Abstract
Typical methods for the treatment of waste pickling solutions include precipitation by alkaline reagents, most commonly calcium hydroxide. As a result, large volumes of galvanic sludge form, containing iron, calcium, sulphates, and a relatively small quantity of zinc (<20%), making Zn recovery not profitable. In summary, state-of-the-art Zn galvanization processes entail the loss of valuable metals and the irrational and expensive handling of spent pickling solutions (SPSs). The resulting conclusion is that there is room for a significant improvement in the way SPSs are treated, with the double goal of enhancing Zn galvanization methods’ economic viability and achieving a lesser impact on the environment’s processes. The experimental results show that it is possible to use SPS as a coagulant to treat the process wastewaters, kept separated, and added with sodium hydroxide. The results in obtaining precipitates with Zn contents higher than 40%, increasing the added advantage of making Zn recovery profitable. The results show the possibility of using SPS as a coagulant in the process of physical-chemical wastewater treatment and sodium hydroxide to obtain a precipitate with a zinc content of more than 40%.
Highlights
Applying a zinc coating to increase the corrosion resistance of steel is called “galvanization”, a neologism created in honor of the Italian scientist Luigi Galvani, the discoverer of bio-electricity
Most methods have in common the initial steps, which aim to prepare the steel surface for bonding with Zinc
Wastewaters from Zn galvanization may be grouped into two main types: A mix of rinse water (MRW) and spent pickling solutions (SPS)
Summary
Applying a zinc coating to increase the corrosion resistance of steel is called “galvanization”, a neologism created in honor of the Italian scientist Luigi Galvani, the discoverer of bio-electricity. 70% of contaminants and are periodically dumped into rinsing water, typically in one go, which leads to possible violations of the legal purification standards as well as the loss of valuable components Another pejorative factor is the reduced length of the pickling stage, which ordinarily is carried out in the industry in order to contain treatment time. The resistance of steel to corrosion is obtained with a number of industrial processes based on Zn galvanization All these methods bear a relatively high price tag due to the cost of zinc plates and electrolytes as well as the formation of hazardous wastewaters. Wastewaters from Zn galvanization may be grouped into two main types: A mix of rinse water (MRW) and spent pickling solutions (SPS). Our method’s main novelty was the re-utilization of part of the effluents as a coagulant in the purification process
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