Chemical characterization of 'tooth brush' tree (Salvudora persica L.) sticks was carried out using a pyrolysis/ gas chromatograph coupled to an ion-trap detector mass spectrometer. Electron impact and chemical ionization mass spectra, along with chromatographic profiles obtained by both flame ionization and nitrogen/phosphorous detectors,enabled the structure of some eighty pyrolysis fragments to be proposed. These were mainly lignin and polysaccharide derivatives of phenolic and furanic natures, respectively. However, compared with the pyrograms of other well-studied lignocellulosic materials, S. persica showed several unique nitrogen-containing compounds, some of which were tentatively identified as pyrrolidine, pyrrole and piperidine derivatives on the basis of their mass spectra and chromatographic elution order.

The surface complexation approach has been applied to describe the adsorption of lead and proton onto a heterogeneous natural porous medium (red pozzolan) at constant ionic strength (0.1 mol L-1). Acid−base titration experiments were used to determine the minimum number of sites needed to describe the surface heterogeneity. Lead adsorption tests at several pH and total lead concentration were used to complete the model structure, whose adjustable parameters (site concentrations and apparent formation constants) were determined by nonlinear multivariate regression of titration and adsorption data. The final model represents the acid−base properties of the surface by the presence of two amphoteric sites, SOH and TOH, and a monoprotic one, MOH; whereas lead adsorption is considered only onto SOH and MOH sites. The model allows a good representation of the experimental behavior in the whole experimental range (pH = 4−10 for titration, pH = 3.5−6.0 and total lead concentration from 8.8 × 10-5 to 7.3 × 10-4 mol L-1 for adsorption experiments). Theoretical surface speciation shows that lead adsorption occurs mostly onto site MOH at low pH level and on both SOH and MOH sites at higher values. The model was independently validated by simulating Pb and pH breakthrough experiments performed in small chromatrographic columns. Experimental breakthroughs are well predicted by an advection−dispersion transport model coupled with the chemical equilibrium routine (IMPACT), without any parameter adjustment. A large spreading of Pb and pH breakthroughs was calculated and experimentally observed, even in the absence of any kinetic effect. That spreading is explained in terms of the concomitant presence of competitive adsorption and surface heterogeneity.

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