Removal and kinetic analysis of arsenic and cadmium during coal flotation: a study focused on their occurrence modes

To investigate the occurrence modes of arsenic (As) and cadmium (Cd) in coal and their removal rules during flotation. Representative coal samples from the Shendong (C1) and Zhunneng (C2) coal preparation plants were selected. The occurrence modes of As and Cd in different density fractions were determined through sequential chemical extraction experiments and float – sink experiments. The removal rules of As and Cd were explored through flotation experiments and kinetic analysis. The results showed that As and Cd in C1 were mainly bound to organic matter and aluminosilicates, while those in C2 were mainly bound to sulfides and aluminosilicates. Both elements were enriched with the increase of coal samples density and ash content, showing an obvious inorganic affinity. The removal efficiency of As and Cd was significantly affected by their occurrence modes. As the collector dosage increased, the clean coal yield increased but the removal efficiency decreased, indicating that excessive reagent promoted the entrainment of organic matter or mineral particles. The flotation behaviors of As and Cd in two coals conformed to the first-order kinetic model (R2 > 0.99). Cd exhibited a slower flotation rate than As.