Overview
Cadmium in phosphate rock is not an impurity a producer may ignore. The EU caps cadmium in mineral fertiliser at 60 mg/kg P₂O₅, with a stated path to 40 and then 20. A plant has exactly one answer today: bury the cadmium together with the whole phosphogypsum stream in a stack, permanently. ARBOK-Cadmium is the same gravity column of dense brine used for phosphogypsum, applied to take the cadmium out before the stack rather than after — inside the existing wet process, without stopping the line.
Applications
Bringing phosphoric acid and fertiliser into compliance with cadmium limits; removing cadmium ahead of the stack rather than managing it afterwards; retrofit into a running wet-process line. Users: phosphoric acid and phosphate fertiliser producers, legacy stack operators.
Operating Principle
Milled phosphogypsum slurry is fed into a vertical column of saturated brine. Particles stratify by density: cadmium and the other heavy metals settle to the bottom of the column, radionuclides and cadmium are immobilised into a compact saline mass, and cleaned gypsum is drawn from the transition zone. The process is continuous and gravitational — no reagents, no vacuum.
Key Parameters
| Parameter | Value |
|—|—|
| Separation driver | density, in saturated brine |
| Process | continuous, gravitational |
| Reagents | none |
| Vacuum | not used |
| Products | cleaned marketable gypsum + compact heavy-metal concentrate |
Advantages
Meets a regulatory limit that tightens on a published schedule, using a physical stage rather than a chemical one. Converts a permanent storage obligation — area, monitoring, compliance — into a one-time treatment that also yields saleable gypsum.
Market Potential
The market here is set by regulation rather than by metal demand: every operating phosphoric acid plant is obliged to bring cadmium down in its product. Regions holding the bulk of world phosphate reserves with high cadmium content are the priority sites.
Related Technologies
ARBOK-PHOSPHOGYPSUM · ARBOK-Phosphate · ARBOK-Finishing