Ferric Sulphate Coagulant Obtained by Leaching from Coal Tailings

A ferric sulphate solution was produced from pyritic coal tailings for potential use as a coagulant for water and wastewater treatment. Laboratory-scale leaching experiments were carried out with four tailings with different concentrations of pyrite. The tailings were characterized for: total sulphur, pyritic sulphur, sulphate sulphur, organic sulphur, and elemental analysis of carbon, hydrogen, and nitrogen. X-ray diffraction analyses were also conducted to assess the mineral composition of the samples. The leaching was carried out using a laboratory column constructed as a packed bed reactor with a closed-circuit sprinkling system. After 4 weeks of leaching, the liquor was filtered and evaporated to reach an iron concentration of about 12% w/w, which is typical of most commercial FS coagulants in Brazil.