Recovery of lactic acid from fermentation broth by the two-stage process of nanofiltration and water-splitting electrodialysis

The Application of the Nanofiltration Membrane NF270 for Separation of Fermentation Broths

The potential for nanofiltration (NF) in removing both relatively low molecular weight (MW) organic species and charged solutes from complex media is noteworthy. The main aim of the current work was to improve understanding of the separation mechanisms of fermentation broths components in the NF process. For this purpose, the experimental investigations were performed using the commercial polyamide NF270 membrane. The feed solution was ultrafiltered 1,3-propanediol (1,3-PD) broths. The separation results were analyzed and discussed in light of the detailed characteristics of both the membrane and the broth components. It has been noted that the membrane ensured the complete 1,3-PD permeability and significant rejection of some feed components. A thorough analysis showed that the retention of carboxylic acids was based on both the Donnan effect and sieve mechanism, according to the following order: succinic acid > lactic acid > acetic acid > formic acid. Indeed, acids retention increased with increasing charged acids ions valency, Stokes radius (rS) as well as MW, and decreasing diffusion coefficient (D). In turn, for ions, the following orders retention was determined: SO42− = PO43− > Cl− and Ca2+ > Na+ > NH4+ ~ K+. It indicated that the ions retention increased with increasing ions charge density, hydrated radius (rH), and hydration energy (Eh). It showed that the separation of the ions was based on the Donnan exclusion, sieving effect, and dielectric exclusion.

Lactic Acid and Salt Separation Using Membrane Technology

Acid whey is a by-product of cheese and yoghurt manufacture. The protein and lactose within acid whey can be recovered using nanofiltration and electrodialysis, but this leaves a waste stream that is a mixture of salts and lactic acid. To further add value to the acid whey treatment process, the possibility of recovering this lactic acid was investigated using either low energy reverse osmosis membranes or an electrodialysis process. Partial separation between lactic acid and potassium chloride was achieved at low applied pressures and feed pH in the reverse osmosis process, as a greater permeation of potassium chloride was observed under these conditions. Furthermore, lactic acid retention was enhanced by operating at lower temperature. Partial separation between lactic acid and potassium chloride was also achieved in the electrodialysis process. However, the observed losses in lactic acid increased with the addition of sodium chloride to the feed solution. This indicates that the separation becomes more challenging as the complexity of the feed solution increases. Neither process was able to achieve sufficient separation to avoid the use of further purification processes.

Reuse of manganese sulfate as raw material by recovery from pesticide's wastewater using nanofiltration and electro-electrodialysis: process simulation and analysis from actual data

Reuse of wastewater, as well as recovery of valuable, toxic or harmful products in industrial discharges, still represents an important issue, not only because it reduces the effect on receiving water bodies, but also because of the economic resources it represents for industry itself. In this research, in situ regeneration of Mn₂SO₄ is evaluated, for its reuse as the main raw material in the original process of a fungicide plant. The regeneration is evaluated by selective recovery of Mn²⁺, Zn²⁺ and SO₄ ⁼ present in the wastewater produced by the industrial plant, and utilizing nanofiltration, electro-electrodialysis and chemical precipitation as separation alternatives. Each alternative was designed and evaluated technically and economically through simulations in Aspen Plus^®, with data and information of the real process supplied by the company. Because zinc concentration is relatively low, its selective recovery was not attractive. The resulting Mn₂SO₄ solution and treated water quality in conventional alternatives were significantly poor with high costs. In contrast, nanofiltration and electro-electrodialysis alternatives generate water and by-products of higher quality and reuse potential with significantly lower costs. However, their viability depends on the membrane performance. The results were satisfactory, but future experimental studies are required to optimize the alternatives and define the correct pretreatment process.

Separation of galactose, 5-hydroxymethylfurfural and levulinic acid in acid hydrolysate of agarose by nanofiltration and electrodialysis

A two-stage membrane process for the separation of galactose, 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) has been proposed. The first step of nanofiltration (NF) is to remove 5-HMF and LA from galactose solution obtained by the hydrolysis of agarose, the main component of red algal galactan for the reduction of its microbial toxicity. 5-HMF and LA are inhibitory to fermentation but at the same time useful compounds themselves with many applications. The second step of electrodialysis (ED) is to separate 5-HMF and LA in the permeate from NF. More than 91% of 5-HMF and up to 62% of LA could be removed from agarose hydrolysate, while galactose was almost completely retained by NF. Further removal of LA was expected to be possible with no loss of galactose by operating the NF process in a diafiltration mode. 5-HMF and LA could be effectively separated from each other by ED.