Silicon Incorporation Reduces the Reactivity of Short-range Ordered Aluminosilicates Toward Organic Acids

Abstract The structure and composition of short-range ordered aluminosilicates (SROAS) may control their affinity for organic acids with potential effects on soil matter stabilization. Adsorption mechanisms model were studied to resolve the effect Si incorporation. oxalic, salicylic, octanoic acid Al-rich (Al:Si = 3.7) Si-rich 1.4) SROAS was quantified by analyses dissolved carbon using catalytic high-temperature combustion. initial pH 5 6.5 increased 6.3–8.2 during adsorption oxalic salicylic acid, demonstrating hydroxyl release ligand exchange. Minor changes in indicated weak interactions both SROAS. Adsorbates characterized Fourier-transform infrared spectroscopy. Asymmetric stretching carboxylate groups at 1720 1700 cm –1 , symmetric 1430 evinced formation chelate complexes acid. An absorption band centered 1545 partial inner-sphere binding Silicon-rich adsorbed 80–90% less than SROAS, suggesting that controlled surface aluminol groups. Fast kinetics oxalate Al sites a conductivity-based stopped-flow technique. Ligand exchange proceeded rate constant 3.5 s (25°C), similar solute complexation, an activation energy up 34.1 kJ mol . A slow process 0.13 (25°C) attributed diffusion or into particles. As supported structural characterization much lower susceptibility relates speciation. tetrahedral precludes its complexation carboxyl