Phosphoric Acid Filtration & Purification Solutions – VSEP® High-Shear Membrane Technology
VSEP (vibratory shear enhanced processing) is used in wet‑process phosphoric acid (WPA) because its vibratory shear prevents membrane fouling in high‑solids, low‑pH, scaling‑prone streams. It filters out colloids, silica gels, fluorosilicates, organics, and metals that overwhelm crossflow membranes allowing VSEP to be used for phosphoric acid filtration.
After beneficiation and reaction with sulfuric acid, the process consists of:
- Coarse gypsum filtration– removes CaSO₄·2H₂O.
- Chemical precipitation step– using reagents to form insoluble metal compounds.
- Clarifier / Settling step– removes the precipitated solids by gravity settling
- Polishing filtration– removes remaining fine solids.
- Optional downstream purification(membranes, solvent extraction, carbon)
- Evaporation – To increase acid from 26% P2O5 to 52%.
What is weak phosphoric acid (WPA)? – It is the acid prior to evaporation that is roughly 26% acid
Why does VSEP work in weak‑process phosphoric acid (WPA)?
VSEP works in WPA because its vibratory shear prevents membrane fouling in high‑solids, low‑pH, scaling‑prone streams.
The 50 Hz torsional oscillation disrupts gel layers, eliminates concentration polarization, and keeps gypsum, silica, organics, and metals from attaching to the membrane surface. The open‑channel design also allows high suspended solids without plugging.
What contaminants limit merchant‑grade phosphoric acid?
Merchant‑grade phosphoric acid is limited primarily by heavy metals, radionuclides, fluorides, silica, organics, and suspended solids. Key restricting impurities include iron, aluminum, magnesium, calcium, and fluoride compounds (e.g., total F), along with silica (SiO₂) and organic carbon. Trace contaminants such as arsenic, cadmium, and rare earths also influence grade specifications. In addition, uranium and thorium can restrict merchant‑grade qualification due to radioactivity. Typical merchant‑grade specifications list Fe, Al, Mg, Ca, F, SiO₂, organic carbon, solids, and trace metals as the primary limiting factors
How is VSEP Used in the Phosphoric‑Acid Process?
- Microfiltration of WPA – VSEP MF removes remaining suspended solids and colloids after coarse filtration, producing a zero‑TSS feed for evaporation.
Best placement: After coarse filtration and precipitation, but before evaporation bypassing clarifier.
- Problem: Clarifiers use chemicals and are prone to upsets.
- Answer: VSEP MF removes essentially 100% TSS without chemicals.
- Benefit: Reduced OPEX, 100% TSS removal.
- Microfiltration of Clarified Wet‑Process Phosphoric Acid (WPA) – VSEP MF removes100% of remaining TSS
Best placement: After Flocculation and Clarifier, but before evaporation.
- Problem: Clarifiers leave 1–4% residual solids that cause evaporator scaling.
- Answer: VSEP MF removes essentially 100% TSS without chemicals.
- Benefit: Reduced evaporator fouling, fewer shutdowns, lower OPEX.
- Nanofiltration of Clarified Wet‑Process Phosphoric Acid (WPA) – VSEP NF removes soluble metals and contaminants.
Best placement: After Flocculation and Clarifier, but before evaporation.
- Problem: Acid still contains metals, sulfates, organics, and silica.
- Answer: VSEP NF removes divalent cations, silicates, radionuclides, and organics.
- Benefit: Replaces more expensive polishing steps, produces better quality product
- Treating Recycle Acid Streams (Mixed H₂SO₄ + H₃PO₄)
Best placement: On recycle acid loops from leach/attack tanks.
In plants with sulfuric‑phosphoric recycle loops, impurities gradually build up:
- Mg, Ca, Fe, Al
- Rare earths
- Radionuclides species (U, Th)
- Organics
The Nolans Project used VSEP specifically to purify recycled mixed acid, stabilizing the impurity load and improving upstream operations. [d3e2i5nuh7…dfront.net]
Advantages
- Reduces impurity accumulation in reactors.
- Allows higher throughput and improved P₂O₅ recovery.
- Maintains stable reaction conditions.
- Acid Recovery from Solvent Extraction Raffinate
Best placement: Treating raffinate after solvent has removed most of the PA.
Why this works
- Raffinate contains: metals (Fe, Al, Mg), fluorides, sulfuric acid, organics, and residual H3PO4.
- Microfiltration remove many contaminants before the acid is recycled.
Thus, VSEP could:
- Purge contaminants and colloids
- Recover lost acid
- Reduce effluent discharge
- Water Recovery and Waste Minimization (Gypsum Stack Water / Pond Water)
Best placement: On gypsum-stack return water or process wastewater.
WPA plants generate large volumes of:
- Fluoride-rich pond water
- Suspended solids
- Acidic wastewater
Thus, VSEP could:
- Reduce pond-water volume
- Recover reusable process water
- Lower freshwater demand
- Reduce fluoride and metals in discharge
Summary — How VSEP Adds Value With Phosphoric Acid Filtration
VSEP can:
- Purify phosphoric acid to merchant‑grade specifications
- Reject metals, radionuclides, and phosphate beneficiation fines
- Remove fluorosilicic acid complexes
- Recover phosphoric acid from difficult mixed streams
- Reduce chemical consumption
- Minimize scaling in evaporators
- Treat gypsum stack process water
- Replace clarifiers, polishing filters, and some chemical cleanup stages
What problems occur with clarifiers – Colloids not completely removed, high chemical usage, large footprint, prone to upsets.
Most common placements in WPA plants:
- After coarse filtration + clarification → microfiltration for colloid removal
- After Clarifier → nanofiltration for metals, organics, and radionuclide removal
- On recycle acid loop → impurity control
- On waste/pond water → RO for water recovery
- Pre‑evaporator → reduce scaling and improve concentration efficiency
VSEP Limitations & Design Considerations for Phosphoric Acid Filtration
- Recovery limited by osmotic pressure and viscosity
- Acid recovery NF depends on speciation
- Temperature typically limited to 60°C
- Prescreening may be required to remove solids >100 µm
- VSEP cannot accept aromatic solvents and oxidizers
Design note: Actual performance is stream‑specific. We pilot test to select membrane type, flux, recovery, and pretreatment options. Phosphoric acid chemistry varies by ore body, beneficiation method, and plant configuration. Final system sizing, membrane selection, and performance projections are only provided after pilot validation
How do We Validate Performance?
- Bench-scale testing
- Onsite pilot testing (7-30 days typical)
- Parameters measured: flux, temperature, pressure, rejection rates, recovery rate
- Deliverables: projection reports, membrane selection, pretreatment design
How does VSEP® Technology Work?
VSEP® uses torsional oscillation to create high shear at the membrane surface—far greater than crossflow systems can achieve.
Technical Highlights
- 50 Hz vibratory motion, ½” peak to peak
- Prevents concentration polarization
- Stops scaling and gel layer formation
- Allows precipitates to form in the bulk fluid instead of on the membrane
- Open channel flow allows for high suspended solids loading
This makes VSEP ideal for:
- Supersaturated gypsum
- Acidic brines
- High‑hardness wastewater
- Metal‑laden process water
- Tailings pond remediation
Pilot Trial Studies –
Over the past 25+ years, New Logic has conducted WPA pilot studies at phosphate plants worldwide, generating consistent data across a wide range of feed chemistries, temperatures, and impurity profiles. All pilot and bench data are obtained using standardized VSEP pilot procedures that measure flux, recovery, temperature effects, and impurity rejection. Results are repeatable and have been validated at multiple operating phosphate facilities.
Pilot Regime 1 – Microfiltration of WPA
Purpose: Replace clarifier
Typical Results: 39 gfd, 90% recovery, 60 psi, 90ºC, 5% TSS, 0.05 µm MF
VSEP MF Filtrate before Clarifier
Pilot Regime 2 – Microfiltration Solvent Extraction Raffinate with Tri-butyl Phosphate
Purpose: Recover lost acid from waste stream
Typical Results: 22 gfd, 66% recovery, 95 psi, 90ºC, 5% TSS, 0.05 µm MF
Pilot Regime 3 – Solvent Stripper Column Underflow
Purpose: Remove solvent and suspended solids from 40% acid
Typical Results: 1200 gfd, 97% recovery, 95 psi, 60ºC, 0.05 µm MF
Pilot Regime 4 – Gypsum Stack Pond Water
Purpose: Purify for Discharge or water recycling
Typical Results: 27 gfd, 70% recovery, 750 psi, 20ºC, 3% Feed solids, 9% Reject solids, 0.05 µm MF
Pilot Regime 5 – Nanofiltration Purification of WPA
Purpose: Remove silicates, and metals
Typical Results: 12 gfd, 77% recovery, 500 psi, 45ºC, 23% WPA, NF
Purified Phosphoric Acid with VSEP NF
Pilot Regime 6 – Nanofiltration Purification of WPA
Purpose: Remove uranium to make a sellable product
Typical Results: 14 gfd, 75% recovery, 500 psi, 35ºC, 18% WPA, NF, Uranium 60 mg/L → 1 mg/L
Case Study – Arafura Rare Earths – Phosphoric Acid Byproduct
Arafura Rare Earths plans to mine apatite ore at its Nolans mine site near Alice Springs. Apatite ore is high in Phosphorus and when the ground ore is leached with sulfuric acid, concentrated phosphoric acid is produced. This project has completed FEED and is planning to start equipment procurement in Q1 2026. In the initial design phase, New Logic conducted one year of demonstration testing using acid tolerant NF membrane to purify the phosphoric acid removing uranium, thorium, colloids and an assortment of metals so that the phosphoric acid could meet merchant grade requirements. The VSEP system design has been finalized and will be included after the FID is completed.
Nolans Mine VSEP Acid Purification System
The Nolans Project pilot was reviewed and approved by Arafura Rare Earths’ process engineering team, confirming VSEP’s ability to remove uranium, thorium, colloids, and metals to meet merchant‑grade specifications.
Get Started
If you are evaluating ways to improve product quality, reduce chemical consumption, recover acid bleed, recycle water, minimize wastewater risk —VSEP can help.
- Request a Performance Projection: info@vsep.com
- Learn More About the Technology: https://www.vsep.com/technology/
- View Gypsum Stack Info: Phosphogypsum Wastewater
- View Phosphoric Acid Clarification: MF VSEP Clarification of WPA
- View Phosphoric Acid Purification Case Study: NF Purification of Phosphoric Acid
About VSEP and New Logic Research
- More than 450 industrial VSEP systems installed globally
- Technology covered by U.S. and international patents
- Used in mining, chemicals, food, wastewater, and chemical processing
- Engineering team with chemical, metallurgical, and mechanical engineering backgrounds
This page was prepared by New Logic Research’s senior process engineers with backgrounds in chemical, metallurgical, and membrane‑process engineering. Our team has over 30 years of direct experience designing, building, and piloting high‑shear membrane systems for the phosphate and chemical‑processing industries
FAQs
Can VSEP replace clarifiers in phosphoric acid production?
Yes. VSEP microfiltration can replace clarifiers because 0.05 μm MF removes essentially 100% of suspended solids without flocculants, producing a stable, zero‑TSS feed for evaporation after phosphoric acid filtration.
Can VSEP help achieve merchant‑grade phosphoric acid?
Yes. VSEP nanofiltration reduces metals, silica, organics, fluorides, and radionuclides, enabling producers to meet merchant‑grade phosphoric acid specifications.
Can VSEP remove uranium and thorium from phosphoric acid?
Yes. VSEP nanofiltration reduces uranium and thorium to low levels, as demonstrated by pilot data showing uranium removal from 60 mg/L to 1 mg/L.
What operating temperatures does VSEP support?
Typical operating design is ≤60°C, though MF has been successfully piloted at higher temperatures depending on the chemistry of the stream.
Is pretreatment required before VSEP?
Pretreatment is minimal—typically prescreening >100 μm—because VSEP tolerates high suspended solids due to its open‑channel, high‑shear design.