| In recent years, with the rapid development of industrial production, the chromium has already caused great environmental pollutions. There are mainly two kinds of existence forms of chromium in the wastewater, Cr (VI) and Cr (III). In the chemical compound of chromium, Cr (VI) has the strongest toxicity and it is easily dissolved with infiltration of the rainwater, which could seriously pollute the soil, river and underground water source of the surrounding environment. There are many kinds of technologies in treating the wastewater containing chromium and they have both advantages and disadvantages. Within many years' researches, chemical methods were nearly 90% introduced in internal water treating. As one part of chemical methods, electrochemical method contains the processes of electro-coagulation, electro-floatation, electro-oxidation and electro-deoxidation, which make the capability of the management be all-sided. In this paper, we used electrochemical method to treat the wastewater containing Cr which got from the silicic steely mill of Wuhan steely factory, took systematic research to the questions of electrode materials, electrode passivation and concentration polarization, and finally got the best technics. The best technics were as follows: taking iron as the electrode material; throwing 0.8g/L NaCl as the assistant electrolyte; no pretreatment of the original water; the pH value being 3.5; the electric current density being 1.8A; the distance of the electrodes being 7 mm; the electrified time being 30 min; and the change time of the electrodes being 3 min. In the output-water, the high wiping rate of turbidity, the chroma, Cr (VI) and the total Cr reached separately to 96.13%, 92.31%, 97.33% and 90.56%. In this study, we also discussed the chemical reductive method to the wastewater containing Cr. The results showed that this method had great treatment effect while it still had some apparent shortcomings such as more medicament throwing, more smudge output and easier secondary pollution producing. All these verified that the electrochemical method was more comprehensive and it had achieved to such kinds of merits as strong wiping effect to all kinds of targets; no need of medicament throwing, little smudge output, callback of high neat metals, and great treat cost decreasing; and easily operation contrasting with the electroplate method. |
