颗粒状锂铝水滑石吸附剂的制备及锂吸附性能研究

Preparation and lithium adsorption performance of granulated LiAl-LDHs adsorbents

针对传统锂铝水滑石(LiAl-LDHs)锂吸附剂合成过程中颗粒堆积紧密导致吸附容量低的问题,采用十二烷基硫酸钠(SDS)/聚乙烯吡咯烷酮(PVP)作为形貌调控剂,制备出3种具有多孔结构的LiAl-LDHs以提高锂吸附容量,并通过傅里叶变换红外光谱仪、扫描电子显微镜、透射电子显微镜、比表面积及孔隙度分析仪对其结构进行表征。采用相转化法以聚丙烯腈(PAN)作为造粒基体材料,对LiAl-LDHs粉末进行造粒制备了颗粒状吸附剂以提高适用性。颗粒状吸附剂含水量为66.6%,LiAl-LDHs质量分数为80%。结果表明:在温度25℃、质量浓度300mg/L的Li+溶液中,pH=8时颗粒状吸附剂LiAl-LDHs-SDS/PVP吸附容量达到8.0mg/g,吸附行为符合准二阶动力学模型和Langmuir等温吸附模型;在干扰离子Na^(+)、K^(+)、SO_(4)^(2+)、Mg^(2+)存在下该吸附剂对Li^(+)具有较强的选择性吸附能力;循环吸附-脱附5次后吸附量保持在7.0mg/g以上,具有良好的循环稳定性;该吸附剂在大柴旦盐湖卤水中锂吸附容量达到8.21mg/g,具有良好的工业化应用潜力。

To solve the problem of low adsorption capacity due to tight particle stacking during the synthesis of traditional lithium-aluminum hydrotalcite(LiAl-LDHs)lithium adsorbents,sodium dodecyl sulfate(SDS)/polyvinylpyrrolidone(PVP)was used as morphology modifier to prepare three porous LiAl-LDHs to improve the lithium adsorption capacity.The structures were characterized by Fourier transform infrared spectroscopy,scanning electron microscopy,transmission electron microscopy,specific surface area and porosity analyzer.At the same time,the granulated LiAl-LDHs-SDS/PVP adsorbents were prepared by the phase transformation process using polyacrylonitrile(PAN)as the granulation matrix material to improve the applicability.The water content of granulated adsorbent was 66.6%,and the mass fraction of LiAl-LDHs reached 80%.The results showed that at 25℃and in 300mg/L Li+solutions,the adsorption capacity of the granulated adsorbent LiAl-LDHs-SDS/PVP reached 8.0mg/g at pH=8,and the adsorption process conformed to the pseudo-second-order kinetic model and the Langmuir isotherm adsorption model.The adsorbent had good selective adsorption for Li+in the presence of interfering ions Na^(+),K^(+),SO_(4)^(2+),and Mg^(2+).The adsorption amount could remained above 7.0mg/g after five cycles of adsorption-desorption,demonstrating good cyclic stability.The lithium adsorption capacity of the adsorbent in the Da Qaidam Salt Lake brine reached 8.21mg/g.The results indicated that the adsorbent had good potential for industrial application.