Adsorption kinetics, isotherms and thermodynamics of Cr(III) on graphene oxide

Environmental contextExplosive organic compounds such as 2,4,6-trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) are major constituents of ammunition materials. These compounds are of environmental concern because they can have a significant impact on ecosystems and humans. Through investigations of adsorption kinetics, isotherms and thermodynamics, we demonstrate the suitability of pseudographitic carbon for removing TNT and RDX from groundwater, and additionally confirm the viability of the use of pseudographitic carbon through comparison with other adsorbents. Abstract2,4,6-Trinitrotoluene (TNT) and hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) – common explosives in military munitions – can easily enter groundwater supplies and have an adverse impact on human health. There is great concern about the need to remove these explosives from groundwater, and this study presents pseudographitic carbon (PGC) prepared from edible sugar as a material to remove explosives from contaminated groundwater via adsorption. The purity and physicochemical characteristics of the PGC were characterised using advanced spectroscopic techniques. The adsorption mechanism and its efficiency were investigated in terms of the non-linear adsorption kinetics, isotherms and thermodynamics using TNT and RDX adsorption data. The results of the non-linear modelling indicate that TNT and RDX adsorption was determined by rate-limiting monolayer exothermic adsorption on the homogeneous PGC surface. Ionic strength was studied with various ions, and the results indicate that the adsorption of TNT and RDX was significantly influenced by divalent cations and the carbonate anion. The results of desorption and re-use tests indicate that acetone and acetonitrile are the best desorbing agents. The PGC can be recycled and re-used for up to 3 cycles, with insignificant loss in adsorption efficiency. Finally, the PGC was applied to real spiked groundwater to evaluate its applicability in the field in removing TNT and RDX. The overall results indicate that PGC is a cost-effective and efficient adsorbent that effectively removes the organic explosives from groundwater, thereby reducing risk to humans and the aqueous environment.

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Impedimetric Detection of Albumin-Bound Fatty Acids Using Graphene Oxide Electrode

Chemosensors ◽

10.3390/chemosensors9090240 ◽

2021 ◽

Vol 9 (9) ◽

pp. 240

Author(s):

Zihni Onur Uygun ◽

Soner Duman ◽

Ismail Oran

Keyword(s):

Graphene Oxide ◽

Adsorption Kinetics ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Single Frequency ◽

Molar Ratio ◽

Albumin Concentration ◽

Limit Of Quantification ◽

Faradaic Impedance ◽

Kinetics Of

The fatty acid/albumin (FA/Alb) molar ratio is ≤1 in healthy subjects; this ratio can reach 3–4 in patients with acute myocardial ischemia. We describe the spontaneous desorption–adsorption kinetics of FAs from albumin to a graphene electrode at neutral pH. Albumin-depleted human serum was prepared via ultrafiltration and then mixed with defatted human albumin and sodium oleate at different FA/Alb molar ratios, at a final albumin concentration of 0.6 mM. A commercially available screen-printed graphene oxide (GO)-modified carbon electrode was used for the electrochemical experiments. Frequency-ranged Faradaic electrochemical impedance spectroscopy (EIS) and a single-frequency non-Faradaic impedance measure (chronoimpedance) were used to derive the desorption–adsorption kinetics. The surface of the GO electrode was finally evaluated with the aid of X-ray photoelectron spectroscopy (XPS). With the chronoimpedance experiment, the measured impedance increased accordingly to the FA/Alb ratios. The frequency-ranged EIS showed good linearity between the impedance and the FA/Alb ratio, with a limit of quantification value of 1.06. XPS surface analysis revealed that the FA was adsorbed onto the electrode, with the amount of the adsorbed FA proportional to the FA/Alb ratio. The electrochemical method applied on this peculiar desorption–adsorption kinetics of FAs has the ability to differentiate serum having excess FAs.

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