Electrospun Nanostructured Membrane Engineering Using Reverse Osmosis Recycled Modules: Membrane Distillation Application

Abstract

As a consequence of the increase in reverse osmosis (RO) desalination plants, the number of discarded RO modules for 2020 was estimated to be 14.8 million annually. Currently, these discarded modules are disposed of in nearby landfills generating high volumes of waste. In order to extend their useful life, in this research study, we propose recycling and reusing the internal components of the discarded RO modules, membranes and spacers, in membrane engineering for membrane distillation (MD) technology. After passive cleaning with a sodium hypochlorite aqueous solution, these recycled components were reused as support for polyvinylidene fluoride nanofibrous membranes prepared by electrospinning technique. The prepared membranes were characterized by different techniques and, finally, tested in desalination of high saline solutions (brines) by direct contact membrane distillation (DCMD). The effect of the electrospinning time, which is the same as the thickness of the nanofibrous layer, was studied in order to optimize the permeate flux together with the salt rejection factor and to obtain robust membranes with stable DCMD desalination performance. When the recycled RO membrane or the permeate spacer were used as supports with 60 min electrospinning time, good permeate fluxes were achieved, 43.2 and 18.1 kg m−2 h−1, respectively; with very high salt rejection factors, greater than 99.99%. These results are reasonably competitive compared to other supported and unsupported MD nanofibrous membranes. In contrast, when using the feed spacer as support, inhomogeneous structures were observed on the electrospun nanofibrous layer due to the special characteristics of this spacer resulting in low salt rejection factors and mechanical properties of the electrospun nanofibrous membrane.

Modified Electrospun Membranes Using Different Nanomaterials for Membrane Distillation

“…These approaches may offer the direct formation of superhydrophobic ENMs with special morphologies, ultimately yielding high flux and better MD performance with self-cleaning membrane characteristics [ 97 ]. Recycled RO membranes, RO feed spacers and RO permeate spacers from discarded RO membrane modules have been used as ENM supports for the MD process and compared to the performance by Jorge et al [ 159 ]. ENMs fabricated from recycled plastics have not yet been employed for MD process testing.…”

Research Progress of Water Treatment Technology Based on Nanofiber Membranes

“…In this system, water transport is divided into three steps: absorption to the membrane surface, diffusion through the thickness of the membrane, and desorption from the permeate surface of the membrane. RO needs to be driven by applying a pressure greater than the osmotic pressure of the solution during operation, resulting in a positive pressure difference to produce a chemical potential difference (concentration gradient) across the membrane, which makes the liquid cross the membrane against the natural direction of osmosis, while the salts are retained on the influent surface of the membrane [ 89 , 90 ]. Therefore, RO can be used to purify saltwater to produce fresh water on the low-pressure side of the membrane.…”

“…Therefore, RO can be used to purify saltwater to produce fresh water on the low-pressure side of the membrane. RO technology has been increasing globally and has gradually replaced the conventional distillation method [ 89 , 90 , 91 ].…”

Recycled Synthetic Polymer-Based Electrospun Membranes for Filtering Applications

“…[20]; fibers can be functionalized before, during, and after spinning [2,21]. Electrospun materials could be used in wide application range such as packaging [22], wound healing [23], tissue engineering [24], drug-releasing systems [25], membranes [26], sensors [27], batteries [28], solar cells [29], supercapacitors [30], catalysts [31], environmental remediation [32], protecting clothing [33], and in many others. Due to all the mentioned advantages, electrospinning is the primary choice for fabricating nanomaterials.…”