Recovery of nitrates from leaching solutions using seawater

The objective of this work is to investigate the use of seawater to recover potassium and nitrate from the waste tails of SQM operations. The use of seawater as an alternative to fresh water is an attractive option for the resource-rich northern Chilean mines, especially for those operating in the Salar de Atacama Desert where fresh water is scarce.In this study, the performance of four leaching agents was evaluated for recovering potassium and nitrate from discarded salts: 1) freshwater; 2) seawater; 3) seawater saturated with chloride ions; and 4) seawater saturated with chloride, sulfate and magnesium ions. The tests were performed in columns loaded with the same quantity of salt and irrigated at the same rate for a period of 152 hours. These tests showed that leaching with seawater provides nearly the same potassium and nitrate leaching efficiency as when fresh water is used. However, leaching with seawater saturated with chloride, sulfate and magnesium ions yielded approximately 10% lower potassium and nitrate recoveries compared with the tests when seawater was used alone. In contrast, the use of saturated seawater is expected to yield a geomechanically more stable heap because most of the chloride-, sulfate- and magnesium-containing salts will remain unleached.

► Sea water found successful in leaching nitrate minerals
► Four alternatives were evaluated for recovering nitrates using sea water.
► Freshwater, seawater and seawater saturated leaching agent were employed.