SORPTION OF OXOCHROMATE(VI)-ANIONS FROM WATER BY SOME SORBENTS
Journal: HERALD OF TECHNOLOGICAL UNIVERSITY
Rubrics: 1. CHEMISTRY
Authors:
1.
Udmurt State University
2.
Udmurt State University
3.
Udmurtskiy gosud. universitet
Type:
Article
Pages:
from 23
to 27
Status:
Language:
Russian
Keywords:
CHROMIUM, BEMITE, MAGNETITE, MODIFIED MAGNETITE-CHITOSAN (M/CZ), SORPTION
Abstract:
The results of investigation of the process of oxochromate(VI)-anions sorption from aqueous solutions are presented. The obtained sorption materials - magnetite, bemite, chitosan-modified magnetite - were characterised by IR spectroscopy. The sorption experiment was performed under static conditions. 0,1 mol/dm3 KNO3 was used as a background electrolyte. Photometric determination with definylcarbazide at λ=540 nm was used to establish the residual concentration of oxochromate(VI)-anions. The kinetic equilibrium on bemite and magnetite is reached rapidly (20-30 minutes), whereas in the case of modified magnetite it takes 1 hour to fully reach equilibrium. It was found that the sorption of oxochromate(VI)-anions on the studied sorbents depends on the pH value of the solution. On bemite in acidic medium sorption gradually increases up to pH~2,5, and at pH~3-5 - practically does not change, which is probably due to the change of electrostatic interaction between negatively charged adsorbed oxochromate(VI)-anions and the surface of bemite. On magnetite, the degree of sorption decreases smoothly up to pH~6, after which there is a sharp decline. Sorption of oxochromate(VI)-anions by magnetite is probably due to electrostatic attraction and ion exchange. For the modified magnetite, the pH dependence of the sorption degree is to some extent similar to that of ordinary magnetite. However, in acidic medium the maximum degree of sorption is higher than on magnetite, which can be explained by the participation in the sorption of oxochromate(VI)-anions protonated in acidic medium amino groups of chitosan. The obtained sorption isotherms were processed using theoretical Langmuir and Freundlich models. Bemite (Gmax=1,03 mmol/g) and modified magnetite (Gmax=0,92 mmol/g) showed the maximum sorption capacity towards oxochromate(VI)-anions. On the basis of experimental and literature data it can be stated that the greatest contribution to the extraction of oxochromate(VI)-anions on bemite is made by chemical sorption, on magnetite - by electrostatic interaction of the sorbent surface and adsorbate, on modified magnetite - by electrostatic interaction, not excluding chemisorption, ion exchange and complexation. The obtained sorbents can be recommended for use in the removal of oxochromate(VI)-anions from aqueous media.
The results of investigation of the process of oxochromate(VI)-anions sorption from aqueous solutions are presented. The obtained sorption materials - magnetite, bemite, chitosan-modified magnetite - were characterised by IR spectroscopy. The sorption experiment was performed under static conditions. 0,1 mol/dm3 KNO3 was used as a background electrolyte. Photometric determination with definylcarbazide at λ=540 nm was used to establish the residual concentration of oxochromate(VI)-anions. The kinetic equilibrium on bemite and magnetite is reached rapidly (20-30 minutes), whereas in the case of modified magnetite it takes 1 hour to fully reach equilibrium. It was found that the sorption of oxochromate(VI)-anions on the studied sorbents depends on the pH value of the solution. On bemite in acidic medium sorption gradually increases up to pH~2,5, and at pH~3-5 - practically does not change, which is probably due to the change of electrostatic interaction between negatively charged adsorbed oxochromate(VI)-anions and the surface of bemite. On magnetite, the degree of sorption decreases smoothly up to pH~6, after which there is a sharp decline. Sorption of oxochromate(VI)-anions by magnetite is probably due to electrostatic attraction and ion exchange. For the modified magnetite, the pH dependence of the sorption degree is to some extent similar to that of ordinary magnetite. However, in acidic medium the maximum degree of sorption is higher than on magnetite, which can be explained by the participation in the sorption of oxochromate(VI)-anions protonated in acidic medium amino groups of chitosan. The obtained sorption isotherms were processed using theoretical Langmuir and Freundlich models. Bemite (Gmax=1,03 mmol/g) and modified magnetite (Gmax=0,92 mmol/g) showed the maximum sorption capacity towards oxochromate(VI)-anions. On the basis of experimental and literature data it can be stated that the greatest contribution to the extraction of oxochromate(VI)-anions on bemite is made by chemical sorption, on magnetite - by electrostatic interaction of the sorbent surface and adsorbate, on modified magnetite - by electrostatic interaction, not excluding chemisorption, ion exchange and complexation. The obtained sorbents can be recommended for use in the removal of oxochromate(VI)-anions from aqueous media.
Keywords:
CHROMIUM, BEMITE, MAGNETITE, MODIFIED MAGNETITE-CHITOSAN (M/CZ), SORPTION
CHROMIUM, BEMITE, MAGNETITE, MODIFIED MAGNETITE-CHITOSAN (M/CZ), SORPTION
