本文選題：稻殼 + 巰基改性磁性介孔二氧化硅��； 參考：《江南大學》2017年碩士論文

【摘要】：水生環(huán)境中的重金屬污染正威脅著生態(tài)系統(tǒng)平衡和公眾健康,其中鎘污染尤為突出。研發(fā)高吸附率、可再生、低成本的重金屬吸附材料,已成為廢水中重金屬消減的重要研究方向。本論文在以稻殼灰為硅源和Fe3O4為磁性材料制備磁性介孔二氧化硅(Magnetic Mesoporous Silica,MMS)的基礎上,以高效吸附鎘為目的,研究MMS的改性工藝,優(yōu)化MMS和巰基改性磁性介孔二氧化硅(Thiol-modified Magnetic Mesoporous Silica,TMMS)的吸附工藝,建立吸附動力學模型和等溫吸附模型,探討兩種材料對Cd~(2+)的吸附和解吸機制,初步探索TMMS在鎘大米除鎘廢水中的應用。本研究對稻殼灰的高效利用以及工業(yè)廢水中Cd~(2+)的富集脫除具有重要意義。經(jīng)初探,MMS巰基改性后對Cd~(2+)的吸附效果要優(yōu)于氨基改性。據(jù)此,本研究對MMS的巰基改性工藝條件進行優(yōu)化,結(jié)果表明,以巰丙基三甲氧基硅烷為硅烷偶聯(lián)劑,在反應時間8 h、反應溫度80oC、氨水添加量750μL時,制備的TMMS具有最好的Cd~(2+)吸附性能,其表面巰基濃度為0.131 mmol/L。采用磁鐵分離、靜態(tài)氮吸附、X衍射、紅外光譜、Zeta電位等方法,分析MMS和TMMS的結(jié)構(gòu)與性質(zhì)。結(jié)果表明,在施加外磁場后,MMS和TMMS材料均可以和水相很好的分離;MMS和TMMS材料孔徑分布均較為集中,MMS的平均孔徑和比表面積分別為4.58 nm和581.77 m2/g,而TMMS分別為4.86 nm和367.67 m2/g,巰基接枝后材料的比表面積減小;X衍射結(jié)果表明,MMS與TMMS材料均為孔道有序的六方結(jié)構(gòu),Fe3O4均為標準的尖晶石結(jié)構(gòu);在MMS及TMMS的紅外光譜圖中均有SiO2、Fe3O4的特征吸收峰,TMMS的光譜圖中有-CH2-CH2-CH2-SH的特征碳氫鍵伸縮振動吸收峰,說明巰基成功接枝到MMS表面;Zeta電位測定結(jié)果顯示,MMS與TMMS的等電點分別為3.4和3.2。在鎘標準溶液(初始濃度為1.50 mg/L)體系中,MMS的最佳吸附條件為pH 5、溫度30oC、吸附時間5 h,在此條件下,MMS對Cd~(2+)的單位吸附量和吸附率分別為2.71 mg/g和79.46%;MMS對Cd~(2+)的吸附過程同時符合準二級動力學模型和顆粒內(nèi)擴散模型,擬合得到的平衡吸附量值為2.81 mg/g;MMS對Cd~(2+)的等溫吸附同時符合Langmuir模型和Freundlich模型,推測吸附過程可能同時存在化學作用力和物理作用力,30oC時,MMS對Cd~(2+)的飽和吸附量為17.86 mg/g。在初始濃度為1.50 mg/L的鎘標準溶液體系中,TMMS的最佳吸附條件為pH 5、吸附時間4 h、吸附溫度30oC,在此條件下,其單位吸附量和吸附率分別為2.88 mg/g和95.12%。TMMS對Cd~(2+)的吸附過程符合準二級動力學模型,推測以化學吸附為主,擬合得到TMMS的平衡吸附量為2.91 mg/g;TMMS的吸附反應速率常數(shù)k2是MMS的3倍,說明TMMS吸附Cd~(2+)的速率較快。TMMS對Cd~(2+)的等溫吸附符合Langmuir模型,為單分子層吸附,30oC時的飽和吸附量為33.33 mg/g,約是MMS的2倍,說明改性在一定程度上提高了材料的吸附效果。MMS和TMMS的解吸行為研究表明,MMS吸附Cd~(2+)后,在0.1 mol/L HCl中解吸4 h即可達到解吸平衡,此時的解吸率為96.58%,重復吸附/解吸4次后,第5次的吸附率僅為29.18%;TMMS吸附Cd~(2+)后,解吸速率稍慢,在相同濃度的鹽酸中需要解吸5 h才可達到解吸平衡,此時的解吸率為96.10%,與MMS相比,TMMS具有較好的重復利用性能,其重復吸附/解吸4次后,第5次的吸附率仍在70%以上。MMS與TMMS的解吸過程均符合準二級解吸動力學方程,推測解吸可能是一個化學反應的過程,TMMS的解吸速率常數(shù)比MMS小,說明MMS對Cd~(2+)的解吸速率較快,而TMMS與Cd~(2+)結(jié)合的作用力較強,不易被解吸,解吸速率慢。以TMMS為吸附劑,在最佳吸附條件下對鎘大米除鎘廢水(Cd~(2+)濃度為1.36 mg/L)中的Cd~(2+)進行富集脫除,Cd~(2+)吸附率為78.80%。
[Abstract]:Heavy metal pollution in the aquatic environment is threatening the balance of the ecosystem and public health, especially the cadmium pollution. The development of heavy metal adsorption materials with high adsorption rate, renewable and low cost has become an important research direction for the reduction of heavy metals in wastewater. In this paper, the magnetic mesopore was prepared by using rice husk ash as a silicon source and Fe3O4 as magnetic material. On the basis of silica (Magnetic Mesoporous Silica, MMS), in order to efficiently adsorb cadmium, the modified process of MMS was studied, the adsorption process of MMS and Mercapto modified magnetic mesoporous silica (Thiol-modified Magnetic Mesoporous Silica, TMMS) was optimized. The adsorption kinetics model and isothermal adsorption model were established, and two kinds of materials were discussed. The mechanism of adsorption and desorption was used to preliminarily explore the application of TMMS in cadmium removal from cadmium rice. This study is of great significance to the efficient utilization of rice husk ash and the enrichment and removal of Cd~ (2+) in industrial wastewater. The adsorption effect of MMS mercapto on Cd~ (2+) is better than that of ammonia based modification. Accordingly, the sulfhydryl modified process bar of MMS is studied in this study. The results show that with mercapto trimethoxy silane as silane coupling agent, the TMMS has the best Cd~ (2+) adsorption properties when the reaction time is 8 h, the reaction temperature is 80oC and the amount of ammonia is added to 750 u L. The surface sulfhydryl concentration is 0.131 mmol/L. by magnetite separation, static nitrogen adsorption, X diffraction, infrared spectrum, Zeta potential and so on. The structure and properties of MMS and TMMS are analyzed. The results show that after the external magnetic field is applied, both MMS and TMMS materials can be well separated from the aqueous phase; the pore size distribution of MMS and TMMS materials are all concentrated, the average pore size and specific surface area of MMS are 4.58 nm and 581.77 m2/g respectively, while TMMS are 4.86 nm and 367.67 m2/g, and the ratio of the sulfhydryl graft materials X diffraction results show that both MMS and TMMS are six square structures with orderly channel, Fe3O4 is the standard spinel structure, and the characteristic absorption peaks of SiO2, Fe3O4 in the infrared spectra of MMS and TMMS, and the characteristic hydrocarbon expansion vibration absorption peaks of -CH2-CH2-CH2-SH in the spectrum of TMMS, indicate that the sulfhydryl group is successfully grafted to the MMS table. The Zeta potential determination results show that the isoelectric points of MMS and TMMS are 3.4 and 3.2. in the cadmium standard solution (initial concentration of 1.50 mg/L), and the best adsorption conditions for MMS are pH 5, temperature 30oC, and adsorption time 5 h. Under this condition, the unit adsorption and adsorption rate of MMS to Cd~ (2+) are 2.71 and 79.46% respectively. The process conforms to the quasi two stage dynamic model and the internal particle diffusion model. The equilibrium adsorption amount is 2.81 mg/g, and the isothermal adsorption of Cd~ (2+) to Cd~ (2+) conforms to the Langmuir model and the Freundlich model. It is presumed that the adsorption process may have both chemical and physical forces. 30oC, MMS to Cd~ (2+) saturated adsorption capacity is 17.. 86 mg/g. in the cadmium standard solution system with an initial concentration of 1.50 mg/L, the optimum adsorption condition for TMMS is pH 5, the adsorption time is 4 h, and the adsorption temperature is 30oC. Under this condition, the adsorption capacity and adsorption rate of the unit are 2.88 mg/g and 95.12%.TMMS to Cd~ (2+), respectively, which conforms to the quasi two order kinetic model. The equilibrium adsorption capacity of TMMS is 2.91 mg/g, and the rate constant K2 of TMMS is 3 times of MMS, indicating that TMMS adsorption Cd~ (2+) is faster than.TMMS on Cd~ (2+). The adsorption of Cd~ (2+) is consistent with the single molecular layer, and the saturated adsorption amount is 33.33 times, which is about 2 times, indicating that the modification has been improved to a certain extent. The desorption behavior of.MMS and TMMS shows that after MMS adsorption Cd~ (2+), desorption of 4 h in 0.1 mol/L HCl can achieve the desorption equilibrium, and the desorption rate is 96.58%, and the adsorption rate is only 29.18% after repeated adsorption / desorption for 4 times, and the desorption rate is slightly slow after TMMS adsorption Cd~ (2+), and 5 h in the same concentration of hydrochloric acid needs to desorption 5 h. The desorption equilibrium can be achieved. The desorption rate at this time is 96.10%. Compared with MMS, TMMS has better reutilization performance. After 4 times of repeated adsorption / desorption, the adsorption rate of fifth times more than 70%.MMS and TMMS is consistent with the quasi two desorption kinetics equation. It is presumed that the desorption may be a chemical reaction process and the desorption speed of TMMS. The rate constant is smaller than MMS, indicating that the desorption rate of MMS to Cd~ (2+) is faster, while TMMS and Cd~ (2+) are stronger, not easily desorption, and the desorption rate is slow. With TMMS as an adsorbent, the enrichment and removal of the cadmium removal of cadmium waste water (Cd~ (2+) concentration is 1.36 mg/L) under the optimum adsorption conditions
【學位授予單位】：江南大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TQ424;X703

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