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

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

Removal of Lead from Aqueous Solution by Palm Kernel Fibre

The sorption of lead on palm kernel fibre, an agricultural waste product, has been studied. The sorption process was studied as a function of initial lead concentration and initial solution pH. The percentage lead removal was found to increase with increasing initial solution pH up to pH 5 and then to decrease as pH was increased to 6. The pseudo-second order kinetic rate model was employed in the analysis of the kinetics of lead uptake onto the palm kernel fibre. The results show that the pseudo-second order model fits the experimental data with high coefficients of determination (r2). The equilibrium sorption capacity was found to be 33.33 mg g–1 when 1.0 g of fibre was contacted with 90 mg dm–3 of lead solution at pH 5. Mathematical expressions were derived to relate the pseudo-second order rate constant, k, and the change in solution pH with initial lead concentration.Keywords: Palm kernel fibre, kinetics, lead(II), sorption, change in solution pH