不同電荷密度之層狀雙氫氧化物對對苯二甲酸的吸附反應
Other Title
Adsorption Mechanism of Terephthalic Acid Using Mg/AlLayered Double Hydroxides with Varying Layer Charge
Journal
土壤與環境
Journal Volume
12
Journal Issue
1&2
Start Page
23
End Page
31
ISSN
1029-2950
Date Issued
2009
Author(s)
Abstract
苯二甲酸性質穩定，在環境中不易被降解，在自然環境pH範圍中此污染物以陰離子型態存在且具高的移動性。層狀雙氫氧化物（LDHs）擁有高比表面積與高陰離子交換容量，被認為具有移除水溶液環境中苯二甲酸的潛能。對苯二甲酸（Terephthalicacid; TPA）為苯二甲酸三個同分異構物之一，本研究係探討對苯二甲酸（Terephthalicacid; TPA）陰離子在與具有不同電荷密度且層間硝酸根離子位向排列方式相異下的Mg/Al-NO3-LDHs之吸附反應。三個具有不同Mg（上標2+）：Al（上標3+）莫耳比之2：1、3：1及4：1型Mg/Al-NO3-LDHs被加以合成並與TPA進行吸附實驗，經15分鐘反應平衡下，發現具高電荷密度且LDH層間硝酸根離子以垂直方向排列的2：1型Mg/Al-NO3 LDH對TPA有最高的吸附能力與較快的吸附速率，其TPA包覆於LDH外圍並插入層間。相較於3：1及4：1型Mg/Al-NO3 LDHs而言，因LDH層間對TPA低的親和性，所以對TPA吸附能力比較低。本實驗證明LDHs的層間電荷密度對TPA的吸附特性是高度相關，使用高電荷密度且層間硝酸根離子位向排列以垂直方向排列的Mg/Al-NO3 LDH在水溶液中可移除最大量的TPA污染物。
Benzenedicarboxylic acid is stable and poorly degradable in the environment. In the pH range that exists in the natural environment, this contaminant exists in its anionic form and has a high mobility in the environment. With large specific surface area and high anion exchange capacity, layered double hydroxides (LDHs) have be considered to be promising scavengers for anionic contaminants. In this study, the adsorption of terephthalic acid (TPA), one of the three isomers of benzenedicarboxylic acid, on Mg/Al-NO3 LDHs with varying layer charge density were investigated with particular attention on the effect of the orientation of the interlayer nitrate. Three Mg/Al LDHs were synthesized with Mg(superscript 2+)：Al(superscript 3+) molar ratios of 2：1, 3：1 and 4：1. The results showed that the adsorption could reach equilibrium in 15 minutes. Among the samples, 2：1 LDHs has the highest layer charge density and contains nitrate with an orientation perpendicular to the hydroxide sheets, so this material exhibited the highest TPA adsorption capacity and can be exchanged for TPA more rapidly; the TPA was adsorbed on both the external and interlayer surfaces. Comparatively, 3：1 and 4：1 LDHs has a lower TPA adsorption capacity due to the low accessibility of TPA to the interlayer spaces. This work has demonstrated the dependence of TPA adsorption characteristics on the layer charge density of the LDHs. The removal of TPA in water may be maximized using Mg/Al- NO3 LDHs containing a large charge density and perpendicularly oriented interlayer nitrate.
Subjects
層狀雙氫氧化物
陰離子交換
對苯二甲酸
吸附反應
電荷密度
Layered double hydroxides
Anion exchange
Terephthalic acid
Adsorption
charge density
Type
journal article