氮改質煅燒牡蠣殼提升水中亞甲基藍染料 吸附和光催化降解之研究;Nitrogen-doped Calcined Oyster Shells as Adsorbents and Photocatalysts for the Removal of Methylene Blue Dye in Water

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Title:	氮改質煅燒牡蠣殼提升水中亞甲基藍染料吸附和光催化降解之研究;Nitrogen-doped Calcined Oyster Shells as Adsorbents and Photocatalysts for the Removal of Methylene Blue Dye in Water
Authors:	吳佩珊;WU, PEI-SHAN
Contributors:	環境工程研究所
Keywords:	牡蠣殼;氧化鈣;氮摻雜;紫外/可見光催化氧化法;過氧化氫;亞甲基藍
Date:	2024-01-23
Issue Date:	2024-09-19 17:41:25 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究的目的是以亞甲基藍(Methylene blue, MB)染料作為目標污染物，牡蠣殼煅燒製備的生物氧化鈣(biogenic calcium oxide)作為光觸媒，進行 MB 的吸附和光催化氧化降解研究。首先以高溫煅燒(Calcined)鹼洗後的牡蠣殼(uncalcined oyster shell, UOS)，製備成氧化鈣(heated oyster shell, HOS)，再加入 2%(w/w)、5%(w/w)、 10%(w/w)尿素(urea)以溶膠凝膠(sol-gel method)進行表面改質，再將此粉體於高溫爐中以 600°C 煅燒 2 小時，合成氮摻雜氧化鈣(2%N-HOS、5%N-HOS、10%N-HOS)。從 BET 比表面分析得知，比表面積從 2.9370 m2 g-1(UOS)提高至 72.3785 m2 g-1(HOS) 和 71.4240 m2 g-1(2%N-HOS)。XRD 及 EDS 結果證明氮元素成功參雜在 HOS 表面; 以 UV-vis 量測及 Talc plot 計算氮參雜氧化鈣粉體能隙值介在 4.37 - 4.45eV。在光催化過程添加過氧化氫(hydrogen peroxide, H2O2)，可以提高有機污染物的降解效率，因為它還有多種優點，包括提高氫氧自由基(hydroxyl radical, •OH)量、防止電子-電洞再結合。本研究探討在紫外光線(ultraviolet light, UV)、可見光(visible light, vis)及暗反應下，添加過氧化氫，氧化鈣對亞甲基藍(Methylene blue, MB)染料之光催化降解效率。由可見光光催化實驗結果顯示，氮摻雜氧化鈣因帶隙距縮短，可有效利用長波長能量小的可見光波段，故在 MB 濃度 10 mg L-1、添加 0.84 g L-1 的 2%N- HOS、H2O2 (0.23%)(將 H2O2 溶液添加在亞甲基藍染料中，經計算得出濃度約為 0.23%)、反應溫度為 60°C下，在反應時間在 120 min，2%N-HOS 具有最佳的光降解效率，去除率達 99.8%。由氧化鈣及氮摻雜氧化鈣在添加過氧化氫對 MB 之動力實驗結果顯示，反應遵循一階動力學模式，表示反應時間對降解 MB 為正相關。 ;The primary objective of this research is to investigate the adsorption and photocatalytic oxidation degradation of Methylene Blue dye using nitrogen-doped calcium oxide (N-HOS) as the photocatalyst. The procedure involves the initial conversion of oyster shells through calcination and alkali washing to produce heated oyster shell (HOS). Subsequently, surface modification is accomplished by introducing urea in varying proportions (2% (w/w), 5% (w/w), and 10% (w/w)) via the sol-gel method. The resulting powder undergoes high- temperature annealing at 600°C for 2 hours, resulting in the synthesis of nitrogen-doped calcium oxide (2%N-HOS, 5%N-HOS, 10%N-HOS). BET surface area analysis illustrates a substantial augmentation in surface area, progressing from 2.9370 m2 g-1 (UOS) to 72.3785 m2 g-1 (HOS) and 71.4240 m2 g-1 (2%N-HOS). Further substantiating this, XRD and EDS analyses confirm the successful integration of nitrogen onto the HOS surface. The evaluation of energy bandgap values, conducted through UV-visible measurements and Tauc plots revealed a bandgap energy of 4.5 eV for calcium oxide, whereas the bandgap of nitrogen- doped calcium oxide ranged from 4.37 to 4.45 eV. Nitrogen doping effectively reduced the bandgap, thereby enhancing light absorption capabilities. To intensify the concentration of hydroxyl radicals (•OH) during photocatalytic reactions, hydrogen peroxide (H2O2) is introduced into the aqueous solution. Subsequent assessments encompass the investigation of the photocatalytic degradation efficiency of Methylene Blue (MB) under different conditions, encompassing ultraviolet light (UV), visible light (vis), and dark adsorption. The experiments pertaining to visible light photocatalysis underscore the multifaceted attributes of nitrogen-doped calcium oxide, highlighting its competence in MB adsorption and visible light photocatalysis. Specifically, II under conditions characterized by a 10 mg L-1 MB concentration, 0.84 g L-1 of 2%N-HOS, and 0.23% H2O2 (calculated concentration), executed at a reaction temperature of 60°C, and sustained for a duration of 120 minutes, 2%N-HOS emerges as the most proficient photocatalyst, delivering a remarkable removal efficiency of 99.8%.
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