1. Core Differentiation Index: Iron Content
Low-iron Aluminum Sulfate: Normally with iron (Fe) content ranging from 0.3% to 0.7%, it is conventional refined grade product.
Iron-free Aluminum Sulfate: Strictly controlled iron content ≤0.005%, classified as high-purity grade. The iron impurity content is their fundamental distinction.
2. Appearance & Color Difference
Low-iron Aluminum Sulfate: Pale yellowish-green crystalline particles, tinted by trace ferric ions.
Iron-free Aluminum Sulfate: Pure white translucent granules or powder with no discoloration, distinguishable visually.
3. Application Classification
(1) Low-iron Aluminum Sulfate (Cost-effective General Grade)
Widely applied in industrial wastewater treatment, regular paper sizing, mineral flocculation and concrete additives. It works for flocculating and settling suspended solids in water treatment with favorable cost performance and the largest market consumption.
(2) Iron-free Aluminum Sulfate (High-purity Fine Grade)
① Sizing for high-grade paper such as white cardboard and specialty paper to prevent paper yellowing and browning; ② Drinking water purification, fine daily chemical additives and printing & dyeing mordants; ③ Titanium dioxide production and premium leather tanning. Excessive iron content will trigger product discoloration and scrapped finished goods.
4. Drawback Comparison in Application
Excessive iron in low-iron grade will cause uneven yellow discoloration on finished products when used for white paper, textile dyeing and drinking water treatment. Iron-free aluminum sulfate requires extra iron removal processes in production, leading to higher manufacturing cost and unit price.
5. Product Selection Guidance
For wastewater disposal, regular papermaking and industrial raw water treatment: choose low-iron aluminum sulfate to cut procurement cost.
For specialty white paper, potable water treatment, textile printing & dyeing and fine chemical industries: select iron-free aluminum sulfate to guarantee whiteness and end-product quality.