Research data (the surfactant role)
Description
Emulsion Liquid Membranes (ELMs) are known as a useful and versatile technique with widespread uses, including wastewater treatment, metal ions and organic substances recovery. In wastewater treatment applications, many researchers have removed pharmaceutical derivatives. The main objective of this last type of work focuses on the efficiency of the pharmaceutical derivatives recovery process. At the same time, some properties such as the interaction of pharmaceutical derivatives and extractants are studied. Nevertheless, there are not many reports that describe the main role of surfactants in mass transfer mechanisms. In the present research work a methodology to recover naproxen from aqueous solutions using ELMs was developed, in order to propose a way by which surfactant molecules interact with all the chemical species of both the drug and extractant in the media, and how these chemical interactions affect or benefit the extraction and stripping processes. The results obtained show how the extraction and stripping percentages are modified in presence or absent of surfactant.
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Liquid-Liquid Extraction (LLE) process was carried out by mixing equal volumes of organic phase and aqueous phase. The organic phase consisted of dodecane (Merck) or a mixture of 0.1% w/V of trioctylamine in dodecane, while the aqueous phase consisted of for 50 mgL-1 of naproxen (NPX) in deionized water at different pH values and in phosphates buffer solutions at pH 5.5. pH values were adjusted with NaOH or/and HCl solutions. For the stripping process, the aqueous phase used was a NaOH solution at different concentrations (0.01 - 0.20 molL-1). Once both phases were in contact, the mixture was stirred for 60 minutes in a ping-pong stirrer (Cole Palmer 5022). Then the mixture was allowed to separate into the phases by gravity and the aqueous phase’s pH was measured using an automatic titrator (Tritino 716 of Metrohom), using a combined glass electrode. Naproxen in the aqueous phase was quantified with UV/Vis spectroscopy using a Varian spectrophotometer Cary 50 Scan at 272 nm. Equal volumes of organic phase (OP) and internal aqueous phase (IAP) were used to obtain Emulsion Liquid Membranes (ELMs). The IAP was a 0.1 molL-1 NaOH solution. The OP was a mixture of carrier (TOA; 0% w/V - 10% w/V), surfactant (Abil EM 90®; 1% w/V - 5% w/V) and as a solvent, dodecane. Both the OP and IAP were put in contact and then stirred at 15 000 rpm, using a high speed stirrer (T18 digital Ultraturrax®, IKA), for 10 minutes at a constant temperature (25 + 0.5°C). After that, a known volume of emulsion phase (EP) was put in contact with an equal volume of external aqueous phase (EAP), which consisted of naproxen (50 mgL-1) in a phosphate buffer at pH 5.5, and the mixture was stirred at 320 rpm for a range of times (5 - 20 minutes). Then, the phases were separated and the emulsion phase was breaking using a thermal shock in order to recover the internal aqueous phase and the naproxen was quantified in both the internal aqueous phase and the external aqueous phase using a Varian spectrophotometer Cary 50 Scan at 272 nm. The pH of both phases was measured before and after the extraction process. The extraction percentage (naproxen transference from the external aqueous to the organic phase) was determined by: Extraction (%)= ([F]_(ext,final)/[F]_(ext,initial) )x100 where: 〖[F]〗_(ext,final)= Final concentration of drug (NPX) in the external aqueous phase. [F]_(ext,initial)= Initial concentration of drug (NPX) in the external aqueous phase. Finally, the recovery percentage (mass transfer from the external aqueous phase to the internal aqueous phase), was determined as follows: Recovery (%)= (V_int [F]_(int,final))/(V_ext [F]_(ext,initial) ) where: V_int= Internal aqueous phase volume. V_ext= External aqueous phase volume. [F]_(int,final)= Final naproxen concentration in the internal aqueous phase. [F]_(ext,initial)= Initial naproxen concentration in the external aqueous solution.