Sulfate control removal from salt

All of the iron sulfate and a major portion of the alkali sulfates can be removed from the add extract water by a sequence of heating and lime treatment to form insolnble minerals such as gypsum. This water ean then be recycled to the water wash train. Under some (very earefiilly controlled) conditions, the predpitate formed ean be a Jarosite-like double salt, which can be easily disposed of or land-filled. 

As the most significant point sources of phosphorus are those from sewage treatment works (STW), control of phosphorus loading is most readily achieved either by precipitation of phosphorus with iron salts (iron(lll) sulfate or iron(lll) chloride) or by biological removal. The latter can only effectively be achieved in STWs using activated sludge and there have been many descriptions of this technique. ... 

In most commercial processes, borax is obtained from lake brines, tincal and colemanite. The primary salt constituents of brine are sodium chloride, sodium sulfate, sodium carbonate and potassium chloride. The percent composition of borax as Na2B40 in brine is generally in the range 1.5 to 1.6%. Borax is separated from these salts by various physical and chemical processes. The brine solution (mixed with mother liquor) is subject to evaporation and crystahzation for the continuous removal of NaCl, Na2C03 and Na2S04, respectively. The hot liquor consists of concentrated solution of potassium salts and borate components of the brine. The insoluble solid particles are filtered out and the liquor is cooled rapidly in continuous vacuum crystallizers under controlled conditions of temperatures and concentrations to crystallize KCl. Cystallization of borax along with KCl from the concentrated liquor must not occur at this stage. KCl is separated from the hquor by filtration. Bicarbonate then is added to the liquor to prevent any formation of sodium... 

For the Kaufmann method,3 even larger amounts of sulfate salt had to be removed before the [BCS] " salt was isolated. This was accomplished by the addition of excess ammonia and coprecipitation of ammonium sulfate and ammonium a-bromocamphor-7t-sulfonate, followed by extraction of the latter compound with ethanol. This method is clearly superior to previous methods, but from our experience the yields are variable, presumably because optimal sulfonation yields are critically dependent on reaction conditions, which consequently need to be carefully controlled. The following method combines... 

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