Comprehensive utilization of lead–zinc tailings, part 1: Pollution characteristics and resource recovery of sulfur

• The lead–zinc tailings mainly consist of pyrite and are potentially acid forming.
• The lead–zinc tailings induce acid mine drainage and heavy metals pollution.
• The sulfur in the lead–zinc tailings can be removed during roasting.
• The SO2 in the flue satisfies the requirement of producing sulfuric acid.
• The cinder is non-acid forming and can be processed for further recovery.

According to the pollution characteristics and current situation of sulfur resources in lead–zinc tailings, the mineral composition, risk assessment and oxidation reaction characteristics of lead–zinc tailings were investigated. The results showed that the main mineral in the lead–zinc tailings was pyrite and the contents of Fe and S were 23.4% and 24.9%, respectively. The heavy metals Pb, Zn, Cu, Cr and Cd were mainly present in the residual fraction, but the Pb, Zn and Cd in the non-residual fraction were 28.21%, 37.49% and 42.92%, respectively. Additionally, the lead–zinc tailings potentially form acid, which poses a potential heavy metals pollution risk to the environment. The reaction characteristics of tailings, including the roasting temperature, filling rate and air–solid ratio, were investigated in a rotary furnace under different conditions. The results showed that the desulfurization rate was 99.0% and the concentration of SO2 was 5.58–5.07% when the roasting temperature was 400 °C, the filling rate was 4.29%, the air–solid ratio was 1.7 L/g and the residence time was 20 min. After roasting in the rotary furnace, the cinder became non-acid forming and the SO2 in the flue gas can be recovered by producing sulfuric acid. Meanwhile, the roasting procedure concentrates metals such as Fe, Ag and Ga, which assists further recovering the resources in the cinder. All of these results provide a new approach for eliminating the pollution of acid mine drainage and recovering the sulfur from lead–zinc tailings.

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