Study on treatment of cationic dye crystal violet wastewater by flotation
HE Xing-cun, CHEN Meng-lin, LAN Liu-chun (Department of Resources and Environmental Science, Guangxi Normal University, Guilin 541004, Guangxi, China)
This paper has presented a new flotation method developed by the author for processing cationic dye wastewater. First of all, the author made a detailed study on the influence of some factors on the flotation efficiency,such as the effect of varying the pH from 3 to 10 on the flotation efficiency, and the effect of adding ethanol on the change of the flotation rate, etc. However, it was proved that the change of CV concentration has little effect on it. The whole study has been done by taking the anionic surfactant, sodium dodecylbenzenesulfonate as the model, which is readily reacted with the crystal violet cation to form a colloidal precipitate (sublate). In our experiment, SDBS has to be present in at least 1.3 molar ratio to CV with an excess of SDBS required to produce a stable foam layer. The experiment result shows that adding a small amount of ethanol (0.05%—1.0%) to the solution may prevent the coalescence of tiny bubbles and increase the flotation rate. Nevertheless, the coexisting ions, such as SO~(2-)_4, Cl~-, NO~-_3, PO~(3-)_4, Ca~(2+), Mg~(2+), Al~(3+) and Fe~(3+) had little influence on flotation efficiency. The flotation rate should have reached 99.7% under the optimum conditions. Being fast, simple and cost-effective, he given method will be beneficial for processing cationic dye wastewater.