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Zirconia had been made through smelting the zircon sand along with NaOH as a flux. The zircon sand as the smelter feed was taken from CV. Kurnia Alam Sejati mine at Palangkaraya, Middle Kalimantan. Major content of the zircon sand was 28.04% ZrO2 and SiO2 51.22% with several minor oxides such as 0.54% HfO2, 2.53% Fe2O3, 10.53% TiO2, 3.27% Al2O3 and less than 1% of alkali, alkaline earth and rare earth elements. In order to economizing the process, zircon sand upgrading was conducted prior to zirconia production. The upgrading process was conducted using several comprehensive equipments, consist of shaking table, magnetic separator and high tension separator (HTS).The upgraded sand contained 65.35% of ZrO2+HfO2 with 73.25% recovery, which was then used for smelting process at 650°C for 2 hours using NaOH as a flux. The product was then leached with water and sulphuric acid then crystallized to get precipitated zirconium hydroxide. The precipitated product was calcined at 900°C for 1 hour to get the zirconia and analyzed for its content. The zirconia content was 97.27% of ZrO2+HfO2 with 65.13% recovery.

A study on lead extraction from lead concentrate had been conducted. Galena is usually associated with other sulfide ores such as sphalerite.The lead concentrate was able to be extracted and purified into its metal through a leaching process using a selective solvent of fluosilicic acid (H2SiF6). Parameters used in this process include ratio (dose) of reactant (H2SiF6:H2O2), temperature (without heating; 30; 50; 70; 80; and 90°C) and particle size (-100+150#, -150+200#, -200+325, dan -325#).The best extraction was achieved using the particle size of -325 mesh. The amount of extracted lead was increased due to the rise of temperature and dose of fluosilicic. The amount of peroxide addition was determined by its optimum influence on the lead extraction because its excess would produce PbSO4. The influence of H2SiF6 and H2O2 doses was calculated using ANOVA. ABSTRAKPemrosesan konsentrat Pb telah dilakukan untuk memperoleh logamnya. Galena pada umumnya berasosiasi dengan mineral sulfida lainnya seperti sphalerit. Konsentrat tersebut dapat diekstraksi dan dimurnikan untuk memperoleh logam melalui proses pelindian menggunakan pelarut selektif seperti asam fluosilikat (H2SiF6). Parameter dalam proses pelarutan adalah jumlah pereaktan (H2SiF6:H2O2), temperatur (tanpa pemanasan, 30; 50; 70; 80 dan 90°C dan ukuran partikel -100+150#, -150+200#, -200+325, dan -325#). Persen ekstraksi terbaik diperoleh menggunakan ukuran partikel -325#. Jumlah Pb yang terekstrak meningkat seiring dengan kenaikan temperatur dan jumlah fuosililat. Jumlah peroksida harus ditentukan jumlah optimumnya karena jika berlebihan tidak akan meningkatkan persen ekstraksi secara signifikan karena pembentukan PbSO4. Pengaruh dosis H2SiF6 and H2O2 dihitung dengan ANOVA. kunci: galena, pelindian, asam fluosilikat, peroksida, presipitasi. Kata

Chemical manganese dioxide has not yet commercially developed in Indonesia. It is supplied by import sector. The fact that Indonesia has manganese resources as many as 60,893,820 tons is inconsistent with above condition. Research on CMD making employed pyrolusite as the raw material with size of-100+150 mesh. The material was then reacted with sulfuric acid 6% and various concentration of molasses as reductant from 10, 20, 30, 50 and 100 %. The manganese sulfate leachate was then purified using sodium hydroxide and then filtered to have a nonferrous manganese sulfate. The Mn was precipitated from manganese sulfate using sodium bicarbonate. The precipitated manganese carbonate was then calcined at 600°C by injecting the air at various flow rates (100, 200, 300, 400 cc/minute) and different calcination time (2, 3, 4 hours) to get manganese dioxide. The best extracted Mn reached 97.58% using 50% of molasses as a reductant. The precipitation of manganese carbonate had produced sodium carbonate as an impurity. The calcination had not yet changed the manganese carbonate into manganese dioxide due to extremely high calcination temperature.

ABSTRAKSodium aluminat (NaAlO2) merupakan bahan kimia anorganik penting yang digunakan sebagai bahan baku untuk pembuatan berbagai macam produk kimia antara lain polialuminum chloride (PAC), alum, dan zeolit sintetik. Dalam penelitian ini, NaAlO2 dihasilkan melalui proses Bayer yaitu pelarutan (digestion) bauksit asal Tayan, Kalimantan Barat, dengan soda kaustik (NaOH) pada skala pilot berkapasitas 100 kg umpan/batch dengan menggunakan uap secara kontak langsung pada suhu sekitar 140 o C dan tekanan 4 atm. Variabel yang diteliti meliputi : lama reaksi (1; 1,5; 2 jam), ukuran butir -0,177 mm (-80 mesh); -0,149 mm (-100 mesh); -0,0965 mm (-150 mesh), dan NaOH berlebih di atas kebutuhan stoikhiometrinya (1,37% sampai dengan 35,25%). Hasil penelitian menunjukkan bahwa waktu reaksi semakin lama, ukuran butir semakin halus, dan NaOH berlebih semakin tinggi sampai batas tertentu, memberikan perolehan alumina (Al2O3) yang semakin tinggi. Kondisi proses terbaik yang diperoleh adalah NaOH berlebih 28,83% , lama reaksi 2 jam dan ukuran butir -150 mesh (-0,105 mm) dengan perolehan alumina tertinggi 93,98%.Kata kunci : digestion, bauksit, proses Bayer, NaOH berlebih, sodium aluminat. ABSTRACT Sodium aluminate (NaAlO2) is an important commercial anorganic chemical material that can be used as raw material for various chemical products such as polialuminum chloride (PAC), alum, and synthetic zeolite. In this research, NaAlO2 was sinthesized through digestion process using bauxite from