| In order to realize the comprehensive utilization of boron resources in underground brine,the separation and recovery of boron from underground brine were carried out in this thesis by the solvent extraction method and the ion exchange adsorption method,respectively.After laboratory and pilot scale experiments,relevant important parameters were obtained.Main conclusions presented in this work are summarized as follows:(1)The recovery of boron by continuous centrifugal extraction was first carried out at laboratory scale using 50 model centrifugal extractors,and the extraction and back-extraction parameters were optimized.The results showed that sulfonated kerosene(SK)and 2-ethyl-1,3-hexanediol(EHD)were used as the extractant,and the five-stage centrifugal extraction rate was more than 98%at the conditions of EHD:SK=3:7,pH=2,and phase ratio R(O/A)=1:2.The organic phase containing boron after extraction was back-extracted using 0.5 mol/L NaOH,and the back-extraction rate was more than 95%by five-stage centrifugal back-extraction at phase ratio R(O/A)=1:1.(2)The recovery of boron in the aqueous phase obtained by back-extraction was further carried out by evaporating concentration and crystallization.The result showed that the solid phase obtained during the evaporating concentration of the aqueous phase after acidification with HCl was identified to be boric acid by XRD.The saturation extraction capacity of the extractant and the extraction mechanism were also investigated and found that the maximum extraction capacity was 11.09 g/L(or 68.04 g/L in boric acid form).The EHD in the extraction organic phase reacted with boric acid in molar ratio of 1:1 to form a stable six-membered ring structure of boric acid ester,by which the boron in brine was extracted into the organic phase.(3)The results of extraction and back-extraction cycle tests showed that the extraction rate was still higher than 93%after six times cycles,and no emulsion phenomenon was observed.All these results demonstrated the stability and reliability of the extraction system and method developed in this work.Based on these parameters obtained by the 50 model extractors,the pilot scale extraction of boron from underground brine by 150 model centrifugal extractors was carried out,and the three-stage extraction and back-extraction rates were more than 90%and 65%,respectively.Even though the back-extraction rate was relatively low,it can be enhanced by increasing the back-extraction stage.(4)The recovery of boron by resin adsorption using the static adsorption method was carried out and found that the equilibrium absorption capacity reached to 9.23 mg/g using D3 resin at the conditions of pH=7-8 and equilibrium time of 2.5 h.The boron on the resin after adsorption could be easily eluted using 0.5 mol/L HCl at Vresin:Veluant=4:1 and elution time of 20 min,and the elution rate of boron was more than 95%under these conditions.(5)Based on the results of static adsorption,the dynamic adsorption experiments were further carried out and found that the contact time between the brine and the resin had important effect on the adsorption of boron,and a good result could be obtained at a low flow rate of the brine.Although the adsorption rate was low,the dynamic desorption of boron from the resin was fast.When a 50×?7 cm adsorption column was used to carried out adsorption and desorption cycle tests,the adsorption and desorption rates remained generally stable,indicating that the resin chosen in this work has high stability. |
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