Selective Extraction of Lactic Acid from Aqueous Media through a Hydrophobic H-Beta Zeolite/PVDF Mixed Matrix Membrane Contactor

Abstract

2-Hydroxypropionic acid, commonly known as lactic acid (LA), is a valuable chemical widely used for the manufacture of green solvents such as ethyl lactate and biodegradable polymers such as poly­(lactic acid) (PLA). LA is manufactured by fermentation molasses and whey. Isolation of LA from aqueous broths by conventional methods is energy intensive. Reactive extraction through membranes using specific reagents could prove to be a cost-effective alternative for LA recovery. This study focuses on reactive separation of LA using a novel indigenously developed hydrophobic H-beta zeolite/polyvinylidene fluoride (PVDF) mixed matrix membrane. Experiments were conducted using a stirred cell assembly consisting of two bell shaped glass pipe reducers containing aqueous LA separated by the membrane from an organic solution of tri-n-octylamine (TOA) carrier in alcoholic medium. Effects of experimental parameters such as the concentration of TOA in organic phase and zeolite loading on the rate of acid extraction were evaluated by increasing the TOA concentration from 206 to 620 mol/m3 and the extent of zeolite loading from 1 to 25% (w/w) of (PVDF) polymer. SEM analysis was carried out to oversee zeolite distribution on the PVDF surface, whereas TGA was used to determine the maximum operating temperature. XRD study was done to investigate the influence of zeolite loading on intersegmental spacing in the polymer, while FT-IR helped in the identification of interactions between the inorganic filler and organic polymer. A mass transfer correlation was deduced by taking into account all possible reactions involved in formation of the complexes. An optimum extraction of nearly 34% was obtained using 25% zeolite loading, 206 mol/m3 TOA in 1-octanol, and 100 mol/m3 acid concentration, at a stirring rate of 400 rpm over a processing time of 1 h. Continuous separation of LA by a membrane contactor could help improve the fermentation yield of the acid by preventing the inhibition of lactate dehydrogenase enzyme, which is affected by the product itself. Such reactive extractions by membrane contactors could be successfully scaled up using a hollow fiber modular configuration.

Zeolite Mixed Matrix Membranes (Zeolite-MMMs) for Sustainable Engineering

“…Sridhar [62] studied reactive separation of lactic acid (LA) using a microporous hydrophobic H-beta zeolite/polyvinylidene fluoride (PVDF) mixed matrix membrane from aqueous streams. Experiments were conducted using a stirred cell assembly consisting of two bellshaped glass pipe reducers containing aqueous LA separated by the membrane from an organic solution of tri-noctylamine (TOA) carrier in alcoholic medium.…”

Mixed-Matrix Membrane Fabrication for Water Treatment

“…Zeolite–MMMs could be considered ideal for the purification industry, since they combine the properties of a polymeric matrix and zeolite inorganic fillers [ 93 ]. Nevertheless, only a few studies have been performed on zeolite–MMMs for water treatment; it was determined that the size of zeolite should be designed to match the expected polyimide active film thickness, thereby providing a preferential flow path through the nanochannels of zeolites [ 94 , 95 ]. Natural zeolite can readily form a suspension to coat the membrane as a support [ 96 ].…”

Recovery and separation of lactic and malic acids from fermentation broth with N,N,N,N-Tetrabutylbutanediamide by reactive liquid−liquid extraction and stripping

“…The activity of lactic acid is assumed to be proportional to the equilibrium concentration of undissociated acid in the aqueous phase. Thus, the apparent equilibrium constant (K ex ) of overall reaction could be written as follows: (8) The distribution coefficient of lactic acid (D) is defined by: (9) The relationship between the equilibrium concentration of the extractant ([B]) and the distribution ratio of lactic acid (D) exhibited as follows： (10) In this process, the distribution ratio (D) is approximately linear with the extraction equilibrium constant, ie: (11) A linear relationship between the distribution coefficient (D) and 1/T could be described:…”

“…Conventionally, many studies are implemented for separation of the lactic acid, including membrane separation, [6][7][8][9] adsorption, 10 ion exchange, 11 direct distillation, 12 reactive distillation, 13 molecular distillation, 14 reactive extraction etc. [15][16][17] Membrane separation can be used to avoid toxicity, but it is difficult to clean and sterilize, which would limit its application.…”