Principle of superposition applied to adsorption experiments to differentiate strong binding mechanisms

A series of adsorption experiments were conducted with naphthalene and 1-naphthol to quantify the processes responsible for the fraction of nonextracted test compounds (Q(NONEX)) from a sandy soil. After a 2 d adsorption period naphthalene was not susceptible to strong binding reactions, instead the nonextracted fraction was caused by rate-limited diffusive processes. The principle of superposition was then applied to the experimental results obtained with 1-naphthol to estimate the contribution of individual processes responsible for the nonextracted fraction. Mass transfer-limited processes accounted for 4.3 ± 1.7% of Q(NONEX) of 1-naphthol in this soil. Biologically mediated oxidative coupling and mineral surface-catalyzed coupling reactions accounted for 49.0 ± 7.3% and 46.7 ± 8.0% Q(NONEX) of 1-naphthol in this soil, respectively.