Study On The Preparation Of Boron Selective Adsorbent And Its Boron Adsorption Capability

With the increasing demand for boron resources in the glass industries,ceramics industries,military industries and so on,the world annual output of boron resources also increases year by year.Excess boron enters into the environment,the environmental problems caused by it are also increasingly prominent.However,the traditional water treatment technology is difficult to treat boron in the water body below the national standard.Compared with the traditional water treatment technology,the boron selective adsorbents have the advantages of high efficiency,low cost and reusability.In this paper,a strong alkali anion exchange resin was used to graft tiron molecules with o-hydroxyl functional groups to synthesize new boron selective adsorbents,The concentration,pH and ionic strength of the tiron solution were used to determine the grafting process by orthogonal experiments.The effects of boric acid solution pH,concentration,coexisting ions and adsorption time on the adsorption of boric acid on tiron resin were studied by static experiments.Finally,it was studied that desorption of tiron resins which were saturated adsorbed boric acid.The conclusions are as follows:1.The optimal grafting conditions for preparation of tiron resins are:?1?the concentration of tiron is 8 mmol/L;?2?the solution pH is equal to 10;?3?The ionic strength was 0,and the maximum grafting yield was 1.20mmol/g.Energy dispersive X-ray spectroscopy?EDX?and scanning electron microscopy?SEM?proved that tiron molecules were successfully grafted into a strongly basic anion exchange resin.2.When the pH of the boric acid solution is in acidic and neutral conditions,the amount of boron adsorbed by the tiron resins is comparable.3.When CO₃^2-,Cl^-,SO₄^2-,NO₃^-,and SiO₄^2-are presented in the boric acid solution,the higher the anion concentration,the more unfavorable adsorption of boric acid by the tiron resin.When[B]:[anion]is 1:50,the removal rate of boric acid can reach over 75%by tiron resins.Considering that the molar ratio of boron and anion in nature is generally less than 1:50,it is considered that the tiron resin has a selective adsorption capacity for boric acid.When Ca²⁺,Mg²⁺,K⁺,and Na⁺are presented in the boric acid solution,the calcium and magnesium cations may form complexes with the tiron,which affects the adsorption of boric acid by the tiron resin.4.The liquid ¹¹B NMR and solid ¹¹B CP MAS NMR show that the complexes of 1:1and 1:2 are formed between the boric acid and the tiron at pH 8.0?0.5,and the amounts of 1:1 complex are large.5.At 25°C,40°C and 55°C,the isothermal adsorption data were fitted with two-parameter and three-parameter isothermal adsorption models.According to the correlation coefficient R²,the best two-parameter was Freundlich model,which indicated multilayer adsorption takes place on the surface.At different temperatures the pseudo-second-order kinetics equation of adsorption kinetics data have the highest correlation coefficient R²,which indicated that the adsorption process belongs to chemical adsorption.According to the data fitted to the intraparticle diffusion equation,the adsorption rate is controlled by adsorption site adsorption at the third stage.Under three temperatures?G and?H were all less than 0,indicating that the adsorption process was spontaneous,exothermal reaction.and the thermodynamic parameters indicated that the adsorption process was based on physical adsorption.Therefore,the adsorption of boric acid by the tiron resin is a complex physical chemical reaction process,mainly based on chemical reactions?coordination reactions?.6.Dilute HCl solution was used as the desorption solution.The best desorption condition is 0.06 mol/L,and the ratio of the desorption solution?mL?to the resin quantity?g?was 600:1.Comparing tiron resin direct recycling and graft recycling,the use of three times the grafting cycle can achieve borate solution removal rate more than 75%,and direct recycling three times removal rate ranges from 83.9%to 31.8%.