PHYSICO-CHEMICAL PATTERNS OF PRECONCENTRATION OF Sm(III), La(III), Er(III) BY A COPOLYMER OF POLYVINYL ALCOHOL, FORMALDEHYDE AND UREA
Belyakovich D.I., Didukh-Shadrina S.L., Losev V.N., Gulieva R.M.
Siberian Federal University
660041, Krasnoyarsk, Svobodny st., 79
Various sorption models are used to study surface phenomena in the preconcentration of rare earth metals. In this work, sorption theories are applied to the preconcentration of Sm(III), La(III), Er(III) with a copolymer of polyvinyl alcohol, formaldehyde and urea (PVF-U).
The PVF-U sorbent quantitatively extracts (recovery rate > 98%) REM from aqueous solutions at pH 4-7. The sorption capacity of the sorbent is relative to La(III), Sm(III), Er(III) is 0.086, 0.078, and 0.057 mmol/g, respectively.
The experimentally obtained sorption isotherms were analyzed by the sorption models of Langmuir, Freundlich, Dubinin-Radzhdankevich, Temkin (see the table).
Parameters of La(III), Sm(III), Er(III) sorption isotherms with PVF-U sorbent
| Sorption theory | Characteristics | La(III) | Sm(III) | Er(III) |
|---|---|---|---|---|
| Langmuir | aмах, mmol/g | 0.085 | 0.074 | 0.057 |
| KL, l/mmol | 3.0 | 2.0 | 3.4 | |
| RL | 0.15–0.94 | 0.23–0.94 | 0.19–0.95 | |
| r | 0.952 | 0.951 | 0.944 | |
| Freundlich | aмах, mmol/g | 0.061 | 0.058 | 0.048 |
| 1/n | 0.44 | 0.62 | 0.48 | |
| n | 2.3 | 1.6 | 2.1 | |
| r | 0.995 | 0.954 | 0.989 | |
| Dubinin-Radzhdankevich | aмах, mmol/g | 0.047 | 0.027 | 0.059 |
| KD, mmol 2/ kJ2 | 0.0042 | 0.0061 | 0.0043 | |
| E, kJ/mol | 10.9 | 9.1 | 10.8 | |
| r | 0.982 | 0.971 | 0.972 | |
| Temkin | AT, l/g | 63 | 35 | 69 |
| B, J/mol | 0.016 | 0.017 | 0.011 | |
| r | 0.912 | 0.962 | 0.900 |
The REM sorption corresponds to the Langmuir model, which indicates the sorption of metals on an energetically homogeneous surface. The values of the separation coefficient (RL) according to the Langmuir model and 1/n according to the Freundlich model are in the range 0-1, which indicates a high adsorption capacity of the sorbent in relation to recoverable REM ions. The calculated free energy of adsorption (E) according to the Dubinin-Radostkevich model indicates the chemical mechanism of sorption, and the energy according to the Temkin model (B) indicates the exothermic process.