In environmental and industrial settings, the distribution and behavior of Rare Earth Elements (REEs) are of great interest due to their unique properties and applications. One critical aspect of understanding REE behavior is distinguishing their distribution among the three main fractions in water systems: colloidal, particulate, and truly dissolved. Particulate fractions refer to particles that are larger than 0.45 μm and settle out of solution under the influence of gravity. Colloidal fractions refer to particles that are between 0.022 and 0.45 (μm) in size and remain suspended in solution due to Brownian motion. Truly dissolved fractions include REEs that are ionized and can pass through a filter with a pore size of 0.022 μm. It is important to distinguish these three fractions because the mobility, bioavailability, and toxicity of REEs can vary greatly depending on their distribution among them. Colloidal and particulate fractions can act as carriers for REEs, affecting their transport and availability to living organisms while truly dissolved fractions are more readily taken up by aquatic organisms. Additionally, industrial applications of REEs often involve specific fractionations, such as the separation of colloidal and particulate fractions for purification purposes. We collected and filtered (through both 0.45 and 0.022 μm) 28 groundwater samples taken on the lower flanks of Etna Volcano (Sicily, Italy). For the determination of 14 lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) plus Y in the aqueous fractions we proposed an improved method based on the coprecipitation of REEs with Mg(OH)2, assisted by the triethylamine (TEA). The particulate fraction, retained on the 0.45 cellulose acetate filters, was assessed by microwave-assisted acid digestion. REE concentrations for the three fractions were measured through inductively coupled plasma-mass spectrometry (ICP-MS). The comparison among the chondritic-C1 normalized patterns proved the strong influence of pH and the redox potential of the solution on the distribution of the REEs into the three phases. The complexation by carbonate and bicarbonate ions had also a major role in the relative concentrations of Heavy REEs over the Lights ones. The competitive scavenging of REEs by Hydrous Manganese Oxides (HMO) and Hydrous Ferric Oxides (HFO) was shown. The very distinct coefficient of distributions (Kd) shown by Yttrium and Cerium demonstrated their peculiar and opposite behaviors, emphasized in the comparison of the solid fraction over the aqueous one.
Partitioning rare Earth element distribution among particulate, colloidal, and truly dissolved fractions: implications for environmental and industrial applications
Fornasaro S.;
2023-01-01
Abstract
In environmental and industrial settings, the distribution and behavior of Rare Earth Elements (REEs) are of great interest due to their unique properties and applications. One critical aspect of understanding REE behavior is distinguishing their distribution among the three main fractions in water systems: colloidal, particulate, and truly dissolved. Particulate fractions refer to particles that are larger than 0.45 μm and settle out of solution under the influence of gravity. Colloidal fractions refer to particles that are between 0.022 and 0.45 (μm) in size and remain suspended in solution due to Brownian motion. Truly dissolved fractions include REEs that are ionized and can pass through a filter with a pore size of 0.022 μm. It is important to distinguish these three fractions because the mobility, bioavailability, and toxicity of REEs can vary greatly depending on their distribution among them. Colloidal and particulate fractions can act as carriers for REEs, affecting their transport and availability to living organisms while truly dissolved fractions are more readily taken up by aquatic organisms. Additionally, industrial applications of REEs often involve specific fractionations, such as the separation of colloidal and particulate fractions for purification purposes. We collected and filtered (through both 0.45 and 0.022 μm) 28 groundwater samples taken on the lower flanks of Etna Volcano (Sicily, Italy). For the determination of 14 lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) plus Y in the aqueous fractions we proposed an improved method based on the coprecipitation of REEs with Mg(OH)2, assisted by the triethylamine (TEA). The particulate fraction, retained on the 0.45 cellulose acetate filters, was assessed by microwave-assisted acid digestion. REE concentrations for the three fractions were measured through inductively coupled plasma-mass spectrometry (ICP-MS). The comparison among the chondritic-C1 normalized patterns proved the strong influence of pH and the redox potential of the solution on the distribution of the REEs into the three phases. The complexation by carbonate and bicarbonate ions had also a major role in the relative concentrations of Heavy REEs over the Lights ones. The competitive scavenging of REEs by Hydrous Manganese Oxides (HMO) and Hydrous Ferric Oxides (HFO) was shown. The very distinct coefficient of distributions (Kd) shown by Yttrium and Cerium demonstrated their peculiar and opposite behaviors, emphasized in the comparison of the solid fraction over the aqueous one.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
