Aluminum Scrap to Hydrogen: Complex Effects of Oxidation Medium, Ball Milling Parameters, and Copper Additive Dispersity

Abstract

An effective combination of oxidation medium, ball milling parameters, and copper additive disperstiy ensuring fast aluminum scrap reaction with high hydrogen yield, was suggested. Different milling parameters (5, 10, and 15 mm steel balls; 1 and 2 h; unidirectional and bidirectional rotation modes) were tested for Al-10 wt.% Cu (50–70 μm) composition. The samples milled with 5 (2 h) and 10 mm (1 and 2 h) balls contained undesirable intermetallic phases Al2Cu and Cu9Al4, while those activated with 15 mm balls (1 h) provided the second-finest powder and best preservation of the original Cu and Al phases. Among the tested (at 60 °C) 2 M solutions NaCl, LiCl, KCl, MgCl2, ZnCl2, BaCl2, CaCl2, NiCl2, CoCl2, FeCl2, and AlCl3, the first six appeared to be almost useless (below 4% hydrogen yield), the following four provided better results, and the ultimate 91.5% corresponded to AlCl3. Samples with Cu dispersity of 50–100 nm, 1–19, 50–70, and 150–250 μm, and with no additive, were milled under the optimal parameters and tested in AlCl3. Their total yields were similar (~90–94%), while reaction rates differed. The highest rate was obtained for the sample modified with 50–70 μm powder.