Crimi Michelle, Quickel Mark, Ko Saebom
Environmental Health Science and Environmental Science & Policy, Clarkson University, PO Box 5805, Potsdam, NY 13699, United States.
J Contam Hydrol. 2009 Feb 27;105(1-2):69-79. doi: 10.1016/j.jconhyd.2008.11.007. Epub 2008 Nov 17.
In situ chemical oxidation using permanganate is an increasingly employed approach to organic contaminant remediation at hazardous waste sites. Manganese dioxide (MnO2) particles form as a by-product of the reaction of permanganate with contaminants and naturally-reduced subsurface materials. These particles are of interest because they have the potential to deposit in the subsurface and impact the flow regime in/around permanganate injection, including the well screen, filter pack, and the surrounding subsurface formation. Control of these particles can allow for improved oxidant injection and transport, and contact between the oxidant and contaminants of concern. Sodium hexametaphosphate (HMP) has previously been identified as a promising aid to stabilize MnO2 in solution when included in the oxidizing solution, increasing the potential to inhibit particle deposition and impact subsurface flow. The goal of the experimental studies described herein was to investigate the ability of HMP to prevent particle deposition in transport studies using four different types of porous media. Permanganate was delivered to a contaminant source zone (trichloroethylene) located within four different media types with variations in sand, clay, organic carbon, and iron oxides (as goethite) content. Deposition of MnO2 within the columns was quantified with distance from the source zone. Experiments were repeated in replicate columns with the inclusion of HMP directly with the oxidant delivery solution, and MnO2 deposition was again quantified. While total MnO2 deposition within the 60 cm columns did not change significantly with the addition of HMP, deposition within the contaminant source zone decreased by 25-85%, depending on the specific media type. The greatest differences in deposition were observed in the goethite-containing and clay-containing columns. Columns containing these two media types experienced completely plugged flow in the oxidant-only delivery systems; however, the addition of HMP prevented this plugging within the columns, increasing the oxidant throughput.
使用高锰酸盐进行原位化学氧化是危险废物场地有机污染物修复中越来越常用的方法。二氧化锰（MnO₂）颗粒是高锰酸盐与污染物及天然还原的地下材料反应的副产物。这些颗粒备受关注，因为它们有可能沉积在地下，影响高锰酸盐注入区域（包括井筛、滤料层和周围地下地层）及其周边的水流状态。控制这些颗粒可以改善氧化剂的注入和传输，以及氧化剂与相关污染物之间的接触。六偏磷酸钠（HMP）先前已被确定为一种有前景的助剂，当它包含在氧化溶液中时，能使MnO₂在溶液中稳定，从而增加抑制颗粒沉积和影响地下水流的可能性。本文所述实验研究的目的是在使用四种不同类型多孔介质的传输研究中，探究HMP防止颗粒沉积的能力。高锰酸盐被输送到位于四种不同介质类型中的污染物源区（三氯乙烯），这些介质在沙子、粘土、有机碳和氧化铁（针铁矿形式）含量上存在差异。通过与源区的距离对柱内MnO₂的沉积进行量化。在重复的柱中进行实验，将HMP直接加入氧化剂输送溶液中，再次对MnO₂沉积进行量化。虽然在60厘米长的柱中加入HMP后，MnO₂的总沉积量没有显著变化，但在污染物源区内的沉积量减少了25% - 85%，这取决于具体的介质类型。在含针铁矿和含粘土的柱中观察到沉积差异最大。在仅输送氧化剂的系统中，含有这两种介质类型的柱出现了完全堵塞的水流；然而，加入HMP防止了柱内的这种堵塞，提高了氧化剂的通量。
