Li Chi-Wang, Chen Yi-Ming, Yen Wei-Shuen
Department of Water Resources and Environmental Engineering, TamKang University, 151 Ying-Chuan Road, Tamsui 25137, Taipei County, Taiwan.
Chemosphere. 2007 Jun;68(2):310-6. doi: 10.1016/j.chemosphere.2006.12.073. Epub 2007 Feb 5.
A fluidized zero valent iron (ZVI) reactor pressurized by CO(2) gas for controlling pH was employed for nitrate reduction. The proposed CO(2) pressurized system potentially has advantages of using less CO(2) gas and reaching equilibrium pH faster than CO(2)-bubbled system. However, due to weak acid nature of carbonic acid, system pH gradually increased with increasing oxidation of ZVI and reduction of nitrate. As pH increased with progress of reaction, nitrate removal rate decreased continuously. The results indicate that nitrate removal efficiency increases with increasing initial ZVI dosage but reaches plateau at ZVI doses of higher than 8.25gl(-1), and initial nitrate concentration up to 100mg l(-1) as N has minimal impact on the removal efficiency. Unlike the fluidized system with pH control by strong acid reported in our pervious study, near 100% of nitrogen recovery was observed in the current process, indicating that nitrate reduction by ZVI with different pH controlled mechanisms will have different reaction routes.
采用由二氧化碳气体加压以控制pH值的流化零价铁（ZVI）反应器进行硝酸盐还原。所提出的二氧化碳加压系统可能具有比二氧化碳鼓泡系统使用更少二氧化碳气体且更快达到平衡pH值的优点。然而，由于碳酸的弱酸性质，随着ZVI氧化和硝酸盐还原的增加，系统pH值逐渐升高。随着反应进行pH值升高，硝酸盐去除率持续下降。结果表明，硝酸盐去除效率随初始ZVI剂量增加而提高，但在ZVI剂量高于8.25 g l⁻¹时达到平台期，初始硝酸盐浓度高达100 mg l⁻¹（以N计）对去除效率影响最小。与我们之前研究中报道的用强酸控制pH值的流化系统不同，在当前工艺中观察到近100%的氮回收率，这表明具有不同pH控制机制的ZVI还原硝酸盐将有不同的反应途径。
