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Membrane Fouling and Scaling in Reverse Osmosis
Published in Andreas Sapalidis, Membrane Desalination, 2020
Nirajan Dhakal, Almotasembellah Abushaban, Nasir Mangal, Mohanad Abunada, Jan C. Schippers, Maria D Kennedy
Precipitation usually occurs when the ionic product of a certain salts exceeds the solubility product (Antony et al. 2011). Therefore, scaling is directly related to the concentrations of inorganic ions in the feedwater and to the recovery (ratio of the permeate water to the feedwater) of the RO system. At higher recovery, the concentrate water in the last stage becomes more concentrated and, therefore, in many cases, exceeds the solubility limit for several types of salts, resulting in scaling (Kucera 2015). Therefore, the concentration factor is calculated as in Equation 12.9: CF=CcCf where, Cc = concentration in concentrate (brine); and Cf = concentration in feed water
Electromembrane Processes in Water Purification and Energy Generation
Published in Sundergopal Sridhar, Membrane Technology, 2018
Sujay Chattopadhyay, Jogi Ganesh Dattatreya Tadimeti, Anusha Chandra, E. Bhuvanesh
On the concentrate side, solute concentration is higher at membrane surface and drops in bulk, but, in the diluate compartment, the bulk concentration is higher than the concentration at membrane surface. Once concentration of salt present in a solution exceeds the solubility product value, the salt precipitates over the membrane surface which increases membrane resistance due to fouling. Thus, membrane performance (F. Li et al., 2005; Balster, 2006; Lee et al., 2006) drops. For industrial application, fouling is eliminated through precipitation and is commonly addressed by periodic reversing of the electrode polarities with consequent alteration of concentrate and diluate flow channels.
Synthesis and properties of sodium isotridecyl polyoxyethylene ether sulfate with different ethylene oxide addition numbers
Published in Journal of Dispersion Science and Technology, 2022
Penghui Li, Shengti Cao, Yueqing Huo, Xiaochen Liu
The tolerance of anionic surfactants to salt or alkali plays a key role in practical applications, such as industrial cleaning, separation process based on oil field or improving oil recovery. Generally, when the content of salt or alkali in the surfactant solution reaches a certain critical value, the micelle structure is destroyed and salting out occurs, and the surfactant will not play its effective role.[41] Therefore, the development of surfactant products with good alkali/salt resistance will help to expand its application range. The transmittance at 500 nm was recorded for 1.0 g/L iC13EOnS solutions containing different NaOH, NaCl, CaCl2, and MgCl2 concentrations, as shown in Figure 9a–d. The results show that with more EO, whether it is NaOH, NaCl, CaCl2, or MgCl2, the greater the concentration required to change the light transmittance, the better the alkali resistance and salt resistance. For ionic surfactant, when the product of its activity and counter ion activity is equal to the solubility product of the salt formed by the surfactant and counter ion, the salt formed begins to precipitate. When EO unit is included in the molecular structure, the solubility of the product can be increased, so the solubility product is high. When the surfactant activity in the solution is similar, the counter ion activity required for precipitation is greater, so the iC13EOnS with more EO number shows better alkali/salt tolerance (Figure 10). [42]
Recovery and reuse of alginate in an immobilized algae reactor
Published in Environmental Technology, 2021
Olga Murujew, Rachel Whitton, Matthew Kube, Linhua Fan, Felicity Roddick, Bruce Jefferson, Marc Pidou
Visual observation of the beads exposed to the three test dissolution solutions revealed obvious differences (Supporting information, Figure S1). For NaCl, no observable dissolution occurred within 150 min with slight changes in the size of the beads observed at 30 and 40 min, including a swelling of the beads after 40 min. In the case of Na2CO3, the beads started dissolving after 30 min and were completely dissolved after 40 min. However, in conjunction with the dissolution process, an increase in turbidity of the solution was apparent. The formation of a precipitate is congruent with the formation of calcium carbonate due to the ion activity product of calcium carbonate (0.09 mol2/L2) being greater than the solubility product of CaCO3 (3.31 × 10−8 mol2/L2 [16]). In contrast, dissolution using sodium citrate was observably rapid and did not result in any formation of precipitates. The beads began to become visually smaller after 10 min and were fully dissolved after 20 min. During the dissolution tests, pH decreased from 7 to 6 when using Na-citrate and it increased to 12 with Na2CO3 due to the alkaline nature of carbonate.
Optimization study of sodium hydroxide consumption in the coal demineralization process
Published in Mineral Processing and Extractive Metallurgy Review, 2018
A. Aditya, A. Suresh, S.K. Sriramoju, P.S. Dash, S. Pati, N.P.H. Padmanabhan
With the increase in alkali concentration, more silica and alumina come into solution in the form of ions. When the concentration of ions exceeds the solubility product (the product of molality of silicate and aluminate ions at equilibrium), sodium aluminosilicates (sodalite) start precipitating. Owing to more dissolution of silica and alumina from the coal matrix, the formation of sodalite increases with increase in NaOH concentration. Equilibrium concentrations of silicate and aluminate ions in the alkali filtrate after leaching increases with increase in alkali concentration (Park and Englezos 1999). Experimentally also, it was seen that an equilibrium concentration of silicate and aluminate ions increases with increase in alkali concentration (Table 6). Increase in equilibrium concentration of ions results in increased solubility product of sodalite formation.