Ferric Sulfate Supplier South Africa

What Is Ferric Sulfate?

Ferric sulfate (iron(III) sulfate, Fe₂(SO₄)₃) is an inorganic iron(III) salt — a yellow-brown powder or granule that dissolves readily in water to give strongly acidic ferric iron solutions. In water, Fe³⁺ hydrolyses to produce iron hydroxide species [Fe(OH)²⁺, Fe(OH)₂⁺, Fe₂(OH)₂⁴⁺, Fe(OH)₃] that carry strong positive charge. These iron hydroxide cations are highly effective coagulants — they neutralise the negative charge on colloidal particles, turbidity, and NOM, causing rapid destabilisation and aggregation into dense, rapidly settling iron hydroxide floc. Ferric sulfate is used as an alternative or supplement to aluminum sulfate (alum) where wider pH flexibility or stronger coagulation is required.

Advantages Over Alum and Key Applications

Ferric sulfate offers two key advantages over aluminum sulfate: wider effective pH range and denser, heavier floc. Alum is effective only between pH 5.5–8; ferric sulfate coagulates effectively between pH 4.5–12, making it suitable for treating alkaline wastewater and for phosphate precipitation at the higher pH values required for effluent polishing. Iron hydroxide floc (Fe(OH)₃ sweepfloc) is denser and settles faster than aluminium hydroxide floc, improving clarifier throughput. Ferric sulfate also strongly oxidises and precipitates hydrogen sulfide (H₂S) in wastewater: 2Fe³⁺ + H₂S → 2Fe²⁺ + S⁰ + 2H⁺, reducing odour and sulphide toxicity. In phosphate removal, ferric sulfate achieves very low residual phosphorus at the higher Fe:P molar ratios used at elevated pH.

Water and Wastewater Treatment Use

In drinking water treatment, ferric sulfate is used for high-turbidity raw water, colour removal (NOM, tannins), and treatment of humic-rich surface waters. In municipal and industrial wastewater treatment, it is used for phosphate removal (effluent TP <0.5 mg/L) and for sludge dewatering improvement (iron flocculation of activated sludge). It is also used in acid mine drainage (AMD) treatment to precipitate metals: at pH 6–9, Fe(OH)₃ co-precipitates heavy metals. Terracore Chemicals supplies ferric sulfate in powder/granule form (25 kg bags, 1 MT bags) for water treatment applications across Southern Africa.