Silica scaling in forward osmosis: From solution to membrane interface

Abstract

14Membrane silica scaling hinders sustainable water production. Understanding silica 15 scaling mechanisms provides options for better membrane process management. In this study, 16we elucidated silica scaling mechanisms on an asymmetric cellulose triacetate (CTA) membrane 17 and polyamide thin-film composite (TFC) membrane. Scaling filtration showed that TFC 18 membrane was subjected to more severe water flux decline in comparison with the CTA 19 membrane, together with different scaling layer morphology. To elucidate the silica scaling 20 mechanisms, silica species in the aqueous solution were characterised by mass spectrometry as 21 well as light scattering. Key thermodynamic parameters of silica surface nucleation on the CTA 22 and TFC membranes were estimated to compare the surface nucleation energy barrier. In 23 addition, high resolution X-ray photoelectron spectroscopy resolved the chemical origin of the 24 silica-membrane interaction via identifying the specific silicon bonds. These results strongly 25 support that silica scaling in the CTA membrane was driven by the aggregation of mono-silicic 26 acid into large silica aggregates, followed by the deposition from bulk solution onto the 27 membrane surface; by contrast, silica polymerised on the TFC membrane surface where mono-28 silicic acid interacted with TFC membrane surface, which was followed by silica surface 29 polymerisation. 30 31 32 33

Emerging forward osmosis and membrane distillation for liquid food concentration: A review

“…Organic fouling is due to the deposition of colloidal particles and organic matters such as polysaccharides (Gu, Wang, Wei, & Tang, 2013;Gryta, 2008), humic acid (Linares et al, 2012;Khayet, Velázquez, & Mengual, 2004), and proteins (Gu et al, 2013;Cheng, Han, Hwang, Ho, & Cooper, 2010). Inorganic fouling is caused by the deposition of inorganic colloidal particles and particulates and/or crystallization or precipitation of hard mineral salts from the feed such as calcium carbonate (Li et al, 2015;Curcio et al, 2010) and silicate (Xie, & Gray, 2017;Karakulski, & Gryta, 2005). And biological fouling is caused mainly by microorganisms such as bacteria (Yoon, Baek, Yu, & Yoon, 2013;Gryta, 2002), fungi (Gryta, 2002), and algae (Zou et al, 2013).…”

A Review of Fouling Mechanisms, Control Strategies and Real-Time Fouling Monitoring Techniques in Forward Osmosis

“…When the concentration of these salts in the feed exceeds their solubility at higher water recovery rates, precipitation may occur near or on the membrane surface, leading to scaling of the membrane surface and flux decline [44,45]. Amongst the various scaling compounds reported in the literature are silica, calcium carbonate, gypsum and calcium sulphate [45][46][47][48][49][50].…”

“…Several studies have investigated silica scaling in forward osmosis [45,46]; but literature on silica scaling and cleaning behaviour is rather limited [27]. Mi and Elimelech [45] investigated silica scaling and cleaning behaviour in forward osmosis.…”

“…A recent publication by Xie and Gray [46] also shows the impact of silica scaling on cellulose triacetate (CTA) and thin-film composite (TFC) membranes. The study concluded that the silica scaling mechanisms on the CTA and TFC membranes were largely different.…”

“…The CTA membrane was more resistant to silica scaling and exhibited a gradual flux decline compared to the TFC membrane. The TFC membrane is characterized by a high density of carboxylic acid functional groups, which leads to its high fouling propensity [46]. The presence of dipoles in carboxylic functional groups allows easy participation in favourable hydrogen bonding interactions [52].…”