Lin Yi-Hung, Kim Jung Min, Beckingham Bryan S
Department of Chemical Engineering, Auburn University, Auburn, AL 36849, USA.
Department of Chemical Engineering, University of Virginia, Charlottesville, VA 22903, USA.
Polymers (Basel). 2023 Mar 10;15(6):1387. doi: 10.3390/polym15061387.
Produced water is a by-product of industrial operations, such as hydraulic fracturing for increased oil recovery, that causes environmental issues since it includes different metal ions (e.g., Li, K, Ni, Mg, etc.) that need to be extracted or collected before disposal. To remove these substances using either selective transport behavior or absorption-swing processes employing membrane-bound ligands, membrane separation procedures are promising unit operations. This study investigates the transport of a series of salts in crosslinked polymer membranes synthesized using a hydrophobic monomer (phenyl acrylate, PA), a zwitterionic hydrophilic monomer (sulfobetaine methacrylate, SBMA), and a crosslinker (methylenebisacrylamide, MBAA). Membranes are characterized according to their thermomechanical properties, where an increased SBMA content leads to decreased water uptake due to structural differences within the films and to more ionic interactions between the ammonium and sulfonate moieties, resulting in a decreased water volume fraction, and Young's modulus increases with increasing MBAA or PA content. Permeabilities, solubilities, and diffusivities of membranes to LiCl, NaCl, KCl, CaCl, MgCl, and NiCl are determined by diffusion cell experiments, sorption-desorption experiments, and the solution-diffusion relationship, respectively. Permeability to these metal ions generally decreases with an increasing SBMA content or MBAA content due to the corresponding decreasing water volume fraction, and the permeabilities are in the order of K > Na > Li > Ni > Ca > Mg presumably due to the differences in the hydration diameter.
采出水是工业作业的副产品，比如用于提高石油采收率的水力压裂作业，由于其包含不同的金属离子（例如锂、钾、镍、镁等），在处置前需要进行提取或收集，因此会引发环境问题。为了利用选择性传输行为或采用膜结合配体的吸收-摆动过程来去除这些物质，膜分离程序是很有前景的单元操作。本研究考察了一系列盐在由疏水性单体（丙烯酸苯酯，PA）、两性离子亲水性单体（甲基丙烯酸磺酸甜菜碱，SBMA）和交联剂（亚甲基双丙烯酰胺，MBAA）合成的交联聚合物膜中的传输情况。根据膜的热机械性能对其进行表征，其中SBMA含量增加会导致吸水率降低，这是由于膜内结构差异以及铵基和磺酸根基团之间更多的离子相互作用，导致水体积分数降低，并且杨氏模量随MBAA或PA含量的增加而增大。分别通过扩散池实验、吸附-解吸实验以及溶液扩散关系来测定膜对LiCl、NaCl、KCl、CaCl、MgCl和NiCl的渗透率、溶解度和扩散系数。由于相应的水体积分数降低，膜对这些金属离子的渗透率通常会随着SBMA含量或MBAA含量的增加而降低，并且渗透率顺序为K＞Na＞Li＞Ni＞Ca＞Mg，这大概是由于水合直径的差异所致。
