졸-겔 공정을 이용한 표면 개질된 티타니아/실리카 에어로겔 파우더의 합성과 특성평가

Abstract

고도의 산업화 시대인 현대사회의 문제점 중의 하나가 바로 환경오염이다. 산업화로 인한 화학물질 및 중금속 외에도 일상생활에서 나오는 다양한 물질들은 수질오염, 토양오염, 대기오염 등의 문제를 발생시키고 있으며 이러한 환경오염으로 인해 생태계 내에 살고 있는 모든 동식물들은 직·간접적으로 피해를 받고 있고 인간의 생활과도 밀접하게 관련되어 개인의 삶의 질 뿐 만 아니라, 주거 활동에도 큰 문제점을 가지고 있어 이를 개선할 방안에 대한 관심이 높아지고 있다. 환경오염을 개선하기 위한 방안으로 수질 및 대기 오염 물질 처리, 유해물질 포집 등의 다양한 분야에 오염 분해 기능, 항균 및 살균 기능, 공기정화, 냄새 제거 기능, 정수 기능 등의 기능을 가진 광촉매가 많이 응용되고 있다. 광촉매는 빛을 흡수함으로써 촉매작용을 일으키는 물질로, 대표적인 광촉매 물질로는 TiO2가 알려져 있다. 즉, TiO2의 입자를 아주 미세하게 만들어 주면 태양광이나 형광등 빛에 포함되어 있는 자외선에 의해 활성산소가 발생하고, 이 활성산소는 강력한 산화 환원 작용을 나타내어 유기물 분해, 살균작용, 방오 작용, 친수성 등을 나타내게 된다. 유사한 거동을 나타내는 광촉매 재료로는 SrTiO3, CdS, ZnO 등이 있지만 TiO2가 주목 되어지는 이유로는 화학적으로 안정하고 인체에 대해 무해하며 안전성이 높기 때문이다.[1] 하지만, 기존의 상업적으로 판매 되고 있는 순수 TiO2의 물질은 광촉매 활성은 좋게 나오지만, 표면적이 작아서 분해하고자 하는 반응물의 흡착이 잘 이루어 지지 않는다는 문제점을 가지고 있다. 따라서 이러한 문제점을 해결하여 광촉매의 반응 효율을 증가시키고, 반응물의 흡착력을 높이기 위해 표면적을 높일 수 있는 금속 산화물 및 비금속 원소를 첨가하여 복합체를 형성하는 연구가 활발히 진행되고 있다. 그 중 SiO2을 첨가한 Ti02-SiO2 복합 산화물의 경우, SiO2의 높은 비표면적, 높은 기공도, 낮은 밀도와 같은 특성으로 고온에서의 TiO2의 열적 안전성과 광촉매 활성을 향상시킬 수 있다. 본 연구에서는, Ti02-SiO2 에어로겔을 합성하기 위해 기존의 사용되는 고가의 물질이 아닌 값싼 원료를 사용하여 졸-겔 법과 용매치환 및 표면개질 공정을 거쳐 상압하에서 소수성을 갖는 Ti02-SiO2 에어로겔을 합성하여 분말 형태로 제조하였고, 제조된 Ti02-SiO2 에어로겔 분말의 비표면적, 결정도, 물리․ 화학적 결합 구조, 열적 안정성 등의 상관관계에 대한 특성평가를 진행하였다. 또한, 열처리 온도에 따른 Ti02-SiO2 에어로겔 분말의 물성 및 미세 구조를 분석하기 위해 FT-IR, XRD, SEM, TEM, BET 등을 사용하였고, UV에 의해 시료가 첨가된 메틸렌 블루 수용액을 산화시켜 UV-Vis spectroscopy를 통해 광분해 효율에 대해 알아보았다.|Titanium dioxide are being extensive research, which has led to many promising applications in areas ranging from photovoltaics and photocatalysis to photo-/electrochromics and sensors since the photocatalytic splitting of water on TiO2 electrodes was discovered by Fujishima and Honda in 1972. For a more higher efficiency of Ti02 as the most promising photocatalyst, Metal oxide aerogels like silica-titania oxide aerogels combined advantages of silica aerogel and titanium dioxide have received significant attention as a novel class of materials that have been extensively used as catalysts and supports for a wide variety of reactions due to their high phohocatalytic activity in recent years. In the present research, Ti02-SiO2 aerogel was prepared in powder form by using competitively priced precursors and a facile two step process in industry. TiO2 sol was added to SiO2 sol made by through sol-gel process are synthesized a aerogel following several stages with alcogel (gel with alcohol in its pores), hydrogel (gel with water in its pores), aerogel (gel with pores just under 100nm). Synthesis procedures also involved solvent exchange/modification via silylating agent such as TMCS in n-hexane for hydrophobic property. After the Ti02-SiO2 aerogel powders were dried, calcined to study the thermal pore stability. The homogeneity and fine structure of the Ti02-SiO2 aerogel powders was confirmed by TEM, FE-SEM and XRD. The physio-chemical properties were examined by BET, FT-IR, TG/DTA. Photocatalytic efficiency of Ti02-SiO2 aerogel powders was tested to methylene blue. These approach are may perhaps expect to outstanding efficiency of photocatalytic property and easily process. The molar ratio of SiO2:TiO2 was 1:2.3 and the synthetic strategy revealed that TiO2–SiO2 aerogel, had a surface area ∼726m2/g, pore diameter ∼14.9nm, pore volume ~3.0cm3/g, density ∼0.1215g/cm3. FT-IR spectra showed the peaks attributable to the presence of methyl groups at 2969 and 1264 cm-1 and Si-C at 854cm-1. The incorporation of TiO2 in the SiO2 matrix was indicated by the formation of the Ti-O-Si hetero linkage at 950cm-1. Heat treatment of the as-prepared sample showed that the surface area and textural properties increase with increasing the calcination temperature up to temperature <4000C when the aerogel completely lose its hydrophobic properties. XRD results revealed that raw aerogel was amorphous which yields prominent anatase TiO2 crystals after calcination at 8000C. Photocatalytic degradation of methylene blue by TiO2-SiO2 aerogel samples synthesized via this method suggested that hydrophobicity is the main factor influenced the catalytic performance of TSA (as-synthesized sample) and TSA-200 samples. Nevertheless, the discrepancy of activities between TSA-400 and TSA-600 samples could be explained in terms of partial crystalline structure attained as a result of calcination.; Titanium dioxide are being extensive research, which has led to many promising applications in areas ranging from photovoltaics and photocatalysis to photo-/electrochromics and sensors since the photocatalytic splitting of water on TiO2 electrodes was discovered by Fujishima and Honda in 1972. For a more higher efficiency of Ti02 as the most promising photocatalyst, Metal oxide aerogels like silica-titania oxide aerogels combined advantages of silica aerogel and titanium dioxide have received significant attention as a novel class of materials that have been extensively used as catalysts and supports for a wide variety of reactions due to their high phohocatalytic activity in recent years. In the present research, Ti02-SiO2 aerogel was prepared in powder form by using competitively priced precursors and a facile two step process in industry. TiO2 sol was added to SiO2 sol made by through sol-gel process are synthesized a aerogel following several stages with alcogel (gel with alcohol in its pores), hydrogel (gel with water in its pores), aerogel (gel with pores just under 100nm). Synthesis procedures also involved solvent exchange/modification via silylating agent such as TMCS in n-hexane for hydrophobic property. After the Ti02-SiO2 aerogel powders were dried, calcined to study the thermal pore stability. The homogeneity and fine structure of the Ti02-SiO2 aerogel powders was confirmed by TEM, FE-SEM and XRD. The physio-chemical properties were examined by BET, FT-IR, TG/DTA. Photocatalytic efficiency of Ti02-SiO2 aerogel powders was tested to methylene blue. These approach are may perhaps expect to outstanding efficiency of photocatalytic property and easily process. The molar ratio of SiO2:TiO2 was 1:2.3 and the synthetic strategy revealed that TiO2–SiO2 aerogel, had a surface area ∼726m2/g, pore diameter ∼14.9nm, pore volume ~3.0cm3/g, density ∼0.1215g/cm3. FT-IR spectra showed the peaks attributable to the presence of methyl groups at 2969 and 1264 cm-1 and Si-C at 854cm-1. The incorporation of TiO2 in the SiO2 matrix was indicated by the formation of the Ti-O-Si hetero linkage at 950cm-1. Heat treatment of the as-prepared sample showed that the surface area and textural properties increase with increasing the calcination temperature up to temperature <4000C when the aerogel completely lose its hydrophobic properties. XRD results revealed that raw aerogel was amorphous which yields prominent anatase TiO2 crystals after calcination at 8000C. Photocatalytic degradation of methylene blue by TiO2-SiO2 aerogel samples synthesized via this method suggested that hydrophobicity is the main factor influenced the catalytic performance of TSA (as-synthesized sample) and TSA-200 samples. Nevertheless, the discrepancy of activities between TSA-400 and TSA-600 samples could be explained in terms of partial crystalline structure attained as a result of calcination.