利用生物吸附劑、水熱合成碳、生物碳與活性碳去除水中污染之研究

Removal of contaminants from aqueous solution through biosorbents, biochars, hydrochars, and activated carbons

陳阮海(HAI NGUYEN TRAN)

指導教授 ： 游勝傑 ； 趙煥平

中原大學/工學院/土木工程研究所/博士(2017年)

https://doi.org/10.6840/cycu201700670

摘要

在目前污染情況增加與水資源匱乏已成為許多國家必須面對的問題，根據估算結果世界上大約有三分之二的人口到2025年將遭遇可用水量不足的困境，而在目前的水處理技術中，由於吸附對於污染物有相對較高去除效率、較低的操作成本、設計簡單、二次污染物產生量少(例如不會形成污泥)與可以有效將污染物自水中分離等優勢，因此被認為是一種最具經濟性的技術。
在本研究中，一些低成本與可重複使用之吸附劑如生物吸附劑、水熱合成碳、生物碳等被製作合成，其來源為各種具木質纖維素之農業廢棄物如橘子皮、椰子殼與黃金革，這些吸附劑的特性被分析，並被應用於去除水中的毒性污染物質，再藉由吸附數據討論污染物與吸附劑間的主要吸附機制。
對於鉻離子吸附於橘子皮所合成之生物碳之研究中，使用400, 500, 600, 700 與800 °C等不同之熱解溫度，另外設定條件還包括2與6小時之持溫，依照Langmuir方程式所計算出對鎘離子的最大吸附容量可以發現吸附量隨熱解溫度與持溫時間增加而增加，但是增加的量依照統計學上的結果並未有高度差異性(p>0.01)，由生物碳所獲得之鎘離子最大吸附量為115mg/g ，此值將高於以橘子皮直接製成生物吸附劑的54.5mg/g與商用活性碳之26.5mg/g，鎘離子吸附於生物碳的主要機制被認為是Cπ陽離子交互作用力以及鎘離子在吸附劑表面形成(Ca,Cd)CO3，而經由表面沉澱被去除，而吸附在橘子皮上的作用機制則為靜電吸引力。
在另一方面，以新活化方法將黃金革製作活性碳的程序也在本研究中被提出，由黃金革製作之活性碳，先經過傳統的一階段與二階段程序，然後再增加新增的第三階段活化程序，此獲得之活性碳被用於去除中陽離子染料methylene green 5 (MG5)。除此之外，由橘子皮、椰子殼與黃金革所製作之生物吸附劑或是生物碳，連同商用界面活性劑均被應用於去除水中MG5，結果顯示由黃金革依照新方法所製成的活性碳可以顯示出最大吸附容量，對MG5吸附量可達531 mg/g，若用傳統二階段活化方法，吸附量約253–344 mg/g，而商用活性碳對 MG5吸附量為489 mg/g，對於相同的原料，由黃金革製作之吸附劑其吸附量呈現下列順序:活性碳> 生物吸附劑 > 水熱合成碳 > 生物碳，π-π作用力與孔隙填充為MG5吸附於生物碳與活性碳的主要作用機制，靜電吸引力、 氫鍵與 n-π作用力則為MG5在生物吸附劑與水熱合成碳的主要吸附機制。另外，可以藉由含碳物質一個新的表面氧化處理方法，即透過加入丙烯酸進行水熱合成程序判斷作用機制，在此方法中可由MG5的吸附量減少，定義出π-π交互作用力在吸附程序中的重要性。
由本研究中的結果顯示含木質纖維素的廢棄物質可以被作為低成本吸附劑，其可以有效吸附水中污染物。

關鍵字

生物吸附劑 ； 生物碳 ； 水熱合成碳 ； 活性碳 ； 孔雀石綠 ； 鎘離子 ； 吸附機制

並列摘要

Nowadays, the vast increase of population and water scarcity are the major challenges in most countries. It has been estimated that approximately two-thirds of the world’s population could encounter absolute water shortages by 2025. Among current technologies, adsorption is widely acknowledged as the most economically favorable technique due to its high removal efficiency, low operation cost, simplicity of design, minimal generation of secondary by-products (e.g., sludge formation), and feasibility for separating a wide range of potentially toxic pollutants from aquatic environments.
In this dissertation, low-cost and renewable adsorbents (i.e., biosorbent, hydrochar, biochar, and activated carbon) derived from lignocellulose wastes (i.e., orange peel (OP), coconut shell (CC), and golden shower pod (GS)) were prepared, characterized, and applied in the removal of several toxic pollutants from aqueous solution. The primary adsorption mechanism is herein proposed.
For cadmium adsorption, an orange peel-derived biochar (OPB) was prepared derived from different pyrolysis temperatures (400, 500, 600, 700 and 800 °C) and times (2 and 6 h). The results demonstrated that the maximum Langmuir adsorption capacity (Qomax) of Cd2+ ions onto biochar slightly increased with an increase in pyrolysis temperature and time. However, this increase did not indicate a statistically significant difference (p>0.01). The Qomax of biochar was found to be 115 mg/g, which was significantly higher than to that of orange peel biosorbent (OP) (54.5 mg/g) and commercial activated carbon (26.5 mg/g). The primary Cd2+ adsorption mechanism onto biochar were Cπ–cation interaction and surface precipitation in the form of (Ca,Cd)CO3 while electrostatic attraction for OP.
A new chemical activation method for the preparation of activated carbon (GSAC) derived from golden shower pod (GS) was proposed. The GSACs prepared from the traditional methods (one-stage and two-stage processes) and new method (three-stage process) were applied in the removal of cation dye from water media. In addition, biosorbents (OP, CC, and GS), hydrochars (OPH, CCH, and GSH), biochars (OPB, CCB, and GSB), and commercial activated carbon (CAC) were applied in removing methylene green 5 (MG5). The prepared GSAC using the proposed chemical activation method exhibited an excellent adsorption capacity (Qomax = 531 mg/g) compared to the GSACs prepared from the traditional methods (253–344 mg/g) and CAC (489 mg/g). Using the same precursor, the Qomax value of GS-derived adsorbent exhibited the following order: activated carbon > biosorbent > hydrochar > biochar. The principal mechanisms that control the MG5 adsorption for biochar and activated carbon are π-π interaction and pore filling. Meanwhile, electrostatic attraction, hydrogen bonding, and n-π interaction were deemed responsible for MG5 adsorption onto biosorbent and hydrochar. The new oxygenation method for surface modification of carbonaceous materials through a hydrothermal process with acrylic acid resulted a decrease in MG5 adsorption and identified to be significant for π-π interactions during adsorption process.
The lignocellulose residue can serve as a potential low-cost and promising adsorbent for efficient adsorption of contaminants in aqueous solution.

並列關鍵字

Biosorbent ； biochar ； hydrochar ； activated carbon ； methylene green 5 ； cadmium ； adsorption mechanism.

參考文獻

1. Birkenholtz, T., Drinking Water, in Eating, Drinking: Surviving: The International Year of Global Understanding - IYGU, P. Jackson, W.E.L. Spiess, and F. Sultana, Editors. 2016, Springer International Publishing: Cham. p. 23-30.

2. Arenas-Sánchez, A., A. Rico, and M. Vighi, Effects of water scarcity and chemical pollution in aquatic ecosystems: State of the art. Science of The Total Environment, 2016. 572: p. 390-403.

3. Raval, N.P., P.U. Shah, and N.K. Shah, Adsorptive amputation of hazardous azo dye Congo red from wastewater: a critical review. Environmental Science and Pollution Research, 2016. 23(15): p. 14810-14853.

4. Glusko, C.A., et al., An experimental and theoretical study on the photophysical properties of methylene green. Dyes and Pigments, 2011. 90(1): p. 28-35.

5. Nordberg, G.F., Historical perspectives on cadmium toxicology. Toxicology and Applied Pharmacology, 2009. 238(3): p. 192-200.