Abstract
phase), and citric acid aqueous solutions (feed phase). Two factorial designs (2 5–1 and 2 3 ) were used to define suitable operating conditions, in a single stage, producing citric acid solutions at 0.25 g mL –1 from aqueous feed solutions at 0.10 g mL –1 . The parameters investigated and the best operating conditions obtained were pH of the feed phase (pH = 1.5), surfactant (w s = 2 %) and carrier concentrations in the membrane phase (w c = 20 %), stirring speed (v = 145 rpm), and permeation time (t = 10 minutes) and the response variables were the citric acid concentration in the inner and feed phases and inner phase swelling. Under these conditions, an extraction greater than 50 % and swelling equal to 80 % were obtained. Use of recycled membranes as well as extraction in multiple stages was also evaluated. Experiments of recycling revealed that the membranes can be reused for at least three times with good performance. Extraction in multiple stages showed high efficiency for the citric acid separation (~100 %) after three steps of operation.
Highlights
The liquid surfactant membrane technique (LSM) is an extraction process developed by Norman N
At the feed/membrane interface, the solute reacts with the carrier, in this case a tertiary amine (R3N), forming the complex (R3NH+)3(C6H5O7)3–. This new molecule diffuses through the membrane until it reaches the membrane/inner phase interface, where the citric acid is stripped with CH3COONa
Two factorial designs were used to conduct the first part of the experiments, which revealed the influence of the variables pH of the feed phase, carrier concentration in organic phase, and permeation time on final concentration of the citric acid, in the feed and inner phase, and on the swelling
Summary
The liquid surfactant membrane technique (LSM) is an extraction process developed by Norman N. Its recovery from the fermentation broth is performed by precipitation or solvent extraction In both cases, the processes require many separation steps and, especially for precipitation, large quantities of residues are produced.[12] In this context, the study of other separation methods, such as LSM technique, aims to evaluate an alternative way of carrying out the citric acid recovery in order to search for better operating conditions to accomplish the separation. The mechanism proposed to explain the citric acid extraction by liquid surfactant membrane with tertiary amines is classified as simple carrier transport with chemical reaction This new molecule diffuses through the membrane until it reaches the membrane/inner phase interface, where the citric acid is stripped with CH3COONa
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