Eutectic Freeze Crystallization
CHE3049W – EFC Report
Synopsis
This report provides a detailed investigation into the operation of the Eutectic Freeze Crystallisation
(EFC) process in order to determine its effectiveness as a separation technique for purification of waste water streams. The objective of is to evaluate the ability of the EFC process in reducing the volume of a 5 wt% CuSO4 aqueous waste water stream significantly while simultaneously producing potable (drinking) water. In order to evaluate this effectiveness, the yield and purity of only the ice product is investigated before and after a number of wash cycles. A 1000g solution of 5 wt% CuSO4 underwent crystallization for one hour with the use of ice crystal seeding and the agitation of a stirrer at 500rpm. After the crystallization process, the mass of the ice product and filtrate were recorded. The ice product was then washed with de-ionised water under Buchner vacuum filtration, before the masses were recorded once again. This process was repeated for three wash cycles A sample of the ice product and filtrate were also taken before and after each wash, and these samples were analysed using Atomic Absorption Spectroscopy (AAS).
A temperature probe revealed that the solution did not reach the eutectic temperature of -1,55⁰C during crystallization, and only reached a minimum temperature of -0,75 ± 0,01⁰C. Despite this high temperature, a significant fractional yield of ice product of 67,05 ± 0,01% was recorded. As predicted, the washing of this ice product reduced this yield to 52,08 ± 0,06% after three washes.
Furthermore, the process of washing was found to contaminate the pure washing water; therefore a
‘real’ yield was calculated in order to reveal the true effectiveness of this process in producing fresh water. After crystallization, a purity of 98,95 ± 0,02% was achieved, and the use of three washes improved this to 99,96 ± 0,01%. This confirmed the effectiveness of wash cycles in increasing the purity
Synopsis
This report provides a detailed investigation into the operation of the Eutectic Freeze Crystallisation
(EFC) process in order to determine its effectiveness as a separation technique for purification of waste water streams. The objective of is to evaluate the ability of the EFC process in reducing the volume of a 5 wt% CuSO4 aqueous waste water stream significantly while simultaneously producing potable (drinking) water. In order to evaluate this effectiveness, the yield and purity of only the ice product is investigated before and after a number of wash cycles. A 1000g solution of 5 wt% CuSO4 underwent crystallization for one hour with the use of ice crystal seeding and the agitation of a stirrer at 500rpm. After the crystallization process, the mass of the ice product and filtrate were recorded. The ice product was then washed with de-ionised water under Buchner vacuum filtration, before the masses were recorded once again. This process was repeated for three wash cycles A sample of the ice product and filtrate were also taken before and after each wash, and these samples were analysed using Atomic Absorption Spectroscopy (AAS).
A temperature probe revealed that the solution did not reach the eutectic temperature of -1,55⁰C during crystallization, and only reached a minimum temperature of -0,75 ± 0,01⁰C. Despite this high temperature, a significant fractional yield of ice product of 67,05 ± 0,01% was recorded. As predicted, the washing of this ice product reduced this yield to 52,08 ± 0,06% after three washes.
Furthermore, the process of washing was found to contaminate the pure washing water; therefore a
‘real’ yield was calculated in order to reveal the true effectiveness of this process in producing fresh water. After crystallization, a purity of 98,95 ± 0,02% was achieved, and the use of three washes improved this to 99,96 ± 0,01%. This confirmed the effectiveness of wash cycles in increasing the purity
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