Research On The Treatment And Recycling New Technology Of Waste Water In Pyrite Acid Production

Wastewater from pyrite acid-making usually features large volume of waste water, high turbidity, high acidity and large content of toxic heavy metals and other toxic substances. Most countries have abandoned the method of pyrite acid-making. But considering the basic condition in our country with large consumption of sulfuric acid and rich pyrite resource, Pyrite acid-making is still allowed. So the new standard 《Emission Standard of Pollutants for sulfuric acid industry》GB26132-2010 was published, which imposes a strain on the enterprises for the wastewater disposal.Based on the existing researches, the thesis has done the experimental research on certain wastewater of pyrite acid-making in Zhuzhou and proposes a new method of combined treatment of “stirring and neutralization-aeration and oxidation-sediment and isolation-ferric salt oxidation-CO2 decalcification-coagulation and sediment-recycle of wastewater”. With the single factor experiment and orthogonal test design carried out by the new method; the research on principles of the arsenic removal with ferric salt; the comparative experiment of new and traditional methods.With the single factor experiment carried out by the new method, the improved parameters of all processes are obtained in the new process. The stage of defluorination and arsenic removal: the best p H value of lime slurry neutralization is 11.0; duration of the neutralization reaction is 20min; the best aeration duration in the first stage is 50 min and in the second stage 40 min. The best quantitative ratio of ferricto arsenic is 8. With the orthogonal test design, Relationships between primary and secondary factors as: the p H value> first stage aeration reaction time> iron-arsenic mass ratio> second stage aeration reaction time> and stir in reaction time. Through the research on principles of the arsenic removal with ferric salt, Freundlich Absorption Equation is applied for the fitting, The fitting coefficient R2 is 0.94, presenting a close correlation. It is concluded with a regression analysis on K and that the mathematic model of ferric-arsenic quantitative ratios’ effect on arsenic removal rate is C=(0.88 +482.53)φ..The stage of decalcification: the best value of the wastewater with after aeration adjustment with CO2-compacted air. The best stirring temperature is 50℃. The best stirring duration is 50 min with the best stirring speed at 150r/min. The best dosage of seed crystal is 1g/L. With the orthogonal test design, Relationships between primary and secondary factors as: Decalcification p H> seed dosage> stirring speed> stirring temperature> in and stirring time.If the wastewater is treated with these conditions, the removal rate of fluorine, arsenic and lead in the treated wastewater are respectively 90.09%, 99.64% and 96.26%. The residues are respectively 7.95mg/L, 0.28mg/L and 0.42 mg/L. The contents of other heavy metals also meet the standard. The decalcification is carried out in the wastewater that has been treated with defluorination and arsenic removal. The calcium ion concentration in the treated wastewater doesn’t reach the saturation.Through the comparative experiment of new and traditional methods, it has been found that the new method is better than the traditional one regarding economic and environmental efficiency. Compared to the traditional methods, new technology aeration time is less 60 min oxidation than the original technology, and the amount of reagent is less 2m L.