Comparative impact of SiO₂ and TiO₂ nanofillers on the performance of thin‐film nanocomposite membranes

Abstract

Nanoparticle (NP) additions can substantially improve the performance of reverse osmosis and nanofiltration polyamide (PA) membranes. However, the relative impacts of leading additives are poorly understood. In this study, we compare the effects of TiO2 and SiO2 NPs as nanofillers in PA membranes with respect to permeate flux and the rejection of organic matter (OM) and salts. Thin‐film nanocomposite (TFN) PA membranes were fabricated using similarly sized TiO2 15 nm and SiO2 (10 – 20 nm) NPs, introduced at four different NP concentrations (0.01, 0.05, 0.2, and 0.5% w/v). Compared with PA membranes fabricated without NPs, membranes fabricated with nanofillers improved membranes hydrophilicity, membrane porosity, and consequently the permeability. Permeability was increased by 24 and 58% with the addition of TiO2 and SiO2, respectively. Rejection performance and fouling behavior of the membranes were examined with salt (MgSO4 and NaCl) and OM (humic acid [HA] and tannic acid [TA]). The addition of TiO2 and SiO2 nanofillers to the PA membranes improved the permeability of these membranes and also increased the rejection of MgSO4, especially for TiO2 membranes. The addition of TiO2 and SiO2 to the membranes exhibited a higher flux and lower flux decline ratio than the control membrane in OM solution filtration. TFN membranes' HA and TA rejections were at least 77 and 71%, respectively. The surface change properties of NPs appear to play a dominant role in determining their effects as nanofillers in the composite membrane matrix through a balance of changes produced in membrane pore size and membrane hydrophilicity.

Novel High Flux Poly(m-phenylene isophtalamide)/TiO2 Membranes for Ultrafiltration with Enhanced Antifouling Performance

“…The obtained data are also confirmed by the previous research, where it was shown that the addition of hydrophilic particles into the polymer matrix increased the stratification during membrane preparation due to increased thermodynamic instability [ 47 ], which resulted in membrane with higher porosity, pore radius, and surface porosity. This indicates that the addition of TiO 2 in PA modified the pore system of the membrane and changed its hydrophilicity and pore structure, causing an increase in membrane pure water and water solution permeability [ 29 ].…”

“…As membrane permeability (and thus surface pore size) increases compared to the pristine PA membrane, it may promote increased availability of the selective layer structure for the pollutant (coolant lubricant) facilitating its penetration inside the pores [ 49 ]. However, the optimal content of TiO 2 (0.3%) in the PA matrix forms a balance between surface hydrophilicity, roughness, and pore size of the membrane, maintaining high performance (fluxes) and FRR [ 29 ]. Despite the increase in surface hydrophilicity of the PA/TiO 2 (0.5 and 0.75 wt.%) membranes, their higher surface roughness compared to the PA and PA/TiO 2 (0.3 wt.%) membranes ( Table 1 ) caused an increase in the specific area of the selective layer for the adsorption of coolant lubricant molecules.…”

“…There are only a few works devoted to the application of composite polyamide/TiO 2 in membrane technology, particularly for the preparation of membranes for nanofiltration [ 27 , 28 , 29 , 30 , 31 , 32 ], reverse osmosis [ 33 , 34 , 35 , 36 , 37 , 38 ], pervaporation [ 39 ], and microfiltration [ 40 ]. In [ 27 , 28 , 29 , 30 ], the nanofiltration thin film nanocomposite (TFN) membranes based on PA were subjected to the modification with TiO 2 . The TFN PA membrane modified by TiO 2 was developed for improved salt rejection [ 27 ].…”

“…The GO nanosheets promoted solvent channels and TiO 2 provided super surface hydrophilic properties resulting in the formation of a permeable hydrophilic membrane with enhanced antifouling properties. The comparison of the effect of TiO 2 (15 nm) and SiO 2 (10–20 nm) as nanofillers in the TFN PA membrane in terms of flux and rejection of organic matter (humic and tannic acids) and salts (MgSO 4 and NaCl) was carried out in [ 29 ]. The permeability of modified PA membranes was increased by 24 and 58% with the incorporation of TiO 2 and SiO 2 , respectively.…”

Performance improvement of thin film nanocomposite membranes by covalently bonding with Janus porous hollow nanoparticles for nanofiltration applications

“…Furthermore, the preparation of nanocomposite membranes is easy to realize, subsequently reducing the cost for fabricating membranes. Diverse nanofillers have been incorporated into the separation layer of the thin film composite (TFC) nanofiltration membranes, including nonporous nanofillers (e.g., metallic oxide, 12,13 graphene oxide [GO], 14 organic fillers 15 ), porous nanofillers (e.g., metal organic frameworks (MOF), 16 covalent organic frameworks (COF), 17 porous organic polymers 18,19 ), and hollow nanomaterials (e.g., halloysite nanotubes, 20 carbon nanotubes, 21 and hollow polymeric nanoparticles 22 ). Janus nanoparticles used as nanofillers have been reported for gas separation membranes, 23 fuel cell membranes, 24 and ultrafiltration membranes, 25 while the study on nanofiltration membranes was limited.…”