Introduction. Phosphates of metals are widely used in the chemical and the petrochemical industry as anticorrosive coatings for equipment, pipelines and other products. Production of metal phosphates from industrial wastes, in particular from chloride salts, is an actual problem. One of perspective directions is production of concentrates from industrial wastes in the kind of complex metal chloride compounds. The processing of lead slags by chloridosublimation method allows produce metals as chlorides of metals - ZnCl2, PbCl2, FeCl2 and other. At the decomposition of metal chlorides by phosphoric acid it is possible to obtain phosphates of metals and hydrochloric acid [1,2].
Aim of the Research. Исследование процесса разложения хлоридов металлов с фосфорной кислотой.
Materials and methods. The preliminary fulfilled thermodynamic calculations show a thermodynamic probability of the chemical reaction of zinc chloride with phosphoric acid with formation of Zn(H2PO4)2 • 2Н2О, FeHPO4 and HCI, hereof a negative value of the Gibbs energy (-AGT °) testifies.
ZnCl2 + 2Н3РО4 + 2H2O = Zn(H2PO4)2 • 2Н2О + 2HCl (1)
FeCI2 + H3PO4 = FeHPO4 + 2HCl (2)
The calculation of the Gibbs energy values was carried out in a temperature interval of 298-433К using a computer program.
The formation of zinc and iron phosphates occurs according to the reactions (1) and (2). The process takes place at intensive hashing in a temperature interval of 60-120°С and duration of 40-60 minutes. In the process hydrogen chloride is liberated in a gas phase and Zn(H2PO4)2 and FeHPO4 are precipitated.
Results and discussions. The influence of the temperature and the duration of the process on a degree of transformation of zinc and iron chlorides in the corresponding phosphates (atransf) is presented in the table 1 from which follows, that with the increase in temperature and duration of the chemical interaction, a degree of transformation of zinc and iron chlorides in zinc and iron phosphates increases and simultaneously a residual content of chlorine in the products decreases.
Table 1 - Influence of temperature and duration of the chemical reaction on a degree of the zinc chloride decomposition
|
# of an experi-ment |
Temperature, °C |
Duration, minute |
Content, % |
Degree of transformation (a), % |
||
|
P2O5 |
ZnO |
Cl |
||||
|
1 |
80 |
40 |
54,69 |
30,5 |
1,2 |
98,90 |
|
2 |
80 |
60 |
54,71 |
31,2 |
0,9 |
99,05 |
|
3 |
80 |
90 |
54,74 |
31,4 |
0,4 |
99,61 |
|
4 |
100 |
40 |
54,60 |
31,1 |
0,12 |
99,90 |
|
5 |
100 |
60 |
54,71 |
31,3 |
absent |
100 |
|
6 |
100 |
90 |
54,71 |
31,36 |
absent |
100 |
|
7 |
120 |
40 |
54,73 |
31,4 |
absent |
100 |
The results presented in the (table 1) show that with the increase in temperature and duration of the chemical reaction, a degree of transformation of zinc chloride in monozincphosphate increases and simultaneously a residual content of chlorine in the product decreases. The received hydrochloric acid containing 28-30 % HCl meets the qualifying standards to quality of a technical hydrochloric acid. The (table 2) contains the results of iron chloride decomposition by phosphoric acid.
According to the data of the table 2 with the increase in temperature and duration of the process the FeHPO4 yield increases simultaneously with the decrease of the FeCl2 and free acid contents in the product. Thus the FeHPO4 yield at 170°С makes 5,94 g and the chlorine is practically absent [3].
Conclusion. Thus, the carried out researches have proved a possibility of monozincphosphate obtaining from zinc chloride, and the X-ray phase and infrared spectral analyses have shown the presence of Zn(H2PO4)/2H2O and FeHPO4 and the absence of chlorine in the product.
List of literature
- Anarbayev А.А, Kabylbekova B.N., etc. Research of the technology of chlorine-containing waste processing on composite protective materials//News of Kazakhstan science, № 2, 2005.- P.100-102.
- Anarbayev А.А, Kabylbekova B.N., etc. Kinetics of the decomposition of chloride compounds of soda slimes by phosphoric acid//Chemistry and chemical technology: International theoretical and practical conference proceedings, St. Petersburg, 2006.- P.69-72.
- Doroshkevich A.P., Hudjakov I.F. Complex raw materials use at the processing of scrap metal and wastes of heavy nonferrous metals. - M.: Metallurgy, 1985. - 155 p.