| 1. |
- Khaliha, Sara, et al.
(author)
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Defective graphene nanosheets for drinking water purification : Adsorption mechanism, performance, and recovery
- 2021
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In: FlatChem. - : Elsevier. - 2452-2627. ; 29
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Journal article (peer-reviewed)abstract
- Defect-rich graphene oxide (dGO) was used as sorbent for organic contaminants of emerging concern in tap water, including drugs and dyes, and the performance compared to those of lower-defects graphene types. The role of holes and carbonyl- carboxylic groups on graphene nanosheets surface on the adsorption mechanism and efficiency was investigated. dGO showed enhanced adsorption capacity toward two fluoroquinolone antibiotics (ofloxacin, OFLOX, and ciprofloxacin, CIPRO) in tap water with a maximum capacity of 650 mg/g, compared to 204 mg/g for Hummers derived commercial GO (hGO) and 125 mg/g for less defected Brodie derived GO (bGO) for OFLOX. The role of defects on the selective adsorption of OFLOX was also modelled by MD simulations, highlighting a mechanism mainly driven by the shape complementarity between the graphene holes and the molecules. Adsorption isotherms revealed different adsorption model for dGO, with a Langmuir fitting for dGO and BET fitting for all the other investigated samples. The maximum adsorption capacity of dGO for OFLOX was about six times higher than that of Granular Activated Carbon (95 mg/g), the industrial adsorption standard technology. Finally, it was also demonstrated that dGO can be recovered from treated water by ultrafiltration, this preventing secondary contamination risks and enabling safe use of graphene nanosheets for water purification.
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| 2. |
- Khaliha, Sara, et al.
(author)
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Upcycling of plastic membrane industrial scraps and reuse as sorbent for emerging contaminants in water
- 2024
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In: Environmental Science: Water Research and Technology. - 2053-1419 .- 2053-1400. ; 10:5, s. 1097-1107
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Journal article (peer-reviewed)abstract
- Scraps obtained as waste of the industrial production of polysulfone and polysulfone-graphene oxide hollow fiber membranes (PSU-HF and PSU-GO-HF, respectively) were converted into granular materials and used as sorbents of several classes of emerging and standard water contaminants, such as drugs, heavy metal ions, and a mixture of per- and poly-fluoroalkyl substances (PFASs). The millimetric sized granules (PSU and PSU-GO, respectively) outperformed granular activated carbon (GAC), the industrial sorbent benchmark, in the adsorption of lead, diclofenac, and PFOA from tap water. Adsorption mechanism insight was achieved by molecular dynamics simulations, demonstrating the key role of graphene oxide (GO) on PSU-GO material performance. With respect to GAC, PSU-GO adsorption capacity was two times higher for diclofenac and PFOA and ten times higher for lead. Material safety was assessed by surface enhanced Raman spectroscopy, excluding GO nanosheets leaching, and combined potability test. Overall, our work proves that scrap conversion and reuse is a valuable strategy to reduce plastic industrial waste disposal and to integrate standard technology for enhanced water purification.
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| 3. |
- Kovtun, Alessandro, et al.
(author)
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Core-shell graphene oxide-polymer hollow fibers as water filters with enhanced performance and selectivity
- 2021
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In: Faraday Discussions. - : Royal Society of Chemistry (RSC). - 1359-6640 .- 1364-5498. ; 227, s. 274-290
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Journal article (peer-reviewed)abstract
- Commercial hollow fiber filters for micro- and ultrafiltration are based on size exclusion and do not allow the removal of small molecules such as antibiotics. Here, we demonstrate that a graphene oxide (GO) layer can be firmly immobilized either inside or outside polyethersulfone-polyvinylpyrrolidone hollow fiber (Versatile PES (R), hereafter PES) modules and that the resulting core-shell fibers inherits the microfiltration ability of the pristine PES fibers and the adsorption selectivity of GO. GO nanosheets were deposited on the fiber surface by filtration of a GO suspension through a PES cartridge (cut-off 0.1-0.2 mu m), then fixed by thermal annealing at 80 degrees C, rendering the GO coating stably fixed and unsoluble. The filtration cut-off, retention selectivity and efficiency of the resulting inner and outer modified hollow fibers (HF-GO) were tested by performing filtration on water and bovine plasma spiked with bovine serum albumin (BSA, 66 kDa, approximate to 15 nm size), monodisperse polystyrene nanoparticles (52 nm and 303 nm sizes), with two quinolonic antibiotics (ciprofloxacin and ofloxacin) and rhodamine B (RhB). These tests showed that the microfiltration capability of PES was retained by HF-GO, and in addition the GO coating can capture the molecular contaminants while letting through BSA and smaller polystyrene nanoparticles. Combined XRD, molecular modelling and adsorption experiments show that the separation mechanism does not rely only on physical size exclusion, but involves intercalation of solute molecules between the GO layers.
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| 4. |
- Zambianchi, Massimo, et al.
(author)
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Graphene oxide-polysulfone hollow fibers membranes with synergic ultrafiltration and adsorption for enhanced drinking water treatment
- 2022
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In: Journal of Membrane Science. - : Elsevier BV. - 1873-3123 .- 0376-7388. ; 658
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Journal article (peer-reviewed)abstract
- Polysulfone-graphene oxide hollow fiber membranes (PSU-GO HFs) with simultaneous adsorption and ultrafiltration capabilities are herein described and proposed for enhanced and simplified Point-of-Use (POU) drinking water purification. The PSU-GO HFs were prepared by phase inversion extrusion by a customized semi-industrial plant and their morphology, surface properties, and porosity were investigated by combined Scanning Electron Microscopy (SEM), contact angle and Raman confocal microscopy, in relation to different GO:PSU ratios (1–5% w/w GO vs PSU) and to the final adsorption-ultrafiltration properties. Filtration modules of PSU-GO HFs of filtering surface (FS) in the range 0,015–0,28 m2 showed same ultrafiltration capability of PSU-HF standard filters. Synergic adsorption properties were demonstrated by studying the adsorption maximum capacity of ciprofloxacin antibiotic (CIPRO) vs GO ratio in dead end in-out configuration, the standard configuration used for PSU HFs commercial modules. Loading of 3,5% GO vs PSU was selected as case study, representing the best compromise between performance and GO nanofiller amount. Heavy metals (Pb, Cu and Cr(III)) and polyfluoroalkyl substances (PFAS) removal capabilities from tap water were competitive and in some cases outperformed Granular Activated Carbon (GAC), the standard industrial sorbent. Ciprofloxacin removal from tap water was also under real operational conditions. Moreover, release of GO from working PSU-GO modules was excluded by Surface Enhanced Raman Spectroscopy (SERS) analysis of treated water having the state-of-the-art limit of quantification of 0.1 μg/L for GO nanosheets.
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