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

Samson O Akpotu; Isiaka A Lawal; Brenda Moodley; Augustine E Ofomaja

doi:10.1016/j.chemosphere.2019.125729

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

Chemosphere. 2020 May:246:125729. doi: 10.1016/j.chemosphere.2019.125729. Epub 2019 Dec 26.

Authors

Samson O Akpotu¹, Isiaka A Lawal², Brenda Moodley³, Augustine E Ofomaja²

Affiliations

¹ Wastewater Treatment Research Laboratory, Faculty of Applied and Computer Sciences, Department of Chemistry, Vaal University of Technology, Vanderbijlpark, 1911, South Africa. Electronic address: samsonakpotu@yahoo.com.
² Wastewater Treatment Research Laboratory, Faculty of Applied and Computer Sciences, Department of Chemistry, Vaal University of Technology, Vanderbijlpark, 1911, South Africa.
³ School of Chemistry and Physics, University of Kwazulu-Natal, Durban, 4000, South Africa.

PMID: 31901661
DOI: 10.1016/j.chemosphere.2019.125729

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.

Keywords: 17β-estradiol; Adsorption; Hydrophobicity; Methoxylether polyethylene glycol; Polyamide carbonic groups; Reduced graphene oxide; Wastewater treatment.

MeSH terms

Adsorption
Carbon
Estrogens / chemistry*
Graphite / chemistry*
Hydrophobic and Hydrophilic Interactions
Models, Chemical
Nanocomposites
Organic Chemicals
Polyethylene Glycols / chemistry*
Silicon Dioxide

Substances

Estrogens
Organic Chemicals
SBA-15
graphene oxide
Polyethylene Glycols
Carbon
Silicon Dioxide
Graphite