現今的高科技產業製程中，產生的高濃度含砷廢水，因廢水中同時含各種陰、陽離子，於以之處理去除水中砷離子過程中許多尚未被釐清的離子競爭現象，進而影響水中砷的去除效果。本研究探討電磁場輔助奈米級零價鐵處理高濃度之含砷廢水，研究過程分別以批次實驗進行單一離子對砷離子之影響，另一併觀察水中pH、DO、ORP、Fe2+、總鐵濃度等參數的變化情形。另外並以27-3 部分因子實驗設計(27-3Fractional Factorial Design；27-3FFD)探討去除砷過程中之混合離子對砷離子去除競爭。
實驗結果發現，條件於起始pH=4單一離子系統中，具負面影響之競爭性陰離子依序為：PO43->Br->NO3->SO42-，而系統中Ca2+與F-可提昇砷離子去除之效率。於複合離子之FFD實驗中，由所得效應估計值與離子交互作用推估結果，發現PO43-，SO42-，F-與Ca2+為去除砷重要之影響因子，另外Cl-、Br-、NO3-及Ca2+則為As去除之促進因子。此複合離子系統中FFD實驗結果顯示，各離子對As去除之競爭性強弱依序為： NO3->Cl->Ca2+>Br-> F->SO42->PO43-。
比較單一離子及混合離子兩系統研究結果，發現於單一離子系統中砷離子之去除率(52%~70%)多高於複合離子系統(26%~5%)，且可知複合離子的影響並不等於所有離子的加總，此表示離子之間複雜的交互作用確實存在於系統中。 Wastewaters with high concentration of arsenic generated from many high technology industries in the manufacturing process compleat with other anions and cations. Treatmentof these wastewaters becomes more difficult because of the ion competition phenomenon, resulting in adverse effects on the removal of arsenic. In this study, high concentration arsenic in wastewater is treated by nanoscale zero-valent iron reactor assisted with electric-magnetic field. Batch experiments were conducted with a single ion specie as well as multi-ions species to test the various single ion and complex ions on arsenic removal. The pH, DO, ORP of the treatment system as well as the generation of Fe2+ and total iron were monitored. In addition, a 27-3 Fractional Factorial Design (FFD) was employed for screening main competitive factors in this As removal process.
Results showed that for single ion process at an initial pH 4 ,the presence of the following ion, antagonistic behavior on arsenic removal were in the order of : PO43- > Br- > NO3- > SO42-. However, the presence of Ca2+ as well as F- showed synergistic effect by promoting the As removal. Further, based on the FFD estimates of major effects and interaction, PO43-,SO42-, F- and Ca2+ were important factors on As removal. For the multi-ion, the following were the promoters for the As removal: Cl-, Br-, NO3-, and Ca2+. The promoter effect of the ion on As removal in the multi-ion system were in the following order of : NO3-> Cl-> Ca2+> Br-> F-> SO42-> PO43-.
The result between single (52%~70%)and multi-ion (26%~5%)system showed that the presence of the background species will have impact of arsenic removal, implying that there were some complex ion interactions in the multi-ion system which must be taken into consideration when designing an arsenic treatment system.
