Diverse utilization of surfactants in coal-floatation for the sustainable development of clean coal production and environmental safety: a review.

The rapidly increasing modern industrial world demands a huge uninterrupted energy supply, where high-quality coal (HQC) is one of the major sources of the required energy. In this regard, a gigantic amount of solid waste including ash and toxic chemicals, such as heavy metals, nitrate and sulphur, gases including NOx and SOx are emitted during the direct incineration process of low-rank coal. About 10 Gt of CO and about one-fifth of total greenhouse gases in the world are emitted each year due to coal combustion in power plants, making it the single largest cause of climate change.