COPYRIGHT on the article "Phosphate adsorption in highly absorbent clay minerals soils in Southwest Brazilian Amazon". DOI: http://doi.org/10.6008/CBPC2179-6858.2022.008.0001
ID Fraction: Collection Year 2022 #432 NFT Stock of CBPC (Brazil)

Abstract: This study assessed the phosphate fixation capacity in soils from different parental materials. We evaluated soils from five environments in southwest Brazilian Amazon for phosphate adsorption and desorption. Soil samples of 2.5 g, in replicates, were equilibrated with 25 mL of 0.01 mol L-1 CaCl2 solution containing 0, 10, 20, 40, 80, 120, 160, 200, 260, and 320 mg L-1 of P. After shaking for 24 h, the P content in the equilibrium solution was determined and the P amount adsorbed was calculated by difference. The Langmuir equation determined the maximum phosphate adsorption capacity and binding energy. The same samples were desorbed by adding 25 mL of 0.01 mol L-¹ CaCl2 to the samples and shaking for 24 h in the same adsorption process. The presence of highly absorbent clay silicates favored phosphate adsorption in an acidic environment. The adsorption process was associated to reactive sites represented by hydroxy-Al interlayered smectites and illites in dissolution, which react with phosphate anions, in adsorption reactions and, or, chemical precipitation. The maximum phosphate adsorption capacity and binding energy occur at higher rates than those in soils with minerals from Fe and Al oxides.