SYNTHESIS AND PROPERTIES OF COMPLEX FORMING IONITES

ABSTRACT

In this article, the sorption of Cu²⁺ ion to ionite synthesized on the basis of N-vinylmorpholine, acrylic acid and colloidal silica is studied.

АННОТАЦИЯ

В данной статье изучена сорбция иона Cu²⁺ ионитом, синтезированным на основе N-винилморфолина, акриловой кислоты и коллоидного кремнизола.

Keywords: azobisisobutyronitrile, N-vinylmorpholine, acrylic acid,  DFMA, copolymerization.

Ключевые слова: динитрил азбисизомасляной кислоты, N-винилморфолин акрыловой кислоты, ДФМА, сополимеризаця.

Introduction

Nowadays, ionites are widely used as a modern and effective method of extracting non-ferrous metals from wastewater. Cationites are mainly used for the extraction of metal cations. Depending on which ions of the ionite are exchanged with the environment, they can be divided into the following groups:

1. cationites - anionite and ionite containing an aniogenic group, which replace cations in the environment;
2. anionites - cationite and ionite containing a cationic group, which are exchanged with anions;
3. ampholytes are ionites containing cationic and anionic groups, and under specific conditions, both cationic and anionic functions. 

In the process of extracting d-metals from wastewater, it is carried out with the help of ionites that have the electron-donor group, which has the property of metal sorption due to donor-acceptor bonds. Such ionites sorb metals as a result of interaction with molecules and ions that hold empty orbitals and form a complex. The main parameters of complex-forming ionites are sorption capacity, selectivity, stability constants and structure of the complex.

One of the methods that allows easy influence on the composition, structure and properties of hybrid sorption materials is sol-gel synthesis with inorganic and organic matrix. Products obtained by the sol-gel synthesis method are characterized by thermal stability and high mechanical strength. Polymer compounds with nitrogen atoms in their macromolecule allow not only to increase the high efficiency of metal separation, but also to improve the technical properties of hybrid materials.

Polymer molecules can interact to form three-dimensional structures in space. Branched structures can also be formed during polymerization or from macromolecules. Three-dimensional structured meshes are obtained on the basis of welding, solidification, vulcanization reactions. Crosslinking of macromolecules can occur due to the connection of two active groups in their composition. Monomers or oligomers containing an active group act as a crosslink (bridge) of macromolecules. Molecules involved in conjugation must be polyfunctional or at least bifunctional or possess an active double bond that is capable of polymerization.

In addition to functional groups, the operational properties and selectivity of ionite depend on its structure and functional groups. Based on the above, complex-forming hybrid ionites were synthesized and their sorption properties were studied.

Materials and methods

The process of copolymerization of N-vinylmorpholine (N-VM) and acrylic acids (AA) was carried out in the presence of dinitrile azobisisomoic acid at a temperature of 60 °C for 6 hours in a DMFA solution. The process of radical solomerization takes place at the expense of vinyl groups. After the copolymerization process, the product was subjected to two precipitations, treated with colloidal silica (CS), and then dried to a constant mass under vacuum. The resulting white ionite solid was washed with distilled water and dried in a drying oven to constant mass.

Figure 1. IR spectrum of the synthesized VM-AA-CS composition ionite

The sorption activity of the synthesized sorbent for d-metal ions was determined by the static method. It was studied in relation to the Cu²⁺ ion in hydrochloric acid solutions, in such solutions the metal exists in the form of an acidocomplex. Ionite mass - 0.025 g (accuracy of 0.0002 g) was measured and filled with copper sulfate solution with concentration - 1-7 mg/ml until volume - 50 ml and left for 3 hours. After the end of the experiment, the composite was separated from the solution by filtration, and the filter was washed with distilled water. Then the concentration of Cu²⁺ ions remaining in the solution was determined. 15 ml of a 20% solution of  KI, 2 ml of 2 N sulfuric acid and an aliquot (25.00 ml) of the test solution are poured from the graduated cylinder into the titration flask. Covering the flask with a watch glass, the mixture was left in the dark for 5 minutes (to complete the reaction). After that, it was titrated with sodium thiosulphate solution, the titration was carried out in the presence of starch solution (5 ml), the precipitate and the solution acquired a light yellow color when mixed. An excess of one drop of sodium thiosulphate solution causes the blue color of the liquid to disappear and reappear after a certain time, indicating that the titration is nearing completion. The titration rate is slowed down and continued until no color appears. When the solution turns copper iodide color, the titration is complete.  To obtain an accurate result, the titration was repeated 2-3 times and the results were averaged.

Figure 2. Adsorption kinetics of Cu2+ ions in the tested sorbent material samples

As can be seen from the graph 1, the sorption of copper ions increases with time according to the laws. In the ionite consisting of  VM-AA-CS, it is observed that another copper forms an internal complex due to the hydrogen of the hydroxyl group in colloidal silicon sol, and the sorption of copper takes place in a small amount compared to nickel and aluminum.

Conclusion

The influence of the concentration of monomers on the radical copolymerization reaction in the presence of DAA of N-VM and AA was studied. From the obtained results, it was known that the optimal concentration for the copolymerization reaction of N-VM and AA under constant conditions is 0.90:0.10. A composite sorbent material with a high sorption capacity was obtained with the presence of nitrogen-retaining copolymer and colloidal silica.

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