Method for treatment and cyclic utilization of sulfuric acid waste water containing heavy metal

[0027] For the process flow of the method of the present invention, see figure 1. Sulfuric acid wastewater containing heavy metals 1 (containing H 2 SO 4 4.37%, As 39.1mg/L, Pb 5.4mg/L, F 102.6mg/L) enter the machine-mixed reaction tank A, and add lime 2 for treatment under mechanical mixing. The treatment time is 15 (or 10, 20) minutes. The pH value is 11.4 (or 11.0, 12.0), which causes the fluorine in the wastewater to form calcium fluoride precipitation; the effluent of the machine-mixed reaction tank A enters the aeration reaction tank B, which is 4 (or 6, 8) based on the Fe/As molar ratio ) Add ferrous sulfate 3 and compressed air 4 for treatment, the treatment time is 30 (or 20, 40) minutes, and the pH value is 11.1 (or 10.5, 11.5), so that the ferrous iron in the wastewater is oxidized to trivalent iron , Arsenic produces iron arsenate and iron arsenite precipitation, and lead produces flocculation precipitation; the effluent of the aeration reaction tank B enters the filter press C for filtration; the arsenic, lead, fluorine and other sediments are filtered out and filtered by the filter press After the filter residue has a moisture content of less than 40%, the filter residue 5 is sent to the cement plant for use; the filtered water 6 enters the secondary reaction tank D, and the Fe/As molar ratio is 12 (or 10, 20). Ferrous sulfate 3 is added and compressed Air 4 is processed, the processing time is 20 (or 30, 40) minutes, and the pH value is 10.7 (or 10.0, 11.0), so that the remaining heavy metals in it will further react to form precipitates; the effluent of the secondary reaction tank D enters the carbon dioxide decalcification Reaction tank E, aeration treatment with compressed air 7 containing 1.6 (or 0.5, 5)% carbon dioxide, the treatment time is 20 (or 10, 30) minutes, the pH value is 9.8 (or 9.5, 10.5), and a small amount of water Calcium hydroxide reacts with carbon dioxide to form fine calcium carbonate crystals, which reduces the stability of supersaturated calcium sulfate in the water; the effluent of carbon dioxide decalcification reaction tank E enters coagulation reaction tank F, and inorganic flocculant 8 and PAM are added as usual 9 Carry out coagulation treatment, the treatment time is 15 (or 5, 20) minutes, forming co-precipitation conditions, the inorganic flocculant 8 is aluminum sulfate (or ferric sulfate, polyferric sulfate, polyaluminum sulfate, polyaluminum iron sulfate and sulfuric acid The compound of iron and aluminum sulfate, the compound of polyferric sulfate and polyaluminum sulfate, etc.); PAM 9 is a commercial polyacrylamide; the effluent from the coagulation reaction tank F enters the sedimentation tank G, and the precipitation time is 2.5 (or 1 4) Hours, the precipitation that occurs is the co-precipitation of calcium carbonate, calcium sulfate, arsenic, lead, fluorine and other precipitates with the coagulant, which not only makes the concentration of arsenic, lead, and fluorine in the effluent reach the emission standard, but also The calcium concentration is reduced from the supersaturated state to the unsaturated state. The sediment 10 of the sedimentation tank G is regularly pumped to the filter press C for filtration; the effluent 11 of the sedimentation tank G enters the pH adjustment tank H, with carbon dioxide 1.6 (or 0.5, 5) % Compressed air 7 is aerated and its pH is adjusted to 6.3 (or 6.0, 8.0); the effluent 12 of the pH adjustment tank H enters the reuse water storage tank I. After the heavy metal-containing sulfuric acid wastewater is treated by the method of the present invention, the pollutant concentration is reduced to As 0.067mg/L, Pb 0.013mg/L, F 5.1mg/L, and the calcium concentration is 514mg/L, which not only meets the emission standard, but also meets the sulfur Water requirements for the purification process of iron ore acid production process. The reused water 12 is sent to the pyrite acid production purification process for recycling.