Poly Ferric Sulfate CAS 35139-28-7

Introduction to Poly Ferric Sulfate

Poly Ferric Sulfate is supplied as a pale-yellow amorphous powder or a reddish-brown liquid, an inorganic pre-polymerised iron(III) coagulant built from polynuclear hydroxy complexes [Fe₂(OH)ₙ(SO₄)₃₋ₙ/₂]ₘ. The pre-formed Fe(III)-hydroxo species carry a higher positive charge per iron atom than simple ferric sulfate. Plants use it to clarify drinking water, treat municipal sewage, and polish dyeing, electroplating, and coal-washing effluents.

Because polymerisation happens in the reactor rather than in the dosing tank, PFS consumes less alkalinity and builds flocs 2–3× denser than simple iron salts, cutting settling time by 30–50% at raw-water temperatures down to 5 °C. One practical caution: the liquid grade is strongly acidic (pH 2–3) and attacks carbon steel; dose from FRP, PP, or PE-lined tanks with EPDM-diaphragm pumps, and never share a line with alkaline streams—premature neutralisation precipitates Fe(OH)₃ and blocks injection quills.

Key Features of Poly Ferric Sulfate

• High charge density, pre-hydrolysed. Polynuclear [Fe₂(OH)₄]⁴⁺-type species neutralise negative colloidal charge on contact; floc formation begins within seconds of dosing, with no waiting for in-situ hydrolysis.
• Wide pH and temperature window. Effective from pH 4 to 11 without alkaline correction, and floc density holds at 5 °C raw water where simple salts slow down.
• Phosphorus and colour removal. Fe(III) precipitates phosphate as insoluble FePO₄, driving total phosphorus below 0.5 mg/L; charge neutralisation collapses dye colloids, cutting colour 60–90% in dyeing effluent.
• Dense, fast-settling flocs. Bridged flocs reach 2–3× the density of alum flocs, cutting clarifier retention time 30–50% and raising sludge cake solids by 2–5 percentage points.
• Low residual iron at correct dose. Jar-test-optimised dosing keeps effluent iron below 0.3 mg/L, avoiding the yellow tint that overdosed simple iron salts leave in treated water.

Poly Ferric Sulfate Chemical & Physical Properties

Applications of Poly Ferric Sulfate

Drinking water clarification: Dosed at 5–30 mg/L as product. Polynuclear Fe(III) species neutralise turbidity colloids and sweep fine particles into dense flocs; residual turbidity below 1 NTU after settling. Jar-test each raw-water source before fixing the dose.

Municipal wastewater treatment: Used at 30–100 mg/L at the primary or secondary clarifier. Charge neutralisation plus FePO₄ precipitation holds total phosphorus below 0.5 mg/L and cuts COD 30–60% ahead of biological stages.

Industrial effluent (dyeing, electroplating, leather): Dosed at 100–500 mg/L. Hydroxide floc sweep co-precipitates heavy metals (Cu²⁺, Ni²⁺, Cr³⁺) while charge neutralisation collapses dye colloids, removing 60–90% of colour in a single stage.

Sludge conditioning and dewatering: Added at 2–8 kg per tonne of dry solids before the belt press. PFS re-flocs fine solids and releases bound water, raising cake dry solids by 2–5 percentage points and cutting filtrate turbidity.

Storage & Safety Precautions for Poly Ferric Sulfate

Storage conditions. Solid: keep bags sealed at 5–35 °C in a dry warehouse; PFS powder is hygroscopic and cakes above 65% RH—caked material still dissolves normally after crushing. Liquid: store only in FRP, PP, or PE-lined tanks; carbon steel corrodes at pH 2–3 within weeks. Keep both forms away from alkalis and cyanide salts—acid contact releases toxic fumes.

Safety and PPE. GHS (solid): Eye Irrit. 2 (H319). Liquid: Skin Corr. 1C (H314). Wear an N95 dust mask, chemical-splash goggles, and acid-resistant gloves during bag emptying or pump maintenance. Spills: solid—sweep up dry; liquid—contain and neutralise with soda ash before washing.

Transport classification. Solid: Non-DG, not regulated under IMDG, IATA, or ADR. Liquid: verify with the carrier—acidic grades are commonly assessed as Class 8, UN 3264, PG III.

Practitioner note: Prepare dosing solutions at 5–10% and use within 48 h; longer standing continues polymerisation and deposits basic salts on tank walls. When pairing with anionic PAM, inject PFS first, rapid-mix 20–30 s, then add PAM at slow mix—simultaneous dosing at one point restabilises the colloid and produces weak, sheared flocs.

Poly Ferric Sulfate FAQ

Q: How do I determine the correct dose of Poly Ferric Sulfate (CAS 35139-28-7) for my plant?

A: Run a jar test: 2 min rapid mix at 150 rpm, 15 min slow mix at 30 rpm, 10 min settle. Test 5–500 mg/L in steps matched to your water. Pick the knee point where residual turbidity or TP stops falling, then confirm residual iron stays below 0.3 mg/L—dosing past the knee wastes chemical and tints the effluent yellow.

Q: My PFS powder caked into a hard block after two months. Is it still usable?

A: Yes. Caking is physical moisture uptake, not chemical degradation. Crush the block and check total iron and basicity on the COA method; values within spec mean full coagulation activity. Dissolve as usual—the cake may need 10–15 min extra agitation. Store future bags on pallets with warehouse RH below 60% and reseal opened bags.

Q: Can I dose PFS and anionic polyacrylamide at the same injection point?

A: No. Simultaneous dosing lets the anionic polymer wrap the iron colloid before charge neutralisation finishes, restabilising particles and producing weak, sheared flocs. Inject PFS first with 20–30 s rapid mix, then add PAM at a second point under slow mixing (30 rpm). Spacing the two by one hydraulic stage typically cuts total chemical cost 10–20%.