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.

Silver-Assisted Hydrogen Evolution from Aluminum Oxidation in Saline Media

“…The images of the original aluminum scrap and resulting materials are shown in Figure 1 . In a previous study [ 102 ], composite powders were successfully produced of D16 alloy (duralumin, similar to the AA2024 grade) and copper powder under the same milling parameters (125 mL milling pot, argon atmosphere, 580 rpm.) with lighter 15 mm balls of stainless steel (balls to powder mass ratio 24:1) after as long as 1 h. In the present study, however, the pioneer sample obtained after 1 h of Al milling together with 10 wt.% Ag under Ar with a set of 15 mm tungsten carbide balls (almost twice as heavy as those of steel) represented large chips cold-welded to each other and covered with black powder.…”

“…And the NaCl solution was subjected to negligible hydrolysis at most. As discussed in a previous study [ 102 ], the reaction between aluminum samples and aluminum chloride solution with hydrogen evolution resulted in the formation of the hydroxychloride compound Al m (OH) n Cl 3m−n (m ≥ 1; 0 < n ≤ 3m). Compared to the typical reaction products, AlOOH and Al(OH) 3 , such complex compounds are characterized by a much higher solubility in water.…”

Effects of Bi–Sn–Pb Alloy and Ball-Milling Duration on the Reactivity of Magnesium–Aluminum Waste-Based Materials for Hydrogen Production

“…However, for aluminum-based powders Bi nanoparticles were reported to demonstrate better performance than bigger, micron-sized particles [ 131 ]. In [ 47 ], an intermediate-sized copper powder occurred to provide better aluminum activation than the finer and coarser ones. Most likely, different sorts of additives might have various ‘optimal cathodic structures’ (sizes of the sites enriched with additive components and their distribution over particles) prone to inducing intensive galvanic corrosion of the base metal.…”

“…Hydrothermal temperatures (over 100 °C) are known to increase the diffusivity of water (liquid or gaseous) through the protective oxide layer or product deposit [ 37 , 38 , 39 ]. The original passive film and generating product layers can be removed chemically by their transformation into soluble compounds from their reactions with salt, acid, or alkali (for Al) aqueous solutions [ 40 , 41 , 42 , 43 , 44 , 45 , 46 , 47 , 48 ]. Introduction of metal additives (e.g., Ni, Co, Fe, Cu, Sn, Bi, Zn) to the basic Mg and Al materials by alloying or high energy ball milling was proved to enhance their corrosion with hydrogen production [ 49 , 50 , 51 , 52 , 53 , 54 , 55 ].…”

Hydrothermal Oxidation of Coarse Aluminum Granules with Hydrogen and Aluminum Hydroxide Production: The Influence of Aluminum Purity

“…Another relevant aspect in the production of hydrogen through aluminum oxidation is the utilization of dopants and alloying additives. Recent research by Buryakovskaya et al [28] highlighted the possibility of using a combination of oxidation mediums, ball milling parameters, and copper additives to ensure a fast reaction of aluminum scrap with a high hydrogen yield.…”