Study On The Depth Extraction Of Boron From The Qarhan Salt Lake Brine

Magnesium is the superior resource in Qarhan Salt Lake, and its magnesiumchloride reserves reached4.06billion tons，ranking first in the country. The metalmagnesium integrated projects which started by Qinghai Salt Lake Group in2008isexpected to produce400,000tons of magnesium metal with a total investment of60billion yuan, it is the largest one of the primary magnesium production engineering.The project is to further promote the efficient utilization of salt lake brine resources,give full play to its advantages in resources and speed up the resource transformationprocess; it is of great significance for enriching the magnesium technology in chinaand raising the overall level of the magnesium industry to create magnesium industrialpowerhouse; it can effectively promote the Qinghai and even the country’s rapideconomic and sustainable development. However, the boron content in the existingsalt lake brine is higher （approximately1g/L）,it seriously affected the recovery rateof the electrolytic production of magnesium metal and it has become the majorbottleneck for the project construction process.Therefore it is imperative for the SaltLake brine depth removing boron.Ion exchange and extraction method is the main method of depth of boronremoval.Ion exchange method has better effect on removing boron,it is mainly used insolution system of boron content lessing than30mg/L.this method will use a lot of Ionexchange resin and cost high when the system have higher boron content. Theextraction method is mainly applied to the solution system of boron contentin the2¹8g/L, the low selectivity of existing extractant limited its applicationsystem. Someone suggested that these two methods used in combination to the depthof boron removal, but the process is complex, costly and a heavy workload. Theboron content in Qarhan Salt Lake extracting potassium brine is about1g/L, all ofthe above methods can not effectively solve the technical problems of depth of boron removal.To address the problem,putting forward one-step extraction of depth of boronremoval, selectting the new boron efficient extractant of ExBOR^TMGH81, Using theextracting potassium brine as raw materials in Qarhan Salt Lake, We carried out aseries of in-depth study on the process of depth of the boron removal in this highmagnesium and low boron brine system. We developed a new process of extractiondepth of boron removal,only through the secondary extraction,four stripping,theboron extraction rate can be achieved by99.7%and the boron concentration in theraffinate is less than1mg/L. Specific study content and the results are as follows:1、Using the single factor experiment，I analyzed the impact of brine pH，extractant concentration，Organic phase to aqueous phase ratio （O/A），reaction timeand reaction temperature on the extraction ratio in the single-stage extractionconditions. Selected the best extraction conditions：pH=1，Extractant concentrationis40%，Organic phase to aqueous phase ratio （O/A） is1，reaction time is6minutes，the reaction temperature is40℃.2、Using the single factor experiment，I analyzed the impact of stripping agentconcentration Organic phase to aqueous phase ratio （O/A） and reaction time on thestripping ratio in the single-stage extraction conditions. elected the best extractionconditions：Stripping agent concentration is0.4mol/L，Organic phase to aqueousphase ratio （O/A） is0.5，reaction time is minutes，the reaction temperature is40℃.3、Using the single-stage extraction experiments relevant data in the bestextraction conditions，we can calculate the distribution ratio D=199，according to theboron content in the raw material （1.052g/L）and the Target content（<1mg/L） that weneed to achieve，we can calculated maximum raffinate number is3.0608×10^-3，andthen we can calculate the minimum theoretical stages of extraction required byformula calculation，its value is1.09，we choose2as the minimum theoretical stages.4、I verified the theoretical extraction series by multi-stage countercurrentextraction cycle experiments. Experimental results show that the two counter-currentextraction make the Boron content in the raw materials reduced to less than1mg/L.Most of the boron in organic phase can be eluted out After a four-stripping.The extraction capacity of the regeneration organic phase is still very strong in therecycling process which can meet the production requirements. Therefore，the bestprocess route of depth in addition to boron are as follow：Two countercurrentextraction and four countercurrent stripping.5、Using different concentrations of low boron and magnesium-rich brine to verify the extraction capacity of ExBOR^TMGH81，we find that: After the twocountercurrent extraction and four countercurrent stripping cycle experiment，theamount of boron in the brine raw materials dropped to below1mg/L，this furtherillustrates the ExBOR^TMGH81has a high selectivity and good applicability forboron.