Enrichment of rare-earth elements and yttrium (REY) on coal ash from Tabul, Meragoh, and Naintopo Formation, Tarakan Sub-Basin, North Kalimantan, and Dahor and Warukin Formation, Asem-Asem Basin, South Kalimantan

KEVIN, Dr. Ir. Ferian Anggara, S.T., M.Eng., IPM.

2021 | Skripsi | S1 TEKNIK GEOLOGI

Cekungan Asem-Asem dan Sub-Cekungan Tarakan merupakan cekungan-cekungan penghasil batubara di Indonesia yang menarik untuk dikaji lebih lanjut karena memiliki potensi pengayaan REY pada batubara. Secara umum, batubara yang diproduksi dari cekungan ini digunakan untuk PLTU, dimana batubara akan mengalami pengayaan REY pada abu batubara yang dihasilkan dari proses pembakaran. Batubara dan abu hasil pembakaran batubara diidentifikasi sebagai salah satu alternatif REY yang kelimpahannya dapat menyamai dan bahkan melebihi pada deposit konvensional. Seiring dengan meningkatnya permintaan dan kebutuhan REY di dunia yang diprediksi akan semakin meningkat setiap tahunnya, maka penelitian mengenai keterdapatan REY pada batubara dan abu batubara semakin digencarkan. Penelitian ini dilakukan untuk memberikan gambaran infromasi konsentrasi REY pada batubara dan abu batubara, serta moda keterdapatan REY pada abu batubara. Sampel batubara berasal dari beberapa lokasi penambangan aktif PT. Anjas Anita Jaya, PT. Duta Tambang Rekayasa, dan PT. Pipit Mutiara Jaya pada Sub-Cekungan Tarakan, serta PT. Arutmin pada Cekungan Asem-Asem. Sampel abu batubara dihasilkan dari proses ashing menggunakan furnace pada suhu 1000C selama 1 jam. Pengambilan sampel dilakukan dengan metode bulk sampling. Sampel kemudian dilakukan preparasi untuk selanjutnya dilakukan analisis petrografi sayatan tipis, petrografi sayatan poles, analisis proksimat, analisis geokimia Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) dan Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), X-Ray Powder Diffraction (XRD), dan Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). Hasil penelitian menunjukkan bahwa konsentrasi REY pada batubara berkisar 2,22-68,78 ppm, sedangkan pada abu batubara berkisar 45,41-2108,98 ppm, dimana hanya sampel K3 yang memiliki konsentrasi REY lebih tinggi daripada konsentrasi rata-rata REY di dunia dan USA. Konsentrasi REY yang terkandung pada abu batubara mengalami pengayaan 10-30 kali jika dibandingkan dengan konsentrasi REY pada batubara asal. Moda keterdapatan REY pada komponen penyusun abu batubara tidak dapat ditentukan. REY pada abu batubara kemungkinan akan tersebar di seluruh bagian komponen penyusunnya, baik terikat pada komponen organik maupun inorganik. REY menempel pada permukaan komponen penyusun abu batubara melalui mekanisme physical adsiorption pada saat proses ashing batubara berlangsung.

Asem-Asem Basin and Tarakan Sub-Basin are coal-producing basins in Indonesia that are interesting to study further because they have the potential for REY enrichment in coal. In general, coal produced from this basin is used for PLTU, where the coal will experience REY enrichment in the coal ash produced from the combustion process. Coal and coal ash from coal combustion was identified as one of the REY alternatives which abundances can match and even exceed those of conventional deposits. Along with the increasing demand and the need for REY in the world which is predicted to increase every year, research on the mode of occurrence of REY in coal and coal ash is increasingly being intensified. This research was conducted to provide an overview of REY concentration information in coal and coal ash, as well as the mode of REY availability in coal ash. The coal samples came from several active mining sites of PT. Anjas Anita Jaya, PT. Duta Tambang Rekayasa, and PT. Pipit Mutiara Jaya in the Tarakan Sub-Basin, and PT. Arutmin in the Asem-Asem Basin. Coal ash samples were produced from the ashing process using a furnace at a temperature of 1000C for 1 hour. Sampling was done by the bulk sampling method. The sample was then prepared for further thin-slice petrography analysis, polished-slice petrography, proximate analysis, geochemical analysis of Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Inductively Coupled Plasma-Atomic Emission Spectrometry (ICP-AES), X-Ray Powder Diffraction (XRD), and Scanning Electron Microscopy-Energy Dispersive Spectroscopy (SEM-EDS). The results showed that the REY concentration in coal ranged from 2,22-68,78 ppm, while in coal ash it ranged from 45,41-2108,98 ppm, where only the K3 sample had the REY concentration higher than the average REY concentration in the world and USA. The REY concentration contained in the coal ash was enriched 10-30 times when compared to the REY concentration in the original coal. The mode of occurrence of REY in coal ashes cannot be determined. REY in coal ash is likely to be spread throughout its constituent components, both bound to organic and inorganic components. REY attaches to the surface of the coal ash constituent components through the physical adsorption mechanism during the coal ashing process.

Kata Kunci : abu batubara, batubara Cekungan Asem-Asem, batubara Sub-Cekungan Tarakan, rare earth element dan yttrium (REY)