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首页> 外文会议>2011 water quality technology conference amp; exposition: An Oasis of Ideas for a Changing Environment. >Effects of Oxidants and Reductants on the Dissolution Rates of the Lead Corrosion Product PbO_2
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Effects of Oxidants and Reductants on the Dissolution Rates of the Lead Corrosion Product PbO_2

机译：氧化剂和还原剂对铅腐蚀产物PbO_2溶解速率的影响

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Lead(Ⅳ) oxide (PbO_2) is an important corrosion product in lead service lines, and itsrnstability can affect lead release to drinking water. The dissolution rate rather than the equilibriumrnsolubility of PbO_2 can control the dissolved lead concentration in distribution systems with PbO_2rnpresent. The dissolution of PbO_2 is affected by the specific water chemistry in a distributionrnsystem. Understanding the kinetics of PbO_2 dissolution could provide a quantitative view tornunderstand lead release to drinking water from lead service lines.rnThe dissolution rates of plattnerite (β-PbO_2) were investigated as a function of pH, thernpresence of free chlorine, and iodide concentration using continuously stirred tank reactorsrn(CSTRs). Each experiment was conducted for 24 hours to ensure that the system reached steadyrnstate. The pH, free chlorine concentration, and dissolved lead concentration were monitoredrnperiodically in each set of the experiments, and the steady-state concentrations of dissolved leadrnwere used to calculate the dissolution rate. The solids were characterized at the end of selectedrnexperiments by X-ray diffraction and scanning electron microscopy to determine whether arnsecondary solid phase had formed.rnIn the absence of free chlorine and iodide, the plattnerite dissolution rate increased withrndecreasing pH values until reaching a plateau below pH 3.5. The steady-state lead concentrationsrnwere above the lead action level (0.015 mg/L) only when the pH was below 6.7. The presence ofrnfree chlorine inhibited the dissolution of PbO_2, which might be due to the elevated oxidationrnreduction potential (ORP) of the system that inhibited the chemical reduction of Pb(Ⅳ) in PbO_2 tornmore soluble Pb(Ⅱ) species.rnThe presence of the chemical reductant iodide enhanced the dissolution of PbO_2, and therndissolution rate increased with increasing iodide concentration. At the highest iodide concentrationrnstudied (100 μM), the reductive dissolution was sufficiently fast that the lead(Ⅱ) carbonaterncerrusite (PbCO_3) formed as secondary solid from the transformation of PbO_2. The present studyrnshowed that the dissolution rate of PbO_2 increased with the order of free chlorine, water, andrniodide, which is consistent with a trend of decreasing ORP of the system, indicating that chemicalrnreduction was important in controlling the dissolution of PbO_2.
机译：氧化铅（PbO_2）是铅服务管线中的重要腐蚀产物，其稳定性会影响铅向饮用水中的释放。 PbO_2的溶解速率而不是平衡溶解度可以控制存在PbO_2的配电系统中溶解的铅浓度。 PbO_2的溶解受分配系统中特定水化学的影响。了解PbO_2溶解的动力学可以提供定量的观点，以了解铅从铅服务管线向饮用水中的释放。rn研究了连续不断地研究铂铁矿（β-PbO_2）的溶解速率与pH值，游离氯的存在和碘化物浓度之间的关系。搅拌釜反应器每个实验进行24小时，以确保系统达到稳态。在每组实验中定期监测pH值，游离氯浓度和溶解的铅浓度，并使用溶解态铅的稳态浓度来计算溶解速率。在选定的实验结束时，通过X射线衍射和扫描电子显微镜对固体进行表征，以确定是否形成了第二级固相。在没有游离氯和碘化物的情况下，铂矿的溶解速率随着pH值的降低而增加，直到达到低于pH的平台。 3.5。仅当pH值低于6.7时，稳态铅浓度才高于铅作用水平（0.015 mg / L）。游离氯的存在抑制了PbO_2的溶解，这可能是由于系统中较高的氧化还原电位（ORP）抑制了PbO_2中Pb（Ⅳ）进一步溶解的Pb（Ⅱ）物种中化学还原的缘故。还原剂碘化物可提高PbO_2的溶解度，且溶解度随碘化物浓度的增加而增加。在最高碘化物浓度（100μM）下，还原溶解速度足够快，以至于碳酸铅（Ⅱ）铬铈矿（PbCO_3）是由PbO_2转化而形成的次级固体。本研究表明，PbO_2的溶解速率随游离氯，水和碘化物的增加而增加，这与系统ORP降低的趋势一致，表明化学还原对控制PbO_2的溶解很重要。

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