Studi Struktur dan Sifat Penyerapan CO2 Material Penangkap CO2 Berbasis CaO-ZrO2 dari Batu Kapur Alam

Munawaroh, Fatimatul (2025) Studi Struktur dan Sifat Penyerapan CO2 Material Penangkap CO2 Berbasis CaO-ZrO2 dari Batu Kapur Alam. Doctoral thesis, Institut Tknologi Sepuluh Nopember.

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Abstract

Penelitian ini bertujuan mengevaluasi struktur dan sifat penyerapan CO₂ dari material berbasis CaO-ZrO2 yang disintesis dari batu kapur alam dengan fasa dominan kalsit. CaO murni (CZ0) disiapkan melalui metode sol-gel, sedangkan material CaO-ZrO₂ (CZ10-CZ40) diperoleh melalui pencampuran basah CaO dengan ZrO₂ dalam variasi konsentrasi 10, 20, 30, dan 40 wt%. Fokus utama penelitian ini adalah mengkaji peran ZrO₂ dalam meningkatkan kestabilan fasa, stabilitas struktur kristal, dan kapasitas penyerapan CO₂ selama siklus kalsinasi-karbonasi-dekarbonasi (calcium looping) pada temperatur tinggi. Karakterisasi struktur kristal dilakukan menggunakan difraksi sinar-X (XRD) untuk identifikasi fasa, sementara gugus fungsi material dianalisis melalui Fourier-transform infrared spectroscopy (FTIR). Transformasi fasa selama pemanasan dipantau secara real-time dengan XRD in-situ berbasis radiasi sinkrotron (SR-XRD). Struktur lokal atomik dikaji menggunakan X-ray Absorption Near Edge Structure (XANES) untuk menentukan keadaan oksidasi dan koordinasi lokal, serta Extended X-ray Absorption Fine Structure (EXAFS) untuk memperoleh informasi jarak dan jenis ikatan atom. Morfologi dan distribusi unsur dianalisis dengan Field Emission Scanning Electron Microscopy dilengkapi Energy Dispersive X-ray Spectroscopy (FESEM-EDS), untuk mengamati bentuk, ukuran partikel, dan distribusi elemen pada permukaan. Kapasitas penyerapan CO₂ dan stabilitas termal dievaluasi melalui Thermogravimetric Analysis (TGA), sedangkan karakterisasi tekstur permukaan dilakukan menggunakan metode Brunauer-Emmett-Teller (BET) dan Barrett-Joyner-Halenda (BJH) untuk menentukan luas permukaan spesifik dan distribusi ukuran pori. Selain itu, temperature-programmed desorption of CO₂ (TPD-CO₂) digunakan untuk mengevaluasi kekuatan interaksi CO₂ dengan situs adsorptif pada permukaan sorben. Hasil XRD menunjukkan bahwa penambahan ZrO₂ melalui metode pencampuran basah meningkatkan kristalinitas dan stabilitas material. Pada sampel CZ20, proses karbonasi menghasilkan pembentukan CaCO₃ yang optimal dengan struktur kristal stabil, sedangkan kelebihan ZrO₂ pada CZ30 dan CZ40 menurunkan kemampuan penyerapan akibat hambatan difusi CO₂. Sebelum karbonasi, morfologi CaO tampak berpori dengan distribusi Zr yang homogen berdasarkan analisis EDS. Setelah karbonasi, terbentuk kristal CaCO₃ berukuran 50-200 nm tanpa perubahan spektrum Zr, yang mengindikasikan sifat inert ZrO₂ selama proses berlangsung. Analisis Rietveld terhadap data XRD in-situ berbasis sinkrotron selama kalsinasi dan dekarbonasi menunjukkan bahwa CZ20 memiliki stabilitas termal dan struktur terbaik. Stabilitas ini ditunjukkan oleh kemampuan mempertahankan fasa aktif CaO, ketahanan terhadap sintering, serta pembentukan fasa CaZrO₃ yang memperkuat kestabilan kristalin pada suhu tinggi. Hasil XANES dan EXAFS juga memperlihatkan perubahan koordinasi lokal pada atom Ca dan Zr akibat proses karbonasi dan dekarbonasi, yang berkontribusi pada peningkatan ketahanan struktur dan performa material dalam penangkapan CO₂. Uji TGA menunjukkan bahwa kehilangan massa sebelum karbonasi menurun dari 19,91% (CZ0) menjadi 12,32% (CZ40). Sedangkan setelah karbonasi, CZ20 mencatat kehilangan massa tertinggi sebesar 36,44% pada suhu dekarbonasi 619 °C, menunjukkan kapasitas sorpsi dan efisiensi termal tertinggi di antara seluruh sampel. Dari sisi tekstur, penambahan ZrO₂ meningkatkan luas permukaan spesifik (8,65 menjadi 13,25 m²/g), volume pori (0,0776-0,1499 cm³/g), dan rata-rata ukuran pori (16-24 nm), mengindikasikan terbentuknya struktur mesopori terbuka. Selain itu, ZrO₂ juga meningkatkan jumlah dan kekuatan situs basa aktif. Meskipun CZ40 mencatat kapasitas adsorpsi CO₂ tertinggi (0,0652 g CO₂/g sorben), CZ20 dinilai paling seimbang karena memiliki nilai basicity yang tinggi (0,7466 mmol/g), energi desorpsi CO₂ yang moderat (76,11 dan 101,70 kJ/mol), serta regenerasi struktur yang baik selama siklus berulang. Dengan demikian, CZ20 merupakan kandidat sorben paling potensial untuk aplikasi penangkapan CO₂ suhu tinggi karena menawarkan kombinasi optimal antara kestabilan struktural, resistensi terhadap sintering, dan performa penyerapan.
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This study aims to evaluate the structure and CO₂ sorption properties of CaOZrO₂-based materials synthesized from natural limestone with calcite as the dominant phase. Pure CaO (CZ0) was prepared using the sol-gel method, while CaO-ZrO₂ materials (CZ10–CZ40) were obtained by wet mixing CaO with ZrO₂ at concentrations of 10, 20, 30, and 40 wt%. The primary focus of this research is to investigate the role of ZrO₂ in enhancing phase stability, crystal structure integrity, and CO₂ capture capacity during high-temperature calcination, carbonation, and decarbonation cycles (calcium looping). The crystal structure was characterized by X-ray diffraction (XRD) for phase identification, while functional groups were analyzed using Fourier-transform infrared spectroscopy (FTIR). Phase transformations during heating were monitored in real-time using in-situ synchrotron-based XRD (SR-XRD). The local atomic structure was examined by X-ray Absorption Near Edge Structure (XANES) to determine oxidation states and local coordination, and Extended X-ray Absorption Fine Structure (EXAFS) to obtain information on atomic bonding distances and coordination environments. The morphology and elemental distribution were analyzed using Field Emission Scanning Electron Microscopy equipped with Energy Dispersive X-ray Spectroscopy (FESEM-EDS) to observe particle shape, size, and surface elemental distribution. CO₂ capture capacity and thermal stability were evaluated through Thermogravimetric Analysis (TGA), while surface textural properties were characterized using Brunauer-Emmett-Teller (BET) and Barrett-Joyner-Halenda (BJH) methods to determine specific surface area and pore size distribution. In addition, temperature-programmed desorption of CO₂ (TPD-CO₂) was conducted to evaluate the strength and quantity of CO₂ adsorption sites on the sorbent surface. XRD results indicate that the addition of ZrO₂ via wet mixing enhances both crystallinity and material stability. For the CZ20 sample, carbonation led to optimal CaCO₃ formation with a stable crystal structure, whereas excessive ZrO₂ in CZ30 and CZ40 reduced CO₂ uptake due to diffusion limitations. Before carbonation, CaO exhibited a porous morphology with a homogeneous Zr distribution as confirmed by EDS analysis. After carbonation, CaCO₃ crystals with sizes of 50–200 nm were formed without changes in the Zr spectrum, confirming the inert nature of ZrO₂ during the process. Rietveld analysis of in-situ synchrotron XRD data during calcination and decarbonation revealed that CZ20 exhibited the best thermal and structural stability. This stability is attributed to its ability to retain the active CaO phase, resist sintering, and form CaZrO₃, which reinforces the crystalline stability at high temperatures. XANES and EXAFS results also demonstrated changes in the local coordination of Ca and Zr atoms due to carbonation and decarbonation, contributing to improved structural resilience and CO₂ capture performance. TGA measurements showed that the pre-carbonation weight loss decreased from 19.91% (CZ0) to 12.32% (CZ40). After carbonation, CZ20 exhibited the highest weight loss of 36.44% at a decarbonation temperature of 619 °C, indicating the highest sorption capacity and thermal efficiency among all samples. In terms of textural properties, the addition of ZrO₂ increased the specific surface area (from 8.65 to 13.25 m²/g), pore volume (0.0776-0.1499 cm³/g), and average pore size (16- 24 nm), indicating the formation of an open mesoporous structure. Moreover, ZrO₂ enhanced both the quantity and strength of basic sites. Although CZ40 showed the highest CO₂ adsorption capacity (0.0652 g CO₂/g sorbent), CZ20 was found to be the most balanced material due to its high basicity (0.7466 mmol/g), moderate CO₂ desorption energy (76.11 and 101.70 kJ/mol), and good structural regeneration during repeated cycles. Therefore, CZ20 is considered the most promising sorbent for high-temperature CO₂ capture applications, offering an optimal combination of structural stability, sintering resistance, and sorption performance.

Item Type:	Thesis (Doctoral)
Uncontrolled Keywords:	batu kapur alam, CaCO3, CaO-ZrO2, penangkapan CO2, sol-gel, natural limestone, CaCO3, CaO-ZrO2, CO2 capture, sol-gel
Subjects:	Q Science > QC Physics
Divisions:	Faculty of Natural Science > Physics > 45001-(S3) PhD Thesis
Depositing User:	Fatimatul Munawaroh
Date Deposited:	19 Aug 2025 01:04
Last Modified:	19 Aug 2025 01:11
URI:	http://repository.its.ac.id/id/eprint/128132

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