Battery Precursor Liquid: Why Carbon and Resin Adsorption Stalls on TOC

Ternary precursor production liquid is an awkward stream to treat, and the awkwardness is structural rather than incidental. It contains various saturated sulfate solutions with pH held in the 2-3 range, so any treatment step has to survive prolonged acid exposure. Organic reagents used earlier in production leave both oil content and TOC, measured as total organic carbon, at levels high enough to degrade downstream product performance. The treatment target is therefore narrow: reduce oil and TOC without destroying the ionic composition or contaminating purity.

Why the incumbent route costs more than it looks

Most of the industry currently relies on adsorption — specifically combined activated carbon and resin adsorption. The process works, in the sense that it removes some of the load, but four separate costs accumulate:

• The liquid's own characteristics require coconut shell activated carbon and special-grade resin, which drives up the bill of materials.
• Once saturated, spent activated carbon is hazardous waste, and disposal must be outsourced to specialised agencies, adding a recurring operating cost that scales with throughput rather than with production.
• Operation is cumbersome: saturated carbon must be replaced promptly, usually every two days, which requires dedicated staff on duty around the clock.
• Resin regeneration needs ethanol, imposing very high on-site safety requirements and carrying real risk.

There is also a performance ceiling that rarely appears in the cost comparison. Activated carbon and resin are adsorption media, and their effect on TOC in this matrix is close to nil — they will hold some oil, they will not mineralise dissolved organics. A site can therefore be fully compliant with its own replacement schedule and still fail the TOC specification.

A different mechanism: oxidise rather than hold

The alternative developed by SINOKLE centres on applying CDOF, the ozone flotation integrated unit, together with a self-developed modified heterogeneous ozone catalyst. Instead of transferring contaminants onto a consumable surface, the process oxidises them in place, and the flotation stage removes what the oxidation liberates.

The CDOF unit integrates ozone catalytic oxidation, hydrocyclone separation and flotation oil removal, with the modified heterogeneous catalyst providing the reaction surface. That catalyst has strong adsorption capacity and catalytic oxidation performance for both oils and TOC: under the dual action of adsorption and catalytic oxidation, greases and TOC are rapidly oxidised and decomposed by ozone, while dissolved oil separates out and demulsifies. Oil removal and TOC degradation therefore happen in the same vessel rather than in sequence.

Treatment results are directly measurable. Oil content including dissolved oil can be reduced below 2 ppm, sometimes lower, and TOC removal reaches more than 60%. The gap against the incumbent route is widest on TOC, where traditional activated carbon and resin have almost no removal effect at all — so the comparison is not a matter of degree.

The operating economics, stated honestly

Consumable replacement is what separates the two routes over a multi-year horizon. The CDOF process needs no frequent consumable replacement, which greatly reduces the hazardous waste stream: both saturated activated carbon and non-regenerable resin are hazardous waste, and both must leave site through a licensed handler. Removing that stream removes a cost that grows every time production rises.

Ozone utilisation is high and energy consumption low, so operating cost runs at only one-third to one-half of activated carbon or resin adsorption processes. Beyond consumables, the process adds no chemicals and produces no secondary pollution, and it has no adverse effect on downstream production processes. Residence time in the unit is short and the equipment footprint is compact, which saves site resources in a plant where floor area is usually already allocated to production.

Process integrity: the part that protects product quality

For precursor duty, an oxidation process has to answer a question an adsorption process does not: does it change the liquid chemistry? Three design features address that.

The unit operates in an enclosed, pressurised mode that prevents ozone leakage, meeting safety and environmental requirements without affecting on-site personnel or the surrounding area. The catalyst is acid-resistant and works stably in acidic environments without causing metal ion contamination, which is the specific risk in a sulfate matrix at pH 2-3 — a catalyst that leaches manganese, iron or cobalt would contaminate the very product the treatment is meant to protect. And the ionic composition is left intact, so the treated liquid returns to production rather than becoming a waste stream that has to be reconstituted.

The process also runs fully automatically with remote guidance support and needs no on-site staffing, which matters because the alternative requires round-the-clock attendance for carbon changes. Treatment results are precisely controllable rather than approximate: oil content including dissolved oil can be reduced below 2 ppm and TOC removal stably reaches more than 60%.

Where this route is the wrong choice

Two boundaries are worth stating before selection. If the organic load is dominated by free oil rather than dissolved species, a mechanical separation step ahead of the oxidation stage is cheaper and should be specified first — ozone spent on free oil is wasted. And if the site has no competent ozone generation and off-gas destruction capability, the safety case becomes the binding constraint regardless of treatment performance.

The strategic point is simpler than the process detail. Adsorption postpones a problem and bills you for the postponement; oxidation resolves it in the unit. On a stream where TOC is the specification that matters, only the second approach reaches the number.