To sell into the second graphite market, a project must purify graphite to a level far above battery-anode specification, at a cost and environmental footprint that clears both commercial and policy tests. There are two routes to that outcome. They are very different, and the choice between them is not primarily about chemistry: it is about the source rock.
The historical answer: caustic bake and hydrofluoric acid
The industry-standard route for high-purity graphite has been chemical for decades. Graphite concentrate is roasted with sodium hydroxide at 500 to 700°C, then leached in hydrofluoric acid at temperatures below 100°C. Additional steps bring the material to purity levels above 99.95%C. The route works. It has produced most of the world's high-purity graphite for anode and non-anode markets alike.
It also carries real costs. It consumes reagent at every stage. Hydrofluoric acid handling requires specialised containment and trained personnel. Waste streams (fluoride-bearing salts, spent caustic, acid wash water) require dedicated treatment. Permitting a new HF-based facility in a NATO-aligned country in 2026 is a materially different challenge than it was in 2006.
The alternative: single-step halogen-free thermal purification
Heat graphite hot enough, in a controlled atmosphere, and most impurities vaporise or migrate to a boundary and leave. Single step, halogen-free. No hydrofluoric acid, no caustic bake, no acid wash. The process Zentek is advancing on Albany material is fluidised bed reactor (FBR) thermal purification. In a fluidised bed, every graphite particle is suspended in the process atmosphere, all surfaces exposed. Heat and mass transfer are exceptional.
Why crystallinity decides
Whether the thermal route works for a given deposit is set by two things: what the source rock brings in, and what the process does to it. Albany's crystals are small, with impurities concentrated at crystal boundaries and surfaces rather than threaded through the lattice — a geometry that responds well to thermal treatment. And at the ~2,800 °C the FBR reaches, graphitization advances further: defect density drops, turbostratic disorder resolves, and crystallinity improves. The rock and the process work together. Both are visible on X-ray diffraction before and after treatment.
Published Albany purity results
The following results have been publicly disclosed by Zentek and are reproduced here without derivation. They are published data points, not forward-looking claims.
Each of these results appears in a Zentek news release with full technical context. Readers wanting the source releases can access the Company's disclosure record on SEDAR+ and EDGAR.