Department of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Material Science, University "Politehnica" of Bucharest, Bucharest 060042, Romania.
Power Engineering Faculty Hydraulics, Hydraulic Machines, and Environmental Engineering Department, University "Politehnica" of Bucharest, Bucharest 060042, Romania.
Ultrason Sonochem. 2021 Apr;72:105404. doi: 10.1016/j.ultsonch.2020.105404. Epub 2020 Dec 7.
Platinum group metals, such as Pd and Pt, found in three-way catalyst converters were recycled in a two-step method: hydrodynamic cavitation followed by sonoelectrochemical dissolution. High shear forces were obtained by using a convergent nozzle with a throat diameter of 0.2 mm, feeded by a plunger pump at a pressure of 60 MPa. Cavitating submerged jets acted locally on the water dispersed waste catalyst. As-obtained samples were analyzed by scanning electron microscopy and transmission electron microscopy. Electron microscopy on the initial sample showed that round shaped Pd and Pt nanoparticles were randomly distributed on the AlO matrix. Cavitated samples show two zones in which Pt and Pd were partially and completely separated from the cordierite. The hydrodynamic cavitation separates the Pd and Pt from the cordierite leading to an apparent increase in Pd and Pt concentrations of 9% and 34% respectively. Conventional electrochemistry showed a dissolution of 20% in 1 h. To further accelerate the dissolution, a sonotrode operating at 20 kHz and 75 W was placed inside an electrochemical cell in order to increase the mass transport and obtain high dissolution rates. Indeed, the results showed that 40% of the available Pd and Pt can be recycled in just 1 h. In the absence of hydrodynamic cavitation and using conventional electrochemistry less than 10% of the available Pt and Pd is recovered in 1 h. The cost analysis showed that Pd and Pt can be recovered at less than 10 EUR per g which is 5 times smaller than their current market price.
在两步法中回收三效催化剂中所含的铂族金属（如 Pd 和 Pt）：空化水动力学 followed by 超声电化学溶解。通过使用收敛喷嘴以 0.2mm 的喉径和由柱塞泵在 60MPa 的压力下进料来获得高剪切力。空化淹没射流对分散在水中的废催化剂局部作用。所得样品通过扫描电子显微镜和透射电子显微镜进行分析。初始样品的电子显微镜显示，圆形 Pd 和 Pt 纳米颗粒随机分布在 AlO 基体上。空化样品显示出两个区域，其中 Pt 和 Pd 部分和完全从堇青石中分离出来。空化水动力学将 Pd 和 Pt 从堇青石中分离出来，导致 Pd 和 Pt 的浓度分别明显增加 9%和 34%。传统电化学显示在 1 小时内溶解 20%。为了进一步加速溶解，将工作在 20kHz 和 75W 的声电极放置在电化学电池中，以增加质量传递并获得高溶解速率。实际上，结果表明，仅在 1 小时内即可回收 40%的可用 Pd 和 Pt。在没有空化水动力学的情况下并使用传统电化学，在 1 小时内仅回收不到 10%的可用 Pt 和 Pd。成本分析表明，Pd 和 Pt 的回收率可以低于每克 10 欧元，这比它们目前的市场价格低 5 倍。
