A review: Hydrophobicity and surface charge of coals and coal-associated minerals

The hydrophobicity and surface charge of coals and coal-associated minerals play important roles in froth flotation and dewatering in coal preparation plants. These properties are also important for respirable dust control and the application of surfactants. This paper discusses techniques for the measurement of hydrophobicity and surface charge and then uncovers literature values for contact angles and surface charge for coals of varying rank, including some maceral analyses. It also provides a review of literature data for contact angle and surface charge for the major minerals in coal. Readers can use these data for understanding mineral removal or recovery using various preparation techniques, including fine desliming, froth flotation, selective agglomeration, and other processes that are influenced by hydrophobicity and surface charge as we continue to develop the need for ultra clean coals.