Method and system for the enhanced recovery of oil, using water that has been depleted in ions using magnetic particles

A method of depleting an ion from a water source is provided. The method is applicable to water used in oil recovery, water used in natural gas recovery, the treatment of water wells, and for water used in hydraulic fluids for fracturing processes, such as water to be used in proppants or fracking fluids. The method involves depleting an ion from a water source, said method comprising contacting a water source with a superparamagnetic or paramagnetic nanoparticle; complexing the ion with the particle; and removing the ion-particle complex by applying a magnetic field so as to provide a water source with depleted ion content. The depleted water can then be pumped into one or more connecting injection well(s) in an oil field pushing the crude oil towards one or more production well(s) thereby allowing for enhanced oil recovery from the production wells.