By Senjie Filter Press Engineering Team · Last updated: 2026-09-14
Quick answer: A filter press for lithium battery slurry and black mass recycling uses 800 to 1500 mm PP or glass-reinforced PP plates, membrane squeeze at 1.5 to 2.0 MPa and an enclosed design. It dewaters leach residue and lithium carbonate to 15 to 25% moisture in 40 to 90 minute cycles, with acid-resistant plates rated to 90 or 120 °C.
A black mass recycling line may leach at pH 0.5 to 1.5 and 60 to 90 °C, then precipitate lithium carbonate at pH 11 to 12. This guide covers the filtration duties, materials, cake moisture targets and sizing for membrane filter presses in lithium battery service.
Where is a filter press used in lithium battery slurry and black mass recycling?
A filter press is used at four points: dewatering black mass leach residue (graphite and impurities), washing precipitated impurity and cathode metal salts, dewatering lithium carbonate crystals, and recovering solids from anode slurry and electrode coating wash water.
Black mass is the shredded, sieved fraction of spent cells. It contains 30 to 50% graphite, 20 to 40% nickel-cobalt-manganese oxides, 3 to 7% lithium and residual electrolyte. After sulphuric acid leaching, the metals dissolve and the graphite plus undissolved material remains as a slurry at 8 to 20% solids. This residue is filtered and washed to recover the pregnant leach solution (PLS) held in the cake.
Downstream, iron, aluminium and copper removal produces gelatinous hydroxide precipitates that filter slowly, while nickel and cobalt sulphate crystals filter easily. Lithium carbonate precipitates as dense crystals at 90 °C and needs hot filtration and washing to remove sodium sulphate. Water-based anode slurry and coating-line wash water carry graphite and binder solids that a small chamber press recovers before treatment.
What cake moisture can a filter press achieve on black mass leach residue?
A membrane filter press achieves 15 to 25% cake moisture on black mass leach residue, compared with 30 to 40% on a standard chamber press, because the graphite-rich residue compresses well under 1.5 to 2.0 MPa squeeze and responds to air blow-through.
Every percentage point of moisture in the residue is PLS containing dissolved nickel, cobalt and lithium. The table gives typical values by duty, assuming feed at 0.6 to 1.0 MPa, squeeze at 1.5 to 2.0 MPa where noted and a 0.4 to 0.6 MPa air blow.
| Duty | Feed solids | Press type | Cake moisture | Cycle time | Cake wash |
|---|---|---|---|---|---|
| Black mass leach residue | 8–20% | Membrane | 15–25% | 45–90 min | 2–3 displacement washes |
| Fe/Al/Cu hydroxide impurity cake | 3–8% | Membrane | 45–60% | 60–120 min | 1–2 washes |
| Lithium carbonate crystals | 15–30% | Membrane or chamber | 10–18% | 30–60 min | Hot water, 1–2 volumes |
| Nickel/cobalt sulphate crystals | 20–35% | Chamber | 8–15% | 30–45 min | Saturated solution wash |
| Anode slurry / coating wash water solids | 2–6% | Chamber | 35–50% | 60–120 min | None |
Hydroxide impurity cakes are the exception. They are gelatinous and hold water even under squeeze; 0.5 to 2 kg/t of flocculant or seeded precipitation improves both filtration rate and final moisture. For benchmarks in other sectors, see the table of typical filter cake moisture content by industry.
Which filter plate and frame materials resist acid leach and hot lithium liquor?
Polypropylene (PP) plates rated to 90 °C handle leach and precipitation liquors up to 20% sulphuric acid, and glass-reinforced PP plates rated to 120 °C are specified where hot lithium carbonate filtration or steam cleaning exceeds 90 °C.
PP chamber and membrane filter plates are inert to acid leach solution, chloride and hot alkaline lithium liquor within their temperature rating. The weak points are the metal parts.
- Plates: PP below 90 °C; glass-reinforced PP for 90 to 120 °C. Specify a PP membrane for sulphuric acid above 10%.
- Frame and beams: carbon steel with rubber lining or 2 to 3 mm PP cladding for acid service; SS316 side beams and head plates where the frame is acid-washed or exposed to chloride mist.
- Feed manifold and piping: PP, PVDF or PTFE-lined steel. Avoid bare SS304 in acid feed.
- Plate hangers and shifting chain: SS316 or PP-coated steel.
- Filter cloth: PP monofilament or multifilament for acid duties; PET only for neutral liquor. See the filter press cloth range.
Lithium carbonate is filtered at 85 to 95 °C, where a PP plate rated to 90 °C creeps under 20 to 25 MPa hydraulic closing pressure; glass-reinforced PP plates hold their shape. Perry’s Chemical Engineers’ Handbook, 9th ed. gives filtration theory and material compatibility tables for detailed design.
Why does black mass and lithium filtration need an enclosed filter press?
An enclosed filter press is needed because black mass slurry releases hydrogen and residual electrolyte vapour, acid leach liquor forms aerosol during air blow, and lithium and cobalt compounds are classified dusts that must not escape during cake discharge.
An enclosed design adds three elements. A drip tray with a sealed drain returns filtrate and wash liquor to the process. Side and top panels enclose the plate pack, with an extraction port to a scrubber at 2 to 4 air changes per minute. A bomb-bay door under the plate pack opens only during discharge so cake drops into a hopper under negative pressure.
A PLC-controlled press with automatic plate shifting and cloth washing at 8 to 10 MPa discharges cake without anyone entering the enclosure. Filtrate containing free acid should be piped in PP or PVDF, never through an open launder.
What size filter press does a battery recycling plant need?
A 5000 to 10000 t/year black mass hydrometallurgical plant typically needs one to two membrane filter presses with 1000 to 1250 mm plates and 100 to 250 m² of filter area on the leach residue duty, plus smaller 630 to 800 mm presses for impurity and lithium carbonate cakes.
Black mass leach residue has a wet cake density of about 1.3 to 1.5 t/m³. A 1000 mm membrane plate at 32 mm chamber depth holds roughly 25 to 28 litres of cake; a 1250 mm plate holds 40 to 45 litres; a 1500 mm plate holds 65 to 75 litres.
| Black mass processed | Leach residue (dry) | Plate size | Plates per press | Filter area | Cycles per day |
|---|---|---|---|---|---|
| 1,000–2,000 t/year | 1.5–3 t/day | 800 mm | 30–50 | 35–60 m² | 4–6 |
| 3,000–5,000 t/year | 4–7 t/day | 1000 mm | 40–70 | 70–130 m² | 5–8 |
| 5,000–10,000 t/year | 7–14 t/day | 1250 mm | 50–90 | 140–250 m² | 6–10 |
| 10,000–20,000 t/year | 14–28 t/day | 1500 mm | 60–110 | 250–450 m² | 8–12 |
The method for converting daily solids to plate count is in the guide on how to calculate filter press capacity. For feed, air-operated diaphragm pumps in PP or PVDF suit acid residue up to 0.7 MPa; a PVDF-lined progressing cavity pump is used for 1.0 MPa feed.
How long is a filter press cycle in lithium carbonate and cathode salt filtration?
A lithium carbonate filtration cycle on a membrane press takes 30 to 60 minutes: 10 to 20 minutes of feed, 5 to 10 minutes of hot displacement wash, 5 to 10 minutes of squeeze and air blow, and 5 to 10 minutes of discharge.
The wash step controls product purity. Sodium sulphate mother liquor is displaced with 1 to 2 cake volumes of deionised water at 80 to 90 °C; cold wash water redissolves lithium carbonate and lowers yield. Membrane squeeze before washing compacts the cake so wash water moves as a plug instead of channelling.
Black mass leach residue cycles run 45 to 90 minutes because two or three washes are needed to recover PLS from the porous graphite cake. Impurity hydroxide cakes run 60 to 120 minutes and set the bottleneck in many plants.
Why buy a lithium battery slurry filter press from Senjie?
Senjie is a China-based manufacturer of chamber, membrane and fully automatic filter presses, filter plates, filter cloth and feed pumps. Changzhou Senjie Environmental Equipment Co., Ltd. has built filter presses since 2014 and exports to more than 40 countries across Southeast Asia, India, Africa, the Middle East and Latin America.
For battery recycling duties, Senjie supplies membrane presses with 800 to 1500 mm PP or glass-reinforced PP plates, PP-clad or SS316 frame components, enclosed cabinets with extraction ports, drip trays, PVDF feed manifolds and PLC-controlled plate shifting and cloth washing, with a factory test run before shipment.
Send your slurry data (solids %, pH, temperature, particle size and daily tonnage) to the Senjie engineering team for a sizing proposal and quotation.
Frequently Asked Questions
Can a filter press handle sulphuric acid leach slurry from black mass?
Yes. Polypropylene plates and PP cloth are inert to sulphuric acid at the 5 to 20% concentrations used in black mass leaching, up to 90 °C. The frame, feed manifold and hangers must be PP-clad, rubber-lined, PVDF-lined or SS316 to avoid corrosion.
What cake moisture is possible on lithium carbonate with a filter press?
A membrane filter press reaches 10 to 18% cake moisture on lithium carbonate crystals after squeeze at 1.5 to 2.0 MPa and air blow-through. A chamber press without squeeze gives 18 to 25%.
Do I need a membrane filter press or is a chamber press enough?
Use a membrane press for black mass leach residue, hydroxide impurity cakes and lithium carbonate, where 10 to 15 percentage points lower moisture recovers solution or product. A chamber press is sufficient for nickel and cobalt sulphate crystals and anode slurry solids.
What plate size is typical for a battery recycling filter press?
Most battery recycling plants use 800 to 1500 mm plates. Plants under 2000 t/year of black mass run 800 mm presses; 5000 to 10000 t/year plants run 1000 to 1250 mm; larger lines use 1500 mm.
Why should the filter press be enclosed for black mass?
Black mass slurry can release hydrogen and electrolyte vapour, acid liquor forms aerosol during air blow, and cobalt and lithium compounds are hazardous dusts. An enclosed press with a drip tray, extraction port and bomb-bay discharge door contains all three.