Potassium Alum Supplier South Africa

What Is Potassium Alum?

Potassium alum (potassium aluminium sulfate, KAl(SO₄)₂·12H₂O) is the naturally occurring double sulfate of potassium and aluminium — historically the first “alum” used in water purification, textile dyeing, and medicine. It is a colourless, crystalline solid that dissolves readily in water to give an acidic solution (pH ~ 4–4.5) with hydrolysis of Al³⁺ to aluminium hydroxide species, in exactly the same manner as commercial aluminum sulfate (filter alum). Potassium alum is chemically identical in coagulation behaviour to aluminum sulfate in the context of water treatment — both provide Al³⁺ as the active coagulating species. The potassium ion (K⁺) is an essential plant nutrient and has no negative effect in water treatment applications.

Water Treatment Coagulation

In water treatment, potassium alum functions identically to aluminum sulfate — Al³⁺ hydrolyses to cationic aluminium hydroxide species that coagulate colloidal turbidity, clay particles, and NOM in raw water. Potassium alum is used in smaller-scale water treatment plants, portable water treatment, and batch water treatment operations. Historically, alum crystal was the household/community water treatment mineral — a piece of alum crystal stirred into a vessel of turbid water would coagulate and settle the particles within minutes. In modern water treatment, liquid or dry aluminum sulfate is preferred at large scale due to lower cost, but potassium alum remains specified in some food-grade and pharmaceutical water applications.

Food, Cosmetic, and Industrial Applications

Potassium alum has a long history in food applications: as a food-grade acidulant and firming agent (E522), a leavening agent constituent in baking powder (reacts with sodium bicarbonate to produce CO₂), and as a pickling additive to keep vegetables crisp. In cosmetics and personal care, potassium alum crystal is used as a natural deodorant/astringent (the aluminium ions contract proteins on the skin surface, reducing perspiration) and as an aftershave astringent. In textile dyeing, alum is used as a mordant to fix natural dyes to textile fibres. In leather tanning (alum tawing), it is an alternative to chrome tanning. Terracore Chemicals supplies food-grade and technical-grade potassium alum in 25 kg bags across Southern Africa.