Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, Australia.
Curtin Water Quality Research Centre, Department of Chemistry, Curtin University, Australia; Facultad de Ingenieria, Universidad Catolica Santiago de Guayaquil, Ecuador.
Chemosphere. 2018 Oct;209:950-959. doi: 10.1016/j.chemosphere.2018.06.145. Epub 2018 Jun 26.
The influence of dissolved organic matter (DOM) properties on its interfacial interactions with MnO and on catalytic oxidation processes was studied by Time-Resolved Dynamic Light Scattering (TR-DLS) and Atomic Force Microscopy (AFM) under varied solution conditions. Four DOM fractions of different characteristics (e.g., SUVA, hydrophobic character, structural properties) were selected. Bared-MnO nanoparticles readily aggregated in NaCl and CaCl solutions. Classic DLVO Theory successfully described critical coagulation concentrations and aggregation behaviors. In NaCl solution, DOM adsorbed on MnO nanoparticles and provided electrosteric stabilization. The two DOM fractions of higher hydrophobic (HPO) character were more efficient in decreasing the aggregation rates. Enhanced MnO aggregation was observed at high Ca concentrations due to charge screening and cation bridging between carboxyl groups in DOM structures. The addition of oxidant (HO) induced a high aggregation of bared-MnO nanoparticles, possibly due to the release of Mn (i.e., complexation mechanisms) and generation of reactive species (O, HO, and H). Contrasted with their hydrophilic (HPI) counterparts, HPO isolates adsorbed on MnO significantly decreased the catalytic oxidation processes between HO/MnO; suggesting a more efficient and stronger DOM coating. Interfacial forces measured by AFM, showed weaker interactions between HPI isolates and MnO; suggesting unfavorable polar interactions. Conversely, the high adhesion forces between MnO/HPO isolate would indicate stronger bonds and hydrophobic interactions. This study provided a nanoscale understanding of the impact of DOM characteristics on: a) performance of the MnO coated ceramic membranes in water treatment, and b) biogeochemical cycle of Mn-oxides in the environmental.
通过时间分辨动态光散射（TR-DLS）和原子力显微镜（AFM）研究了在不同溶液条件下，溶解有机质（DOM）性质对其与 MnO 界面相互作用和催化氧化过程的影响。选择了四个具有不同特性（如 SUVA、疏水性、结构特性）的 DOM 分数。裸露的-MnO 纳米颗粒在 NaCl 和 CaCl 溶液中容易聚集。经典的 DLVO 理论成功地描述了临界聚沉浓度和聚集行为。在 NaCl 溶液中，DOM 吸附在 MnO 纳米颗粒上并提供静电稳定作用。具有较高疏水性（HPO）特征的两种 DOM 分数更有效地降低了聚集速率。由于电荷屏蔽和 DOM 结构中羧基之间的阳离子桥接作用，在高 Ca 浓度下观察到 MnO 增强聚集。由于 Mn（即络合机制）的释放和活性物种（O、HO 和 H）的生成，添加氧化剂（HO）会导致裸露-MnO 纳米颗粒的高聚集。与亲水性（HPI）相比，吸附在 MnO 上的 HPO 隔离物显著降低了 HO/MnO 之间的催化氧化过程；表明 DOM 涂层更有效且更强。AFM 测量的界面力表明，HPI 隔离物与 MnO 之间的相互作用较弱；表明不利的极性相互作用。相反，MnO/HPO 隔离物之间的高粘附力将表明更强的键合和疏水相互作用。这项研究从纳米尺度上了解了 DOM 特性对：a）在水处理中 MnO 涂覆陶瓷膜的性能，和 b）环境中 Mn 氧化物的生物地球化学循环的影响。
