Chen Shiao-Shing, Hsu Bao-Chrung, Hung Li-Wei
Institute of Environmental Engineering and Management, National Taipei University of Technology, No. 1, Section 3, Chung-Hsiao East Road, Taipei 106, Taiwan.
J Hazard Mater. 2008 Apr 15;152(3):1092-7. doi: 10.1016/j.jhazmat.2007.07.086. Epub 2007 Jul 31.
Waste iron was used to treat high concentration chromate (534 mg/L as Cr) from electroplating wastewater by plug flow reactor (PFR) due to the following reasons: (1) two wastes are treated simultaneously, (2) low pH of the electroplating wastewater ( approximately 2) benefits the reaction between these two wastes, (3) effluent pH is elevated in the PFR, reducing the base requirement to meet the pH discharge standard for wastewater (pH 6-9). Complete chromate reductions were achieved at pH 1.7 for hydraulic retention time (HRT) of 98 min, pH 1.5 for HRT of 40 min and pH 1.3 for HRT of 20 min. Consequently, optimum HRT for complete chromate reduction was obtained for different pHs. Although more acids were used to lower influent pH to reduce HRT, effluent pH was higher due to more hydrogen ion reacting with chromate. Eventually, fewer bases are required to fulfill the discharge pH requirement of wastewater. Effluent pH 3-5 was observed with high turbidity, indicating the precipitations of chromium oxide and hydroxide were enhanced by the dissolved iron coagulation. X-ray diffraction was conducted to examine the remaining species. Other than chromium oxide and hydroxide species, an iron-chromium complex (Cr2FeO4) was also observed.
采用废铁通过推流反应器（PFR）处理电镀废水中的高浓度铬酸盐（以Cr计为534 mg/L），原因如下：（1）同时处理两种废物；（2）电镀废水的低pH值（约为2）有利于这两种废物之间的反应；（3）在PFR中废水的pH值升高，降低了满足废水pH排放标准（pH 6 - 9）所需的碱量。在pH值为1.7、水力停留时间（HRT）为98分钟，pH值为1.5、HRT为40分钟以及pH值为1.3、HRT为20分钟的条件下实现了铬酸盐的完全还原。因此，针对不同的pH值获得了铬酸盐完全还原的最佳HRT。尽管使用了更多的酸来降低进水pH值以缩短HRT，但由于更多的氢离子与铬酸盐反应，出水pH值更高。最终，满足废水排放pH要求所需的碱更少。观察到出水pH值为3 - 5且浊度较高，表明溶解铁的混凝作用增强了氧化铬和氢氧化铬的沉淀。进行了X射线衍射以检查剩余的物质。除了氧化铬和氢氧化铬物质外，还观察到了一种铁铬复合物（Cr2FeO4）。
