The pressure for saving water by closing the water loops in mineral processing is increasing continuously. The drivers for higher recirculating rates include water scarcity in dry areas, environmental legislation that is becoming stricter in most countries, limitations set for wet tailings management and the increased demands for social licenses to operate. At the same time, to make mineral processing sustainable, the recovery of valuable minerals should be maximized. This leads for a need to close the process water circulation. To see the effect of closed water circulation on metallurgical performance, flotation tests were carried out with nickel concentrate thickener overflow water before and after the process of water purification by dissolved air flotation (DAF). Both total nickel recovery and concentrate grade in laboratory scale flotation tests to the Ni rougher-scavenger concentrate increased after DAF treatment. Chemical and mineralogical characterizations revealed that after DAF treatment, the process water contained fewer metal hydroxides and less fine-grained silicate mineral particles, which is most likely the reason for the improvement in the nickel flotation performance. Based on the feasibility study, improved nickel recovery by DAF treatment of process water can bring economic benefits at a concentrator plant.

Blending of different ore types in the concentrator feed contributes significantly to maintaining a high recovery of valuable minerals with required grades in the concentrate. It is feasible to develop an ore-blending scheme over the life of a mine already in the design phase of the plant. In addition to ore characteristics, water quality is known to impact mineral recovery. A blending plan could also be developed for the different water streams of a future concentrator. This paper describes a novel modeling and simulation approach to predict metallurgical response combining ore types and water quality. The model is based on kinetic laboratory flotation test data, and it was tested on a case study. As a result, rougher flotation grade-recovery curves dependent on ore types and water quality are presented over the predicted life of the mine. The simulation results can be exploited in project design to maximize the recovery of valuable minerals and to ensure environmentally sound and profitable mining operations. Overall, the developed modeling tool can be applied widely for minerals processed by using froth flotation and water types available for kinetic laboratory flotation tests.