Evaluation of adsorption parameters and charge densities of some selected soils: application to lead

An attempt to evaluate adsorption parameters and charge-based densities for Pb is reported in the paper. The method was based on the calculation of Langmuir adsorption maximum (amax), and the bonding energy term (b). The parameters were the outcome of well-established linear relationships of Ce/S versus Ce (Ce, equilibrium concentration and S, amount adsorbed). The use of charge-based sorption density parameter (SDCEC), which expressed the number of accessible charges for Pb adsorption, evidenced the occurrence of two main adsorption phases, characterised by two different slopes. The first ones, varying from 0.536 to 3.144 were suggested to be attributed to ‘high attractive sites’, whereas the second with slopes from 0.011 to 0.259, probably represented ‘low attractive sites.