Covalently linked graphene oxide/reduced graphene oxide-methoxylether polyethylene glycol functionalised silica for scavenging of estrogen: Adsorption performance and mechanism. (May 2020)

• Record Type: Journal Article
• Authors: Akpotu, Samson O.; Lawal, Isiaka A.; Moodley, Brenda; Ofomaja, Augustine E.
• Is Part Of: Chemosphere. Volume 246(2020)
• Publication Date: 2020-05
• Subjects: 17β-estradiol -- Adsorption -- Polyamide carbonic groups -- Reduced graphene oxide -- Methoxylether polyethylene glycol -- Hydrophobicity -- Wastewater treatment; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.125729
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Water pollution by pharmaceuticals is a global issue and its remediation is important. To overcome this, we synthesised super hydrophobic nanoporous 3-dimensional ordered nanomaterials with multi-functional binding chemistry for highly efficient adsorption of estrogen (17β-estradiol). Graphene oxide (GO) was synthesised via Tours method and methoxylether polyethylene glycol (mPEG) was covalently introduced onto GO surface via facile amidation mild process to give GO-mPEG. GO-mPEG was anchored on nanoporous SBA-15 and homogenously reduced in-situ to SBA-rGO-mPEG. XRD analysis confirmed successful synthesis of SBA-15 and cross-linked GO/rGO-mPEG on SBA-15 surface. Image analysis revealed the architecture of SBA-15 as porous 3-dimensional silica network and presence of interwoven/crosslinked thin-films of GO-mPEG on SBA-15 surface. EDX mapping/elemental analysis showed expected elements were present. FTIR and textural analysis revealed the presence of different functional groups and high surface area as well as porosity, respectively. Optimal molar ratio experiments showed that 0.5SBA-rGO-mPEG had the highest sorption capacity. The relatively large surface area, 3-dimensional nanoprous silica structure and excess of polyamide/amido-carbonic functional groups on nanocomposites were suited for adsorption of 17β-estradiol. Equilibrium time was 30 min and effect of pH on adsorption was negligible. Sorption kinetic process of SBA-rGO-mPEG suited the pseudo-second-order model and equilibrium data fitted both Freundlich and Langmuir models. Qm values of 57.1, 78.5, 102.6 and 192.3 mg/g was recorded for SBA-GO, 0.1SBA-rGO-mPEG, 0.25SBA-rGO-mPEG and 0.5SBA-rGO-mPEG, respectively. H-bond, hydrophobic and π−π interactions were the sorption mechanism of SBA-rGO-mPEG after detailed analysis of data. Adsorbents was regenerated/re-used after 4 cycles with high remediation from environmental/real water samples. Highlights: Novel hydrophobic amido-carbonic groups from mPEG was covalently introduced to GO/SBA-15 surface. 3-dimensional SBA-rGO-mPEG had high sorption capacity and fast removal for 17β-estradiol. Maximum adsorption capacity of 17β-estradiol onto 0.5SBA-rGO-mPEG was 192.3 mg/g at pH 4 and 25 °C. Regenerated SBA-rGO-mPEG-performed excellently in sorption of 17β-estradiol from river water. Removal mechanism was due to synergistic 3 processes; H-bond, hydrophobic and π−π interactions.