Abstract
Active clays are swelling clays that do not agglomerate, settle or consolidate easily when mixed with water. They can cause significant challenges for mining operators by tying up large volumes of water and requiring extra resources for treatment. Their presence in mineral slurries complicates slurry behaviors in rheology, solids-water separation and solids settling, causing difficulties in many processes, such as extraction, flotation, flocculation, thickening, hydrotransportation and consolidation. A brief description of basic clay structures and water chemistry will be presented to help understand the clay challenges.
The Saskatchewan Research Council (SRC) is developing an automated, online active clay analyzer that can be applied in mining industries, such as potash, uranium, kimberlite, oil sands and many mineral processes that contain clays or active clays. The analyzer is based on the current standard ASTM/CANMET methylene blue index (MBI) method but uses different approaches to identify and quantify active clays and clay activity by measuring the spectra absorbance of a filtrate using methylene blue (MB) as an indicator.
A controlled volume of slurry sample is automatically withdrawn from a process and conditioned in a mixing chamber. Controlled volume of MB solution is injected in increments into the sample mixture. A filtrate is automatically extracted and analyzed by a spectrophotometer to determine the MBI value, as well as clay activity and quantity of active clays in the mineral sample. The data can be used to achieve better process control, save water and reduce cost for tailings management, as well as reduce tailings volume and footprint.