Extraction Of Boron Using Centrifugal Extraction Technique From Underground Brine

Boron compounds are widely used as chemical raw materials and novel optoelectronic materials. Along with the development of industry, demand for boron compounds is increasing sharply. Sichuan Pingluo underground brine is rich in available element. In this paper, boron was extracted via centrifugal extraction technique from Pingluo underground brine. The processes of extraction and stripping have been optimized. Meanwhile, fluid residence time in extractor ring gap were investigated. Also the properties of borates abtained from different stripping solution with different p H value were tested.The process of centrifugal extraction for boron has been carried out. It was found that single-stage extraction efficiency was below 20 % using isooctanol as extractant. To improve efficiency, on the one hand, magnesium content was raised to increase salting out effect. On the other hand, 2-ethyl-1,3-hexanediol was added in monohydric alcohol to improve complexing effect between boron and extractant. With the selected extractant, the optimum condition was determined by single factor process and could show as brine of 6, organic and water phase volume ratio of 1:1.5, rotating speed of 3500r/min. Under the optimal conditions, extraction efficiency reached above 96 % via continuous counter-current. Meanwhile, extraction capacity, extractant reusability and separation factor were analyzed.In Centrifugal stripping process, effect of kinds and concentration of stripping agent, phase ratio, rotating speed, stripping stages were discussed for abtaining optimum stripping efficiency. With Li OH solution as stripping reagent, the optimized conditions are concentration of 0.3 mol/L, organic and water phase volume ratio of 1.2:1, rotating speed of 3500 r/min with 95.54 % stripping efficiency and 92.2 % total recovery. With 0.3 mol/L Na OH and 0.25 mol/L KOH solution as stripping reagent, under the optimized conditions, that is organic and water phase volume ratio of 1.2:1, rotating speed of 3000r/min, the stripping efficiency is 97.82 % and 96.36 %, respectively. With different stripping solution containing boron, various borate products have been abtained via evaporation crystallization process. And those products chemical phase were analysed by XRD.Fluid shape and fluid residence time in centrifugal extractor annular were discussed with distilled water as the medium.(1) Fluid Reynolds and Taylor number were calculated under different rotating speed. And fluid shape was investigated depending on Taylor number. Rotation speed below 3500 r/min, Taylor number less than 10000, the fluid showed annular laminar flow. With higher rotation speed, laminar flow was transiting to turbulent Taylor vortex.(2) Using alizarin red as a tracer, fluid residence time in annular was studied by pulse tracer method. Samples alizarin red concentration could be determined by spectrophotometry at 263 nm wavelength. When flow rate is 20 m L/min and rotating speed reaches 2000 r/min, the fluid average residence time is 13.43 s. The residence time is lengthened with increase of rotational speed and is shortened with increasing flow rate.