The complex and diverse forms of boron in aqueous solutions have presented a major challenge for boron separation. Boron can be chemically complexed with polyols to achieve the purpose of separation. It is of great significance to clarify the mechanism of polyol ligand capturing boron anion for optimizing the best ligand. The facile environmentally friendly functionalization of cotton linter polymer with amino-polyol was successfully demonstrated and resulted in essential polyhydroxy ligands containing amines for strong interactions with boron. The adsorption capacity of the boron adsorbents with the most –OH and N is up to 27.88 mg/g. The presence of the N, high vicinal diol content, and the branched structure all have a positive effect on the complexation efficiency. Optimization of the ligand structure is helpful to increase the boron uptake and it is of great significance to design the best adsorbent for boron separation from salt lake brine.
Chun Bai,Kexin Li,Dezhen Fang,Xiushen Ye,Huifang Zhang,Quan Li,Jun Li,Haining Liu,Zhijian Wu
A novel flotation agent named N-octadecyl-N-methyl- D -glucamine (NO-NMDG), was designed and prepared using N-methyl- D -glucamine as a polyhydroxy molecule and 1-bromooctadecane as the provider of a long-chain alkyl group . The results of characterization by NMR, MS and FT-IR showed that the target compound was successfully synthesized. NO-NMDG can effectively separate boron from aqueous solutions because of its complexing ability for boron and its foamability. The flotation experiments results showed that the flotation isotherm was in better accordance with the Langmuir model, indicating that the surface reaction in flotation by NO-NMDG belongs to the single molecular layer trapping. The response surface experimental results indicated that under the optimum conditions, the boron recovery rate can reach to 89.12%. The boron recovery rate in Xiao Chaidan brine could reach to 97.26% by NO-NMDG. The mechanism analysis exhibited that the meglumine group in NO-NMDG can complex with boron, and the long-chain alkyl group can attach to the surface of the bubble and enter into the bubble layer to separate boron from the aqueous solution.
A new type of absorbent was synthesized by grafting N-methyl-D-glucamine (MG) onto the surface of chitosan beads to separate boron element. The physicochemical properties of modified chitosan beads (CTS-MG) were examined by FT-IR and SEM analyses. The results indicated that MG had grafted on chitosan beads (CTS) successfully. Compared to surface of pure CTS, CTS-MG had a rougher surface. While the pH value ranged 3–8, CTS-MG would have a high efficiency of adsorption to boron. The characteristics of the adsorption process were evaluated by Langmuir and Freundlich adsorption isotherms , and the maximum adsorption capacity of CTS-MG was 20.36 mg·g −1 . When mass of absorbent was not lower than 0.1 g, the concentration of 10 ml boron solution would decrease from 50 to 0.5 mg/L. This absorption process fit to the pseudo-second-order kinetic model. CTS-MG had a comparatively high selectivity because general competing ions had little influence on the absorptive ability of CTS-MG. After 5 times adsorption-desorption cycles, absorptive capacity of CTS-MS did not decrease obviously. CTS-MG was hopefully used in the process of boron desorption in salt lake brine.
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