Determination of Uptake and Release of 2,4-Dichlorophenol on the Nigerian Clay Soil using Gas-Liquid Chromatography

Abstract

The uptake and release of 2,4-dichlorophenol on Nigerian clay soil was studied by introducing varying concentrations of the chlorophenol in 0.01 M aqueous calcium chloride solution at pH 4.5 into pretreated clay (0.6% OM) samples. The clay soil was treated with hydrogen peroxide followed by varying  concentrations of sulphuric acid (0.1, 2.0, 4.0 and 6.0 N). The uptake of 2,4-dichlorophenol was higher for treated clay soil samples with lower cation exchange capacity. The sorption isotherm plots were  non-linear, suggesting that sorption of sorbate onto sorbent is by adsorption mechanism and that charged species are involved. The sorption process was well described by the Freundlich isotherm. Clay soil samples with higher cation exchange capacities released smaller amounts of the adsorbed chlorophenols, therefore retaining close to half of the adsorbed amount due to strong adsorption of the charged species on the clay surface. The clay soils with lower cation exchange capacities released higher amounts of the adsorbed chlorophenols, due to the higher contribution of hydrophobic interaction between organic matter and hydrophobic sites on the clay surface.

KEYWORDS: 2,4-dichlorophenol, adsorption, sulphuric acid treatment, hydrophobic interaction, desorption.