The extraction of aurocyanide by activated carbon probably involves the adsorption of neutral ion-pair species [M ^jAuCCN)^. The large hydrophobic aurocyanide anion associates with the cation in order to minimize the disruption of the water structure whereby lowering its free energy

No description available.

Thesis (M.S.)--University of Wisconsin--Madison, 1963. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves [141-155]).

Several conflicting theories of the adsorption of aurocyanide onto activated carbon presently exist. To resolve the mechanism, adsorption and elution of aurocyanide are examined by several techniques, including Mossoauer spectroscopy, X-ray photoelectron spectroscopy, X-ray diffractometry, Fourier Transform Infrared spectrophotometry, ultraviolet-visible spectrophotometry and scanning electron microscopy. The evidence gathered indicates that, under normal plant conditions, aurocyanide is extracted onto activated carbon in the form of an ion pair M n+ [Au(CN) 2 ] n, and eluted by hydroxide or cyanide. The hydroxide or cyanide ions react with the carbon surface, rendering it relatively hydrophilic with a decreased affinity for neutral species. Additional adsorption mechanisms are shown to operate under other conditions of ionic strength, pH, and temperature. The poor agreement in the literature regarding the mechanism of adsorption of aurocyanide onto activated carbon is shown to be due to the fact that different mechanisms operate under different experimental conditions. The AuCN produced on the carbon surface by acid treatment is shown to react with hydroxide ion via the reduction of AuCN to metallic gold with formation of Au (CN) 2 , and the oxidation of cyanide to cyanate. Other species, such as An(CN)5 and Ag(CN)g adsorb onto activated carbon by a similar mechanism to that postulated for Au(CN)2 . Ion association of MAu(CN) 2 salts in aqueous solution is demonstrated by means of potentiometric titration and conductivity measurements, and various associated species of KAu(CN), salts are shown to occur in organic solvents by means of infrared spectrophoteaietric and distribution measurements. A kinetic model was developed for elution of aurocyanide from activated carbon and was found to predict gold elution performance successfully using the Zadra procedure. The influence of the surface chemistry and structure of activated carbon on adsorption of aurocyanide was investigated by characterization of activated carbons that were synthesized or oxidized under various conditions. Synthetic polymeric adsorbents with characteristics similar to activated carbons were also studied. The evidence suggests that a large micropore volume is important in providing suitable active sites for adsorption. Another important factor is the presence of basic functional groups within the micropore, which act as solvating agents for the ion pair. The aim is to provide a self-consistent adsorption mechanism that accounts for all observations presented in the literature. Interpretation of results in terms of preconceived ideas, and neglect of observations of other authors has greatly contributed to current disagreement in the literature.

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活性碳是一種擁有優異吸附能力的材料。與其他活性碳相比，活性碳纖維有以下優點。使首先, 它擁有大量微孔，比表面積大；其次，纖維結構有利於快速吸附；最後，它能編織成氈或者布，不但無阻氣流，而且便於使用後回收。但是，由於缺乏廉價的原材料，它的生產成本遠比其他活性碳高，不利於廣泛使用。所以，我們希望透通過使用廉價的棉花作為原材料，生產出優質的活性碳纖維。 / 在這項研究中，我們成功地用普通的棉花，通過氯化鋅活化，生產出活性碳纖維；我們研究了活化時的燒結溫度，浸潤時的氯化鋅濃度和活化後的後處理對活性碳纖維的影響，而且通過不同表徵方法來分析樣品。結果表明，它們不但保留棉花的纖維結構，而且擁有少量碳氧表面官能基。它的孔結構以微孔為主，BET比表面積和孔體積分別高達~2050m²/g和1 cm³/g，比市場上的活性碳或其他研究的活性碳高。 / 我們測試了棉花活性碳纖維在吸附亞甲基藍的吸附速度和吸附等溫線，發現它有很高的吸附速度，只需大約一個小時，吸附已差不多到達平衡。因為它很高的BET比表面积，它吸附亞甲基藍的最高容量達到597 mg/g，比市場上的活性碳高。我們也研究了溶液的pH值對其吸附能力的影響，發現鹼性環境有利亞甲基藍的吸附，相反，酸性環境不利亞甲基藍的吸附。 / 我們也測試了棉花活性碳纖維對水蒸氣，乙醇蒸氣、甲醇蒸氣和丙酮蒸氣的吸附速度，吸附容量和解吸過程。它只需十分鐘便完成乙醇蒸氣、甲醇蒸氣和丙酮蒸氣的吸附。它在水蒸氣中的吸附也比市場上的矽膠快。所有吸附物只需低於200 °C即可完全解吸。蒸氣吸附的最高容量高達1 cm³/g，較其他研究為高。 / Activated carbon (AC) is an important functional material due to its outstanding adsorption ability. Activated carbon fiber (ACF) has many advantages over other types of AC: It mainly possesses micropores and has large surface area. Its fibrous structure assures fast intraparticle adsorption kinetics. Finally, it can be made into felt and fabric forms, which would not hinder gas flow and could be easily recollected after use. However, ACF is expensive due to the lack of low cost precursor so its application is restricted. This work aims to use low cost cotton fiber as an ACF precursor. / In this work, ACF was successfully synthesized by using raw cotton via ZnCl₂ activation. The effects of the sintering temperature during activation, the ZnCl₂ concentration during infiltration and the post-treatment after activation on our samples were studied. Our ACF products were characterized via various methods. It was found that our samples retained the fibrous structure of cotton. They contained trace of carbon-oxygen surface groups and were mainly composed of micropores. Their BET surface area (S[subscript Bsubscript Esubscript T]) and pore volume (V[subscript psubscript osubscript rsubscript e]) were up to~ 2050 m²/g and 1 cm³/g, respectively. / The adsorption kinetics and adsorption isotherm of our samples in the Methylene blue (MB) adsorption were studied. The adsorption was very fast and almost reached equilibrium after an hour. Because of their high S[subscript Bsubscript Esubscript T], the saturated MB capacity in our ACF was found to be 597 mg/g and higher than other commercial AC. The effect of solution pH value on MB adsorption capacity was studied. We found that the basic condition favored MB adsorption while acidic condition lowered the adsorption ability. / Adsorption kinetics, saturated adsorption volume (V[subscript asubscript dsubscript s]) and desorption process of moisture, ethanol vapor, methanol vapor and acetone vapor by our samples were also evaluated. The adsorption of methanol vapor, ethanol vapor and acetone vapor reached equilibrium within 10 minutes. Our sample also adsorbed moisture faster than commercial silica gel. Less than 200 °C was required for complete desorption of these adsorbed species. V[subscript asubscript dsubscript s] of our samples was up to 1 cm³/g and higher than other related works. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Chiu, Ka Lok = 棉花活性碳纖維的製作, 定性分析及其應用 / 趙家樂. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Chiu, Ka Lok = Mian hua huo xing tan xian wei de zhi zuo, ding xing fen xi ji qi ying yong / Zhao Jiale. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgment --- p.iv / Table of contents --- p.v / List of figure captions --- p.viii / List of table captions --- p.xii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- What is activated carbon --- p.1 / Chapter 1.2 --- Development of activated carbon --- p.2 / Chapter 1.3 --- Morphology of activated carbon --- p.3 / Chapter 1.4 --- Surface groups on activated carbon --- p.7 / Chapter 1.5 --- Fabrication of activated carbon --- p.8 / Chapter 1.6 --- Applications --- p.9 / Chapter 1.7 --- Activated carbon fiber --- p.10 / Chapter 1.8 --- Raw materials --- p.11 / Chapter 1.8.1 --- Precursors of powdered activated carbon and granular activated carbon --- p.11 / Chapter 1.8.2 --- Precursors of activated carbon fiber --- p.12 / Chapter 1.8.3 --- Cotton as activated carbon fiber precursor --- p.12 / Chapter 1.9 --- Previous work and objectives of current work --- p.13 / References --- p.14 / Chapter Chapter 2 --- Methodology and background theory --- p.19 / Chapter 2.1 --- Samples preparation --- p.19 / Chapter 2.2 --- Characterization methods --- p.21 / Chapter 2.2.1 --- Study of processing --- p.21 / Chapter 2.2.1.1 --- Thermogravimetric analysis --- p.21 / Chapter 2.2.1.2 --- In-situ wide angle X-ray powder diffractometry --- p.22 / Chapter 2.2.2 --- Characterization of samples --- p.23 / Chapter 2.2.2.1 --- Scanning electron microscopy --- p.23 / Chapter 2.2.2.2 --- Transmission electron microscopy --- p.24 / Chapter 2.2.2.3 --- Ex-situ wide angle X-ray powder diffractometry --- p.25 / Chapter 2.2.2.4 --- Small angle X-ray scattering --- p.25 / Chapter 2.2.2.5 --- Raman scattering spectroscopy --- p.26 / Chapter 2.2.2.6 --- Fourier transform infrared spectroscopy --- p.27 / Chapter 2.2.2.7 --- N₂ adsorption surface analysis --- p.27 / Chapter 2.2.2.8 --- Zeta potential analysis --- p.29 / Chapter 2.3 --- Evaluation of Methlyene blue adsorption --- p.29 / Chapter 2.3.1 --- Pseudo second order adsorption model --- p.30 / Chapter 2.3.2 --- Langmuir isotherm --- p.31 / Chapter 2.4 --- Evaluation of vapor adsorption --- p.31 / Chapter 2.4.1 --- Vapor adsorption kinetics --- p.31 / Chapter 2.4.2 --- Saturated adsorption capacity --- p.33 / Chapter 2.4.3 --- Desorption --- p.34 / Chapter 2.5 --- Conclusions --- p.34 / References --- p.35 / Chapter Chapter 3 --- Results of characterization --- p.37 / Chapter 3.1 --- Study of the fabrication processes --- p.37 / Chapter 3.1.1 --- Thermogravimetric analysis --- p.37 / Chapter 3.1.2 --- In-situ wide angle X-ray powder diffractometry --- p.38 / Chapter 3.2 --- Characterization of samples --- p.39 / Chapter 3.2.1 --- Appearance --- p.39 / Chapter 3.2.2 --- Yield of the sample --- p.41 / Chapter 3.2.3 --- Scanning electron microscopy --- p.42 / Chapter 3.2.4 --- Transmission electron microscopy --- p.45 / Chapter 3.2.5 --- Ex-situ wide angle X-ray powder diffractometry --- p.46 / Chapter 3.2.6 --- Raman scattering spectroscopy --- p.48 / Chapter 3.2.7 --- Fourier transform infrared spectroscopy --- p.53 / Chapter 3.2.8 --- Nitrogen gas sorption surface analysis --- p.57 / Chapter 3.2.9 --- Small angle x-ray scattering analysis --- p.61 / Chapter 3.2.10 --- Zeta potential analysis --- p.65 / Chapter 3.3 --- Discussions --- p.66 / Chapter 3.3.1 --- Effects of ZnCl₂ on carbonization --- p.66 / Chapter 3.3.2 --- Pore formation --- p.68 / Chapter 3.3.3 --- Graphitic layers --- p.69 / Chapter 3.3.4 --- Effects of post treatment --- p.70 / Chapter 3.4 --- Conclusions --- p.71 / References --- p.72 / Chapter Chapter 4 --- Methylene blue adsorption --- p.74 / Chapter 4.1 --- Results --- p.74 / Chapter 4.1.1 --- Adsorption kinetics --- p.74 / Chapter 4.1.2 --- Adsorption capacity versus pH level --- p.76 / Chapter 4.1.3 --- Adsorption isotherm --- p.77 / Chapter 4.1.4 --- Adsorption capacity in different synthetic conditions --- p.78 / Chapter 4.2 --- Discussions --- p.80 / Chapter 4.2.1 --- Relationship between adsorption capacity and zeta potential --- p.80 / Chapter 4.2.2 --- Relationship between MB adsorption capacity and SBET --- p.81 / Chapter 4.2.3 --- Comparison with other related works --- p.83 / Chapter 4.3 --- Conclusions --- p.85 / References --- p.86 / Chapter Chapter 5 --- Vapor adsorption --- p.87 / Chapter 5.1 --- Results --- p.87 / Chapter 5.1.1 --- Adsorption kinetics --- p.87 / Chapter 5.1.2 --- Saturated adsorption capacity --- p.93 / Chapter 5.1.3 --- Saturated ethanol vapour adsorption volume --- p.94 / Chapter 5.1.4 --- Desorption --- p.96 / Chapter 5.2 --- Discussions --- p.99 / Chapter 5.2.1 --- Relationship between saturated ethanol vapor adsorption volumes and V[subscript psubscript osubscript rsubscript e] --- p.100 / Chapter 5.2.2 --- Comparison with other related works --- p.101 / Chapter 5.3 --- Conclusions --- p.103 / References --- p.104 / Chapter Chapter 6 --- Conclusions and Suggestions --- p.105 / Chapter 6.1 --- Conclusions --- p.105 / Chapter 6.2 --- Suggestions for future work --- p.106 / References --- p.107

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 171-183). Available also in a digital version from Dissertation Abstracts.

Includes bibliographical references (p. 159-170).

Includes bibliographical references (p. 245-271).

Thesis (PhD)--University of South Australia, 2000