Aggregating fine hydrophilic materials in froth flotation to improve separation efficiency through a homo-aggregation flotation process

As a versatile separation technology, froth flotation has gained extensive applications in both primary resource recovery and secondary resource recycling. It exploits differences in the water-wettability of solid surfaces to separate value components from wastes. Hydrophobic (water-repelling) particles attach to gas bubbles, float away from hydrophilic (water-loving) particles and become froth products. However, flotation separation deteriorates with low efficiency and low selectivity when treating fine (< circa 20 μm) and ultrafine (< circa 5 μm) particles. Particularly, fine hydrophilic particles affect value mineral recovery and froth product grade by attaching indiscriminately to value minerals, increasing pulp viscosity, and entering froth products by entrainment. Many mitigation measures have been proposed in the literature to target the fine hydrophilic particles in the flotation process, mainly from physical/mechanical perspective. Notably, recent investigations suggest that selectively aggregating fine hydrophilic particles could reduce their entrainment to froth products and increase froth product grade. In this review, we first analyze the adverse effects of fine hydrophilic particles on froth flotation and summarize current mitigation methods. Following the review, a homo-aggregation flotation (HAF) concept different from conventional approaches is proposed to improve the separation efficiency of fine particles in froth flotation. We present case studies highlighting the necessity of aggregating fine hydrophilic materials to improve separation efficiency in froth flotation, noting that hydrophobic aggregation is a natural process in water.