Low-temperature one-pot synthesis of Fe-doped hydrotalcite for enhanced boron adsorption and reduced dissolution loss

Based on the anion exchangeability between the layers of layered double hydroxides (LDHs) and the properties of metal element doping to reduce the dissolution rate. The synthesis strategies for MgAl-LDHs and Fe-doped LiAlLDHs were obtained by one-step, low temperature (40 degrees C) and rapid synthesis and were used for the separation of boron in brine. It was found that Fe-doped LiAl-LDHs (42.07 mg/g) had the characteristics of promoting boron adsorption compared to MgAl-LDHs (5.38 mg/g). In addition, the adsorption of boron from solution is due to the anion exchange between layers, and pH has a serious influence on boron adsorption by Fe-LiAl-LDHs. According to the DFT calculations, LiAl-LDH/Fe-LiAl-LDH can only adsorb B(OH)4-, and its boron adsorption mechanism is interlayer anion exchange. Furthermore, Fe doping increases LiAl-LDH stability while promoting B(OH)4- adsorption. In addition, Fe-doped LiAl-LDHs (0.446 %) had a low Al dissolution rate compared to LiAl-LDHs (4.359 %) after 10 cycles of adsorption and desorption. The Langmuir and pseudo-second-order kinetic models were consistent with the boron adsorption behavior of Fe-doped LiAl-LDHs, and the boron adsorption benefitted from temperature increased. The weak acid desorption process not only preserved the structural integrity of the Fe-LiAl LDHs but also showed a remarkable adsorption capacity of 32.16 mg/g when applied to the brine of Xiao Qaidam salt lake. These results highlight the potential of using this adsorbent for efficient boron separation in brines.