Preparation and Characterization of Graphene Oxide for Pb(II) and Zn(II) Ions Adsorption from Aqueous Solution: Experimental, Thermodynamic and Kinetic Study

Abstract

A thermodynamic and kinetic study of the adsorption process of Zn (II) and Pb (II) ions from aqueous solution on the surface of graphene oxide (GO) to establish the mechanisms of adsorbate–adsorbent interaction on this surface. The effect of pH on the retention capacity was studied and adsorption isotherms were determined from aqueous solution of the ions; once the experimental data was obtained, the kinetic and thermodynamic study of the sorption process was carried out. The data were fitted to the Langmuir, Freundlich, Dubinin-Raduskevich and Temkin isotherm models. The results showed that Zn(II) and Pb(II) on the GO adsorbing surface fitted the Langmuir model with correlation coefficients (R2) of 0.996. Kinetic models studied showed that a pseudo-second-order model was followed and thermodynamically, the process was spontaneous according to the values of Gibbs free energy (ΔGo). N2 adsorption isotherms were determined and modeled with the NLDFT (nonlocal density functional theory) and QSDFT (quenched solid density functional theory) kernels.

Graphene Oxide: Study of Pore Size Distribution and Surface Chemistry Using Immersion Calorimetry

“…GO was prepared in our laboratory [86] from graphite sheets (Flakes, Sigma-Aldrich, St. Louis, MO, USA, CAS 7782-42-5) using the improved Hummers method reported in the literature and taking into account the changes suggested by several authors to carry out a procedure with good performance and laboratory safety [86]. A brief summary of the procedure carried out is as follows: a main process consisting of oxidation.…”

“…This latter solvent was removed by carefully heating the solution at 45 • C. GO was then peeled off with ethanol using an ultrasound bath (Fisher Brand, Model CPXH, Boston, MA, USA) for 90 min. Finally, the GO was dried at 80 • C for 24 h and ground in an agate mortar, until it passed through a 100 mesh [86].…”

“…The protocol used to carry out the measurements and ensure good reproducibility in the data consisted initially degassing the samples at a temperature of 250 • C, applying a high vacuum (10 −5 mbar) for 5 h, a procedure that ensures eliminate all those pre-adsorbed species that could affect the measurements. The Brunauer-Emmett-Teller (BET) model [85][86][87][88] was used to evaluate the specific surface area taking the data in the range at a P/P o between 0.05-0.35, which presents a good linearity. On the other hand, the Dubinin-Radushkevich models (DR) [89][90][91][92][93] and the functional theory of density (DFT) [94] were used to complement the studies of the textural properties of the solids under study.…”

“…N 2 gas adsorption-desorption isotherms of samples and pore size distribution (PSD) calculated with quenched solid density functional theory (QSDFT) kernel: (a) graphite (Gr) (b) graphene oxide (GO) (c) Simulation of Gr with non-local density functional theory (NLDFT) and QSDFT (d) Simulation of GO with NLDFT and QSDFT[86].…”

Novel Activated Carbon Nanofibers Composited with Cost-Effective Graphene-Based Materials for Enhanced Adsorption Performance toward Methane

“…Among the samples, GRHA/ACNF possessed the highest R 2 value, of 0.9737. It suggests that the adsorption of CH 4 towards ACNFs obeyed the pseudo-second-order kinetic models, indicating that the sorption kinetics of CH 4 occurred on the microporous structure of ACNFs involved in the chemisorption [ 60 ]. This result is in good agreement with the N 2 adsorption isotherm and SSA data.…”