University of Notre Dame, Department of Civil and Environmental Engineering and Earth Sciences, USA.
University of Notre Dame, Department of Chemical and Biomolecular Engineering, USA.
Water Res. 2020 May 1;174:115593. doi: 10.1016/j.watres.2020.115593. Epub 2020 Feb 7.
The catalytic hydrogel membrane reactor (CHMR) is an interfacial membrane process that uses nano-sized catalysts for the hydrogenation of oxidized contaminants in drinking water. In this study, the CHMR was operated as a continuous-flow reactor using nitrite (NO) as a model contaminant and palladium (Pd) as a model catalyst. Using the overall bulk reaction rate for NO reduction as a metric for catalytic activity, we evaluated the effect of the hydrogen gas (H) delivery method to the CHMR, the initial H and NO concentrations, Pd density in the hydrogel, and the presence of Pd-deactivating species. The chemical stability of the catalytic hydrogel was evaluated in the presence of aqueous cations (H, Na, Ca) and a mixture of ions in a hard groundwater. Delivering H to the CHMR lumens using a vented operation mode, where the reactor is sealed and the lumens are periodically flushed to the atmosphere, allowed for a combination of a high H consumption efficiency and catalytic activity. The overall reaction rate of NO was dependent on relative concentrations of H and NO at catalytic sites, which was governed by both the chemical reaction and mass transport rates. The intrinsic catalytic reaction rate was combined with a counter-diffusional mass transport component in a 1-D computational model to describe the CHMR. Common Pd-deactivating species [sulfite, bisulfide, natural organic matter] hindered the reaction rate, but the hydrogel afforded some protection from deactivation compared to a batch suspension. No chemical degradation of the hydrogel structure was observed for a model water (pH > 4, Na, Ca) and a hard groundwater after 21 days of exposure, attesting to its stability under natural water conditions.
催化水凝胶膜反应器（CHMR）是一种界面膜过程，使用纳米级催化剂将饮用水中氧化污染物加氢。在这项研究中，以亚硝酸盐（NO）为模型污染物，钯（Pd）为模型催化剂，将 CHMR 作为连续流反应器运行。以 NO 还原的总体体相反应速率作为催化活性的度量标准，我们评估了向 CHMR 输送氢气（H）的方法、H 和 NO 的初始浓度、水凝胶中 Pd 的密度以及存在使 Pd 失活的物质对 CHMR 的影响。在存在水合阳离子（H、Na、Ca）和硬地下水混合离子的情况下，评估了催化水凝胶的化学稳定性。使用通气操作模式向 CHMR 腔室输送 H，其中反应器密封并且腔室定期吹扫至大气中，允许结合高 H 消耗效率和催化活性。NO 的总反应速率取决于催化位点处 H 和 NO 的相对浓度，这由化学反应和质量传递速率共同控制。本征催化反应速率与 1-D 计算模型中的反扩散质量传递组件相结合，以描述 CHMR。常见的 Pd 失活物质[亚硫酸盐、连二硫酸盐、天然有机物]会阻碍反应速率，但与批处理悬浮液相比，水凝胶为失活提供了一些保护。在暴露 21 天后，模型水（pH>4、Na、Ca）和硬地下水对水凝胶结构没有观察到化学降解，证明其在天然水条件下稳定。
