本文關(guān)鍵詞：鉻在蒙脫石及改性蒙脫石中的吸附和解吸附產(chǎn)物及機(jī)制對比研究　出處：《南京大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 蒙脫石 鉻 吸附 遷移 八面體

【摘要】：蒙脫石由于具有一定層間陽離子交換能力、大表面積、化學(xué)穩(wěn)定性以及對環(huán)境作用較溫和等而被廣泛應(yīng)用。前人主要針對一價、二價金屬陽離子,如:Li+、Cd2+、Cu2+等在蒙脫石中吸附和遷移變化進(jìn)行研究,較少針對Cr3+等三價陽離子進(jìn)行研究。另外Cr3+被廣泛運(yùn)用于在制革、電鍍和顏料等工業(yè)生產(chǎn),過量的鉻能破壞生物體內(nèi)的新陳代謝,對人體健康產(chǎn)生有害影響,被認(rèn)為是16種污染最嚴(yán)重的重金屬元素之一,也是非常強(qiáng)的致癌物質(zhì),理解其吸附遷移機(jī)制對生產(chǎn)和環(huán)境來說有巨大意義。本文一方面研究了鈣基蒙脫石吸附Cr3+前后變化,并對產(chǎn)物進(jìn)行了不同溫度熱處理(200℃、300℃、500℃、600℃、700℃)及復(fù)水條件研究。另一方面利用不同濃度的十六烷基三甲基溴化銨(CTAB)交換層間原Ca2+得到改性蒙脫石,吸附Cr3+。在加熱250℃的條件下,探討其結(jié)構(gòu)變化和離子遷移狀況。最后研究了含鉻蒙脫石和含鉻改性蒙脫石在酸堿性條件下的解吸附情況。結(jié)果表明:鈣基蒙脫石吸附Cr3+后,Cr3+主要以[Cr(H2O)6]3+的形式替代TOT結(jié)構(gòu)片層間Ca2+。當(dāng)熱處理溫度小于500℃時,d001降低,OH伸縮振動和中波數(shù)段向高波數(shù)偏移,ESR信號峰也有所增加。與加熱的樣品相比較,復(fù)水后d001值有部分的增加,OH伸縮振動峰也向低波數(shù)偏移,ESR信號峰也有變化,表明Cr3+在六方孔較淺部位。當(dāng)溫度大于500℃時,根據(jù)XRD圖譜以及ESR的g=1.97強(qiáng)度變化,出現(xiàn)綠鉻礦(Cr2O3),d060由尖銳的窄峰減弱變寬,表明可能有類似于葉臘石的相出現(xiàn),由于復(fù)水后OH伸縮振動區(qū)域稍微地向低波數(shù)偏移,此時Cr3+處在六方孔的深部。而在CTAB改性蒙脫石中,CTAB以不同的形式排列在層間使其高度d001大大增加,其吸附Cr3+能力下降,根據(jù)ICP-AES得到的反應(yīng)后溶液中Al3+離子濃度以及紅外結(jié)果顯示出現(xiàn)3564 cm-1屬于Cr3+Cr3+OH的振動峰,表明此時Cr3+進(jìn)入八面體甚至取代了部分八面體中的Al3+;而在加熱250℃時,CTAB封閉層間之后,Cr3+Cr3+OH的振動峰仍然存在,同時結(jié)合ESR中g(shù)因子的變化情況,表明改性后的蒙脫石吸附Cr3+后,部分Cr3+因受分子間的吸引力以及熱動力而逐漸向蒙脫石結(jié)構(gòu)中遷移,遷移到六方孔中及部分八面體中。酸性條件下,含鉻蒙脫石的解吸附明顯多于堿性條件下的解吸附,這與H+和表面Cr3+發(fā)生交換、H+和蒙脫石的結(jié)構(gòu)羥基使得結(jié)構(gòu)部分發(fā)生解體、崩塌有關(guān),而堿性條件下即便發(fā)生解吸附,也能因?yàn)槊撍绒D(zhuǎn)變?yōu)闅溲趸t而穩(wěn)定在蒙脫石的顆粒之間,但相對來說CTAB改性后更易保存。
[Abstract]:With montmorillonite interlayer cation exchange capacity, large surface area, chemical stability and environmental effect is mild and is widely used. The former mainly for two monovalent, divalent metallic cations, such as Li+, Cd2+, adsorption and in migration of Cu2+ changes in montmorillonite, less for trivalent cations were Cr3+ study. In addition Cr3+ is widely used in the tanning, electroplating and paint and other industrial production, excessive chromium can damage the organism The new supersedes the old., have harmful effects on human health, is considered one of the most serious pollution of heavy metals in 16, is also very strong carcinogen, understanding the adsorption mechanism is of great significance to migration the production and the environment. This paper researches the changes of calcium montmorillonite before and after adsorption of Cr3+, and the products were heat treated at different temperatures (200 c, 300 C, 500 C, 600 C, 700 C) and Study on the rehydration conditions. On the other hand the use of sixteen alkyl three methyl bromide (CTAB) with different concentrations of interlayer exchange Ca2+ modified montmorillonite, heating at 250 DEG C under the condition of adsorption of Cr3+., discusses its structure changes and ion mobility conditions. Finally the chromium chromium containing montmorillonite and modified montmorillonite in acid under the condition of desorption. The results showed that calcium montmorillonite after the adsorption of Cr3+, Cr3+ mainly [Cr (H2O) 6]3+ in the form of alternative TOT structure layers Ca2+. when the heat treatment temperature is less than 500 DEG C, D001 decreased, OH stretching vibration and wave number in Duan Xianggao wavenumber offset, ESR signal peak is also increased. Compared with the heating of the sample, after water D001 value is part of the increase of OH stretching vibration peak is shifted to lower wavenumbers, ESR signal peak changes also showed that Cr3+ in the six square hole in the shallow part. When the temperature is greater than 500 degrees, according to the XRD pattern and ESR g=1. 97 strength changes appear eskolaite (Cr2O3), D060 by the narrow peak weakened wider, suggesting that there may be similar to the phase of pyrophyllite, because after water OH stretching region slightly shifted to lower wavenumbers, at Cr3+ in the deep hole. In six CTAB modified montmorillonite in CTAB, in a different arrangement so that its height D001 in between layers is greatly increased, decreased the adsorption ability of Cr3+, according to Al3+ ICP-AES the ion concentration in solution after reaction and the IR results show that vibration peak 3564 cm-1 belongs to Cr3+Cr3+OH, indicating that Cr3+ entered the eight face even replace part of the surface of the body eight Al3+; and heating at 250 DEG C, CTAB closed layer after the vibration peak of Cr3+Cr3+OH still exist, combined with the changes of ESR g factor, that the modified montmorillonite adsorption of Cr3+ after Cr3+ due to thermal power and attraction between molecules And gradually migrated to the structure of montmorillonite, migrated to six square hole and part of the eight surface body. Under acidic conditions, desorption of chromium containing montmorillonite was more than the adsorption solution under alkaline conditions, and the H+ and Cr3+ on the surface of the exchange structure, hydroxyl H+ and montmorillonite makes structure disintegrated, the collapse. But under alkaline conditions even solution adsorption, but also because of dehydration into chromium hydroxide and stable between montmorillonite particles, but relatively CTAB modified and easy storage.

【學(xué)位授予單位】：南京大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：P579;X703

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