Batch and continuous flow systems during the acid pre-extraction stage in the alginate extraction process

Dl Arvizu-Higuera,Ye Rodríguez-Montesinos,G Hernández-Carmona

doi:10.7773/cm.v21i1.983

Abstract

Acid pre-extraction in the production process of alginates was investigated in two stages using Macrocystis pyrifera as raw material. In the first stage, the possibility of reducing the normality of the hydrochloric acid used in a continuous flow system was tested by varying the concentration of the acid between 0.2 and 0.006N. The percentage of calcium ions exchanged was considered as the variable response. lt was found that with this system it is possible to use 0.05N as the minimum concentration of hydrochloric acid without affecting the alginate yield. In the second stage, the continuous flow system using the conditions established in the first stage was compared to a three batch system at pH 4. It was found that the continuous flow system exchanges 76% of the ions present in the algae, while the batch system exchanges 50%. There is no significant difference in the yield, but the quality of the alginates, measured in terms of viscosity, is 55% greater using the batch system. The use of the batch system reduces hydrochloric acid consumption by 85.9%, water consumption by 25% and therefore reduces production costs.

Highlights

El alga parda Macrocystis pyrifera es una importante fuente de alginatos, debido a que cumple dos de las principales caracteristicas para ser seleccionada como especie de importancia industrial: existe en cantidades abundantes y los alginatos obtenidos de ella pueden aplicarse, por sus propiedades, en diversas industrias
The stage of acid pre-extraction in the alginate production process is important since it allows the alginate salts to be converted into alginic acid inside the alga, and be extracted in the form of sodium alginate when treated with the corresponding alkali (Haug. 1964)
The results obtained in the first part of this study show that if a continuous tlow system is applied, it is feasible to reduce the normality of the acid during the pre-extraction stage to a minimum of O.O5N, which is different from that suggested by other authors (Haug. 1964; Myklestad, 1968; Duville, 1986, HernándezCarmona and Aguirre-Vilchis, 1987; Hernández-Carmona et al, 1992; and Reyes-Tisnado et al, 1992) since there is no significant difference in the yields

Summary

Introduction

El alga parda Macrocystis pyrifera es una importante fuente de alginatos, debido a que cumple dos de las principales caracteristicas para ser seleccionada como especie de importancia industrial: existe en cantidades abundantes y los alginatos obtenidos de ella pueden aplicarse, por sus propiedades, en diversas industrias. El proceso de extracción de alginatos se basa en una serie de reacciones de intercambio iónico, que tienen por objeto extraer el alginato existente en el alga como parte de la pared celular y la matriz intercelular (Hernández-Carmona y Aguirre-Vilchis, 1987). El ácido algínico se encuentra presente principalmente como una sal mixta del ácido algínico, donde el calcio es el catión más importante, que da propiedades de insoluble al alginato dentro del alga; pero se sabe que también pueden estar presentes otras sales, como magnesio, potasio y sodio (McHugh, 1987), por lo que el proceso tiene como objeto convertir estas sales insolubles en alginato de sodio soluble. Dicho proceso se puede llevar a cabo de manera directa tratando las algas con un Alcali, que generalmente es

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