Khine Ei Ei, Kaptay George
Institute of Physical Metallurgy, Metal Forming and Nanotechnology, University of Miskolc, 3515 Miskolc, Hungary.
ELKH-ME Materials Science Research Group, University of Miskolc, 3515 Miskolc, Hungary.
Materials (Basel). 2023 Jan 12;16(2):776. doi: 10.3390/ma16020776.
Several metal oxide nanoparticles (NPs) were already obtained by mixing NaOH solution with chloride solution of the corresponding metal to form metal hydroxide or oxide precipitates and wash-dry-calcine the latter. However, the complete list of metal oxide NPs is missing with which this technology works well. The aim of this study was to fill this knowledge gap and to provide a full list of possible metals for which this technology probably works well. Our methodology was chemical thermodynamics, analyzing solubilities of metal chlorides, metal oxides and metal hydroxides in water and also standard molar Gibbs energy changes accompanying the following: (i) the reaction between metal chlorides and NaOH; (ii) the dissociation reaction of metal hydroxides into metal oxide and water vapor and (iii) the reaction between metal oxides and gaseous carbon dioxide to form metal carbonates. The major result of this paper is that the following metal-oxide NPs can be produced by the above technology from the corresponding metal chlorides: AlO, BeO, CaO, CdO, CoO, CuO, FeO, FeO, InO, LaO, MgO, MnO, NdO, NiO, PrO, SbO, SmO, SnO, YO and ZnO. From the analysis of the literature, the following nine nano-oxides have been already obtained experimentally with this technology: CaO, CdO, CoO, CuO, FeO, NiO, MgO, SnO and ZnO (note: CoO and SnO were obtained under oxidizing conditions during calcination in air). Thus, it is predicted here that the following nano-oxides can be potentially synthesized with this technology in the future: AlO, BeO, InO, LaO, MnO, NdO, PrO, SbO, SmO and YO. The secondary result is that among the above 20 nano-oxides, the following five nano-oxides are able to capture carbon dioxide from air at least down to 42 ppm residual CO-content, i.e., decreasing the current level of 420 ppm of CO in the Earth's atmosphere at least tenfold: CaO, MnO, MgO, CdO, CoO. The tertiary result is that by mixing the AuCl solution with NaOH solution, Au nano-particles will precipitate without forming Au-oxide NPs. The results are significant for the synthesis of metal nano-oxide particles and for capturing carbon dioxide from air.
通过将氢氧化钠溶液与相应金属的氯化物溶液混合，形成金属氢氧化物或氧化物沉淀，然后对后者进行洗涤、干燥和煅烧，已经制备出了几种金属氧化物纳米颗粒（NPs）。然而，该技术能够良好适用的金属氧化物纳米颗粒的完整列表尚付阙如。本研究的目的是填补这一知识空白，并提供一份该技术可能适用的完整金属列表。我们采用的方法是化学热力学，分析金属氯化物、金属氧化物和金属氢氧化物在水中的溶解度，以及伴随以下过程的标准摩尔吉布斯自由能变化：（i）金属氯化物与氢氧化钠之间的反应；（ii）金属氢氧化物分解为金属氧化物和水蒸气的解离反应；以及（iii）金属氧化物与气态二氧化碳反应形成金属碳酸盐。本文的主要结果是，通过上述技术可由相应的金属氯化物制备出以下金属氧化物纳米颗粒：AlO、BeO、CaO、CdO、CoO、CuO、FeO、FeO、InO、LaO、MgO、MnO、NdO、NiO、PrO、SbO、SmO、SnO、YO和ZnO。通过对文献的分析，已经通过该技术实验制备出了以下九种纳米氧化物：CaO、CdO、CoO、CuO、FeO、NiO、MgO、SnO和ZnO（注意：CoO和SnO是在空气中煅烧的氧化条件下获得的）。因此，在此预测，未来通过该技术可能合成以下纳米氧化物：AlO、BeO、InO、LaO、MnO、NdO、PrO、SbO、SmO和YO。次要结果是，在上述20种纳米氧化物中，以下五种纳米氧化物能够从空气中捕获二氧化碳，至少可将残留CO含量降低至42 ppm，即至少将地球大气中目前420 ppm的CO水平降低十倍：CaO、MnO、MgO、CdO、CoO。第三结果是，通过将AuCl溶液与氢氧化钠溶液混合，金纳米颗粒将沉淀，而不会形成金氧化物纳米颗粒。这些结果对于金属纳米氧化物颗粒的合成以及从空气中捕获二氧化碳具有重要意义。
