Abstract
The electrochemical treatment of wastewater is widely used for cleaning due to its efficiency. In this paper, two-dimensional (2D) and three-dimensional (3D) electrochemical systems were used to treat cyanide wastewater. The effect of the applied voltage and the material of the main electrode on the removal of various ions and the characteristics of chemical reactions were mainly studied. The results show that the applied voltage was the key effect of the electrochemical treatment process. The removal of ions from the wastewater at 2 V is mainly due to the effect of electro adsorption and enrichment precipitation, while at 4 V, it is mainly due to anodization and cathodic deposition. The treatment effect of the 3D electrode system was significantly better than the 2D system. The 3D electrode system by used granular activated carbon as the particle electrode, with the carbon filled stainless mesh (CM) and coal based electrode (CB) as the main electrode, the treatment effect were better than main electrode of stainless steel mesh (M). The 3D system with CB as the main electrode had an applied voltage of 4 V, a treatment time of 5 h, plate spacing of 10 mm, and the dosage of activated carbon particles was 2 g. The removal rates of CNT, Cu, Zn, CN−, and SCN− were 94.14, 94.53, 98.14, 98.55, and 93.13%, respectively. The main reaction in anode was the electroly oxidation of CN− and SCN−, while the electrolytic deposition of Cu, Zn, and other metal ions in the cathode surface. There were not only adsorption and electric adsorption of various ions, but also an electrolytic deposition reaction of Cu, Zn, and other metal ions on the surface of the activated carbon particle electrode. During the electrochemical reaction, the concentration of hydrogen ions near the anode increases locally, which produces the precipitation of CuSCN, Cu2Fe(CN)6, and Zn2Fe(CN)6, etc. in the solution, which are helpful for the removal of cyanide and heavy metal ions in cyanide wastewater.
Highlights
Cyanide wastewater treatment has been the subject of research due to the difficulty of treating its complex composition, which contains a large number of free cyanide and copper, zinc, iron metal cyanide complex ions
Treatment cyanide wastewater used the main electrodes of M, carbon filled stainless mesh (CM), and coal based electrode (CB), respectively, under 2 and 4 V conditions by the 2D system
It can be seen from the results that the removal rates of ions for the three kinds of main electrodes were relatively low at 2 V, basically no more than 60%
Summary
Cyanide wastewater treatment has been the subject of research due to the difficulty of treating its complex composition, which contains a large number of free cyanide and copper, zinc, iron metal cyanide complex ions. The 3D electrode system achieved results in terms of process and basic theory (Lei et al, 2013; Ting et al, 2018) At present, it is used for the electrochemical oxidation-reduction treatment of inorganic heavy metal ions including lead, zinc, copper, nickel, and chromium, and organic industrial wastewater from dyeing, papermaking, coking, and other industries. To examine the effect of voltage on the treatment of cyanide wastewater with a 3D electrode, Yao et al (2017) used self-made coal based electrode material as an anode and cathode, and commercial activated carbon as particle electrodes to treat cyanide gold extraction wastewater. The electrochemical treatment of cyanide wastewater by 2D and 3D systems and the effects of electrode materials and applied voltage on the removal law of various ions in cyanide wastewater and its mechanism was studied.
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