Saputra, Andika Ade Indra (2026) Geopo-Liner: Material Pelapis Berbahan Dasar Geopolimer Untuk Mencegah Kontaminasi Limbah Cair Asam Berbahaya. Doctoral thesis, Institut Teknologi Sepuluh Nopember.
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Abstract
Degradasi material pelapis pada lingkungan agresif merupakan permasalahan penting dalam rekayasa geoteknik karena dapat menurunkan fungsi penghalang terhadap migrasi kontaminan, khususnya pada paparan limbah cair asam berbahaya yang mengandung sulfat serta logam Fe dan Mn seperti air asam tambang (AAT). Permasalahan ini mendorong pengembangan material pelapis melalui dua pendekatan utama, yaitu modifikasi material sintetis atau pemanfaatan limbah sebagai alternatif material. Dalam penelitian ini, limbah padat berupa circulating fluidized bed combustion (CFBC) fly ash dimanfaatkan sebagai prekursor yang diaktivasi dengan alkali untuk mengembangkan material berbasis geopolimer agar mampu menghasilkan struktur gel aluminosilikat yang padat dan stabil pada lingkungan asam. Material yang dihasilkan selanjutnya disebut Geopo-Liner, dengan target nilai konduktivitas hidrolik < 1 × 10-9 m/detik dan kuat tekan > 200 kPa sebagai persyaratan material pelapis.
Penelitian dilaksanakan melalui tiga tahapan utama, yaitu optimasi komposisi geopolimer berbasis CFBC fly ash, evaluasi kinerja konduktivitas hidrolik pada variasi komposisi dengan kepadatan awal seragam, serta pengujian interaksi semi-dinamik dengan AAT selama 28 hari. Karakterisasi perubahan mikrostruktur pada Geopo-Liner dilakukan menggunakan XRD, FTIR, SEM, dan EDS untuk mengidentifikasi respon material terhadap penetrasi sulfat serta ion Fe dan Mn. Selain itu, penelitian juga mengkaji pengembangan Geopo-Liner melalui penambahan palm oil fuel ash (POFA) yang juga merupakan limbah padat sebagai sumber silika eksternal untuk mengoptimalkan proses geopolimerisasi dan meningkatkan kinerja material. Hasil penelitian menunjukkan bahwa NaOH 8 M merupakan konsentrasi aktivator optimum untuk CFBC fly ash dalam memaksimalkan proses geopolimerisasi, namun pada kadar CFBC fly ash di atas 50% diperlukan upaya pemadatan tambahan untuk meningkatkan kontak antara prekursor dan aktivator. Konduktivitas hidrolik yang dihasilkan lebih dipengaruhi oleh densifikasi kimia melalui pembentukan gel geopolimer yang mengisi pori dibandingkan densifikasi fisik akibat pemadatan awal, dengan kinerja terbaik dicapai pada G60 yang menghasilkan nilai terendah sebesar 3,77 × 10-11 m/detik. Selama 28 hari paparan AAT, G60 menunjukkan kestabilan kepadatan, namun terjadi penurunan kecepatan rambat gelombang dan kuat tekan yang mengindikasikan degradasi mikrostruktur internal. Interaksi awal dengan AAT juga mengakibatkan perubahan mikrostruktur permukaan melalui pelepasan awal Fe, Mn, dan sulfat yang diikuti pembentukan presipitasi goethite dan schwertmannite yang membatasi penetrasi lebih lanjut. Penambahan POFA sebagai sumber silika eksternal mampu menurunkan konduktivitas hidrolik dari 9,65 × 10-9 menjadi 1,57 × 10-10 m/detik melalui peningkatan proporsi pori tertutup. Secara keseluruhan, Geopo-Liner berbasis CFBC fly ash mampu menunjukkan kinerja yang memenuhi persyaratan material pelapis serta mempertahankan integritas mikrostruktur inti meskipun terjadi reaksi permukaan selama interaksi jangka pendek dengan AAT.
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A critical issue in geotechnical engineering is the degradation of barrier functions against contaminant migration, particularly under exposure to hazardous acidic liquid waste containing sulfate and metal ions such as Fe and Mn, as found in acid mine drainage (AMD). This challenge has driven the development of liner materials through two main approaches: modification of synthetic materials and utilization of waste-based alternatives. In this study, solid waste in the form of circulating fluidized bed combustion (CFBC) fly ash was utilized as a precursor and alkali-activated to develop a geopolymer-based material capable of forming a dense and stable aluminosilicate gel structure in acidic environments. The developed material, referred to as Geopo-Liner, was designed to achieve a hydraulic conductivity of < 1 × 10-9 m/s and a compressive strength of > 200 kPa, which are the performance requirements for liner materials. The research was conducted through three main stages: optimization of CFBC fly ash-based geopolymer composition, evaluation of hydraulic conductivity performance across different compositions under uniform initial density conditions, and semi-dynamic interaction testing with AMD over a 28-day exposure period. Microstructural changes in the Geopo-Liner were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS) to identify the material response to sulfate and Fe/Mn ion penetration. Furthermore, the development of Geopo-Liner was investigated through the incorporation of palm oil fuel ash (POFA), another solid waste material, as an external silica source to optimize geopolymerization and enhance material performance. The results indicate that 8 M NaOH was the optimum alkaline activator concentration for CFBC fly ash to maximize geopolymerization; however, CFBC fly ash contents above 50% required additional compaction efforts to improve the contact between precursor particles and the activator solution. The resulting hydraulic conductivity was governed more by chemical densification through geopolymer gel formation and pore filling than by physical densification associated with initial compaction. The best performance was achieved by G60, which exhibited the lowest hydraulic conductivity value of 3.77 × 10-11 m/s. During 28 days of AMD exposure, G60 maintained its bulk density stability; however, reductions in ultrasonic pulse velocity and compressive strength indicated internal microstructural degradation. AMD interaction induced surface microstructural alterations through the initial release of Fe, Mn, and sulfate ions, followed by the formation of goethite and schwertmannite precipitates that restricted further contaminant penetration. The incorporation of POFA as an external silica source reduced hydraulic conductivity from 9.65 × 10-9 to 1.57 × 10-10 m/s by increasing the proportion of closed pores. Overall, the CFBC fly ash-based Geopo-Liner demonstrated the capability to satisfy liner material requirements while maintaining core microstructural integrity despite surface reactions during AMD short-term interaction.
| Item Type: | Thesis (Doctoral) |
|---|---|
| Uncontrolled Keywords: | Air asam tambang, CFBC fly ash, Kepadatan awal seragam, Konduktivitas hidrolik, Material pelapis, Acid mine drainage, CFBC fly ash, Hydraulic conductivity, Liner material, Uniform initial bulk density. |
| Subjects: | T Technology > TA Engineering (General). Civil engineering (General) > TA434 Inorganic polymers |
| Divisions: | Faculty of Civil, Planning, and Geo Engineering (CIVPLAN) > Civil Engineering > 22001-(S3) PhD Thesis |
| Depositing User: | Andika Ade Indra Saputra |
| Date Deposited: | 04 Aug 2026 06:26 |
| Last Modified: | 04 Aug 2026 06:26 |
| URI: | http://repository.its.ac.id/id/eprint/143169 |
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