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Environmental fate & pathways

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Zirconium, acetate lactate oxo ammonium complexes consists of a ammonium [NH4]+ and a zirconium [Zr]4+ ion as well as an acetic acid [CH3COO]2- and a lactic acid [CH3CH(OH)COO]2- anion. A complete dissociation of zirconium, acetate lactate oxo ammonium complexes resulting in ammonium (NH4+), zirconium oxide (ZrO2), acetic and lactic acid, may be assumed under environmental conditions. Batch equilibrium experiments with solutions of water-soluble ZrOCl2 indicated a very fast adsorption of zirconium to soil (1/k = ~ 3 min) and gave Kd values of 6000 and 30000 L/kg (dw) for an acidic soil and a calcareous soil, respectively. It was argued that that the most important process is most likely adsorption to ferric oxides. However, it should be kept in mind that very low soil/solution-ratios, favour adsorption, were used because otherwise concentrations in solution would become unquantifiable. Hence, resulting Kd values are somewhat overestimated. Desorption experiments indicated very limited desorption, suggesting that non-reversible adsorption processes such as inner sphere complexation or surface precipitation are involved. However, recovery of the added zirconium was not discussed. According to QSAR, acetate has a low log Kow of -0.17 (experimental data base match, EpiSuite v.4.11) and QSAR-estimated adsorption coefficients (KOCWIN v2.00) range from 1 L/kg (MCI method) to 1.153 L/kg (Kow method), which points to a low potential for adsorption in the environment. Regarding dissociation product lactate, it has a low log Kow of -0.72 (experimental data base match, EpiSuite v.4.11) and estimates of the adsorption coefficients (KOCWIN v2.00) range from 1 L/kg (MCI method) to 0.2218 L/kg (Kow method), pointing towards a low potential for adsorption in the environment. Available data of adsorption-desorption batch experiment with lactic acid and silicalite (i.e. sorbent) gave Kd values from 0.07 to 1.87 L/kg (adsorption) and 0.43 to 2.38 L/kg (desorption), suggesting that lactic acid is highly mobile in soil. Finally, the experimental log Kow determination is not possible for ammonium, however, this parameter is expected to be very low, making an accumulation of ammonium in the environment highly unlikely. Moreover, ammonium is not expected to be permanently adsorbed to soils, sediment or suspended matter since it is held by ion exchange and forms (soluble) inorganic or organic salts with other counter ions present in soil and water. In sum, all dissociation products except zirconium are assumed to be mobile in soil, but rapidly biodegraded. Therefore, Zirconium, acetate lactate oxo ammonium complexes are assumed to be mobile under environmental conditions, too.

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