Technology Research On Major Element Extraction From Underground Brine In Jiangling Depression

Sodium,potassium,boron,lithium and rubidium et al,were rich in Jiangling brine,in which the content of major component sodium chloride,potassium chloride and boron were 281.83 g/L,17.12 g/L and 2.48 g/L,respectively,easily outstripping the industrial grade and worthy to be exploited.Impurities in the brine such as sediment,ferrum and sulfur had influence on recovery of valuable components and needed to be purified preliminary.Otherwise,salts of sodium,potassium and boron were easy to be mixed through evaporating,which resulted in more difficulties in purifying the potassium products;meanwhile,in the stage of salting out Na Cl,boron lost partially by entrainment and thus the recovery rate of boron was low.To solve the problem above,purification process,solvent extraction of boron and separation process of potassium and sodium were studied in this paper.Impurities in the brine such as sediment,ferrum and sulfur were purified by natural sedimentation,chemical precipitation and air aeration,respectively.Experiments on purifying process showed that when the brine was heated,lots of sodium chloride salted out and were abandoned.Because of it,the purification process was divided into two steps.The first step: At room temperature,the ferrum in the brine was transforming to ferric hydroxide by adding sodium hydroxide into the brine.The second step: The brine without ferrum was enriched through evaporating,in which the sodium chloride reached saturation firstly and salted out.The experimental results indicate that the purifying rate of ferrum can reach more than 99 %,while the purifying rate of sulfur is more than 95 %.The recovery rate of sodium chloride can reach 71.04% while the potassium and boron are almost no loss.Solvent extraction was employed in this study,and most of boron in the brine was planned to be extracted to product boric acid before extracting potassium.The influence of organic phase,extractant concentration,phase ratio(O/A),extraction time had been investigated.The optimizing extraction conditions were: 15 %2-ethyl-1,3-haxanediol,35 % iso-octyl and 50 % sulfonated kerosene as the organic phase,1:1 as the ratio of organic phase to brine,15 minutes as extraction time,under which the one-stage extraction rate of boron was 96.91 %.And the influence of stripping concentration,phase ratio(O/A),extraction time on the stripping had also been concerned.The optimizing conditions of stripping were: 0.625 mol/L sodium hydroxide as the stripping agent,15 minutes as the back extraction time,under which the one-stage stripping rate of boron was 93.97 %.Inspissation method was used to recover sodium chloride.Controling the concentration multiple reaches 3 to 4,about 75 % sodium chloride can be recovered from the brine,while the potassium and boron were enriched without any loss.After the boron extraction process for the concentration solution,potassium chloride was extracted from raffinate by using inspissation-cold crystallization process in two stages.In the first stage,the average recovery rate of potassium chloride and sodium chloride were 60.86 % and 58.29 % with almost no loss of lithium,rubidium,cesium,bromine and iodine.And in the second stage,the average rate of potassium chloride and sodium chloride were 31.06 % and 51.93 %.On the whole,the total recovery rate of potassium chloride and sodium chloride were 73.02 % and 95.34 %.The quality of potassium chloride could achieve the excellent grade of state standard GB/T 7118-2008,and the quality of sodium chloride could achieve the insolation industrial-grade products of state standard GB/T 5462-2003.