With the improvement of environmental awareness, people have paid more attention to the pollution of heavy metals in various products. The research shows that the cement used as the base material of mixed concrete also contains a lot of heavy metals, of which water-soluble hexavalent chromium is the most harmful to human health.
In the treatment of reducing chromium in cement,ferrous sulfate has always been the first choice of reducing chromium in cement plants because of its low cost and good effect of reducing chromium, but the research team found that it also has some disadvantages. Let's analyze it through some data.
Comparison of chromium reduction effect of ferrous sulfate in different states
From the analysis results in the above table, it can be seen that ferrous sulfate heptahydrate can significantly reduce the content of hexavalent chromium in cement at room temperature, while ferrous sulfate oxide has the worst effect. To achieve the same effect as ferrous sulfate heptahydrate, more anhydrous ferrous sulfate or ferrous sulfate oxide need to be added. It should be noted that when using ferrous sulfate heptahydrate as a chromium-reducing agent, due to the high water content of ferrous sulfate heptahydrate, the storage of products needs to be more careful.
Comparison of chromium reduction effect after adding ferrous sulfate at high temperature
It can be clearly seen from the results in the table that the content of water-soluble hexavalent chromium in cement decreases significantly after adding ferrous sulfate at normal temperature, but at simulated high temperature, with the increase of temperature, the content of hexavalent chromium can rebound to the level of cement without adding ferrous sulfate. This shows that ferrous sulfate oxidizes and loses water at high temperature, resulting in loss of reduction effect.