Experimental Study on Formation Conditions of Ammoniojarosite and Its Environmental Significance

摘要

Formation conditions of ammoniojarosite In system Fe_2(SO_4)_3-(NH_4)_2SO_4-H_2O are investigated in this paper. The results show that ammoniojarosite can be formed rapidly under normal temperature and pressure by controlling suitable pH value and Fe_2(SO_4)_3 and (NH_4)_2SO_4 concentrations. The pH value, temperature and concentration of Fe_2(SO_4)_3 medium are key factors influencing the formation of ammoniojarosite. Under normal temperature, precipitation of ammoniojarosite can be seen within 24 hours at pH values between 2.6 - 3.1, and a great quantity of ammoniojarosite is formed within 48 hours. At about 90 deg C, the pH value range forming ammoniojarosite extends to 1.2 - 3.1, and within this range the rise of pH value is advantageous to the formation of ammoniojarosite and high Fe_2(SO_4)_3 concentration is also advantageous. Relative pure ammoniojarosite is synthesized under high Fe_2(SO_4)_3 concentration (>=0.05 M) and ammoniojarosite containing melanterite and colloid amorphous hydroxide vitriol Iron Is formed at low Fe_2(SO_4)_3 concentration. The deposition process of ammoniojarosite can be used to harness wastewater from mines and other industries and remove S, Fe and other toxic and harmful elements, such as As, Cr, Hg, Pb in water. Rapid formation of ammoniojarosite and other jarosite analogs under normal temperature and pressure has a good potential prospect for harnessing acid wastewater by means of precipitation of jarosite and its analogs.