The previous study indicates that both reagent usage and the variation of water conductivity affect froth stability and therefore coal flotation behavior. In this study, Central Composite Rotatable Design (CCRD) was conducted to investigate the interaction of saline water with collector (diesel) and frother (MIBC) in controlling froth stability which was indicated by air recovery. The results show that a significant interaction (see footnote 1) existed between flotation reagents and water conductivity, which affected froth stability, combustible matter recovery and the mineral matter content of flotation concentrate. Frother and salt ions had a joint action in producing a more stable froth. On the other hand, collector and salt ions had a joint action in reducing the combustible matter content of flotation concentrate and the combustible matter recovery. A methodology was developed to avoid overly stable froth and maximize coal flotation performance by adjusting reagent additions based on water conductivity. (C )2016 Elsevier B.V. All rights reserved.