Research On Treatment Of Ammonia-nitrogen Wastewater Produced From Tungsten-molybdenum Metallurgy Process

Ammonia-nitrogen can cause water eutrophication and quality deterioration, the state of ammonia nitrogen wastewater discharge of strict control. Many domestic and foreign researchers had a lot of in-depth research on ammonia nitrogen wastewater treatment and no economic efficient processing method yet. According to the treatment research on ammonia-nitrogen in life wastewater, agricultural wastewater and chemical wastewater, treatment methods include air stripping, chemical precipitation and biological method, and ion exchange method, membrane method, chemical catalyst method are still in the laboratory stage.This paper studied the methods of treatment high concentration ammonia-nitrogen wastewater from tungsten-molybdenum metallurgy process, and obtained good effect, expected to be applied to metallurgical industry wastewater treatment. Specific research process is as follows:This paper removal high concentration ammonia-nitrogen wastewater which is ammonium molybdate acid precipitated mother liquor (CN=31.474g/L, pH=6.1) as raw material liquid. Wastewater ammonia-nitrogen concentration lower than the national standard of ammonia-nitrogen concentration with jet to take off most of the ammonia and then deep treatment low concentration ammonia solution with chemical precipitation and oxo-process.Firstly jet to take off the ammonia in self-restrainted equipment, the effects of pH value, pressure, temperature and stripping time on the air stripping efficiency of ammonia-nitrogen are investigated. The experimental results indicate that the air stripping efficiency of98.7%is achieved with pH value of12and pressure of0.0018MPa at60℃for80mins of air stripping in circles. The concentration of ammonia-nitrogen in wastewater can be removed from31.474g/L to382mg/L under the above condition.In the treatment of ammonia-nitrogen in the air stripped wastewater with the method of MAP chemical precipitation, the effects of pH value, reaction temperature and reactant ratio on the removal efficiency are investigated. Further more, using the pyrolytic products adsorption ammonia-nitrogen of air stripped wastewater which is pyrolysised in tubular furnace, the recycling process of pyrolysis MAP and the effects of pH value, initial ammonia-nitrogen concentration and dosing on the removal efficiency are investigated. The experimental results indicate that the residual of ammonia-nitrogen concentration is159mg/L whiches initial concentration is301mg/L can be achieved with MgCl2·6H2O and Na3PO4·12H2O as the precipitation agent and dosing ratio for n (Mg): n (N):n (P)=1.1:1:1at25℃for mixing30mins on the pH value of9.0, and MgCl2·6H2O should be joined after Na3PO4·12H2O dissolved.Ammonia-nitrogen adsorbent of main component is MHP can be prepared through the magnesium ammonium phosphate(MAP) pyrolysis. Improve pyrolysis temperature is beneficial to the ammonia-nitrogen break away from MAP. The magnesium ammonium phosphate(MAP) pyrolysis experiments indicate that the most efficient of ammonia-nitrogen removing can be achieved at105℃. The experimental results indicate that the residual of ammonia-nitrogen concentration is82mg/L whiches initial concentration is381mg/L.In the treatment of ammonia-nitrogen in the air stripped wastewater with the method of oxo-process by chlorine bleach(Ca(C10)2), the effects of pH value, dosing way and dosing quantity of the oxidant, reaction temperature and reactant time on the removal efficiency are investigated. The experimental results indicate that the residual of ammonia-nitrogen concentration is9mg/L whiches initial concentration is469mg/L can be achieved with oxidant dosing ratio for n(N):n(ClO)=1:3.0at room temperature for reaction30mins on the pH value of6.0, and the air stripped wastewater should be joined after oxidant.To sum up, ammonia-nitrogen concentration of waste water can meets emission standard below by the treatment method which the jet to take off processing and oxidation processing combined in treatment ammonia-nitrogen wastewater produced from tungsten-molybdenum metallurgy process in the best condition.