Adsorption isotherms of copper and zinc in clay minerals of calcareous soils and their effects on X-ray diffraction

作者：Baghernejad M^*; Javaheri F; Moosavi A A

来源：Archives for Agronomy and Soil Science, 2015, 61(8): 1061-1077.

DOI：10.1080/03650340.2014.982549

• sorption isotherms
• Ferundlich
• smectite
• XRD
• Langmuir

Reactions of elements with the water mineral interface are important and affect their bioavailability and transportation within soil. Effects of metal sorption on X-ray-diffraction (XRD-photographs) of clay minerals have been not studied. Therefore, sorption experiments were done on clay fractions of two calcareous soils using 12 concentrations of 0-2000mgL(-1) Zn(NO3)(2) and Cu(NO3)(2). Langmuir and Freundlich isotherms' coefficients were determined. After sorption, XRD-diffraction were prepared and compared with those of initial samples. Langmuir (R-2=0.996-0.999 and SE=0.001-0.002) and Freundlich equation were the best-model for Zn and Cu-sorption, respectively. Sorption energy was higher for Zn than Cu, whereas the maximum concentration of sorbed-Cu was higher than that of Zn. Distribution coefficient (K-d) of Cu were more (threefold) than that of Zn. The K-d values representing the slope of Freundlich isotherms decreased according to linear regression equations (R-2 = 0.72-0.91) as the equilibrium concentrations of metals increased. No significant differences were observed among XRD-photographs of applied concentrations (some negligible differences were found in position/sharpness of peaks). Dry-XRD-method resulted in omission of intensity peaks at 2 theta which may interfere in recognition of clays that show a maximum intensity >1.4 nm in the mentioned 2 theta. Zinc can become more leachable especially in Shekarbani-soil-series, whereas, Cu highly adsorb on clay minerals and can show less tendency to transportation.

• 出版日期2015-8-3