許多研究指出，活性碳對於六價鉻有優異的去除能力，亦提出吸附劑對於六價鉻會發生還原機制，然而這些文獻中卻未區隔吸附劑的吸附能力與將六價鉻還原為三價鉻的能力，因此本研究欲探討活性碳對於鉻酸鹽的還原以及吸附機制。
由pH=1~10的實驗得知，總鉻去除率在pH=3的環境下去除效果最佳，約可達64%，而隨著pH值與pH3差距越大，總鉻去除效果越差，去除率的反應以擬二階動力模式最符合反應速率的變化，計算可得活性碳對於六價鉻濃度100ppm在pH=3的平衡吸附量為6.4mgCrtot/gGAC ，而pH值越低、活性碳將六價鉻還原為三價鉻的速率就越快，以一階動力模式最符合反應速率的變化，若使用2克的活性碳欲將200ml六價鉻濃度100ppm去除率達99%，在pH=1的條件下，需52.5分鐘，在pH=6條件下則需1439.1分鐘。由於pH>3以後，活性碳表面帶正電荷之官能基減少，因此吸附容量下降，然而當pH值越低、活性碳將六價鉻還原為三價鉻的效果越好，造成低pH值時六價鉻大量還原為無法被吸附的三價鉻，因而形成總鉻吸附率減少。
另外、溫度的上升可加速還原反應速率，在pH=1時，去除時間由25℃的52.45分鐘縮短為35℃的41.90分鐘，不過溫度的上升不利於活性碳對六價鉻的吸附，在相同pH之下，35℃的飽合吸附量＜30℃的飽合吸附量＜25℃的飽合吸附量。
吸附飽和後的活性碳若以強酸為再生液使活性碳帶有正電荷的官能基，反而不利於六價鉻的脫附，必須依賴強酸將吸附於活性碳上的六價鉻還原為三價鉻後才能脫附，反之、氫氧化鈉使活性碳表面帶有負電荷，於是可輕易將六價鉻脫附而出。

Hexavalent chromium ions, Cr(VI), have been shown to be adsorbed or reduced on the surface of GAC. The tendency of Cr(VI) reduction by various adsorbents has been mentioned by several researchers, but the mechanisms have not been investigated in great details.
Removal of Crtot and Cr(VI) was studied at pH ranging from 1 to 10. The results show that remvoal efficiency of Crtot increases with increasing pH, reaches maximum (64%) at pH3, and decreases with pH afterward. The kinetics of Crtot removal can be fitted by the pseudo-second-order model. On the other hand, the Cr(VI) remvoal increases with decreasing pH, and kinetics of Cr(VI) removal can be described by pseudo-second-order model.
The amount of positively charged functional groups on activated carbons decreases with increaseing pH, resulting in reducing sorption capacity of GAC for Cr(VI). As pH of less than 3, Cr(VI) was reduced to Cr(III) readily, and as the result the amount of Cr(VI) removed by adsorption process is much less than reduction. Increasing temperature from 25℃ to 35℃ accelerates reduction rate but retard adsorption rate of GAC for Cr(VI).
Chromium-loaded GAC was regenerated with HCl or NaOH. The former increases  positively charged functional groups on GAC surface and Cr(VI) is not desorbed readily. On the other hand, the latter makes negatively charged functional groups on GAC surface and Cr(VI) is desorbed easily.

目錄
目錄	I
表目錄	IV
圖目錄	V
第一章  前言	1
1-1  研究起源	1
1-2  研究目的	4
第二章  文獻回顧	5
2-1  以離子交換去除鉻酸鹽的機制	5
2-2  以吸附去除鉻酸鹽的機制	6
2-3  以氧化還原去除鉻酸鹽的機制	7
2-4  溫度對去除率的影響	9
2-5 各種活性碳去除鉻酸鹽的結果	9
2-6  化學反應動力學	11
2-6-1  零階動力模式	12
2-6-2  一階動力模式	12
2-6-3  二階動力模式	13
2-6-4  擬一階動力模式	13
2-6-5  擬二階動力反應模式	14
2-7  活性碳再生	15
第三章  實驗設備與方法	18
3-1  實驗材料	18
3-1-1  實驗材料	18
3-1-2  實驗設備	21
3-2  實驗步驟	21
3-2-1  活性碳在不同pH下對六價鉻的去除	21
3-2-2  活性碳在不同pH下對三價鉻的去除	21
3-2-3  溫度對於去除率的影響	22
3-2-3  管柱實驗	22
3-2-4  活性碳再生	23
3-3  分析方法	24
3-3-1  六價鉻的分析	24
3-3-2  總鉻的分析	25
3-3-3  三價鉻的分析	25
第四章  結果與討論	27
4-1  pH對於去除率的影響	27
4-2  總鉻的去除與化學動力模式	32
4-3  六價鉻的去除與化學動力模式	36
4-4  溫度的影響	42
4-5  活性碳重複使用對於去除率的影響	47
4-6  活性碳對三價鉻的吸附與綜合分析	51
4-7  管柱結果	54
4-8  再生	57
第五章  結論	64
參考文獻	66

 
表目錄
表1  吸附作用的分類	6
表2  各種去除方式的優劣與處理效率的比較	10
表3  實驗所需藥品	19
表4  分析所需藥品	20
表5  以擬二階動力模式推估總鉻反應常數k2值	35
表6  以ㄧ階動力模式計算六價鉻反應常數k值	42
表7  溫度對於六價鉻去除率的ㄧ階動力模式結果	45
表8  溫度對於總鉻去除率的擬二階動力模式結果	47
表9  各pH值4小時後的去除率	54
表10  再生液與脫附結果1	58
表 11  再生液與脫附結果2	61
表12  再生後的六價鉻去除率一階動力模式	63

 

圖目錄
圖1  Distribution diagram of Cr(VI) species as a function of pH modeled by MINEQL+. Cr(VI)=2×10-3M.	3
圖2  Distribution diagram of Cr(III) species as a function of pH modeled by MINEQL+. Cr(III)=2×10-3M.	3
圖3  Speciation diagram of surface functional groups on activated carbons. (Park and Jang, 2002)	17
圖4  Column Experimental set-up	23
圖5  Crtot and Cr(VI) analyzed procedures	26
圖6  Variation of Cr concentration as function of time at the condition of pH 1.0. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25℃.	28
圖7  Variation of Cr concentration as function of time at the condition of pH 1.5. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25℃.	28
圖8  Variation of Cr concentration as function of time at the condition of pH 2.0. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1,Temperature = 25℃.	29
圖9  Variation of Cr concentration as function of time at the condition of pH 3.0. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25℃.	30
圖10  Variation of Cr concentration as function of time at the condition of pH 4.0. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25℃.	31
圖11  Variation of Cr concentration as function of time at the condition of pH 6.0. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25 ℃.	31
圖12  Effect of pH on Crtot removal efficiency. Reaction time = 4 hours, Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	33
圖13  Pseudo-second-order equation of Crtot , GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25 ℃.	34
圖14  Time variation of Crtot removal efficiency at different pHs. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1 (Curves are drawn by Pseudo-second-order equation)	35
圖15  Effect of pH on Cr(VI) removal efficiency as a function of time. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	37
圖16  Variation of pH and titration volume of 1M HNO3. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Initial pH=1, Temperature = 25℃.	38
圖17  Variation of pH and titration volume of 1M HNO3. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Initial pH=2, Temperature = 25℃.	38
圖18  Variation of pH and titration volume of 1M HNO3. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Initial pH=3, Temperature = 25℃.	39
圖19  Variation of pH and titration volume of 1M HNO3. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Initial pH=4, Temperature = 25℃.	39
圖20  Variation of pH and titration volume of 1M HNO3. GAC = 10 g l-1, Initial Cr(VI) =0, Initial pH=1, Temperature = 25℃.	40
圖21  First-order equation of Cr(VI) removal. GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25 ℃.	41
圖22  Effect of temperature on Cr(VI) removal efficiency as a function of time. pH=1, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	44
圖23  Effect of temperature on Cr(VI) removal efficiency as a function of time. pH=2, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	44
圖24  Effect of temperature on Crtot removal efficiency as a function of time. pH=1, 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	46
圖25  Effect of temperature on Crtot removal efficiency as a function of time. pH=2,  GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	46
圖26  Variation of Cr removal efficiency by number of GAC repeated used. pH=1,  GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1, Temperature = 25℃, Reaction time =1 hr.	50
圖27  Variation of Crtot adsorption by number of GAC repeated used. pH=1, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1, Temperature = 25℃, Reaction time =1 hr.	50
圖28  Variation of Cr concentration as function of time by the eleventh repeated used .pH=1.0, GAC = 10 g l-1, Initial Cr(VI) =100mgl-1, Temperature = 25 ℃.	51
圖29  Effect of pH on Cr(III) removal efficiency as a function of time. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(III) = 100 mg l-1.	52
圖30  Distribution diagram of Cr(III) species as a function of pH modeled by MINEQL+. Cr(III)=2×10-3M.	52
圖31  Ce/C0 vs. number of empty bed volume. Empty bed volume=36.316cm3. Empty bed contract time=7.263min, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1, Initial pH = 1.	55
圖32  Ce/C0 vs. number of empty bed volume for two different empty bed contract time. Empty bed volume =36.316cm3, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1, Initial pH = 1.	56
圖33  Ce/C0 vs. number of empty bed volume for three different pH. Empty bed volume =36.316cm3, Empty bed contract time=7.263min, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	57
圖34  Cr(VI) removal efficiency for different GAC regeneration solutions. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	59
圖35  Crtot removal efficiency for different GAC regeneration solutions. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	60
圖36  Cr(VI) removal efficiency for different GAC regeneration solutions. Temperature = 25℃, GAC = 10 g l-1, Initial Cr(VI) = 100 mg l-1.	62

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譯者:楊萬發, 1999. 水及廢水處理化學. 茂昌圖書有限公司.