层层自组装水滑石层板掺杂荷电杂化膜正渗透体系构建及传质机理研究

A novel forward osmosis (FO) process was established to reduce internal concentration polarization and, which consists of a novel layer-by-layer deposition of polyelectrolytes onto a positively charge membrane mixed exfoliated layered double hydroxide nanosheet [PAH/PSS]n/EHT-PSF and a temperature-responsive microgel (P(NIPAM-co-AA)) as the draw solutions. The separation performance and mechanism of antibiotics pollutant were investigated. The preparation mechanism and regulation rule on characteristics and separation performance of charged exfoliated layered double hydroxide nanosheet mixed matrix membrane based on layer-by-layer assembly are demonstrated, the relationship between membrane structure and pertraction capability and the influence of operation conditions on forward osmosis performance and kinetic characteristics were also discussed to discover the technology to reduce internal concentration polarization. By using molecular dynamics (MD) simulation method, the morphological microstructure of charged membrane and antibiotics and the interaction mechanism between them were revealed. Based on the boundary layer theory, solution-diffusion model and space charge model, the mechanisms of antibiotics pollutant rejection and water molecules transfer were discussed and the mass transfer models were built. These models can be providing the theory basis for the positively charge FO membrane design and mass transfer mechanism.

针对正渗透体系存在严重内浓差极化与反扩散的问题，本项目采用层层自组装技术制备水滑石层板掺杂荷电正渗透杂化膜[PAH/PSS]n/EHT-PSF，以N-异丙基丙烯酰胺(P(NIPAM-co-AA))温敏微凝胶为汲取液，构建新型正渗透体系，研究其对水体中抗生素类污染物的脱除性能与机制。探寻含水滑石层板荷电膜的成膜机理及调控规律；阐明荷电膜的组成结构与正渗透性能之间的构效关系和规律；揭示各因素对正渗透性能及动力学特性的影响规律，探索降低内浓差极化的方法；应用分子动力学揭示荷电膜与抗生素的微观形态与相互作用机制；基于边界层理论、溶解-扩散模型及空间电荷模型阐明抗生素类污染物与水分子在该体系中传质过程与机理，并建立传质模型；为荷电正渗透膜材料的设计制备与传质机理研究提供理论依据。

针对正渗透体系存在严重内浓差极化与反扩散问题，本项目采用原位剥离制备新型荷电纳米粒子并与层层自组装LbL技术相结合，设计制备层层自组装聚电解质沉积聚苯乙烯磺酸钠(PSS)/聚烯丙基氨盐酸盐(PAH)-水滑石层板(exfoliated layered double hydroxide, EHT)掺杂聚砜(PSF)正渗透复合膜[PAH/PSS]n/EHT-PSF，并与透明质酸-聚乙烯醇电敏水凝胶(PVA-HA)汲取剂，构建新型正渗透体系，研究其对水体中抗生素类污染物的脱除性能与机制；探寻含水滑石层板荷电膜的成膜机理及调控规律。. (1) XRD、ATR-IR研究表明，PAH和PSS可以通过静电作用在EHT-PSF膜表面有效的吸附自组装形成聚电解质多层膜。在最优制备条件下，膜通量Jw达到42.5 l∙m-2·h-1(FS: DI water, DS: 0.5 mol∙l-1NaCl)，相比于商业化正渗透膜（HTI-CTA和HTI-TFC）水通量提高了4-5倍，反扩散通量Js仅为0.88 g∙m-2h-1。.(2) 经SEM、AFM、Zeta电位、BET、亲水接触角、EDX等表征，所制备的水滑石层板掺杂荷电正渗透膜材料具有更高的亲水性与孔隙率。EHT增强了基膜正电性，Zeta电位由-9.8mV上升至+5.2mV；基膜表面粗糙度由122nm降至17.0nm，聚电解质PAH/PSS层层自组装后，皮层粗糙度为67.1nm。具备低的结构参数(S=241μm)，有效地减轻膜ICP。制备的[PAH/PSS]n/EHT-PSF具有较好的选择渗透性(A=10.33×10-12 m∙s-1Pa-1，B=1.75 ×10-7 m∙s-1)。.(3)以PVA-HA为汲取剂，20 mg∙l-1 抗生素溶液为料液条件下，Jw达1.7 l∙m-2h-1，截留率>97%，抗生素富集因子(EF)可达1.15；料液pH值对正渗透性能影响显著，针对膜面上液体流动状况、温度及料液浓度对传质的影响进行了探讨，得到了Kov与雷诺数(Re)及温度之间关系的数学模型。电敏凝胶有效避免汲取液反扩散，再生性能良好。针对正渗透过程中液膜边界层传质、膜内扩散传质及支撑层中传质的特点，建立总传质模型，实验值与模拟计算值吻合较好，相对误差在5%左右。