Abstract

Tannic acid (TA) is a polyphenolic compound which is categorized in dissolved organic matter (DOM) classification. This matter has toxicity for aquatic organism, such as fish, phytoplankton, algae and invertebrates. TA is an anionic organic matter and its molecular weight is 1700 g/mol. This compound contributes to the production of disinfection by products (DBPs) during chlorination process in water treatment. Thus, it is significant to remove tannic acid from environment in terms of human health and environment. In this study, the performance of nano polyamidoamine-G7 (PAMAM-G7) dendrimer in removal of tannic acid from aqueous solution was investigated. Polyamidoamine dendrimer (PAMAM) with ethylene diamine core synthesized by the Tomalia method. Then, the adsorbent was characterized by Fourier transform infrared (FT-IR) spectroscopy and transmission electron microscopy (TEM). The effect of various experimental parameters such as pH solution, adsorbent dosage, contact time and temperature was evaluated. The concentration of tannic acid was determined at 278 nm by UV−VIS spectrophotometer. The adsorption of TA has been studied in term of pseudo-first and second-order kinetics, thermodynamic parameters (ΔG°, ΔS° and ΔH°), Langmuir and Freundlich isotherms models. The results showed in optimized conditions (pH 7, TA concentration = 5 mg/L, shaking = 200 rpm, adsorbent dose = 0.005 g/L, temperature = 25°C) maximum adsorption capacity and removal efficiency of TA were 38.02 mg/g and 98.83%, respectively. The adsorption kinetics of TA onto PAMAM-G7 followed a pseudo-second-order model (controlled by chemical process) and it is well described by Langmuir adsorption model (R² = 0.9076). The adsorption TA capacity for PAMAM-G7 increased with increasing TA concentration and electrostatic force and hydrogen bonding helps to adsorb the TA molecules on adsorbent. The calculated thermodynamic parameters showed that TA adsorption onto PAMAM-G7 was endothermic and spontaneous (ΔS° = 0.263, ΔH° = 70.96 and ΔG° = –7.428 at 25°C). Thus, PAMAM-G7 can be an appropriate adsorbent for removal of tannic acid from aqueous solution.

中文翻译：

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纳米聚酰胺胺树枝状大分子去除水中单宁酸的性能评价。

摘要

单宁酸（TA）是一种多酚化合物，分为可溶性有机物（DOM）分类。该物质对鱼类，浮游植物，藻类和无脊椎动物等水生生物具有毒性。TA是阴离子有机物质，其分子量为1700g / mol。该化合物有助于在水处理的氯化过程中产生副产品消毒剂（DBP）。因此，就人体健康和环境而言，从环境中去除单宁酸意义重大。在这项研究中，研究了纳米聚酰胺-G7（PAMAM-G7）树状聚合物从水溶液中去除鞣酸的性能。通过Tomalia方法合成的具有乙二胺核心的聚酰胺型胺树枝状聚合物（PAMAM）。然后，用傅立叶变换红外光谱（FT-IR）和透射电子显微镜（TEM）对吸附剂进行表征。评估了各种实验参数（例如pH溶液，吸附剂用量，接触时间和温度）的影响。通过UV-VIS分光光度计在278nm处测定单宁酸的浓度。从拟一阶和二阶动力学，热力学参数（ΔG °，ΔS °和ΔH °），Langmuir和Freundlich等温线模型。结果表明，在最佳条件下（pH 7，TA浓度= 5 mg / L，摇动= 200 rpm，吸附剂剂量= 0.005 g / L，温度= 25°C），TA的最大吸附容量和去除效率为38.02 mg / g和98.83％。TA在PAMAM-G7上的吸附动力学遵循伪二级模型（受化学过程控制），并通过Langmuir吸附模型（R ²= 0.9076）。PAMAM-G7的吸附TA容量随TA浓度和静电力的增加而增加，氢键有助于将TA分子吸附在吸附剂上。表明TA吸附到PAMAM-G7是吸热的，自发的计算出的热力学参数（Δ小号°= 0.263，Δ ħ °= 70.96和Δ ģ °= -7.428，在25℃）。因此，PAMAM-G7可能是从水溶液中去除鞣酸的合适吸附剂。