Adsorption of 1-naphthyl-N-methyl carbamate by selected soils from lake Naivasha region in Kenya: adsorption properties and related thermodynamic data

Abstract

The adsorption properties of 1- naphthol N-methylcarbamate (Carbaryl) by soils in aqueous solutions from Lake Naivasha was studied in terms of the first order model of a binary solution, which is expressed as follows: nX  S  SX n andK [SX ]/[X] [S] n  n , …………………………………………………….(1) X is the chemical species of interest, carbaryl (pesticide) , S is the substrate (soil particles), K is the adsorption equilibrium constant and SXn is the particle-pesticide complex. According to this model, the apparent adsorption equilibrium constant K’ is given by equation 2: ln[x]ads =ln(nk’) + n(ln[x]e + [sxn]w )………………………………………………………….….…..(2) where [ X ]ads is concentration of X in adsorbed state. [ X ]e is the concentration of X in solution at equilibrium. [ SXn ]w is the pesticide adsorption site complex in the suspension at equilibrium. The average values of ' K (the apparent adsorption equilibrium constant), n and ∆G’ (the apparent adsorption free energy) for Lake Naivasha soils obtained for Carbaryl were 20.56, 0.63 and -7.26 KJ/mol, respectively.