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Synthesis Of Layered Materials And Their Environmental Applications

Posted on:2006-01-07Degree:DoctorType:Dissertation
Country:ChinaCandidate:M YaoFull Text:PDF
GTID:1101360152996089Subject:Environmental Science
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Saponite and hydrotalcite are two kinds of ionic materials having practical application value among the numerous layered materials. As a member of layered silicate, saponite has great potential in nanocomposite, medicine, sensor and catalyst synthesis. The latter having the large anion exchange capacity has been applied in catalysis and pharmacy fields. HTc, the calcined form of hydrotalcite, has larger adsorption capacity for anion than hydrotalcite.Among the various organic pollutants, the ionic ones have been regarded as the difficult part in practical pollution remediation. Both anionic and cationic materials were synthesized hydrothermally in this work for the aim of ionic pollution control and other applications.Many influencing factors were involved in saponite synthesis by hydrothermal way, though it is a relatively easy work without the consideration of the structure of the as-synthesized product. The starting pH of the gel for thermal treatment was of the great one among theses factors influencing the long range order and atom coordination in the product. For synthesis of saponite with a higher layer charge, this factor becomes more important. 27Al MAS NMR, XRD and FT-IR strictly approved that the influence of starting pH and reaction temperature, which were found the most important factors in saponite synthesis. In addition, SEM, TEM and elemental analysis were employed in the above research.In innovative synthesis method exploration, microwave method was found as a fairly good one for saponite synthesis in libratory scale. By this method, saponite having long range order was obtained. Amorphous SiO2 was found in the analysis of the product synthesized under one atmospheric pressure. It was worthy to note that Si(Al)-O stretching vibration infrared absorption could be regarded as an index in the assessing the quality of the sample. With the increasing pressure, this strong vibration shifted to low frequency in the medium frequency region of the whole infrared spectrum. Since the easiness and simplicity, this infrared index would be meaningful in practical saponite-related minerals analysis. In addition, powder X-ray diffraction and scanning electronic microscopy were employed in the charactering the saponite synthesized by microwave-hydrothermal method in this work.In the research to improvement the hydrophobicity of the smectite by alumina modification, it was observed that alumina pillared montmorillonite prepared by different synthesis procedures, including ultrasonication, microwave radiation and conventional intercalation methods, had the analogous activity in the solid acid catalyzed model reaction of cumene conversion. Employing powder X-ray diffraction determinations, all the pillared products had the similar structure, namely the characteristic interlayer distance of alumina pillared clay. The new methods using ultrasonication or microwave decreased the intercalation time in the synthesis of pillared clay, suggesting the potential application in future industry production.Saponites with different layer charges were employed in the modification by alumina pillar. The detailed structure of theses materials was investigated. Saponite with 1.0 layer charge synthesized under mild reaction conditions was found having the ideal structure of 2:1 type trioctahedal smectite with tetrahedal aluminum substitutions. Pillared material using this ideal mineral had the typical properties of pillared clay according to N2 adsorption at 77 K, elemental analysis and 27Al MAS NMR. Based on the thermal characterization, alumina pillared saponite was stable up to 700 ℃ at least. It was also found that pillared saponite had good adsorption ability for cationicdye using methylene blue as the simulated pollutant. Additionally, pillared saponite with 1.0 layer charge was investigated in the addition of catalytic cracking catalyst. The cracking activity of the pillared saponite added catalysts was determined. A host material improved steam stability of pillared saponite theory was proposed for the observed increased...
Keywords/Search Tags:Saponite, hydrotalcite, adsorption, catalytic cracking, hydrothermal synthesis, layered silicate, smectite, montmorillonite, dye
PDF Full Text Request
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