Pb (II) Recovery by Modified Tuffite: Adsorption, Desorption, and Kinetic Study

Abstract

In this study, Pb (II) removal from wastewater was investigated using a modified vitric crystal tuffite with a BET surface area of 11.7 m2/g. For this purpose, tuffite was used in its natural and modified form with ethylenediaminetetraacetic acid (EDTA). Batch adsorption experiment was performed. The effects of contact time (0–90 min), adsorbent dosage (1–10 g/L), initial concentration (10–200 mg/L), and pH (2–12) on the removal of Pb (II) were investigated. The isotherm data were fitted to Langmuir, Freundlich, Temkin, and Redlich-Peterson isotherm models. Kinetic models such as pseudo-first-order, pseudo-second-order, and intraparticle diffusion models were used. In order to optimize the adsorption system and investigate the kinetic behaviour of adsorption, nonlinear isotherm and kinetic models were used as well as linearized models. Error analyses were made in order to express the obtained results more accurately. pH 5 was the optimum value for adsorption. According to nonlinear isotherm model calculations, Bayburt stone (BS) and its modified form (MBS) had q max values of 335 and 584 mg/g, respectively. The Freundlich model, with its high correlation coefficients of about 1.00, was found to be more suitable for the adsorption of Pb (II) to MBS. The pseudo-second-order kinetic model with mean R 2 and k 2 values of 0.997 and 0.0116 1/min, respectively, was found to be more appropriate. According to the regeneration studies, the maximum desorption efficiency was 97.8%. The thermodynamic equilibrium coefficients obtained at different temperatures and Δ G o , Δ H o , and Δ S o values were observed as -21.4, 46.4, and 163 kJ/mol, respectively. These values indicate that the adsorption of Pb (II) on to MBS was endothermic and spontaneous process. BS and MBS were characterized by different instrumental analyses such as SEM, EDS, FTIR, and zeta potential measurements.

Modification and Application Study of Activated Natural Zeolite for the Treatment of Liquid Waste from Chemical Laboratory

“…The determination of the optimal concentration of the adsorbate is illustrated in Figure 6. The adsorption of metal ions by the adsorbent tends to increase with the increasing concentration of the adsorbate in the solution [33]. However, after reaching equilibrium conditions, there is a decrease in the amount of metal ions adsorbed by the adsorbent.…”

“…At pH 6, the adsorption of Pb 2+ ions increases. Electrostatic forces occur between Pb 2+ ions and the negatively charged surface of the adsorbent, resulting in attractive forces that enhance adsorption efficiency [33]. At alkaline pH, there is a decrease in adsorption efficiency as it surpasses the solubility product constant, and precipitation occurs [14,32].…”

“…Based on the data, it can be concluded that the adsorption of Pb and Cr using the activated natural zeolite follows the pseudo-secondorder kinetics equation. Cr(VI) adsorption onto ZnOgraphene oxide nanocomposite follows the pseudosecond-order kinetics equation [33]. The pseudosecond-order kinetics model is suitable for adsorbents with numerous active sites [30].…”

Overcoming Diffusion Mass Transfer Barriers by Surface Electro-Precipitation (SEP)

“…For example, even though chemical precipitation can be almost instantaneous at high supersaturations, 5 the recovery of the precipitated highly dispersed colloids is either slow (hours) or energy-expensive. The typical adsorption and desorption time for the recovery of dilute species with low surface area sorbents is more than 1 h. 6,7 e-Deposition is nonviable at concentrations below several g/L where the specific energy consumption becomes prohibitively high. 8,9 As known for more than a century, the slow rates of surfacebased separation methods originate from the slow diffusion rates of dilute target ions to the extracting solid (adsorbent) through a stagnant interfacial film called the Nernst diffusion layer δ (Figure 1a).…”

“…As no commonly accepted notation has been established yet, we will henceforth refer to the electrochemically induced precipitation on the electrode surface as surface electrochemical precipitation (SEP), while retaining the name e-deposition for reaction (6). The principal difference between SEP and edeposition is that the former does not change the oxidation state of the deposited metal.…”