This study assesses the adsorption of Pb(II) on natural kaolin waste (KRnatural) and on that treated with 3 mol L-1 H2SO4 and HCl. Equilibrium and thermodynamic parameters were determined. The results indicate that the values of CEC, specific area and SiO2/Al2O3 ratio (4.6-6.0 cmol kg-1, 14.0-16.0 m² g-1 and 1.16-1.30, respectively) vary only slightly for the adsorbents; the concentration of Pb2+ is much higher than that of other species (PbOH+ and Pb(OH)2). The values of R L, ΔGº, ΔHº and ΔSº are typical of feasible, spontaneous, exothermic and ordered adsorption. The chemisorption on KRnatural is more feasible and ordered.

Concentrações de arsênio em perfis de solos com terra preta arqueológica (TPA) e solos de área adjacente (AD) do Sítio Ilha de Terra, Caxiuanã, no Estado do Pará, região Amazônica, podem dar informações sobre as atividades antropogênicas dos habitantes dessa região. Análises químicas e mineralógicas foram realizadas nas amostras desses perfis. Os dados obtidos mostram que as concentrações do Fe e As aumentam com a profundidade dos perfis de solos, enquanto que as concentrações de matéria orgânica (MO) decrescem; as concentrações mais elevadas de Fe e As são observadas no perfil AD. Esses resultados indicam interações entre Fe e As e sugerem que a MO nos solos promove a dissolução da goethita e lixiviação do Fe e As no perfil TPA.

Arsenic concentrations in soil profiles with archaeological black earth (ABE) and surroundings (SA) from the Sítio Ilha de Terra, Caxiuanã, in the State of Pará, Amazon region, may provide information on anthropogenic activity in the Amazonian habitat. The samples of ABE and SA soil profiles were submitted to chemical and mineralogical analysis. The obtained data show that Fe and As concentrations increase with depth while organic matter (OM) decreases. The highest concentrations of Fe and As are observed in the SA profile. These results indicate interactions between Fe and As and suggest that OM promotes the dissolution of goethite and leaching of Fe and As in the ABE profile.