Abstract: Nanofiltration can be used to improve a hydrometallurgical process in which valuable metal is extracted from ore or tailings by leaching with a suitable lixiviant. The process requires at least two nanofiltration subsystems in which raffinate from a solvent extraction process is treated in a nanofiltration subsystem, after which permeate therefrom is combined with a pregnant solution stream and is treated in a second nanofiltration subsystem. This arrangement can lead to advantages in the amount of lixiviant recovered, in the raw materials required, in the effluent produced, in the size of plant, and in overall cost.

Abstract: Methods are disclosed for removing alkali metal iodide from concentrated aqueous alkali metal chloride solutions using ion retardation resins. The methods are suitable for solutions comprising substantially more than 1 ppm iodide and greater than 100 g/l alkali metal chloride and can remove the iodide to levels below 1 ppm. To effect removal, the pH of the solution is adjusted to be less than about 10 and is then flowed through a separation bed comprising the resin in a series of loading and elution cycles. The method is particularly useful for removing iodide impurity from the concentrated feed brine used in chloralkali electrolysis.

Abstract: Hollow fibre membrane modules (1) with a shell-side configuration often comprise a hollow fibre bundle (2) and a perforated hollow internal core (4) inside the bundle. A plug (5) in the core and a baffle (15) in the bundle are typically employed in order to desirably distribute supplied fluid over the bundle for separation purposes. The fluid flow distribution can be improved by incorporating suitable flow distributors (20, 21) within the internal core itself. Such modules are particularly useful for osmotic membrane distillation.

Abstract: Nanofiltration can be used to improve a hydrometallurgical process in which valuable metal is extracted from ore or tailings by leaching with a suitable lixiviant. The process requires at least two nanofiltration sub-systems in which raffinate from a solvent extraction process is treated in a nanofiltration subsystem, after which permeate therefrom is combined with a pregnant solution stream and is treated in a second nanofiltration sub-system. This arrangement can lead to advantages in the amount of lixiviant recovered, in the raw materials required, in the effluent produced, in the size of plant, and in overall cost.

Abstract: Nanofiltration membranes have been identified that can unexpectedly provide for competitive removal of silica and sulfate from brine in alkaline conditions. Such membranes are known as monolithic nanofiltration membranes and are particularly suitable for removing silica and sulfate impurities from a brine stream in a brine electrolysis plant.

Abstract: A method for the reduction of soluble aluminum species in an evaporated salt alkali metal halide brine containing up to 500 ppb aluminum species to provide a brine feedstock suitable for use in a chlor-alkali membrane cell process, said method comprising treating said brine with a magnesium salt in an amount to provide a Mg to Al molar ratio selected from 5-20 to 1 at a Mg concentration selected from 0.5-10 ppm, and sufficient alkali metal hydroxide to provide an excess alkalinity concentration of between 0.1-0.5 g/L alkali metal hydroxide to effect precipitation of a magnesium aluminum hydroxide complex; and removing said complex to provide said brine feedstock.

Abstract: Certain continuous methods for monitoring the quality of ZnSO.sub.4 electrolyte lose sensitivity when the electrolyte contains Sb (V). The sensitivity can be increased by electrochemically reducing Sb (V). A sample of electrolyte which contains impurities including Sb (V) and which may also contain polarization affecting agents is passed through a test cell containing an elongated moving cathode having a predetermined area exposed to the electrolyte, an anode and a reference electrode. A substantially constant current in the range of 0.01 to 0.20 A/cm.sup.2 is applied to the electrodes and the cathode is moved with a speed sufficient to obtain measured values of the cathode polarization potential of zinc deposition on zinc.