Recent advances in pervaporation hollow fiber membranes for dehydration of organics

Highlights

• Hollow fiber membranes display important advantages respect to the flat-sheet ones.

• The advent of hollow fibers in pervaporation dates back to 90s.

• The dehydration of organics by PV using hollow fibers is a very attractive field.

• Impressive pervaporation performance can be achieved using different strategies.

Abstract

Pervaporation (PV) has been potentially identified as a candidate in replacing the conventional distillation since it possesses the ability to separate azeotropic solvent mixtures. At a large scale, PV has been mainly involved within hybrid processes for the dehydration of organics toward their purification. Considering that the membrane is the primary separation barrier, “membranologists” are currently seeking for suitable membranes that can be effective for industrial applications. In this regard, due to its minimal fouling and large effective surface area, hollow fiber configuration is recognized as the most advantageous geometry in comparison with flat sheet or tubular modules. Therefore, the goal of this review paper is to provide an outlook on the studies available so far focusing on the use of hollow fiber membranes for the dehydration of organics by PV. By fully reviewing the literature, the main attention is paid to such works that release relevant insights into new membrane concepts and their performance, together with some brief fundamentals of PV technology. The concluding remarks, future trends and recommendations to the new researchers are also given.

Introduction

Pervaporation (PV) is a membrane-based separation technique identified as a potential candidate to replace distillation process. PV was, for the first time, introduced by Kober in 1917, who found out the selective permeation of water from albumin and toluene aqueous solutions using films (Wang et al., 2013). Since such period, PV was initiated to be explored until achieving today its industrial establishment according to the implementation by membrane manufacturers and operation of pervaporation-hybrid processes. PV is capable to break the azeotropic point of plentiful types of solvent mixtures, including organic–organic, water–organic or organic–water (Castro-Muñoz et al., 2019a, Castro-Muñoz et al., 2019b, Castro-Muñoz et al., 2019c, Castro-Muñoz et al., 2019d, Castro-Muñoz et al., 2019e). Nevertheless, the primary usage of this technique deals with the removal of water from organic solvents. Thereby, PV membranes are firstly proposed in separating several types of binary water–organic model solutions at azeotropic concentrations, such as water–ethanol (Castro-Muñoz et al., 2019a, Castro-Muñoz et al., 2019b, Castro-Muñoz et al., 2019c, Castro-Muñoz et al., 2019d, Castro-Muñoz et al., 2019e, Kudasheva et al., 2015), water–isopropanol (Han et al., 2014), water–acetone (Mangindaan et al., 2014), water–butanol, water–acetic acid (Badiger et al., 2014), water–N,N-dimethylformamide, water–N,N-dimethylsulfoxide, water–N,N-dimethylacetamide, water–hydrogen peroxide (Ong et al., 2016), water–ethylene glycol (Zhang et al., 2017), water–N-methyl-2-pyrrolidone (Prasad et al., 2016), water–tetrahydrofuran (Han et al., 2015), among others. It is worth to mention that PV finds its industrial establishment for solvent purification (i.e. dehydration of isopropanol and ethanol) and other integrated PV production process (Castro-Muñoz et al., 2018b, Luis and Van Der Bruggen, 2015).

At lab scale, flat-sheet configuration membranes are the most diffused ones in PV applications; however, they are not considered as the most suitable geometry for large scale processes. Hollow fiber modules are more advantageous and thus preferred than flat sheet since fibers are less prone to be fouled and second, they display a larger effective surface area to volume ratios, which allow to obtain high productivities in terms of permeation. In this way, hollow fiber membranes are preferred at industrial scale when compared to the flat sheet and tubular membranes due to the fact that low fouling tends to provide them a longer life and the greater area to volume ratio provides high packing densities (Purkait et al., 2018). Therefore, the current review aims to provide a compelling literature survey on the use of hollow fiber membranes for the dehydration of organics, illustrating the different types of membrane materials used and preparation protocols. In addition, for the new readers in the field, fundamentals of PV technology are provided. Emblematic studies in the field are addressed exhibiting the most relevant concepts of hollow fiber membranes, as well as their insights in the dehydration of organics. According to the current ongoing development researches, the concluding remarks, future trends and recommendation are also addressed.