Copper sulfate, sodium hypophosphite, nickel sulfate, lactic acid, malic acid, etc., are frequently used in electroless nickel and copper plating processes to act as anti-corrosion agents for metal surfaces. Copper sulfate is generally classified into several different grades: electronic grade, electroplating grade, industrial grade, feed grade, and agricultural grade. These grades vary significantly in content, type, and price. Below, we will briefly discuss the traditional preparation principle and method.

I. Preparation Principle Copper is oxidized by air at high temperatures to form copper oxide, which then reacts with sulfuric acid to form copper sulfate. The reaction formulas are as follows:

2Cu + O₂= 2CuO

CuO + H₂SO₄= CuSO₄+ H₂O

It is mainly used in the production of copper salts, mordants, pharmaceuticals, pigments, rayon, leather, electric locks, pesticides, fungicides, and wood protection. However, many commercially available CuSO₄ products no longer use the above method. Especially for agricultural CuSO₄, most are now produced using other low-cost methods derived from recycled electronic waste.

II. Preparation Process

1. Oxidation:

Place the raw material in an oxidation furnace for roasting (or stir-fry in a large iron pot). When the temperature reaches 150°C, stir it every 20 minutes with an iron spatula to accelerate oxidation. When the temperature reaches 450°C, it must be controlled and not exceeded to avoid affecting the oxidation of the product. The oxidation time is about 6 hours, during which copper ash is converted into copper oxide.

2. Acidification:

Place 60 kg of copper oxide into a reaction vessel, then add 125 kg of boiling water and stir thoroughly with a wooden stick. Then add approximately 45 kg of H2SO4 and allow it to react on its own (steam heating may be necessary) until the solution reaches the desired concentration.

3. Crystallization:

Transfer the reacted solution to a crystallization vessel and cool for one to two days. Beautiful blue copper sulfate crystals will precipitate in the vessel.

4. Dehydration:

Remove the copper sulfate crystals from the vessel, wash them with mother liquor, and drain them in bamboo baskets. Then spread them out in a cool place to dry. After drying, they can be packaged. The remaining mother liquor can still be used in the acidification reaction, as it contains not only copper sulfate but also a large amount of dilute H₂SO₄.

The above-described preparation process for copper sulfate is a very primitive and traditional method. Modern large-scale industrial production has long since modernized equipment and reaction processes, resulting in significantly improved production efficiency. The content of copper sulfate, heavy metals, and appearance have all undergone substantial changes.