Gansu Lead-zinc Flotation Wastewater Treatment And Reuse Of New Technology,

The resource of lead and zinc is very rich in the world, especially in Australia, China, the United States, Canada and Russia and so on. According to degree of oxidation, lead-zinc ores are divided into sulfide one, which is that the oxidation rate of lead and zinc is less than 10%, and mixed one, which is that the oxidation rate of lead and zinc is 10%-30%, and oxidation one, which is that the oxidation rate of lead and zinc is more than 30%. In China even in all over the world, the majority of lead-zinc ores are sulfide ones. The beneficiation method of lead-zinc sulfide ore is flotation process. In such flotation process, a large amount of wastewater will be produced, and many kinds of beneficiation reagent will be residual in the waste solution, including some metal ions, suspended solids, decomposed products of organic and inorganic reagents and so on. So beneficiation wastewater involved a large amount of harmful substance will be produced. It will cause serious pollution if the beneficiation wastewater is discharged to the environment directly.Floatation concentrator of Luoba Zinc-Lead Concentrator in Gansu Province has a capacity of 500 tons per day for the run-of-mine ore. The tailing water contains a great amount of metallic ions, suspension, slime and other chemical reagents, which affects on flotation separation. At the same time, the tailing water contains a lot of Ca2+, which is easy to block the pipelines of the concentrators. When the tailing water is discharged into the river course nearby, the bottom of the river course becomes white and the river course gets heavily polluted. Currently, the simple wastewater treatment technology for reuse will surely increase the content of CODcr, pH, Pb2+, Cu2+, worsening the zinc and lead separation. Therefore, the concentration index for zinc and lead will become bad.In order to find a resolution for above situations, detailed investigation on the wastewater processing flow in the concentrator has been conducted, including the measurement of flows and main continents for the overflows of zinc concentrate, lead concentrate, and wastewater from tailing dam. Water quality of tailing water has shown that the influent and treated water belongs to the high alkaline and calcium water. The pH vale varies from 12.89～13.21; Ca2+ 568.6～582.6mg/L; CODcr 140～160mg/L, exceeding the national standards about 1.4～1.6 times; Pb2+ 3.45～5.23mg/L, exceeding the national standards GB8978-1996 for industrial v/astewater about 3.45～5.23times; Zn2+ is about 0.096-1.02mg/L, and other elements meet the requirement of the standards.A comprehensive study has been conducted for this project, including the selection of wastewater treatment scheme and methods, wastewater treatment laboratory tests. Among the laboratory tests, the reagents for wastewater treatment, such as Na2CO3, NaHCO3, NH4HCO3 and LSQ (a new kind of reagent developed and used for removal of Ca2+ effectively), has been conducted covering the combined use of reagents and the reasonable ratio of different combinations. At the same time, agitation time, sedimentation tests, and verifying tests has been carried out too. It should be mentioned that the new reagent LSQ is of environmental-friendly reagent, low price and having the double roles in removal of Ca2+ and flocculation. Through techno-economic comparison on CO2 method, aeration method, and the coagulation-neutralization method, the coagulation-neutralization has proven to be the effective method to treat the wastewater. The recommended reagents' combination in this processing flow as follows:NH4HCO3600mg/L, LSQ+P100mg/L and H2SO4 500 mg/L。Through the implementation of the program, pH vale varies from 7～8, Ca2+ 187.9～190.1mg/L, CODcr70.2～72.3mg/L,Pb2+<0.02 mg/L, Zn2+<0.01 mg/L, it meets the need of national standards on discharge or reuse.At present, the recommended technology Coagulation-Neutralization has been implemented and realized industrialization. It should be mentioned that this technology operates well and is easy to operate in meeting the requirement of purification and reuse. It has been proven to be a practical operation in the said mine.