Retention capacity of soils and amended soils
for heavy metal ions
Syed Abu Sayeed Mohammed*
Faculty of Civil Engineering, HKBK College of Engineering, #22/1, Nagavara, Bangalore 560045, India
* Corresponding author. E-mail: firstname.lastname@example.org
Received: 21 September 2012; revised version accepted: 30 May 2012
Mineral liners play an important role to retain heavy metals from leachates in a landfill. Locally available soils are often used in liner system because of their cost effectiveness. Two important soils in Karnataka State of India one from Bangalore called red soil and another from Belgaum called black cotton soil are studied for their effectiveness to sorb and retain metals like copper and chromium with additives like lime, cement and fly ash. The experimental data obtained from sorption and leaching tests have been applied to fit adsorption isotherms and kinetic models. Langmuir isotherm was found to be more suitable than Freundlich isotherm for both soils. Correlation coefficients obtained fitted well for all models but the ranking was in the order of Elovich> Intraparticle diffusion > Pseudo second order> Pseudo first order. Standard error of estimate proved pseudo second order to be more accurate than first order. Intraparticle Diffusion Model proved surface adsorption and intraparticle diffusion operate concurrently during adsorbent and adsorbate interaction. Scanning electron microscopy (SEM) images and electron dispersive spectroscopy (EDS) showed distinct adsorption of copper and chromium. Soils treated with cement and fly ash were found to be better to attenuate copper and chromium respectively. Generally, black cotton soil was found to be superior than red soil to retain both the metal ions studied.
Keywords: Adsorption; Dilution ratios; EDS; Elovich; Freundlich; Langmuir; pH; SEM.