本文選題：氧化石墨(烯) + 氧化程度�。� 參考：《西南科技大學(xué)》2017年碩士論文

【摘要】：石墨碳原子層之間相互平行疊置且以短程范德華力相聯(lián)系,其間形成相對疏松的層間域,結(jié)構(gòu)層上的π鍵具有金屬鍵的性質(zhì)。因此具有良好的可插層,可氧化及剝分性。然而石墨氧化的難易程度、反應(yīng)速率、反應(yīng)條件及化學(xué)試劑的選擇直接或間接的影響氧化石墨(GO)產(chǎn)物結(jié)構(gòu)中官能團的類型和含量,進而影響結(jié)構(gòu)和陽離子交換性能�？煽刂苽涮囟ü倌軋F類型的GO,既可直接作為優(yōu)良的吸附材料,而且能為基于GO功能化材料在吸附領(lǐng)域的應(yīng)用提供更佳的前軀體。本論文采用濃H_2SO_4和KMnO_4為反應(yīng)體系的Hummers法可控制備不同氧化程度的GO,研究了GO制備過程中的階段性特征;采用甲醛縮合法對不同氧化程度GO的陽離子交換容量(CEC)進行測定,并對GO的干、濕狀態(tài)及陽離子交換過程產(chǎn)物對比研究,查明陽離子交換機制及交換過程對GO結(jié)構(gòu)的影響;在GO制備、結(jié)構(gòu)和理化性質(zhì)(CEC性能)研究基礎(chǔ)上,進一步研究剝離后的GO即單層氧化石墨烯(GOs)對亞甲基藍(MB)的吸附性能及機理。研究表明氧化劑(KMnO_4)足量時,反應(yīng)時間和溫度對產(chǎn)物結(jié)構(gòu)特征有顯著影響�？煽刂苽涞牡蜏�(0~4°C)反應(yīng)時間為180 min,中溫(37°C)反應(yīng)時間為120 min,以及在原始氧化石墨(PGO)中因加水而引起的升溫溫度控制在65~75°C最佳,改變KMnO_4劑量時,石墨(002)面網(wǎng)的最大底面間距隨KMnO_4劑量發(fā)生規(guī)律性變化;可控制備獲得低氧化程度的GO結(jié)構(gòu)層上碳羥基(C-OH)相對含量較高,高氧化程度時環(huán)氧基(C-O-C)和羰基(C=O)含量較高;通過高倍光學(xué)顯微鏡對石墨的氧化過程在線分析發(fā)現(xiàn)KMnO_4是石墨發(fā)生氧化插層的充分條件,而濃H_2SO_4與石墨不發(fā)生插層反應(yīng),氧化過程由邊緣或缺陷處率先發(fā)生,并逐漸向面內(nèi)延伸。不同氧化程度的GO官能團類型和含量上都表現(xiàn)出較大的差異,采用甲醛縮合法測定CEC結(jié)果表明并非隨著氧化程度的增加CEC一直增大,而是與結(jié)構(gòu)中含氧基團C-OH和-COOH含量(即可解離出H+的量)相關(guān),可控氧化過程使GO-4樣品的CEC達到最大值541.81 mmol?(100g)-1,繼續(xù)增大氧化程度,反而使CEC減小;水介質(zhì)中GO層間域內(nèi)的H+與其它陽離子可發(fā)生交換,并在層間域內(nèi)形成水化陽離子層,陽離子交換過程可逆;[NH4(H_2O)6]+和[Ca(H_2O)6]2+以水合陽離子形式在層間域內(nèi)與GO結(jié)構(gòu)層上的C-O-以氫鍵結(jié)合,陽離子交換前后GO結(jié)構(gòu)及官能團未發(fā)生明顯變化。GO結(jié)構(gòu)層上的負電性及開放的層間域環(huán)境使其CEC值為蒙脫石的5~6倍,剝離后的GO(GOs-n)吸附亞甲基藍(MB)的最大飽和吸附量依次為728.44、965.63和807.29 mg·g-1,吸附過程符合準二級動力學(xué)模型,吸附量與GOs結(jié)構(gòu)中C-OH和-COOH含量成正相關(guān);GOs結(jié)構(gòu)上去質(zhì)子化的C-O-和-COO-為主要活性位點與MB+發(fā)生化學(xué)控速的單分子層吸附;在氧化程度低時,GOs結(jié)構(gòu)中C-OH和-COOH官能團之間以離子交換吸附為主導(dǎo)取代H;氧化程度高時,GOs結(jié)構(gòu)中的C-O-C和C=O含量增加與MB以氫鍵吸附作用增強,對吸附量的影響凸顯。
[Abstract]:The graphite carbon layers are parallel to each other and connected by short range van der Waals force, forming a relatively loose interlaminar domain. The 蟺 bonds on the structural layers have the properties of metal bonds. Therefore, it has good intercalation, oxidation and stripping properties. However, the degree of ease of graphite oxidation, reaction rate, reaction conditions and the selection of chemical reagents directly or indirectly affect the type and content of functional groups in the structure of graphite oxide (GOO) products, thus affecting the structure and cation exchange properties. The controllable preparation of specific functional group type goo can be used as an excellent adsorption material directly, and it can provide a better precursor for the application of go functionalized materials in adsorption field. In this paper, the phase characteristics of go preparation process were studied by using Hummers method with concentrated H_2SO_4 and KMnO_4 as reaction system, and the cation exchange capacity of go with different degree of oxidation was determined by formaldehyde condensation method. The dry, wet and cation exchange products of go were compared, and the effects of cation exchange mechanism and exchange process on go structure were investigated, and the preparation, structure and physical and chemical properties of go were studied. The adsorption properties and mechanism of GOs3 on MBM were studied. The results show that the reaction time and temperature have a significant effect on the structure of the product when the quantity of oxidizer KMnO4 is sufficient. The reaction time of controlled preparation is 180 min at low temperature (4 擄C) and 120 min at moderate temperature (37 擄C). The optimum temperature of water added in the raw graphite oxide is 6575 擄C, when the dosage of KMnO_4 is changed, The maximum bottom surface spacing of the graphite mesh varies regularly with the dose of KMnO_4, and the content of C-OH) on the go structure layer with low oxidation degree is relatively high, and the content of C-O-C) and carbonyl cationic acid on the go structure layer with high oxidation degree is higher. The on-line analysis of the oxidation process of graphite by high power optical microscope shows that KMnO_4 is the sufficient condition for the oxidation intercalation of graphite, while the strong H_2SO_4 does not intercalate with graphite, and the oxidation process occurs first from the edge or defect. And gradually extended into the plane. The types and contents of go functional groups with different degree of oxidation showed great differences. The results of CEC determination by formaldehyde condensation showed that CEC did not increase with the increase of oxidation degree. It is related to the content of oxygen group C-OH and -COOH in the structure (the amount of H can be dissociated). The controlled oxidation process can make the CEC of GO-4 sample reach the maximum value of 541.81 mmol / L ~ (100) g / m ~ (-1), and increase the degree of oxidation and decrease the content of CEC. In water medium, H in go interlayer can be exchanged with other cations, and a hydrated cationic layer is formed in the interlayer domain, and the cation exchange process is reversible. [NH4(H_2O)6] and [Ca(H_2O)6] 2 bond with C-O- on go structure layer in the form of hydrated cations in the interlayer domain. There was no obvious change in go structure and functional group before and after cation exchange. The negative electrical properties of go structure layer and the open interlayer environment made the CEC value of go layer 5 times than that of montmorillonite. The maximum saturated adsorption capacity was 728.44965.63 and 807.29 mg g ~ (-1), respectively. The adsorption process was in accordance with the quasi-second-order kinetic model. The adsorption capacity was positively correlated with the content of C-OH and -COOH in the GOs structure. The deprotonated C-O- and -COO- on the GOs structure were the main active sites for monolayer adsorption of MB at chemically controlled rate. When the oxidation degree is low, the adsorption of C-OH and -COOH in GOs structure is dominated by ion exchange adsorption, and the increase of C-O-C and Con O content in GOs structure with high degree of oxidation increases with the hydrogen bond adsorption of MB, and the effect on adsorption capacity is obvious.
【學(xué)位授予單位】：西南科技大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：O613.71

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