Extraction of sulphuric acid with Alamine 308 using pseudo-emulsion based hollow fibre strip dispersion technique Shiva Agarwal, M. Teresa A. Reis ⇑ , M. Rosinda C. Ismael, Jorge M.R. Carvalho Centre for Natural Resources and the Environment and Centre for Chemical Processes, Department of Chemical Engineering, Instituto Superior Técnico, Universidade de Lisboa, Av. RoviscoPais, 1049-001 Lisboa, Portugal article info Article history: Received 15 December 2015 Received in revised form 10 March 2016 Accepted 16 March 2016 Available online 17 March 2016 Keywords: Sulphuric acid extraction Alamine 308 Pseudo-emulsion hollow fibre strip dispersion (PEHFSD) Liquid membranes abstract The extraction of sulphuric acid from aqueous solutions and its recovery as ammonium sulphate using pseudo-emulsion based hollow fibre strip dispersion technique was investigated. The tertiary amine Alamine 308 was used as an extractant in most experiments. The effects on the permeation of various parameters such as the flow rates and the composition of the membrane, strippant and feed phases were studied. The analysis of sulphuric acid transport was made on the basis of the overall mass transfer coef- ficient of permeation, the values being found in the range of 3  10 7 –5  10 6 m/s. The mass transfer resistances were also examined, the relative contribution due to the transport in the membrane being found quite significant. Ó 2016 Elsevier B.V. All rights reserved. 1. Introduction Sulphuric acid is a strong solubilising agent for metals like zinc, copper, nickel, chromium, etc., which justifies its wide application in several processes such as the leaching/decomposition of concen- trates/ores and surfaces treatments. Nowadays, as result of the high demands on metals, a large volume of effluents/wastewaters containing sulphuric acid is produced. The removal of sulphuric acid from these solutions is required in order to achieve the suit- able conditions for an efficient recovery of metals or to treat the wastewater making it suitable for discharge to the environment or reuse elsewhere in the process. The current practice of reducing the acid content of aqueous solutions involves the use of neutral- ization agents like lime. This process presents as main weaknesses the high consume of reagents, the formation of gypsum and a loss of sulphuric acid. A viable alternative could be the use of the sol- vent extraction technique with the possibility of reusing sulphuric acid or recovering it as a saleable product, like ammonium sul- phate. This technique may be associated with the conventional process and being accomplished in mixer-settlers/columns [1–5] or with liquid membrane technologies using hollow fibre contactor [6–9]. The liquid membrane configurations in hollow fibre mod- ules present the benefit of high surface area per unit volume besides other attractive features of liquid membranes like a low energy consumption, high diffusive/mass flux, and high selectivity, easy and economical procedure. The latest smart techniques with strip/organic dispersion methodologies, namely hollow fibre renewal liquid membrane (HFRLM) and pseudo emulsion hollow fibre strip dispersion (PEHFSD), couple the advantages of carrying out the extraction and stripping steps in a single contactor and overcome the problems of membrane stability [10,11]. A literature survey revealed that the most promising extrac- tants for sulphuric acid are the amines and the phosphine oxides. Kesieme et al. [12] carried out a detailed study on the extraction of acid from a feed solution containing 200 g/L of H 2 SO 4 by using TEHA (tris-2-ethylhexylamine), Alamine 336 (tri-octyl/decyl ami- nes) and Cyanex 923(hexyl/octyl phosphine oxides). The authors reported that the use of TEHA, Alamine 336 and Cyanex 923 allowed extracting, respectively, 88%, 91% and 50% of the sulphuric acid from aqueous solutions. In what concerns the percentages of stripping of sulphuric acid from loaded organic phases with deio- nised water it was possible to attain the values of 98% with TEHA, 11% with Alamine 336 and 95% with Cyanex 923. Other authors also highlighted the good performance of TEHA on sulphuric acid recovery [13–18]. Viljoen et al. [1] tested the use of Alamine 336 at pilot scale for the recovery of sulphuric acid from Anglo Platinium’s Base Metal Refinery nickel spent electrolyte (40 g/L H 2 SO 4 ). Using three extraction stages, the sulphuric acid can be recovered with 99% extraction efficiency and stripped with ammonia to yield a liquid liquor containing 300 g/L of (NH 4 ) 2 SO 4 . The production of http://dx.doi.org/10.1016/j.seppur.2016.03.031 1383-5866/Ó 2016 Elsevier B.V. All rights reserved. ⇑ Corresponding author. E-mail address: teresareis@tecnico.ulisboa.pt (M. Teresa A. Reis). Separation and Purification Technology 165 (2016) 10–17 Contents lists available at ScienceDirect Separation and Purification Technology journal homepage: www.elsevier.com/locate/seppur