NaOH (42.8-53.7%)> CA (35.8-38.7%)>D.I. Water (29.6%). During the removal of NP by the EK system, the main proportion of NP was collected on the cathode reservoir, which accounted for 88.3-95.1%. The total amount of NP collected on the cathode reservoir increased as the removal efficiency improved. Therefore, the main removal mechanism was the migration of NP from the anode to cathode terminal by electroosmosis for the EK/NP system in soil phase. 　　The overall result showed that composite catalyst could degrade NP-9 effectively. The degradation efficiency was greater than using TiO2 alone. During the degradation process in photocatalysis, NP-9 was broken down from longer EO chain to shorter EO chain and NP. Additionally, for the removal of NP in soil phase using the EK process, the NP removal efficiency may be enhanced by the conditional selection of other processing fluids and electrode materials.