A residue reutilization strategy on fluorine-containing water purification

Abstract

The comprehensive utilization of coal gangue is a severe problem that many countries and regions confront. Extracting strategic metals from coal gangue and adequately treating the residue constitute a possible complete utilization route of coal gangue. This paper studied the structural characteristics and surface properties of ammonium salt roasting-water leaching residue by XRD, BET, XPS, FTIR, and XRF. The adsorption behaviour of leaching residue for fluorine ions was studied using batch adsorption tests, isothermal models, and fluoride removal tests of mine water. The results show that the leaching residue had a fast adsorption speed (1 min), a wide applicable pH range (4–11), and a wide applicable temperature range (25 °C–50 °C). The removal rate of fluorine in high-concentration (50 mg/L) and low-concentration (5 mg/L) fluorine-containing water reached more than 50%. The primary adsorption mechanism was ion exchange between fluorine ions and Al–OH in the leaching residue. The actual mine water test showed that the leaching residue did not introduce organic pollutants and accelerated the settlement of mine water. This study puts forward a new and environmentally friendly avenue for residue reutilization, which is of positive significance to promoting the comprehensive utilization of coal gangue.