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MINERAL NANOFILTRATION MEMBRANES FOR CANE SUGAR REFINING PROCESS

Objective


As-prepared by AEA sols had particle sizes around 4 nm but ageing the sols increased the size up to 30 nm. Pore size distributions in oxide powders were centred around 5 nm indicating that membranes derived from the sols should exhibit nanofiltration properties. Retention of bromocresol green, vitamin B12, and a dextran showed that the coatings behaved as nanofiltration membranes. It was considered that chemical interactions as well as steric effects contributed to the nanofiltration behaviour. Tech-Sep has screened 4 different inorganic material with inorganic materials with potential to generate nanoporosities: native polyphosphazene, functionnalised polyphosphazene, ZrO2 sol-gel 1 and SIC obtained by chemical vapor disposition. Finally, the best performances were obtained with the ZrO2 sol-gel process. Pilot-plant trials showed that sol-gel zirconia membranes from Tech-Sep could recover brine from ion-exchange effluent.

Protocols for the separation of impurities from raw sugar, affinated sugar and brine solutions were established. High molecular and low molecular weight impurities were separated and characterised using HPLC, GPC, ionic chromatography, and 1H and 13C-NMR. These results lead to the required fingerprint of the impurity profile.

Twelve samples of retentate and permeate from the ultrafiltration and nanofiltration trials of affinated sugar solutions from Tech-Sep were analysed for sugar and colour retention. The colour retention results were in good agreement with those of the Tech-Sep results. Some variations in the sugar retention data were observed but this could be due to different techniques used in the two laboratories.

According to thin layer chromatography trials on brine samples, tested on 20cm length TECH-SEP membranes, there was limited selectivity on the separation of various impurities. Solubility trials in organic solvents revealed that the impurities in brine solutions are charged and not hydrophobic.

A database containing 200 scientific reference literature on impurities present in sugar liquer and brines has been established.
The objective of the Project is the development of mineral nanofiltration membranes (MNFM) to be used in the cane sugar refining process (SCRP). The MNFM will be incorporated in the primary purification process, to remove impurities which both affect the quality and the quantity of produced sugars.

Classical routes will be compared to MNFM process by end 8 users at laboratory scale first, in order to select and identify membranes to be developed for pilot trials.

Five major hurdles will be investigated.

(i) flow rate
(ii) retention selectivity
(iii) thermal resistance (process temperatures up to 90 C could be used)
(iv) chemical resistance (chemical clearing to restore the membranes characteristics after fouling)
(v) life time

During the early stage of the project, different MNFM approaches will be conducted simultaneously and screened at the laboratory scale to fulfill the specific requirements of sugar industry.

An analytical investigation on filtered sugar fractions and impurities will allow a better understanding of nanofiltration membrane selectivity.

Successful completion of MNFM in CSRP should have positive impact on environment by reducing wastes and should result in lower energy consumption.

Call for proposal

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Coordinator

Tech-Sep SA
EU contribution
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Address
5 chemin du Pilon
01703 Miribel
France

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Total cost
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Participants (3)