Q2. What have the authors contributed in "A novel dual-layer bicomponent electrospun nanofibrous membrane for desalination by direct contact membrane distillation" ?
In this paper, a triple-layer membrane composed of a PVDF nanofiber layer, a polyethylene terephthalate ( PET ) support layer was investigated on its performance in air gap membrane distillation ( AGMD ).
Q3. What are the main reasons for the pore wetting?
Some reports have indicated that support layers that are thick, less hydrophobic, and with big pore sizes could lead to pore wetting [13].
Q4. What is the effect of the membrane on the flux performance?
The improvement in flux performance for dual-layer membranes is attributed to: (a) increased top surface hydrophobicity, thereby decreasing the potential wetting of the membrane; (b) higher porosity of the top surface which increases the available surface area for evaporation; (c) and the structure of thinner more hydrophobic surface layer (i.e., PH) (DL2) and thicker less hydrophobic layer (i.e., PAN), which decreases the mass transfer resistance [23].
Q5. What is the common method of forming nanofibers?
Electrospinning involves the use of high electric fields applied on a polymer solution forming elongated and stretched nanofibers and collected on a grounded collector.
Q6. What are the two types of membranes that were fabricated?
There are two kinds of dual-layer membranes that were fabricated: 50/50 PH-PAN and 25/75 PH-PAN referred herein as DL1 and DL2 membranes, respectively.
Q7. Why did Bonyadi and Chung use a dual-layer hollow fiber membrane?
The authors used PVDF-co-HFP because it was reported to have superior hydrophobicity and high free volume compared to PVDF [18]; while PAN has good mechanical and thermal stability, and excellent solvent resistance, and is commonly used for microfiltration and ultrafiltration applications.
Q8. What is the effect of the continuous overlapping of nanofibers?
The continuous overlapping of the nanofibers forming layers upon layers of fibers results to interconnected pores throughout the depth of the membrane.
Q9. What is the effect of beads on the membrane?
the presence of some beads-on-string has added to the roughness of the membrane [22], thus enhancing its hydrophobicity.
Q10. What is the way to improve the DCMD flux performance?
(5) Further optimization of the membranes needs to be carried out by altering the different electrospinning parameters to improve the DCMD flux performance and salt rejection.
Q11. How was the thickness of the membrane controlled?
The thickness of the different membrane layers were controlled by manipulating the electrospinning time duration between 1.5 and 6 h.
Q12. What is the way to improve the flux performance of the dual-layer membrane?
(3) Through DCMD tests, the dual-layer PVDF-co-HFP/PAN with 25/75 thickness ratio showed the highest permeate flux of 30 LMH using 35 g L 1 NaCl feed solution.
Q13. What was the final flux value of the PTFE membrane?
DW and 35 g L 1 NaCl solutions werercialized flat-sheet membrane in DW water as feed, and (b) final flux values of the erature = 60 C, flow rate = 400 ml min 1; permeate: inlet temperature = 20 C, flowused as feed.
Q14. How was the electrical conductivity of the solutions monitored?
The electrical conductivity of the solutionswere constantly monitored using a portable conductivity meter (HQ40d, Hach), and the change in weight of the permeate solution was automatically recorded through a data acquisition system attached to the digital balance (PGW 4502e, Adam) throughout the duration of the test.
Q15. What is the reason for the high LEP of PTFE membrane?
The high LEP of PTFE membrane is mainly attributed to its small average pore size and smaller surface area for penetration (many dense areas) as observed on its morphological structure in Fig. S3a (SI).
Q16. What is the pore size of the PVDF-co-HFP nanofibers?
The following can be deduced from this study:(1) The PVDF-co-HFP nanofibers showed highly porous structure ( 90% porosity) with interconnecting pores.