Enhanced lignite flotation using di(2-ethylhexyl) phosphoric acid (DEHPA) as a novel organic collector and optimization of some flotation parameters via response surface methodology

This study investigates the flotation performance of di(2-ethylhexyl) phosphoric acid (DEHPA) as an organic collector and optimizes key operating parameters using response surface methodology (RSM) for the flotation of Çorum/İskilip lignite from Türkiye. Preliminary flotation experiments were conducted using conventional collectors (kerosene, diesel oil, and fuel oil) to investigate flotation performance. The highest flotation performance was obtained using a binary collector system consisting of 20 kg/t DEHPA combined with 32 kg/t diesel oil (total dosage: 52 kg/t). Following collector optimization, the effects of sodium silicate dosage, pine oil dosage, and flotation time on flotation performance were investigated. Ash rejection and combustible recovery were selected as response variables. A Box-Behnken design (BBD) integrated with RSM was applied to evaluate the individual and interactive effects of these parameters. Model adequacy and statistical significance were assessed using analysis of variance (ANOVA). Optimization results indicated that optimum conditions were a pine oil dosage of 150 g/t and a flotation time of 240 s, while optimum sodium silicate dosage converged to 0 g/t, indicating that a depressant was unnecessary. Under these conditions, maximum ash rejection and combustible recovery were 55.19% and 55.62%, respectively. Overall, DEHPA improved flotation efficiency and ANOVA confirmed the reliability of model.