Abstract
This paper presents experimental results obtained by agitation leaching of hazardous waste sample – flux skimming. Such flux is formed by Zn(OH)Cl and NH4Cl phases. Distilled water and water solutions of hydrochloric acid were selected as a leaching media.The aim of this study was to determine optimal conditions of zinc extraction into the solution. The apparent order of reaction with regard to the initial HCl concentration in the leaching solution is n=0.18 in the concentration range from 0.01 mol.dm-3 to 0.25 mol.dm-3. The obtained results also indicate that the temperature does not significantly affect zinc extraction. The value of apparent activation energy was estimated to Ea=3.985 kJ.mol-1. Optimal liquid to solid ratio L:S=80 for both used leaching media was also determined experimentally as well as the stirring rate at 200 rpm.
Highlights
In the field of surface treatment the technology of zinc hot-dip galvanizing is wide-spread method of anticorrosion protection of steel products
The influence of HCl solution concentration on the zinc extraction at the following conditions was investigated in this experimental part: leaching temperature – 293 K, stirring rate – 200 rpm, L:S ratio – 80:1
4 Conclusions Experiments showed favorable effect of an increasing concentration of hydrochloric acid in the interval of 0.01 to 0.25 M HCl on the zinc extraction, where after 5 minutes of leaching in 0.01 M HCl the zinc extraction was at 51 % and in 0.25 M HCl 92%
Summary
In the field of surface treatment the technology of zinc hot-dip galvanizing is wide-spread method of anticorrosion protection of steel products It is a metallurgical process where the formation of regular zinc coating takes place at the temperature between 450 and 470°C by interaction between the melted zinc and steel part [1 - 6].Zinc hot-dip galvanizing can be divided according to the used technology to continuous and batch. 1.1 Specific waste formation During the wet zinc hot-dip galvanizing process a foam like fluxing agent occurs on the surface of separated part of the zinc bath. Specific waste forming only during the wet hot-dip galvanization is flux skimming It is a spent and inactive fluxing agent which forms on the surface of zinc bath in the separated part of the bath. According to The Europen Waste Catalogue & Hazardous Waste List – Valid from 1 january 2002, flux skimming is placed in the category „ hazardous waste – 11 05 04” [19]
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