![Fig. 7. Schematic illustration of surface and bulk crystallization (adopted from [16])](/figures/fig-7-schematic-illustration-of-surface-and-bulk-3c0ei1r3.webp)
![Fig. 13. Water cost breakdown for BWRO and SWRO [464]](/figures/fig-13-water-cost-breakdown-for-bwro-and-swro-464-1ilbucef.webp)
![Fig. 14. Percentage of energy consumption in SWRO. Data from [461] and [467]](/figures/fig-14-percentage-of-energy-consumption-in-swro-data-from-o2967wb6.webp)
![Fig. 4. Plate and frame membrane module (adopted from [104])](/figures/fig-4-plate-and-frame-membrane-module-adopted-from-104-iurm97ge.webp)
Q2. What is the viable technique to characterize the internal structure of RO membranes?
the free volume cavities in the membrane can be studied using positron annihilation spectroscopy (PAS) which is the most viable technique to characterize the internal structure of RO membranes [114,118,127–131].
Q3. What is the main factor contributing to the enhancement of chlorine resistance?
The use of aromatic diamine with a mono CH3 substituent at the ortho position was believed to be the main factor contributing to the enhancement of chlorine resistance.
Q4. What are the common cleaning methods used for RO membranes?
Acids (e.g. citric acid, hydrochloric acid, nitric acid, and sulfuric acid) and alkaline (e.g. sodium hydroxide) chemicals are usually used for RO membrane cleaning, where organics and biofilms are removed using the alkaline chemicals whereas scaling is removed using the acid agents.
Q5. What is the common type of colloidal fouling?
During colloidal fouling, the colloids present in the feed are driven from the bulk to the membrane surface as a result of permeate flow resulting in formation of a cake layer.
Q6. What is the effect of secondary pore-forming on the performance of TFC membranes?
The secondary pore-forming method resulted in an increased substrate porosity and, consequently, increased flux of the resulting TFC membranes.
Q7. What are the factors that get neglected when quoting the total water price?
Factors that often get neglected when quoting the total water price are subsidization for the energy or the water price for the consumer, inflation rates, distribution cost, financing cost, and overall cost for desalinated water supply at the consumer’s tap.
Q8. What are the benefits of improved membrane performance?
Improved membrane performance also leads to decreased need for chemical use, improved membrane life, and increased capacity to work at higher pressure.
Q9. What are the three common nonporous transport models?
Common nonporous transport models include the solution-diffusion (SD) model, the extended solutiondiffusion (ESD) model, and the solution-diffusion-imperfection (SDI) model.
Q10. What is the effect of zeolite nanoparticles on the membrane flux?
In general, zeolite nanoparticles can improve the flux of RO membranes without significant compromise in the salt rejection by providing favorable flow channels for water molecules.
Q11. What is the recent study on the synthesis of barrier layer in PA TFC membranes?
Recent studies have focused on the aqueous and hydrocarbon solution chemistry and properties involved in the IP technique used for the synthesis of barrier layer in TFC membranes.
Q12. How did Ma and Afonso develop a finite element model for CP?
In order to account for spacerfilled channel, Ma et al. [64] developed a finite element model for CP in spiral wound RO membranes.
Q13. What is the effect of additives on the performance of TFC membranes?
Such additives can alter the monomer diffusion rate and dissolution and, consequently, effect the performance of the resulting TFC membranes [253].
Q14. What is the effect of a nanofiller on the RO membrane?
considerable attention has been given to the use of nanofillers (nanoparticle additives) in the synthesis of RO membranes in order to enhance the membrane performance and thermal, chemical, and mechanical stability.
Q15. What is the role of the pore size in the performance of TFC membranes?
The pore size/porosity of the substrate plays an important role in determining the performance characteristics of TFC RO membranes [272].
Q16. What is the importance of the equilibrium between boron and boric acid in RO membranes?
The importance of this equilibrium is that borate ion is much easier to remove in RO membranes (95% rejection) compared to boric acid (~50% rejection).
Q17. What is the main challenge related to the utilization of the polyamide RO membranes?
Another key challenge related to the utilization of the polyamide RO membranes is the fast degradation and disintegration of the membranes in the presence of chlorine (one of the most common disinfectants in water treatment systems).
Q18. What is the main research line in RO membrane cleaning?
one of the main research lines is directed heavily into attaining a better comprehension of the RO membrane fouling and cleaning mechanisms in order to develop and enhance the membrane fouling preventative measures [382].
Q19. How much permeate gain can be achieved by single and double axis continuous tracking?
Ahmad et al. [492] reported that the yearly permeate gain made by single and double axis continuous tracking PV panels can be up to 60%.
Q20. Why was the TSB model recommended for CP predictions in practical RO processes?
As a result, due to its relative simplicity, the TSB model with plug flow was recommended for CP predictions in practical RO processes.
Q21. What is the name of the new on-line fouling monitor?
a novel on-line flow simulator known as the feed fouling monitor (FFM) was developed for estimating colloidal fouling propensity [162,163].