ABSTRACT
The biosynthesis of the iron oxide nanoparticles was done using Ixoro coccinea leaf extract, followed by the fabrication of iron oxide nanobiocomposites (I-Fe3O4-NBC) using chitosan biopolymer. Furthermore, the synthesized I-Fe3O4-NPs and I-Fe3O4-NBC were characterized, and I-Fe3O4-NBC was applied to remove toxic metals (TMs: Cd, Ni, and Pb) from water. The characterization study confirmed that the nanostructure, porous, rough, crystalline structure, and different functional groups of chitosan and I-Fe3O4-NPs in I-Fe3O4-NBCs showed their feasibility for the application as excellent adsorbents for quantitative removal of TMs. The batch mode strategy as feasibility testing was done to optimize different adsorption parameters (pH, concentrations of TMs, dose of I-Fe3O4-NBC, contact time, and temperature) for maximum removal of TMs from water by Fe3O4-NBC. The maximum adsorption capacities using nanocomposites for Cd, Ni, and Pb were 66.0, 60.0, and 66.4 mg g-1, respectively. The adsorption process follows the Freundlich isotherm model by I-Fe3O4-NBC to remove Cd and Ni, while the Pb may be adsorption followed by multilayer surface coverage. The proposed adsorption process was best fitted to follow pseudo-second-order kinetics and showed an exothermic, favorable, and spontaneous nature. In addition, the I-Fe3O4-NBC was applied to adsorption TMs from surface water (%recovery > 95%). Thus, it can be concluded that the proposed nanocomposite is most efficient in removing TMs from drinking water up to recommended permissible limit.
ABSTRACT
The current study aimed to develop a robust, selective, and sensitive voltammetric method for hexavalent chromium (CrVI) at a chemically modified carbon paste electrode. For the preparation of the electrode, a micropipet tip was packed with modified carbon paste mainly consisting of graphite powder and diphenylcarbazone (5 + 1, w/w). Voltammetric mode, type of electrolyte, pH, volume of electrolytes, accumulation time, accumulation potential, and stirring rate were studied in detail. The current response was linearly dependent on the concentration of CrVI from 0.20 to 2.60 µmol/L. The reproducible results were obtained for replicate analyses (n = 11) of three proposed electrodes of the same composition with RSDs of <2.0%. The LODs and LOQs were found to be 0.052 and 0.174 µmol/L, respectively. The noticeable electrode surface passivation was not observed for the detection of CrVI. The proposed methods were successfully applied for CrVI in different surface waters in Sindh, Pakistan.