Adsorption capacity of lead ions by natural kaolinites modified with iron hydroxide

Samples of kaolinite of yellow latosoil (C1), fund sendiment (C2) and kaolin (C3), collected in the State of Amazonas (Brazil), which were structurally modified with iron hydroxide (Fe(OH)₃) at high temperatures. Nine of the adsorbents were synthesized: C1+Fe(OH)₃ at 600 deg C; C1+Fe(OH)₃ at 700 deg C; C1+Fe(OH)₃ at 900 deg C; C2+Fe(OH)₃ at 600 deg C; C2+Fe(OH)₃ at 700 deg C; C2+Fe(OH)₃ at 900 deg C; C3+Fe(OH)₃ at 600 deg C; C3+Fe(OH)₃ at 700 deg C and C3+Fe(OH)₃ at 900 deg C. The capacity of each synthesized material to adsorb Pb²⁺ (in an automotive battery solution) was evaluated as a function of the time, using the Lagergren's equation of second order. The results show a great affinity of the adsorbents C1+Fe(OH)₃; C2+Fe(OH)₃ and C3+Fe(OH)₃ at 600 deg C to Pb²⁺ ions. After forty minutes those adsorbents were capable to remove selectively approximately 99% of Pb²⁺ from the battery solution. Another characteristic of those adsorbents is their capability to be reused, due to the Pb²⁺ ions been released easily from the surface of the material after treatment with calcium acetate at 500 mg L^-1. An important aspect in this treatment is an increment in the capacity of adsorption of Pb²⁺ in the second adsorption. (author)