Comparison of hydrocyclone and flotation ability in reduction of kaolin ore calcite

Abstract Kaolin, known as china clay, is a fine white clay with industrial usage. Kaolinite is the most common mineral in kaolin ores and iron, titanoferrous, and carbonate minerals are the major impurities. Calcium oxide (CaO) in carbonate form (CaCO3) is the recent critical issue for Zonuz kaolin plant located in the North West of Iran. Therefore, a number of practical and inexpensive processing methods were tried on a raw crushed Zonuz kaolin sample. The sample contained 3.56% CaO. First, sizing based methods like sieve screening and hydrocyclone were tested, because of the smaller size of kaolinite particles compared with most other impurities. However, CaO was removed poorly, much Al2O3 was wasted, and Fe2O3 was enriched in the product. Then, flotation tests were performed on the raw ore. The results were remarkable, because of the highest calcite removal with the lowest Al2O3 loss and Fe2O3 enrichment. Although CaO content was reduced to 1.33% or even less in finer sizes using flotation, these finer sizes led to more Al2O3 loss. Acidic leaching was not evaluated, due to intense reaction between acids and CaCO3, and damaging corrosive acidic conditions.