Zinc oxide powders having hexagonal plate particles were prepared by homogeneous precipitation from boiling aqueous solutions that contained excess urea and 0.075 (Z075) and 0.300 (Z300) M Zn2+. The equilibrium, kinetic and thermodynamics of the adsorption of chromium (VI) from aqueous solution onto Z075 and Z300 were investigated. Thermodynamic parameters and K# equilibrium constant of activation were calculated. Langmuir, Temkin and Dubinin–Radushkevich (D–R) isotherm models were used to describe the adsorption of Cr(VI) onto ZnO powders. The monomolecular adsorption capacity of Z075 and Z300 was determined as 980 and 1050 mg g−1 for Cr(VI), respectively.
In the present study, concentrations of heavy metals viz. chromium (Cr), manganese (Mn), copper (Cu), zinc (Zn), cadmium (Cd), mercury (Hg), lead (Pb), and a metalloid selenium (Se) were examined in kidney, liver and muscle tissues of 15 brown hares (Lepus europaeus) and 9 wild boars (Sus scrofa) obtained from Kırıkkale province located in central Turkey. Significant variation in the concentrations of the studied heavy metals in the selected tissues was recorded. Mean concentrations of Cr (1.02 mg/kg), Mn (6.00 mg/kg), Se (1.15 mg/kg) and Cd (4.49 mg/kg) were the highest in hare kidney compared to other tissues, whereas concentrations of Cu (2.34 mg/kg) and Zn (40.51 mg/kg) were the highest in hare liver, and Pb (7.83 mg/kg) was the highest in hare muscle. On the other hand, mean concentrations of Cr (1.82 mg/kg), Cu (1.25 mg/kg), Se (3.55 mg/kg) and Cd (3.05 mg/kg) were the highest in boar kidney compared to liver and muscle tissues, whereas concentrations of Mn (3.89 mg/kg) and Pb (0.75 mg/kg) were the highest in boar liver, and Zn (45.65 mg/kg) was the highest in boar muscle. Strong positive significant correlations were found between Cr and Hg, and between Cu and Pb concentrations in kidney in all wild boar samples. There were also strong positive significant correlations between Cd and Pb concentrations in liver and Cd and Pb concentrations in muscle in all hare samples. Our results revealed that Hg (1/9 boar kidney; 4/15 hare kidney), Cr (9/9 boar all three tissues; 9/15 hare kidney and 11/15 hare liver), Pb (4/9 boar muscle; 5/15 hare liver, 15/15 hare muscle) and Cd (9/9 boar all three tissues; 15/15 hare all three tissues) concentrations detected in wild boar and hare tissues in the present study were higher than the hygienic limits.
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