Primary biosorption mechanism of lead (II) and cadmium (II) cations from aqueous solution by pomelo (Citrus maxima) fruit peels.

The present work investigates the primary adsorption mechanisms of lead (II) and cadmium (II) cations onto pomelo fruit peel (PFP) from aqueous solution. pH, adsorption time, ion strength, and initial metal cation concentrations, which are factors affecting the uptake of these cations, are investigated. Results show that pH and ion strengths strongly affect the removal of these cations from aqueous solution. Different isotherm adsorption models, such as Langmuir, Freundlich, and Sips, are utilized to fit the experimental data in order to determine the adsorption in nature. The Langmuir monolayer adsorption capacities are found to be 47.18 mg/g for lead (II) and 13.35 mg/g for cadmium (II). Kinetic and thermodynamic studies based on a combination of FT-IR and TG-DSC spectroscopies demonstrate that electrostatic attraction plays a primary adsorption mechanism of lead (II) and cadmium (II) cations onto pomelo fruit peel.

Chitosan-MnO2 nanocomposite for effective removal of Cr (VI) from aqueous solution.

In this report, the adsorption of Cr(VI) onto MnO2/CS nanocomposite material from aqueous solution is investigated. All the factors, which affect the adsorption, such as pH, adsorption time, Cr(VI) initial concentration and adsorbent dosage, are also examined. The results obtained show that the Cr(VI) uptake is strongly affected by pH and ion strength. Analysis within the nonlinear isotherm models indicates that the Sips isotherm combining with the Langmuir and Freundlich models offer the best fit to the experimental data due to the obtained highest R2 and smallest RMSE and χ2 values. The calculated Langmuir monolayer adsorption capacity is 61.56 mg g-1 at pH of 2.0 and adsorption time of 120 min. Moreover, the mechanism studies by combining theoretical models with analytical spectroscopies reveal that the electrostatic attraction plays the important role to the uptake of Cr(VI) onto MnO2/CS nanocomposite. Therefore, the present nanocomposite material can be applied to remove total Cr from wastewater produced by the galvanized manufacturing factory with a relatively high efficiency.