title: Development of a reduced-graphene-oxide based superparamagnetic nanocomposite for the removal of nickel (II) from an aqueous medium via a fluorescence sensor platform.
abstract: Reduced-graphene-oxide based superparamagnetic nanocomposite (GC) was fabricated and applied for the remediation of Ni(II) from an aqueous medium. The as-prepared GC was extensively characterized by Raman, TEM, AFM, SEM-EDX, SQUID, and BET analyses. Quantitative immobilization of Ni(II) in an aqueous solution by the fluorescent sensor platform of GC was explored at varying pH, doses, contact times, and temperatures. The pseudo-second-order kinetics equation governed the overall sorption process at optimized pH of 5 (±0.2). The superior monolayer sorption capacity was 228mgg(-1) at 300K. Negative ΔG(0) indicated the spontaneous sorption nature, whereas the positive ΔH(0) resulted from an increase in entropy (positive ΔS(0)) at the solid-liquid interface during the endothermic reaction. The lower enthalpy agreed with the relatively high regeneration (approximately 91%) of the GC by 0.1M HCl, because of the formation of stable tetrahedral complex. The physisorption was well corroborated by calculated sorption energy (EDR ∼7kJmol(-1)) and the nature of the Stern-Volmer plot of the fluorescence-quenching data with reaction time. The GC played a pivotal role as a static fluorescent sensor platform (fluorophore) for Ni(II) adsorption. Magnetic property also indicated that GC could be easily separated from fluids by exploiting its superparamagnetic property.
authors.affiliation: Department of Civil and Chemical Engineering, University of South Africa (UNISA), South Africa. Electronic address: nandidebabrata87@gmail.com.
authors.forename: Debabrata
authors.initials: D
authors.lastname: Nandi
authors.affiliation: Department of Chemistry, Sripat Singh College, Jiaganj, Murshidabad 742123, India.
authors.forename: Indranil
authors.initials: I
authors.lastname: Saha
authors.affiliation: DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa; Department of Applied Chemistry, University of Johannesburg, South Africa.
authors.forename: Suprakas Sinha
authors.initials: SS
authors.lastname: Ray
authors.affiliation: Department of Civil and Chemical Engineering, University of South Africa (UNISA), South Africa; DST/CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa. Electronic address: amaity@csir.co.za.
authors.forename: Arjun
authors.initials: A
authors.lastname: Maity
mesh_terms: D000327:Adsorption; D002413:Cations, Divalent; D060766:Drinking Water / Q000737:chemistry*; D005453:Fluorescence; D006108:Graphite / Q000737:chemistry*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007526:Isoelectric Point; D007700:Kinetics; D059346:Magnets; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D009532:Nickel / Q000302:isolation & purification*; D010087:Oxides; D055672:Static Electricity; D013816:Thermodynamics; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
chemical_list: D002413:Cations, Divalent; D060766:Drinking Water; D006108:Graphite; D009532:Nickel; D010087:Oxides; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Adsorption; Fluorescence sensing technology; Magnetic separation; Water purification