基於奈米孔道之除鹽：孔道形狀與孔道大小分佈的影響

Abstract

考慮到使用奈米多孔薄膜對水資源在各種用途中重複利用有迫切的需求，我們基於偶合的Navier-Stokes和Poisson-Nernst-Planck（PNP）方程式，研究了在不同條件下奈米多孔薄膜的離子阻擋能力。以下研究將探索薄膜對離子回收和水純化的潛力。 在第一章中，我們考慮了四種奈米孔道形狀：子彈形、圓柱形、沙漏形和喇叭形，每種孔道都可以是單極性或雙極性帶電，從而使設計更加多樣化。此外，奈米孔道的表面帶電會受到pH值影響，因此模擬的結果會更加真實。這邊單種鹽類（包括MgCl2、K2SO4和KCl）和混合鹽類（K2SO4+MgCl2）兩種情況均有進行模擬。奈米孔道中的電動力學行為我們進行了全面的研究，並對其中的潛在機制進行了詳細的討論。上述結果已發表在國際期刊Separation and Purification Technology上。 在第二章中，為了理解離子在薄膜過濾過程中的行為，我們建構了具有不同孔徑大小的多孔薄膜，並以具有對數常態孔徑分佈的膜為主要探討目標。孔道的排列旨在實現最佳的離子阻擋效果和最佳的離子選擇性。為了緩解濃度極化效應，在進料側使用了側流。液相中存在單種鹽類（NaCl）以及存在混合鹽類（NaCl+MgCl2）的情況均有考慮及模擬。我們的結果為設計膜上孔道的排列提供了些必要的資訊。

Considering the urgent needs in recycling water for various usage through a nanoporous membrane, we investigated its ion-rejection performance under various conditions based on coupled Navier-Stokes and Poisson-Nernst-Planck (PNP) equations. The following studies will explore the potential of membranes for ion recovery and purification. In chapter 1, we considered four kinds of nanopore, bullet-shaped, cylindrical, hourglass-shaped, and trumpet-shaped, each can be unipolarly or bipolarly charged, thereby making the design more versatile. In addition, the charged conditions on the surface of a nanopore are pH-regulated so that the results gathered are more realistic. Both the case of single salt (MgCl2, K2SO4, and KCl) and mixed salt (K2SO4+MgCl2) were simulated. The electrokinetic behavior of a nanopore was examined comprehensively, along with a detailed discussed on the underlying mechanism. The above results were published in Separation and Purification Technology. In chapter 2, in order to understand the behavior of the separation of ions though membrane filtration, a membrane of multiple pores having different pore sizes is modeled theoretically, focusing on a membrane having log-normal distributed pore size. The arrangement of pores is aimed to arrive at best rejection and best ion selectivity. To alleviate the effect of concentration polarization, a crossflow is applied on the feed side. Both the case where only single salt (NaCl) is present in the liquid phase and that where mixed salts (NaCl+MgCl2) are present are considered. Our results provide necessary information for designing the arrangement of the pores on a membrane.