Flocculation behavior of two different clay samples from Kırka tincal deposit

Çırak, Mustafa
Kırka Boron Plant in EskiĢehir region has been producing tincal contentrate and boron products since 1972. Depending on the industrial demand for boron products, the plant capacity has been gradually enlarged by reaching over 1.5 million metric tons per year. This increase in the capacity has caused serious tailings disposal problems. In addition to the great amount of the tailings (400.000 ton solid waste per year), the tailing material contains mostly clay minerals that show colloidal character. Their suspensions are very stable in water and cause flocculation difficulties resulting in very high liquid/solid ratio and complications in management of the plant tailings. To identify flocculation characteristics of the most abundant minerals (montmorillonite and dolomite) in the tailings, two different clay samples were taken from the Kırka Tincal Mine. XRF analyses were done for elemental composition and XRD analyses were carried out to identify mineralogy of the clay samples. For advanced mineralogical analysis, the oriented clay samples were prepared and subjected to ethylene glycolation and heat treatment. According to the XRF and XRD results, green clay sample is rich in montmorillonite and represents silicate-rich tailings material whereas white clay sample is rich in dolomite and represents dolomitic tailings. To mimic the actual tailings environment, the green clay and white clay samples were added into borax solutions that buffer pH to 9.40 for the purpose of carrying out controlled experiments. In search of finding alternative ways, the clay suspensions were tried to be flocculated by using new UMA (Unique Molecular Architecture) Magnafloc macropolymers. The flocculation behavior of both green clay and white clay samples was tried to be identified in distilled water and although the very high polymer consumption (up to 2kg/ton) was introduced to the system, the complete flocculation could not be achieved by one stage polymer addition. So, the turbidity of the first stage flocculation were decanted to another beaker and treated with polyethylene oxide at this second stage. As a result, both clays were flocculated by applying two-staged flocculation, respectively UMA Magnafloc and Polyethylene Oxide. Effects of borax concentration, solid/liquid ratio of simulated pulps, pH of solution and cations (calcium and magnesium) on UMA Magnafloc flocculation were also studied in the scope of this thesis. Flocculation was enhanced by increasing borax concentration, lowering solid/liquid ratio, adjusting pH to 7.00 (although requires great amount of acid due to borax buffer effect) and also adding calcium (up to 500 mg/L) into solution. Addition of Mg++ ions into suspensions deteriorated the flocculation of the dolomite-rich white clay and slightly improved the flocculation of the montmorillonite-rich green clay. Furthermore, aging (24 hour) of clay samples also deteriorated flocculation of dolomite-rich clay but it made montmorillonite-rich clay flocculation easier. Then, ATR-FTIR studies were carried out to analyze the changes on clay surfaces. Ca++ and Mg++ addition into the suspensions increased the adsorbed water on both clay surfaces and increased the isolated – OH groups depending on this enhanced water-clay surface interaction. According to the infrared results, it was verified that the polymers attached themselves on mineral surfaces through those isolated – OH groups by using hydrogen bonding mechanism.