Lightweight concrete has been an interest due to its advantages compared to normal concrete. Lightweight concrete can be produced by the use of lightweight aggregates. In this study lightweight concretes were made with the composition of expandable perlite combined natural sand with each volume is 50% and concrete with 100% expandable perlite as the aggregates. The volume of the aggregates was varied from 80% up to 89%. The concretes were measured for their density and tested for the mechanical and absorption properties. As the results, expandable perlite obviously has the effect in reducing the concrete density. Nevertheless, the strength decrease as the expanded perlite aggregate increase. The optimum lightweight concrete that acceptable as the international standard is with the aggregates of expandable perlite combined natural sand having the 50% of each volume with the aggregates composition is 80%.

ABSTRAKLogam Tanah Jarang (LTJ) merupakan sumber material penting dari abad ke-21, banyak digunakan sebagai penunjang kehidupan modern seperti mobil listrik, perangkat identifikasi kesehatan (MRI, X-ray, Scanner, contrast agent, dll), LCD, hard drive komputer, pembangkit listrik tenaga angin, teknologi hijau, perangkat night vision, sistem radar dan peralatan militer. Unsur LTJ antara lain terdapat pada abu hasil pembakaran batubara dari Pembangkit Listrik Tenaga Uap (PLTU). Potensi produksi abu batubara dari PLTU di Indonesia mencapai 10 juta ton per tahun dan merupakan potensi sumber unsur LTJ yang bernilai tinggi. Penelitian ini bertujuan untuk mengidentifikasi keterdapatan unsur LTJ dalam abu batubara dari PLTU Ombilin dan proses peningkatan kadarnya. Identifikasi dilakukan dengan analisis percontoh abu batubara menggunakan XRD, XRF, ICP dan SEM. Hasil analisis menunjukkan abu batubara PLTU Ombilin mengandung Cerium, Neodimium, Lantanum, Ittrium dan Samarium meskipun kadar unsur tersebut relatif rendah, yaitu kurang dari 100 ppm. Upaya peningkatan kadar melalui benefisiasi abu terbang telah dapat meningkatan kandungan unsur Sm dari 2 ppm menjadi 9,3267 ppm pada middling, dan pada ampas meningkat dari 2 ppm menjadi 3,9429 ppm. Kandungan unsur LTJ pada abu terbang lebih tinggi dibandingkan pada abu dasar, maka upaya ekstraksi akan lebih ekonomis dilakukan terhadap abu terbang dan seyogyanya disetarakan sebagai bahan baku atau sumber senyawa LTJ. Pemanfaatan abu terbang sebaiknya didahului oleh ekstraksi unsur-unsur LTJnya, selanjutnya digunakan sebagai bahan bangunan maupun peruntukkan lain seperti yang telah berlangsung saat ini.

Artisanal and small-scale gold mining (ASGM) in Indonesia still uses mercury in amalgamation process to extract gold form the ores. The process easily produces gold but at the same time produces very dangerous mercury waste. In this study, a comprehensive series of tests were carried out on amalgamation tailings from the ASGM in Sekotong area, West Nusa Tenggara. The tailings contain mercury up to 150 ppm, above the safe threshold, and gold up to 20 ppm which is intended to be recovered. Furthermore, mineral liberation analysis (MLA) and gravity recoverable gold (GRG) test were performed to determine the feasibility of recovering gold from the tailings. The liberation degree of the gold started from particle size of 37 \xm causes challenging to recover it. However, the GRG test confirmed that the gold was still feasible to be recovered by gravity concentration.

The availability of energy becomes a major problem in the construction of iron mineral-based smelter to produce ferrous metals in the form of pig iron. Therefore, it is necessary to develop the Krupp-Renn technology that based on coal as a reducing agent to produce pig iron in the form of nuggets. Such a technology employs a rotary kiln that consumes less energy than other furnaces. In this study, reduction process of iron sand concentrates with coal as the reductant was accomplished in a minisized rotary kiln (0.6 m diameter and 6 m length). The process of iron nugget making from iron sand concentrate was conducted in two (2) stages, namely oxidation and reduction processes. The former was accomplished at a temperature above 800°C for 2 (two) hours to produce hematite phase. While the later was carried out at 1250-1300°C for 6-8 hours. Both processes produced iron nuggets that contained more than 90% Fe. The highest Fe content reached 96.49% Fe. Such a nugget could meet the requirement for steel making.Keywords: iron nugget, rotary kiln, Krupp-Renn technology, concentrated iron sand, oxidation and reduction processes. ABSTRAK Ketersediaan energi menjadi masalah utama dalam pendirian smelter berbasis mineral besi untuk menghasilkan produk logam besi dalam bentuk besi wantah, maka teknologi

As a volcanic country, Indonesia is rich in natural mineral resources. One of them is perlite that is spread across several provinces in Indonesia. One of the companies with a mining business permit (IUP) for perlite is CV Abdi Bersaudara, located at Padang Pariaman Regency, West Sumatra Province. Perlite rock can be processed through comminution and heating method. Crushed perlite can be used as sandblasting, slag coagulant, source of silica, foundry and steel industry, special casting sand and metal finishing. Meanwhile, the expanded perlite is a product of heated perlite with a temperature of 700⁰C-900⁰C. This research aimed to investigate the characters of perlite and expanded perlite from West Sumatra. Qualitative and quantitative analysis was conducted by laboratory experiments and testing, such as atomic absorption spectrophotometry (AAS), X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), scanning electron microscope (SEM) and optical microscope (OM). Based on the results of this study, West Sumatera perlite can be used as adsorbents, filter media, filler materials and planting media applications.