The Study On Disposal Of Fluorinated Multi-metal Smelting Waste Water Through The Combination Of Iron-carbon Internal Electrolysis Coprecipitation Method

The acidic waste water containing lead, arsenic, chromium, cadmium and fluoride istypical pollution produced in metal industry, this study focuses on iron-carbon internalelectrolysis coprecipitation method, a new type of technology to treat the smelting wastewater from Yongxing County of precious metal smelting industry. Through beakerexperiment, this study explores the influence elements of wastewater by iron-carbon internalelectrolysis coprecipitation method. Based on it, test study is conducted with iron carbonelectrolysis experiment device. Besides, the analysis device of SEM, XRF, XRD to makeclear of the reaction mechanism. Moreover, process design and cost analysis are also done foriron-carbon internal electrolysis coprecipitation dealing with fluoride multi-metal. Theconclusions are listed below:(1) The optimal operating conditions of iron-carbon internal electrolysis coprecipitationmethod to treat smelting industry waste water are as follows: iron-carbon internal electrolysiswater pH is3, the ration of Fe and C is1, and hydraulic retention time is60min and the pHfor coprecipitation is8. Under this condition, aeration reaction can improve the process ofiron electrolysis. The result also shows that the method has a wonderful efficience with aremoval ration to As, Pb, Zn, Cu and fluoride of98.8%,94.3%,93.5%,93.5%and95.6%.(2) The pilot analysis shows: when the iron-carbon internal electrolysis water pH is2,hydraulic retention time is1h, the ration of Fe and C is1, aeration rate is0.8m3/h.continuous feeding, the removal rate of heavy metals and fluoride can reach the beakerexperiment results. After sustained reaction for40.5h, the removal ratio of As, Cd, Zn, Pband fluoride in wastewater is94.1%,78.6%,69.5%,91.8%and63.1%. After60hours, theFe-C component is no longer in force. After socked in10%H2SO4for3hours, the Fe-Ccomponent can be reused for a removal ration to As, Pb, Cd, Zn and fluoride of94.7%,99.3%,83.4%,39.7%and66.7%, after sustained reaction for27.5h, the removal ratio of As,Pb, Cd, Zn and fluoride in wastewater is75.7%,96.6%,65.9%,10.4%and55.6%.(3) The result shows: when the water pH is2, hydraulic retention time is1h, the rationof Fe and C is1, aeration rate is0.8m3/h. And under the conditions of internal reflux,Intermittent operation, the removal ratio of As, Pb, Cd, Zn, Cr and fluoride in wastewater is 99.6%,88.7%,72.7%,56.86%,98.3%and87.5%; continuous operation, the removal ratio ofAs, Pb, Cd, Zn, Cr and fluoride in wastewater is99.1%,98.4%,75.1%,54.7%and68.1%;The effluent quality effect is reduced greatly by the intermittent operation mode with thebatch number, and the water quality effect with prolonged time of smaller amplitude underthe continuous operation mode, after sustained reaction for22.5h, the removal ratio of As, Pb,Cd, Zn and fluoride in wastewater is91.1%、84%、53.1%、10%and18.4%respectively, withpH remaining4and more.(4) The ultrasonic wave/iron-carbon operation result shows: it is better to use ultrasonicwave/iron-carbon operation rather than pure iron carbon because of time duration and highefficiency. To treat the high concentration wastewater, the removal ratio of As, Pb, Cd, Zn, Crand fluoride in wastewater is96.5%,96.7%,72.4%,90%,97.8%and81.5%after useultrasonic wave/iron-carbon operation, after sustained reaction for21h, the removal rate isstill reached82.6%,94.6%,44.1%,73.5%and76.2%.(5) In order to make clear of the mechanism of reaction, some analysis is conducted suchas XRD and XRF to the surface of Fe/C. Fe/C may formed Fe2+, Fe3+after electrochemicalreaction and then crosslinked with F-, presents complex form at last, such as FeF2+,FeF2+,FeF3, FeF4-, FeF52-and FeF63-and then Na(x-3)FeFx, FeFx(OH)(3-x)are harvested. At the sametime, Cr6+is reduced Cr3+which in the form of Cr(OH)3cooperate with the former.(5) Iron-carbon internal electrolysis coprecipitation method costs9yuan per ton to dealwith the waste water with fluoride multi-metal, which saves20yuan per ton compared withtraditional Fenton oxidation method. Besides, this technology owns simple equipment and iseasy to be conducted.