The adsorption of lead and copper from aqueous solution on modified peat-resin particles

Enhanced Pb(II) adsorption onto functionalized ordered mesoporous carbon (OMC) from aqueous solutions: the important role of surface property and adsorption mechanism

Functionalized ordered mesoporous carbon (MOMC-NP) was synthesized by chemical modification using HNO₃ and H₃PO₄ to enhance Pb(II) adsorption. The phosphate functional group represented by P-O-C bonding onto the surface of OMC was verified by FT-IR and XPS. Batch adsorption experiments revealed the improvement of adsorption capacity by 39 times over the virgin OMC. Moreover, the Pb(II) adsorption results provided excellent fits to Langmuir model and pseudo-second-order kinetic model. The adsorption mechanism of Pb(II) onto MOMC-NP revealed the formation of metal complexes with carboxyl, hydroxyl, and phosphate groups through ion exchange reactions and hydrogen bondings. The calculated activation energy was 22.09 kJ/mol, suggesting that Pb(II) adsorption was a chemisorption. At pH>pH_pzc, the main Pb(II) existing species of Pb(II) and Pb(OH)⁺ combine with the carboxyl, hydroxyl, and phosphate functional groups via electrostatic interactions and hydrogen bonding. All these findings demonstrated that MOMC-NP could be a useful and potential adsorbent for adsorptive removal of Pb(II). Graphical abstract.

Removal of Cd(II) and Pb(II) complexes with glycolic acid from aqueous solutions on different ion exchangers

The sorption of Cd(II) and Pb(II) ions from aqueous solutions on different ion exchangers was investigated by using glycolic acid (GA) as a complexing agent. Glycolic acid is useful for organic synthesis in oxidation–reduction, esterification, and long-chain polymerization. The experiments were carried out by using the following chelating ion exchangers: Purolite S-930, Purolite S-940, Purolite S-950, Diaion CR-20, and Wofatit MC-50 and the cationic ion exchangers: Purolite C-104, Lewatit CNP-80, and Lewatit SP-112. The influence of the initial concentration of Cd(II) and Pb(II) and glycolic acid, pH of the solution, and phase contact time on the sorption percentage was determined in the batch experiments. Pseudo-first-order and pseudo-second-order kinetic models were used to describe the kinetic data, and the rate constants were evaluated. The experimental data, fitted using the Langmuir and Freundlich adsorption models, were applied to describe the equilibrium isotherms and determined the isotherm constants. The Cd(II) and Pb(II) concentrations in the raffinate were determined by the AAS method.

Theoretical models of sorption kinetics including a surface reaction mechanism: a review

A review of a certain class of theoretical models describing the kinetics of pollutants sorption onto various sorbents is presented. These assuming the rate of surface reaction as the rate-limiting step are considered. A special attention is paid to possible theoretical grounds of the most commonly applied mathematical expressions, such as the pseudo-second and the pseudo-first order equations. Simple theoretical considerations based on some fundamental theories suggest that these two formulae do not correspond to any specific physical model. They simply approximate well the behaviours predicted by many different theoretical approaches.

Association of individual soil mineral constituents and heavy metals as studied by sorption experiments and analytical electron microscopy analyses

Sorption characteristics of bulk soil samples and discrete soil mineral constituents were studied by Cu, Zn and Pb batch sorption experiments and analytical electron microscopy analyses. Copper and zinc sorbed mostly on soil mineral constituents, while lead was associated mainly to soil organic matter. Additionally, the competitive situation resulted in increase of the role of iron oxides in Pb sorption. Close association of iron oxides and silicates resulted in significant change in their sorption capacities for all the studied metals. The alkaline conditions due to the calcite content in one of the studied soil samples resulted in both increased role of precipitation for Pb and Cu and elevated sorption capacity for Cu by discrete mineral particles. Using the analytical electron microscopy analyses the sorption characteristics of metals were supported by particular data. When the methods used in this study are combined, they become an extremely powerful means of getting a deeper insight into the soil-metal interaction.