Rubidium recovery using potassium cobalt hexacyanoferrate sorbent

© 2016 Balaban Desalination Publications. All rights reserved. Rubidium (Rb) is a highly valued and economically important metal present in large quantities in many natural and wastewaters. However, its recovery is hampered by its low concentration and extracting agents’ limited selectivity. A batch sorption study showed that a potassium cobalt hexacyanoferrate (KCoFC) sorbent had much higher sorption capacities for Rb and caesium (Cs) than for lithium (Li), sodium (Na) and calcium (Ca). Equilibrium sorption data at pH 7 and 24 ± 1°C for Rb and Cs satisfactorily fitted to the Langmuir model with sorption maxima of 96 and 61 mg/g, respectively. A fixed-bed column (12 cm height) containing a mixture of 2.2 g KCoFC and 19.8 g granular activated carbon had a breakthrough sorption capacity of 61 mg/g when a solution containing 5 mg Rb/L was passed through the column at a velocity of 2.5 m/h (0.7 L/h). When 1 and 5 mg Cs/L were added to the Rb solution, Rb sorption capacity dropped to 46 and 41 mg/g, respectively. During Rb sorption, K from the KCoFC lattice was released. Leaching the column containing sorbed Rb with 0.1 M KCl for 60 min at a velocity of 10 m/h desorbed 99% of sorbed Rb. A process for recovering Rb from sea water reverse osmosis brine is presented

Rubidium extraction using an organic polymer encapsulated potassium copper hexacyanoferrate sorbent

© 2016 Elsevier B.V. Sea water reverse osmosis (SWRO) brine contains significant quantity of Rb. As an economically valuable metal, extracting Rb using a suitable and selective extraction method would be beneficial. An inorganic sorbent, copper based potassium hexacyanoferrate (KCuFC), exhibited high selectivity to extract Rb compared to potassium hexacyanoferrate consisting of other transition metal combinations such as Ni, Co and Fe. An organic polymer (polyacrylonitrile, PAN) encapsulated KCuFC (KCuFC-PAN) achieved a Langmuir maximum Rb sorption capacity of 1.23 mmol/g at pH 7.0 ± 0.5. KCuFC-PAN showed Rb selectivity over a wide concentration range of co-existing ions and salinity of SWRO brine. High salinity (0.5–2.5 M NaCl) resulted in 12–30% sorption capacity reduction. At a molar ratio of Li:Rb (21:1), Cs:Rb (0.001:1) and Ca:Rb (14,700:1) commonly found in SWRO brine, sorption reduction of only 18% occurred. Nevertheless, at a very high K:Rb molar ratio (7700:1), KCuFC-PAN sorption capacity of Rb reduced significantly by 65–70%. KCuFC-PAN was well suited for column operation. In a fixed-bed KCuFC-PAN column (influent concentration 0.06 mmol Rb/L, flow velocity 2 m/h), two sorption/desorption cycles were successfully achieved with a maximum Rb sorption capacity of 1.01 (closely similar to the batch study) and 0.85 mmol/g in the first and second cycles, respectively. Around 95% of Rb was desorbed from the column with 0.2 M KCl. Resorcinol formaldehyde (RF) resin showed promising results of separating Rb from K/Rb mixed solution in effluents from a fixed-bed column, and a subsequent sequential acid desorption, producing 68% purified Rb

Removing rubidium using potassium cobalt hexacyanoferrate in the membrane adsorption hybrid system

© 2017 Elsevier B.V. Highly-priced rubidium (Rb) can be effectively extracted from seawater using potassium cobalt hexacyanoferrate (KCoFC) and ammonium molybdophosphate (AMP) adsorbents in the membrane adsorption hybrid system (MAHS). KCoFC (<0.075 mm), KCoFC (0.075–0.15 mm), and AMP (<0.075 mm) had Langmuir adsorption capacities of 145, 113, and 77 mg/g at pH 6.5–7.5, respectively. When KCoFC (<0.075 mm) at a dose of 0.2 g/L was initially added to 4 L of a solution containing 5 mg Rb/L in the MAHS and 25% of the initial dose was repeatedly added every hour, the amount of Rb removed remained steady at 90–96% for the experiment's 26 h duration. The removal of Rb by AMP under similar conditions was 80–82%. The cumulative Rb removed by KCoFC (<0.075 mm) in MAHS was only 33% reduced in the presence of high concentrations of other cations in synthetic seawater compared to that in solution containing only Rb. Approximately 30% of the adsorbed Rb was desorbed using 1 M KCl. When the desorbed solution was passed through a column containing resorcinol formaldehyde (RF), 35% of the Rb in the desorbed solution was adsorbed on RF. Furthermore 50% of the Rb adsorbed on RF was recovered by 1 M HCl leaching of the column. This sequence of concentration and separation of Rb in the presence of other cations in synthetic seawater is an efficient method for recovering pure Rb from real seawater and seawater reverse osmosis brine

Valuable rubidium extraction from potassium reduced seawater brine

© 2017 Elsevier Ltd Extraction of rubidium (Rb) which is an economically valuable metal from seawater reverse osmosis (SWRO) brine is beneficial. However, potassium (K) in SWRO brine hinders Rb extraction. Natural clinoptilolite zeolite in powder form was able to selectively remove K from SWRO brine (Langmuir maximum sorption, Qmax (cal.) = 57.47 ± 0.09 mg/g). An integrated submerged membrane sorption reactor (SMSR) containing zeolite powder achieved 65% K removal from SWRO brine. Periodic replacement of zeolite in SMSR, coupled with membrane backwashing was effective in maintaining a high K removal efficiency and a stable transmembrane pressure. Less than 5% Rb losses occurred along with K sorption, establishing the high K selectivity by zeolite in SWRO brine. Utilization of K loaded zeolite as a slow release fertilizer would be beneficial for agriculture. In SWRO brine with reduced K contents, the Rb sorption efficiency of polymer encapsulated potassium copper hexacyanoferrate (KCuFC(PAN)) sorbent, increased significantly from 18% to 83%

Ion exchange mechanism of caesium removal by cyanoferrates

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DETERMINATION OF ADDITIVES IN FUELS USING AUTOMATED FLOW INJECTION ANALYSIS WITH CHEMILUMINESCENCE DETECTION

The overall objective of this thesis was to develop field deployable instrumentation for the selective, sensitive determination of additives in diesel fuels using flow injection with chemiluminescence detection. The target analytes were the detergent dodecylamine and the lubricity additive P655. Chapter One describes the types of additives that are used in fully formulated diesel fuels in order to improve performance and outlines the need for robust analytical methods to be able to detect their presence / absences in fuels at the point of distribution, i.e. at the petrol pump. Flow injection (FI), and chemiluminescence (CL) are described as suitable techniques for sample preparation and detection respectively. The application of FI-CL for the quantitative determination of various analytes is reviewed, with the focus on real sample matrices. Finally the technique of solid phase extraction is discussed as a means of selective analyte preconcentration / matrix removal prior to FI-CL detection Chapter Two describes the development and optimisation (both univariate and simplex) of an FI-CL method for the determination of dodecylamine in acetonitrile / water mixtures using the catalytic effect of amines on the peroxyoxalate / sulphorhodamine 101 CL reaction. The linear range for dodecylamine was 0 - 50 mg Lˉ¹ with a detection limit of 190 µg Lˉ¹ and RSDs typically < 4 %. The effect of indigenous diesel compounds on the CL response is also investigated. Chapter Three investigates the applicability of the method developed in Chapter Two to determine dodecylamine in diesel fuels. Solid phase extraction was needed prior to analysis by FI-CL. The development of a solid phase extraction that is compatible with the FI-CL system is detailed. GC-NPD and GC-MS analysis are used in order to validate the solid phase extraction procedure. A range of diesel fuels have been spiked with an additive package containing dodecylamine and have been analysed off-line using FI-CL. Recoveries for all diesel fuels analysed were < 72 % and all fuels could by identified from the corresponding base fuel. Chapter Four describes the design and construction of a fully automated on-line solid phase extraction flow injection chemiluminescence analyser for the determination of dodecylamine in diesel fuel. Details of the automation and programming using LabVIEW are described. Results obtained using the automated on-line system are compared with results obtained using off-line SPE with FI-CL detection from Chapter Three. Recoveries for all fuels except SNV were < 71 %, and all fuels except SNV could be positively identified from the corresponding base fuels. No significant differences were found between the on-line and off-line results (within 95 % confidence limits). Chapter Five investigates the feasibility of determining the lubricity additive P655 in diesel fuel using FI-CL. The optimisation and development of a method using the competing reactions of periodate with alcohols and periodate with the CL oxidation reaction with pyrogallol is discussed, and the development of a solid phase extraction procedure for the extraction of P655 from an organic matrix is described. The limit of detection for P655 using SPE without preconcentration was 860 mg Lˉ¹ and was linear in the range 0 - 10000 mg Lˉ¹ (R² = 0.9965).Shell Global Solutions, Cheshire Innovation Park, Cheste