Abstract:

In order to develop the technologies of saving energy and the efficient utilization of nature resources in manufacturing chemical products from kelp, a series of experiments of the extraction and purification of mannitol (M) in processing wastewater from kelp products were carried out by means of a setup pilot scale device equipped with two spiral wound modules of the polyamide (PA) nanofiltration (NF) membrane with the total effective area of 6.8 m². The transport phenomena of low molecular weight organics and electrolytes were analyzed. The behaviors of the solute transport in the PA membrane-M-NaCl system were investigated. Also the mechanism of integrative effect considering the preferential penetration and space hinder was developed based on the theory of pore exclusion and Donnan balance. The experiment results showed that the R_M of the two modules was in a high level (about 80%) both in the M aqueous solution and in the M-NaCl mixture solution.  S_NaCl of 69% and 38% for 1^# module and 2^# module were obtained respectively at the feed of 0.8%(mass),and increased with the increasing NaCl concentration. Hence, M was preserved effectively by the membrane while NaCl permeated through the membrane preferentially. The transport of M and NaCl in the NF process was well consistent with the result　predicated on the mechanism of integrative effect. This work offers the theoretical basis for the engineering development of the purification and concentration of M in kelp industry by the NF membrane.