Adsorption behavior of Na-bentonite and nano cloisite Na+ in interaction with Pb(NO₃)₂ and Cu(NO₃)₂·3H₂O contamination in landfill liners: Optimization by response surface methodology

Abstract

Contamination of soils and water with Pb (II) and Cu (II) ions are very common in geo-environmental projects, but despite investigations of soil contaminant interactions, the actual process of the interaction involving heavy metals and Nano-clays has not been extensively investigated. Lead can enter the food chain through contaminated soil. Lead poisoning can affect the blood circulation, kidneys, and peripheral and central nervous systems especially in adults. Accumulation of Cu (II) in the human body causes brain, skin, pancreas and heart diseases.In this study, a wide range of the adsorbent / electrolyte and heavy metal concentration was considered to compare the interaction process of Pb (II) and Cu (II) contaminants with Nano cloisite Na⁺ (NCNa) and bentonite. This classification of materials has a unique functionality which may have widespread applications, due to their novel or significantly enhanced properties to use in the Geo-environmental projects. A series of experiments was carried out using a range of Pb (II) and Cu (II) contaminant concentrations from 25 to 275 cmol kg-soil⁻¹, under a range of contaminant/absorbent ratios from 0.01 to 0.02. Response surface methodology (RSM) was used to optimize the results. Generally, the results showed an increase in adsorption with increasing the adsorbent / electrolyte ratio up to 0.015. Bentonite adsorbed up to %50 of the Pb (II) while the concentration was 150 cmol/kg.soil. This amount was %40 for the NCNa in a constant ratio of adsorbent/electrolyte. Also the behavior of bentonite clay adsorbents was likely to favor adsorption of Pb (II) rather than Cu (II), as indicated in the previous research found.