Carbon nanotube-immobilized super-absorbent membrane for harvesting water from the atmosphere

Abstract

25This paper describes the development of a carbon nanotube (CNT) immobilized membrane for 26 harvesting pure water from air. The CNTs were incorporated into a layer of super absorbing 27 poly(acrylamide-co-acrylic acid) which was cast over a porous hydrophilized polypropylene 28 support. The super absorbing polymer tended to bind to the water molecules to form water 29 clusters. The incorporation of CNTs led to the interruption of specific water-polymer as well as 30 water-water interactions to generate more free water which permeated more easily through the 31 membrane. The CNTs were functionalized with carboxylic groups to improve the dispersibility 32 into the polymer matrix. The water vapor extraction efficiency reached over 50%, and the 33 presence of CNTs led to an enhancement in water vapor removal by as much as 45% and in mass 34 transfer coefficient by 44%. 35 36 Water impact: 37 Recent climatic changes, fairly widespread drought and extensive water use are drawing the world 38 into a state of water scarcity. This forces us to look for engineered water sources by conventional 39 methods such as desalination, and also to look for unconventional sources. On-site water generation 40 by extracting water vapor from air via permeating through a polymeric membrane is an attractive 41 alternative approach for generating pure water. Carbon nanotubes (CNTs) immobilized in a 42 membrane containing super absorbent polymer is presented as an effective method to sorb water and 43 then break up water clusters for high permeation flux. Besides addressing the important application 44 of generating drinking water from air, this development opens the door for many other humidity 45 control applications.46 47The supply of potable water all over the world is a growing challenge. To help alleviate 49 this burden, on-site water treatment such as distillation, reverse osmosis (RO) and waste water 50 recycling systems are being developed 1-7 . Besides the methods mentioned above, on-site water 51 generation systems that extract water vapor from air have been developed. The removal of water 52 vapor from gaseous streams also has many industrial applications which include the dehydration 53 of natural and flue gases, the drying of compressed air and the storage of fruits and vegetables 54 under protective atmosphere 8, 9 . In addition, humidity control in closed spaces such as air 55 conditioning in buildings, aviation and space flight are of major importance 10 . 56 Several approaches to water vapor extraction from air to produce clean water have been 57 studied 11-14 . Typical methods of water extraction include cooling and refrigeration, liquid and 58 solid desiccants, and compression. However, these conventional techniques possess inherent 59 disadvantages; for example the condensed water can be contaminated, and desiccant systems 60 involve energy inefficient regeneration steps and may have to be discarded after several uses 15-17 . 61 Selective water vapor transport through polymeric membranes is an attractive approach 6...

Ultrabreathable and Protective Membranes with Sub‐5 nm Carbon Nanotube Pores

“…Contrary to our work, water vapor transport was impeded by a combination of capillary condensation, reverse capillary flow, and rejection/removal at the superhydrophobic MWNT tips . Others have immobilized CNTs on the pores of hydrophobic membranes or into super‐absorbing polymers for application in membrane distillation/pervaporation and water‐vapor harvesting from the atmosphere, respectively. While addition of CNTs improved fluxes in these polymeric membranes, the presence of parallel transport pathways (through the polymer matrix, the tube/polymer interface, and the CNTs) and of other contributing factors did not permit to quantify the flow rate of water vapor inside CNTs.…”

Bundled-firewood like AlOOH-CaCl 2 nanocomposite desiccant

“…Higher the RH, faster the adsorption is ( Figure S7 of SI). This is expected and in agreement with published data [45]. The effect of temperature on the adsorption capacity of BFWLAND is shown in Figure 5C.…”

Immobilization of Graphene Oxide on the Permeate Side of a Membrane Distillation Membrane to Enhance Flux

“…Several hydrophobic polymers, including polytetrafluoroethylene (PTFE), polypropylene (PP), and polyvinylidene difluoride (PVDF) have been utilized as membrane materials [ 9 , 21 , 22 , 23 ], and different methods have been employed for the synthesis and modification of these membranes to improve the performances [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 ]. Nanotechnology has enabled the development of advanced membranes based separation techniques [ 18 , 24 , 26 , 29 , 31 , 32 , 33 , 34 , 35 , 37 , 38 , 39 ]. Nanomaterials (NMs), such as Fe 3 O 4 , TiO 2 , SiO 2 , carbon nanotubes (CNTs), nanodiamonds (NDs), and graphene oxide (GO) have been incorporated via blending or coating method to improve the membrane efficiency [ 10 , 18 , 24 , 32 , 33 , 34 , 35 , 39 , 40 , 41 , 42 ], and different functionalized CNTs were used to fabricate a bilayered structures that have shown significant enhancement in flux [ 32 ].…”