Adsorption isotherms, kinetic and thermodynamic studies on cadmium and lead ions from water solutions using Amberlyst 15 resin.

Adsorption isotherms, kinetic and thermodynamic parameters for Cd(II) and Pb(II) ions in water solutions by using Amberlyst 15 resin were performed and evaluated by utilizing solid phase extraction method with the batch system at 298, 308, and 318 K. Flame atomic absorption spectrometry was utilized for absorbance measurements of Cd and Pb in solutions. The Langmuir, Freundlich, and Dubinin-Radushkevich isotherm models, respectively were implemented to equilibrium results obtained. Experimental and theoretical monolayer adsorption capacities of resin for adsorptions of Cd(II) and Pb(II) by the Langmuir isotherm model were approximately the same and they were 120 and 116 mg/g for Cd(II) and Pb(II) ions, respectively at 318 K. Most appropriate kinetic model for adsorption of Cd(II) and Pb(II) on the resin was found as pseudo-second-order. Contact time and temperature for adsorption of analytes on the resin were optimized at 45 min and 298 K. Activation energies (Ea) and thermodynamic values (ΔG°, ΔH° and ΔS°) were determined and assessed. Results showed that adsorptions of Cd(II) and Pb(II) on Amberlyst 15 were spontaneous, exothermic, and chemical ion-exchange processes.

Solid Phase Extraction of Cadmium and Lead from Water by Amberlyst 15 and Determination by Flame Atomic Absorption Spectrometry.

Preconcentration of Cd(II) and Pb(II) was carried out by using column solid phase extraction method. Amberlyst 15 was used as solid phase for these analytes. The optimum extraction conditions such as pH (4), type and volume of eluent (5 mL of 2 mol L-1 HNO3) sample flow rate (1 mL min-1) and sample volume (100 mL for Cd(II) and 750 mL for Pb(II)) were determined. The recoveries were found for Cd(II) and Pb(II) as 104% ± 1% and 102 % ± 2%, respectively. The limit of detections were found as 0.23 µg L-1 for Cd(II) and 0.13 µg L-1 for Pb(II). The effects of foreign ions were also studied. The method was validated by analyzing standard reference material and spiked water samples. Percent relative error and relative standard deviation were below 3% and 4%, respectively.

Speciation of Cr(III) and Cr(VI) in water after preconcentration of its 1,5-diphenylcarbazone complex on amberlite XAD-16 resin and determination by FAAS.

A simple and sensitive method for the speciation, separation and preconcentration of Cr(VI) and Cr(III) in tap water was developed. Cr(VI) has been separated from Cr(III) and preconcentrated as its 1,5-diphenylcarbazone complex by using a column containing Amberlite XAD-16 resin and determined by FAAS. Total chromium has also been determined by FAAS after conversion of Cr(III) to Cr(VI) by oxidation with KMnO(4). Then, Cr(III) has been calculated by subtracting Cr(VI) from the total. The effect of acidity, amount of adsorbent, eluent type and flow rate of the sample solution on to the preconcentration procedure has been investigated. The retained Cr(VI) complex was eluated with 10 ml of 0.05 mol l(-1) H(2)SO(4) solution in methanol. The recovery of Cr(VI) was 99.7+/-0.7 at 95% confidence level. The highest preconcentration factor was 25 for a 250 ml sample volume. The detection limit of Cr(VI) was found as 45 mug l(-1). The adsorption capacity of the resin was found as 0.4 mg g(-1) for Cr (VI). The effect of interfering ions has also been studied. The proposed method was applied to tap water samples and chromium species have been determined with the relative error <3%.