| Summary: | Pemanasan global telah menjadi salah satu isu global penting kerana kepekatan karbon dioksida (CO2) semakin meningkat. Penjerapan CO2 dengan menggunakan kalsium oksida (CaO) yang diperolehi daripada sisa semula jadi telah menarik perhatian remai penyelidik. Pemanfaatan sorben hijau untuk penjerapan CO2 ini dapat meminimumkan kos sorben yang menguntungkan semua kos pengeluaran. Dalam kajian ini, kerang sisa semulajadi yang merupakan kerang anadara granosa, kerang meretrix meretrik dan kerang venus kerang tekstil telah digunakan sebagai sumber untuk mendapatkan CaO. Dalam analisis pendarfluor sinar-X (XRF), lebih daripada 97 % berat CaO ditemui di dalam kerang sisa semulajadi selepas pengkalsinan pada 900 ℃. Beberapa parameter telah diselidik termasuk tempoh pengkarbonan, suhu pengkarbonan, jenis bahan tambahan logam ditambah dan peratusan berat bahan tambahan logam yang ditambahkan di sorben. Kapasiti penjerapan tertinggi didapati apabila tempoh pengkarbonan adalah 60 minit. Julat suhu pengkarbonan yang dikaji dalam kajian ini adalah 400 – 800 ℃. Kapasiti penjerapan tertinggi untuk kerang anadara granosa yang dikalsin (CaO – AGS) dan kerang meretrik meretrik yang dikalsin (CaO – MMS) didapati pada 800 ℃ manakala kulit kerang venus tekstil (CaO – TVCS) dan CaO komersial mempunyai kapasiti penjerapan yang tertinggi pada 700 ℃. Walau bagaimanapun, CaO komersial mempunyai kapasiti penjerapan tertinggi berbanding dengan yang lain kerana ia mempunyai kawasan permukaan tertinggi (100.63 m2/g). Kajian regenerabiliti juga telah dibuatkan untuk semua pemjerap pada 700 ℃ untuk 11 kitaran. CaO – TVCS telah didapati sebagai sorben terbaik kerana kapasiti pnejerapan yang lebih tinggi dan penurunan kecekapan kecil (24.27 %) dalam kajian regenerabiliti. Kajian kinetik penjerap juga dinilaikan. Tenaga pengaktifan untuk CaO – AGS, CaO – MMS, CaO komersial semasa pertama tahap process pengkarbonan adalah 47.13, 18.19, 26.98 dan 30.18 kJ/mol masing-masing. Tenaga pengaktifan untuk CaO – AGS, CaO – MMS, CaO – TVCS dan CaO komersial semasa tahap kedua process pengkarbonan adalah 20.19, 20.74, 21.09 dan 15.18 kJ/mol masing-masing. Kapasiti penjerapan CaO – TVCS ditambah dengan bahan tambahan logam (Al2O3 dan ZrO2) telah menurun dengan peningkatan peratusan berat bahan tambah logam. Kapasiti penjerapan pemjerap yang ditambah dengan nahan tambahan logam didapati bergantung pada peratusan berat CaO dalam penjerap. Selepas menjalankan kajian regenerabiliti, CaO:ZrO2 dengan peratusan berat 90:10 telah didapati sebagai penjerap terbaik kerana penurunan kecekapan yang lebih rendah (19.05 %) berbanding dengan CaO:Al2O3 dengan peratusan berat 90:10 (22.47 %) dan CaO – TVCS (38.04 %). Oleh itu, dapat disimpulkan bahawa CaO:ZrO2 dengan peratusan berat 90:10 adalah alternatif yang berpotensi untuk CaO kerana ia mempunyai ketahanan dan kestabilan yang lebih tinggi daripada CaO.
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Global warming has become one of the essential global issues as the world concentration of CO2 is rising. Carbon dioxide (CO2) capture by using calcium oxide (CaO) derived from natural waste shells has attracted the attentions of many researchers. Utilization of these green sorbents for CO2 capture is able to minimize the cost of the sorbents which is favourable to the whole production cost. In this research, the natural waste shells which are anadara granosa shells, meretrix meretrix shells and textile venus clam shells were utilized as the sources to obtain CaO. In the X-ray fluorescene (XRF) analysis, more than 97 wt % of CaO was found in the natural waste shells after calcination process at 900 ℃. Several parameters were investigated including carbonation duration, carbonation temperature, type of metal additives added and weight percentage of metal additive added to sorbent. The highest sorption capacity was found when the carbonation duration was 60 minutes. The range of the carbonation temperature studied in this research was 400 – 800 ℃. The highest sorption capacities for calcined anadara granosa shells (CaO – AGS) and calcined meretrix meretrix shells (CaO – MMS) were at 800 ℃ while calcined textile venus clam shells (CaO – TVCS) and commercial CaO had their highest carbonation conversion at 700 ℃. However, commercial CaO had the highest sorption capacity as compared to others since it had the highest surface area (100.63 m2/g). Regenerability study also had been carried for all the sorbents at 700 ℃ for 11 cycles. CaO – TVCS had been found as the best sorbent due to its higher carbonation conversion and minor efficiency drop (24.27 %). Kinetic study of the sorbent samples was evaluated. The activation energy for CaO – AGS, CaO – MMS, CaO - TVCS and commercial CaO during the chemical reaction controlled stage of carbonation reaction were 47.13, 18.19, 26.98 and 30.18 kJ/mol respectively. The activation energy for CaO – AGS, CaO – MMS, CaO - TVCS and commercial CaO during the product layer diffusion controlled stage of carbonation reaction were 20.19, 20.74, 21.09 and 15.81 kJ/mol respectively. The sorption capacities of the CaO – TVCS added with metal additives (Al2O3 and ZrO2) were decreased with the increasing weight percentage of metal additives. The sorption capacities of the sorbent samples added with metal additives were found relied on the weight percentage of CaO in the sorbent samples. After conducting the regeneration study, CaO:ZrO2 with 90:10 weight percentage had been found as the best sorbent samples owing to its lower efficiency drop (19.05 %) in comparison to CaO:Al2O3 with 90:10 weight percentage (22.47 %) and CaO – TVCS (38.04 %). Therefore, it can be concluded that CaO:ZrO2 with 90:10 weight percentage is a potential alternative to CaO as it has higher durability and stability than CaO.
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