Powdered activated carbon to adsorb colorants from sugar beet syrup a pilot plant study

Authors: WIERDAK, ANDREW - Tulane University; CLAYTON, CHARLES - Tulane University; WATTS, NICHOLAS - Tulane University; Lima, Isabel; WALKER, ALEC - Tulane University; Eggleston, Gillian; PARKER, CRAIG - British Sugar Ltd; SARIR, EMMANUEL - Carboua International

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 5/14/2019
Publication Date: 11/6/2019
Citation: Wierdak, A., Clayton, C., Watts, N., Lima, I., Walker, A., Eggleston, G., Parker, C., Sarir, E. 2019. Powdered activated carbon to adsorb colorants from sugar beet syrup a pilot plant study. In: Proceedings of the Advances in Sugar Crop Processing and Conversion 2018 Conference, May 15-18, 2018, New Orleans, Louisiana. 2:30-44.

Interpretive Summary: During sugar beet processing, molasses is subjected to simulated moving bed chromatography to extract high-value betaine and sucrose. The sucrose is then recovered by recycling high color sugar beet extract (SBE) from the chromatography system back into the crystallization unit. Color compounds, if present in large amounts, can make this process unfeasible. One method of reducing color as well as other impurities prior to further processing into white sugar, is the addition of powdered activated carbon (PAC) of high surface area. Pilot plant studies were undertaken to determine the feasibility of using PAC to adsorb both natural and process-formed colorants from SBE. Experiments were performed using a batch decolorization process to maximize color removal and determine optimal distribution of PAC either as a body feed or a filter pre-coat. With initial colors at 4490±256 ICU, 4510±329 ICU, and 4903±324 ICU, measured at pH 4, 7, and 9, respectively, a target of 50% color removal was achieved using 4,000 ppm of PAC, with a recommended distribution of 75% as pre-coat in the filter and 25% as body feed in the process feed tank. A 50/50 distribution of PAC also produced consistent rate of color removal. Overall, PAC was able to remove both processing and native colorants. However, its performance was slightly better for native colorants than factory colorants. Addition of PAC did not incur any sucrose losses and did not have any negative effect on the pH of beet extract.

Technical Abstract: During sugar beet processing, molasses is subjected to simulated moving bed chromatography to extract high-value betaine and sucrose. The sucrose is then recovered by recycling high color sugar beet extract (SBE) from the chromatography system back into the crystallization unit. Color compounds, if present in large amounts, can make this process unfeasible. One method of reducing color as well as other impurities prior to further processing into white sugar, is the addition of powdered activated carbon (PAC) of high surface area. Pilot plant studies were undertaken to determine the feasibility of using PAC to adsorb both natural and process-formed colorants from SBE. Experiments were performed using a batch decolorization process to maximize color removal and determine optimal distribution of PAC either as a body feed or a filter pre-coat. With initial colors at 4490±256 ICU, 4510±329 ICU, and 4903±324 ICU, measured at pH 4, 7, and 9, respectively, a target of 50% color removal was achieved using 4,000 ppm of PAC, with a recommended distribution of 75% as pre-coat in the filter and 25% as body feed in the process feed tank. A 50/50 distribution of PAC also produced consistent rate of color removal. Overall, PAC was able to remove both processing and native colorants. However, its performance was slightly better for native colorants than factory colorants. Addition of PAC did not incur any sucrose losses and did not have any negative effect on the pH of beet extract.