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Komposit merupakan bahan yang terus dikembangkan karena keunggulannya sebagai bahan rekayasa. Dengan lingkungan geografis yang beragam, Indonesia memiliki sumber daya yang dapat digunakan sebagai bahan komposit, tidak terkecuali Provinsi Lampung yang memiliki sumber daya serat basalt dan rotan. Kajian ini diperlukan untuk mengetahui pengaruh penggunaan serbuk basalt sebagai filler dan serat rotan sebagai penguat komposit matriks resin poliester. Basalt direduksi menjadi variasi ukuran 100, 200, dan 325 mesh dengan fraksi massa 2%, 7%, dan 12%. Rotan dibuat menjadi serat dan dicuci dengan NaOH 5%, kemudian dikeringkan. Serat rotan disusun secara acak dengan fraksi massa rotan tetap 10% dengan ukuran serat diameter 2 mm dan panjang 5 cm. Matriks resin poliester SHCP 2668 dengan katalis 2%. Komposit dibuat dengan metode hand lay up dengan menekan 3 ton selama 15 menit dan mengeringkan komposit. Pengujian mekanik meliputi uji kuat tarik berdasarkan standar ASTM D638 dan uji tekuk tiga titik berdasarkan ASTM D790, pengamatan uji makro untuk mengetahui bentuk patahan setelah dilakukan pengujian mekanis. Analisis ANOVA menunjukkan pengaruh signifikan fraksi massa dan ukuran serbuk basalt terhadap kekuatan tarik dengan nilai P < 5%. Ukuran partikel basalt memberikan kontribusi dominan sebesar 84%, sedangkan fraksi massa sebesar 15,6% terhadap kekuatan tarik. Ukuran butir basalt memberikan kontribusi 62,13% terhadap kekuatan lentur dengan pengaruh signifikan nilai P < 10%. Dalam kekuatan lentur, serat rotan memiliki pengaruh yang lebih besar daripada tegangan tarik. Ukuran butir kecil dari basalt memberikan kepadatan ikatan yang lebih padat antara partikel daripada partikel yang lebih besar. Resin dapat mengisi rongga-rongga kecil yang dibentuk oleh partikel-partikel kecil untuk membuat papan komposit lebih tebal dan kokoh.

The various aspects of coal, including its chemical composition, properties, and environmental impacts. The recent research focused on developing new technologies and processes to improve the efficiency and effectiveness of coal comminution, with a particular focus on the use of kinetic energy impact application of coal comminution with linear momentum. We explored the potential benefits of this approach, as well as ongoing research aimed at optimizing the comminution process and improving our understanding of the physics of coal comminution. Ultimately, the goal of this research is to reduce energy consumption and environmental impact associated with coal mining and use. From calculation on comminution of coal samples 10 mm long, 1 mm thick and 1 mm wide using linear momentum kinetic impact energy were carried out to produce coal between 100 mm and 1 mm in size. The main parameters of the process are the configuration of the impact surface of the runway wall, volume, mass and initial size of the sample, as well as the impact distance to the runway. The results of the analysis produce 55 process equations with models per millimetre scale; starting from the equation. The value of the kinetic energy of the fragmentation impact is increasing small if the distribution of energy has an increasing impact Far from static center impact; following with bigger size fragment. With doubling the value of the distribution of impact kinetic energy per millimetre; uniformity size fragment between 100mm to 1mm reached. This first mathematical model is expressed as a comminution dynamic fragmentation linear pattern per millimetre.

Gold adsorption from dissolution of gold ore concentrate at Tanggamus mine using activated carbon from thiocyanate leached solution was investigated in this research. As the pollution of the environment has been raising accordingly with the increasing of cyanidation, thiocyanate is becoming current alternative and less toxic reagent in terms of gold dissolution. However, the research was still limited. The development and implementation of thiocyanate in gold extraction is the core of this research. Solvent and oxidizer concentrations (KSCN and FeCl3) were used in this study with 0.3 M and 0.1 M of concentration, respectively. Adsorption process was carried out for 4 hours using 100 ml of filtrate with activated carbon addition. Adsorption of thiocyanate complex gold compounds was studied by varying the size of activated carbon, the concentration of activated carbon, and the rotary speed of bottle roll. At-10+20# of activated carbon size, the %-adsorption obtained was 93.65%. Meanwhile, 94.31% of gold adsorption was achieved with the concentration of activated carbon at 1500 mg/l and 93.37% of gold adsorption was reached with the rotary speed of 150 rpm. Pseudo second order was applied to calculate the kinetics of gold adsorption with the R2 value obtained was 0.9999.

A study on mineral characterization and nano titanium dioxide synthesis from ilmenite ore of Bangka Island, Indonesia, has been carried out using a caustic fusion method and hydrochloric acid leaching. Comprehensive mineral characterization was conducted using X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) to depict each fractionated particle's elemental composition and mineralogy, i.e., +80, ?80+100, ?100+150, ?150+200, -200+325, and -325 mesh. Other analyses performed are VSM to measure the magnetic properties and SEM to determine the distribution of elements at each particle size. Based on the characteristics of the ilmenite ore, magnetic separation was applied for the initial stage and analyzed gravimetrically. Later processing was the synthesis of nano titanium dioxide, conducted sequentially, including roasting and leaching. Roasting was run at 900°C with and without caustic soda, and then hydrochloric acid was applied. In reference to the elemental analysis, titanium (Ti) concentration is higher in smaller particle sizes and vice versa for iron (Fe) concentration, so the synthesis of nano titanium dioxide was carried out using a -100+150 mesh particle size. The optimum condition for nano titanium dioxide synthesis was 2:1 of NaOH and ilmenite weight ratio, 20% HCl concentration, and 4 hours of leaching time. The nano titanium dioxide (TiO2) obtained was then characterized using XRF, XRD, particle size analyzer (PSA), and transmission electron microscopy (TEM). Roasting with caustic soda showed better nano titanium dioxide purity with 96.04% of TiO2 with particle size in the range of 50–80 nanometers.

Basalt rock has great potential in Lampung Province but is only used as a building construction material. Basalt has superior characteristics such as abrasion/wear resistance, compressive strength and chemical reaction resistance making it suitable as a filler or reinforcement for composites. This study aims to determine the effect of basalt rock powder sintering as a reinforcing filler on the mechanical and physical properties of polymer matrix composites. The parameters used included variations in sintering temperature: 8500C, 9500C, and 1.0500C, variations in particle size: 100 < X < 150 mesh, 150 < Y < 200 mesh and 200 < Z < 270 mesh, and the volume fraction comparison of basalt sintering powder and polyester resin. 70: 30%, 80: 20%, and 90: 10%. The experimental design uses the L9 3^3 taguchi orthogonal array run 9 specimens. Taguchi analysis shows that the parameters that affect the mechanical and physical properties are the sintering temperature. sintering temperature contributed 61.77% to wear, and 87.58% to compressive strength, and 95.32% to composite density. The experimental results with the best value obtained a wear value of 0.235 x 10-7mm2 / kg, a compressive strength of 118.873 MPa, and a density of 2.272 gr/cm3.

AISI 1020 steel is widely applied as the primary material for construction and piping systems on ships. This research was conducted to investigate the effect of electroplating Cu-Mn current density on the corrosion rate of AISI 1020 steel in a 3% NaCl corrosive medium. Corrosion rate testing was carried out using the weight loss method with the immersion of samples in a corrosive NaCl medium for 168 h and variations in current densities of 35, 45, 55, 65, and 75 mA/cm2. The results showed that the higher current density applied to the lower corrosion rate. This is because an increase in electroplating current density will also increase Cu and Mn ions deposited in steel, where deposits of these ions will improve the corrosion resistance of steel. The lowest corrosion rate was obtained at 0,053 mm/y at a current density of 75 mA/cm2. XRD characterization results showed that peaks formed at current densities of 35 mA/cm2 are almost the same as the results of steel characterization after electroplating current density of 75 mA/cm2 a lower intensity. The metallurgical microscope analysis results showed that the formed layer is thicker with increasing electroplating current density.

This study was aimed to increase granite's silica content using the leaching process with HCl concentration variation. The granite used in this study came from Lematang, South Lampung. This study aims to determine the effect of variations in HCl concentration, particle size, and rotational speed on the crystalline phase and chemical elements formed in the silica product produced from granite. The HCl concentration variations were 6.0 M, 7.2 M, 8.4 M, and 9.6 M, the variation in particle size used was 270 and 400 mesh. Variations in rotational speed during leaching were 500 and 750 rpm. Granite powder was calcined at 1000 ºC for 2 hours. Characterization was performed using X-Ray Fluorescence (XRF), X-Ray Diffraction (XRD), and Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP- OES). The results showed that the silica content increased with increasing HCl concentration, the finer the particle size, and the higher the rotational speed. XRF analysis showed that the silica with the highest purity was leached with 9.6 HCl with a particle size of 400 mesh and a rotational speed of of 750 rpm, which was 73.49%. Based on the results above, by leaching using HCl, the Si content can increase from before. The XRD diffractogram showed that the granite powder formed the Quartz phase.

The purpose of this study is to characterize Lampung iron sand and to conduct preliminary experiments on the TiO2 synthesis which can be used for the manufacturing of functional food packaging. The iron sand from South Lampung Regency, Lampung Province that will be utilized as raw material. The experiment was initiated by sieving the iron sand on 80, 100, 150, 200 and 325 mesh sieves. Analysis using X-Ray Fluorescence (XRF) to determine the element content and X-Ray Diffraction (XRD) to observe the mineralization of the iron sand was conducted. The experiment was carried out through the stages of leaching, precipitation, and calcination. Roasting was applied firstly by putting the iron sand into the muffle furnace for 5 hours at a temperature of 700°C. Followed by leaching using HCl for 48 hours and heated at 105°C with a stirring speed of 300 rpm. The leaching solution was filtered with filtrate and solid residue as products. The solid residue was then leached using 10% H2O2 solution. The leached filtrate was heated at 105°C for 40 minutes resulting TiO2 precipitates (powder). Further, the powder was calcined and characterized. Characterization of raw material using XRF shows the major elements of Fe, Ti, Mg, Si, Al and Ca. The highest Ti content is found in mesh 200 with 9.6%, while iron content is about 80.7%. While from the XRD analysis, it shows five mineral types namely magnetite (Fe3O4), Rhodonite (Mn, Fe, Mg, Ca) SiO3, Quart (SiO2), Ilmenite (FeOTiO2) and Rutile (TiO2). The preliminary experiment showed that the Ti content in the synthesized TiO2 powder is 21.2%. The purity of TiO2 is low due to the presence of Fe metal which is dissolved during leaching, so that prior to precipitation purification is needed to remove impurities such as iron and other metals.

Salah satu sumber daya mineral yang berperan penting dalam kehidupan masyarakat di dunia adalah timah. Sumber daya timah dapat diolah menjadi timah sulfat yang memiliki nilai jual dan manfaat yang lebih tinggi. Timah(II) sulfat digunakan dalam aplikasi industri dan manufaktur sebagai agen elektroplating dan produk perawatan permukaan logam. Permintaan timah sulfat di pasar global mengalami peningkatan yang signifikan. Beberapa metode produksi timah sulfat telah dikembangkan untuk meningkatkan kualitas sumber daya timah. Tujuan utama dari penelitian ini adalah untuk mengolah sumber daya timah dengan metode yang efektif dan ramah lingkungan yang terkait sintesis timah(II) sulfat dengan metode elektrolisis. Hasil penelitian menyimpulkan bahwa konsentrasi larutan elektrolit dan tegangan operasi sangat mempengaruhi sintesis timah(II) sulfat. Namun, variabel ini dibatasi oleh luas permukaan yang terbatas. Kondisi terbaik penelitian terjadi pada tegangan operasi 0,6V dan larutan elektrolit dengan konsentrasi 0,05 M.

Nickel pig iron is a raw material in stainless steel manufacturer. Nickel laterite ore is processed becomes nickel pig iron as a primary product and slag as solid waste. However, this slag contains cobalt that is more valuable than a nickel. In this work, the solvent extraction method was used to separate cobalt from its impurities in slag. Cobalt ion in this process is in the aqueous phase from the solvent extraction product. Electrowinning is one method which able to recover cobalt from this aqueous phase. In this work, the tubular electrode is used to improve the performance of electrowinning. This experiment used four parameters to increase the cobalt recovery in the electrowinning, namely applied voltage, electrolysis time, temperature, and boric acid concentration. The Taguchi design experiment was used to analyze and optimize these parameters. From the Taguchi analysis results, the optimum condition of electrowinning using tubular electrode was at 5 volts, 2 hours, 50° C, and 0.5 M boric acid.

Fly ash is the residue from burning coal in industrial furnaces which is hazardous and toxic waste. Fly ash accumulates will be a problem for living things and the environment. One of the efforts to utilize fly ash as a geopolymer product. Geopolymer products need an activator, that is reactive when it reacts with water. In this study, a solid activator made from fly ash containing silica and sodium hydroxide. Making this solid activator by calcination. Fly ash is added with sodium hydroxide which is then calcined at 400 °C, 500 °C, and 650 °C for 2 hours. Then the solid activator is crushed and sieved. The analysis carried out is XRF to determine the chemical composition of fly ash and XRD to determine the crystallinity and mineral content of the fly ash and solid activator in several temperature variations. The results showed that fly ash from Muara Enim, South Sumatra was class F fly ash which mostly contains CaO (8.562%), SiO2 (45.324%), Al2O3 (23.967%), and Fe2O3 (12.998%). Solid activator is good for solid activator of geopolymer products, namely at a calcination temperature of 500 °C because of the higher conversion of active minerals (sodium silicate) in solid activator that is 39.5%.

Indonesia has abundant mineral resources that have the most significant potential. Seeing this phenomenon, many people try to utilize mineral resources both in nature and use the industrial wastes. One of them is slag from the manufacture of nickel pig iron. Slag is categorized as hazardous and toxic waste. However, slag of nickel pig iron still contains multicomponent minerals (Fe, Mn, Co, Pb, Cu), which is high value, one of them is cobalt. To separate cobalt from other components and obtain cobalt with high purity, it can be done by the solvent extraction method from the sulfuric acid leaching solution. In this study, the Taguchi experiment design was analyzed using larger the better of signal to noise ratio. The cobalt extraction process’s optimum condition using 15% v/v of cyanex 272 and versatic from slag of nickel pig iron is at 6 of pH, 10 minutes of extraction time, 2/3 of ratio O/A, and 10% v/v of versatic acid.

The selective reduction of nickel and adequate growth of ferronickel grains is imperative for efficient preparation of ferronickel from nickeliferous laterite ore via the process of direct reduction followed by magnetic separation. The reduction behaviours of a saprolite laterite ore in the presence of sodium sulphate were investigated, with an emphasis on thermodynamic analysis, selective reduction ratios and kinetics. To separate the interactions between Ni and Fe, chemical titration analysis was adopted to determine the contents of various Ni and Fe species in the roasted pellets and a modified equation to assay metallic iron content. This process uses the addition of sodium sulphate as the additive and graphite as the reductant. The additive and reductant are the optimal n the separation process to limit the form of iron oxide. The Na2SO4 dosage plays an important role in the process that causes its behaviour to reduce the growth of iron oxide. In this experiment, the study effect of Na2SO4 dosage with graphite as a reductant on the nickel grade, recovery and grain size of iron-nickel has been investigated in the variation of Na2SO4 dosage of 5, 10, and 15 % with reduction temperature 1150 °C for 60 minutes and the reductant stoichiometry is 0.125 from equilibrium condition is equal 0.63 gram. The mineralogical composition of the raw and reduced samples was analysed by XRD, AAS, and XRF. The grain size was measured with an optical microscope. The optimum Na2SO4 dosage is 15 %, which produces a concentrate with nickel grade, and the recoveries are 5.65 wt.% and 30.33 % when the grain size is greater than the high level of dosage because the liquid phase provides access for the transfer of metal ions and then prompts the growth of ferronickel grains.

Interest on the extraction of valuable metals from secondary resources has been increasing recently due to the environmental consideration. It includes the spent catalyst from hydrodesulfurization process from the natural gas purification unit in fertilizer industry to reduce sulfur content. With composition of molybdenum as one of the active elements, the spent hydrodesulfurization (HDS) catalyst is indeed interesting to study, in order to be able to recover the molybdenum which is increasing within decades in need and unit price. In this study, recovery as well as extraction kinetics of molybdenum will be observed to calculate design parameters for scaling up process. The raw material used in this work is spent catalyst from PT. Pupuk Kujang Cikampek, Karawang, Indonesia. Leaching process was conducted with particle size -200 mesh, solid ratio of 1:5 and leaching time up to 120 minutes in the atmosphere condition by variated temperature (60, 80, 90°C) and pH (1.5, 2, 2.5) of citric acid. The solid samples before leached were analyzed using Energy Dispersive X-Ray (EDX), while the leaching filtrate samples were analyzed using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES). The result of the experiment showed the maximum recovery of molybdenum at temperature of 90°C, during 120 minutes, and acid pH 1.5, 2, 2.5 were 71.20%, 34.66%, and 19.29% respectively. The independent variables used in this study showed a significant effect of molybdenum recovery, especially the acids pH. The kinetic model was evaluated by following the Shrinking Core model which considers diffusion is suitable to predict the leaching mechanism of molybdenum using citric acid.

This research was conducted to determine the effect of solid/liquid ratio (s/v), temperature, and stirring Speed on per cent extraction of iron using oxalic acid from Averrhoa bilimbi. The variation of the solid/liquid (s/v) is 10%, 15% and 20 (%), the temperature variations used are 30, 60 and 90 oC, while the variation of the stirring Speed uses 200, 400 and 600 rpm. Some basalt rock samples are put into the reactor and leached using an oxalic acid solution from Averrhoa bilimbi. Within a certain period of time, the filtrate was taken and analyzed for Fe content using Atomic Absorption Spectroscopy. The residue was analyzed using XRF and XRD. The results showed that the highest percentage of iron extraction for basalt rock leaching experiments using oxalic acid from Averrhoa bilimbi was achieved at a temperature of 90oC, 10% of solid/liquid ratio, 400 rpm stirring speed and 120 minutes of leaching time with a percent iron extraction of 65.90%. XRD analysis results showed that the compounds formed in the residual leaching were Anorthite, Ferrosilite, Cristobalite and quart low.

Kebutuhan ekstraksi nikel dari bijih nikel laterit khususnya jenis bijih limonit dengan kadar nikel yang rendah sangat diperlukan karena kebutuhan nikel yang terus meningkat dengan adanya pengembangan kendaraan bermotor listrik berbasis baterai. Jenis dan karakteristik bijih laterit yang berbeda akan memberikan pengaruh pada hasil ekstraksi nikel. Pada penelitian ini dilakukan ekstraksi nikel dari bijih laterit jenis limonit yang berasal dari Pulau Halmahera (LH)) dan Pulau Sulawesi (LS) menggunakan pelindian atmosferik. Asam sulfat digunakan sebagai agen pelindian. Penelitian dilakukan untuk mengetahui pengaruh karakteristik bijih limonit (LH dan LS) pada berbagai variabel pelindian yaitu suhu (30 o C, 50 o C dan 80 o C), konsentrasi asam sulfat (0,5M; 1M; dan 2M), waktu pelindian (15, 30, 60, 120, dan 240 menit), serta rasio bijih terhadap reagen pelindian (5, 10, dan 20% w/v) terhadap ekstraksi nikel dari bijih limonit. Hasil penelitian menunjukkan bahwa karakteristik bijih laterit sangat berpengaruh pada hasil pelindian dan persen rekoveri nikel. Nikel dari bijih LH yaitu jenis limonit dari Pulau Halmahera dapat diekstrak secara maksimal (100%) pada konsentrasi asam sulfat 0,5M, suhu 80 o C, rasio bijih/larutan asam sulfat 10%, dan waktu pelindian 2 jam. Sedangkan persen ekstraksi nikel dari bijih LS yang terbesar adalah 95% yang diperoleh pada konsentrasi asam sulfat 2M, suhu 80 o C, rasio bijih/larutan asam sulfat 5%, dan waktu pelindian 4 jam. Abstract Nickel extraction from nickel laterite ores particularly low-grade limonite ore is needed along with the increase of nickel consumption on the development of battery electric vehicle. Types and characteristics of nickel laterite ores affect greatly on the nickel extraction from these ores. This research conducted the extraction of nickel from limonite ore from different areas i.e. Halmahera Island (LH) and Sulawesi Island (LS) using atmosferic leaching. Sulfuric acid (1M) was used as leaching reagent. Leaching processes were carried out for investigating the effects of limonite ore characteristics (LH and LS), leaching temperatures (30 o C, 50 o C dan 80 o C), concentration of sulfuric acid (0.5M; 1M; 2M), leaching time (15, 30, 60, 120, and 240 minutes), and ratio of ore amount to volume of leaching reagent on the nickel extraction from limonite ores. Experimental results showed that ore characteristic affected greatly on the leaching result and nickel leaching recovery. Nickel from LH ore could be extracted maximum (100%) using sulfuric acid 0.5M, temperature of 80 o C, and leaching time 120 minutes (2 hours). Whereas, the highest nickel extraction percentage from LS ore is 95% using sulfuric acid 2M, temperature of 80 o C, and leaching time 240 minutes (4 hours).

Local pyrolusite ore from Waykanan regency (Lampung Province, Indonesia) has been treated by sulfuric acid leaching process using various reducing agents to produce manganese sulfate. The ore was detected as pyrolusite ore by XRD and contained Mn (36.8%), Fe (6.6%), and Si (4.1%). Various reducing agents such as molasses, glucosse, fructose, cane sugar, sodium sulfit, tannic acid, oxalic acid, citric acid, black tea, green tea, cellulose, sawdust of candlenut shell, sawdust of Acacia wood, sawdust of coconut shell, sawdust of Albizia chinensis wood, and H2O2 were used. From the experimental results, it can be found that tannic acid and oxalic acid were the most effective reducing agents for manganese leaching in sulfuric acid medium. The manganese recoveries were 100% when tannic acid and oxalic acid used as reducing agent, using 1 M of sulfuric acid and 5% of pulp density at 30°C of leaching temperature, 150 rpm of shaker speed, atmospheric pressure, and 8 hours of leaching period.

Low-grade laterite which has nickel content 0.5% has been processed using solvent extraction and followed by electrowinning process. Cyanex which diluted in toluene was used as an organic solvent to separated cobalt from nickel solvent. In this work, nickel solvent which frees from cobalt was processed using electrowinning. Electrowinning was conducted using batch recycle methods to ensure the electrowinning performed well. Meanwhile, cylindrical cathode electrode was used to increase the performance of electrowinning, easy to operate and easy to harvest. The parameters which have a significant effect in batch recycle methods such as flow rate, voltage and process duration. Taguchi analysis showed the optimum condition and the parameter which has the highest effect towards the mass of nickel electrodeposits.

Gold amalgamation process was widely used to treat gold ore. This process produces the tailing or amalgamation solid waste, which still contains gold at 8-9 ppm. Froth flotation is one of the promising methods to beneficiate gold from this tailing. However, this process requires optimal conditions which depends on the type of raw material. In this study, Taguchi method was used to optimize the optimum conditions of the froth flotation process. The Taguchi optimization shows that the gold recovery was strongly influenced by the particle size which is the best particle size at 150 mesh followed by the Potassium amyl xanthate concentration, pH and pine oil concentration at 1133.98, 4535.92 and 68.04 gr/ton amalgamation tailing, respectively.Gold amalgamation process was widely used to treat gold ore. This process produces the tailing or amalgamation solid waste, which still contains gold at 8-9 ppm. Froth flotation is one of the promising methods to beneficiate gold from this tailing. However, this process requires optimal conditions which depends on the type of raw material. In this study, Taguchi method was used to optimize the optimum conditions of the froth flotation process. The Taguchi optimization shows that the gold recovery was strongly influenced by the particle size which is the best particle size at 150 mesh followed by the Potassium amyl xanthate concentration, pH and pine oil concentration at 1133.98, 4535.92 and 68.04 gr/ton amalgamation tailing, respectively.

Manganese ores from Waykanan region (WK ore) contain pyrolusite (MnO2) as major minerals, whereas the main minerals in manganese ore from Tanggamus region (TG ore) are. The effects on manganese extraction of leaching reagents without reductant, leaching temperatur of non-reducing leaching, and reducing agents of sulfuric acid leaching were determined to investigate the leaching performances of the two manganese ores. Manganese leaching efficiency from WK ore is always higher than that from TG ore under the same leaching conditions. The mineral contents of the ores significantly affected the leaching performances and mineral dissolution behaviors of the samples.

In this experiment, the effect of the addition carbide forming elements on high chromium white cast iron, such as molybdenum, vanadium and boron on its mechanical properties and microstructure was investigated. The high chromium white cast iron was produced by casting process and formed in 50 mm size of grinding balls with several compositions. Characterization of these grinding balls was conducted by using some testing methods, such as: chemical and microstructure analysis, hardness, and impact test. From the results, the addition of molybdenum, vanadium, and boron on high chromium white cast iron provided a significant improvement on its hardness, but reduced its toughness. Molybdenum induced fully austenitic matrix and Mo2C formation among eutectic M7C3 carbide. Vanadium was dissolved in the matrix and carbide. While boron was played a role to form fine eutectic carbide. Grinding balls with 1.89 C-13.1 Cr-1.32 Mo-1.36 V-0.00051 B in as-cast condition had the highest hardness, which was caused by finer ...

Low-grade laterite which contains nickel lower than 0.5 % is difficult to beprocessed using pyrometallurgy. One method which isable to solve this problem is solvent extraction. In thisstudy, a solvent extraction process using batch recycle method s has been successfully applied to separate nickel and cobalt from low-grade laterite. Sulphuric acid was used to leach laterite at atmospheric pressure. Meanwhile, cyanex in toluene was used as an organic solvent. Taguchi experimental design has been used to analyze and optimize the solvent extraction process using batch recycle method s . Taguchi analysis results show that the optimum conditions are at 7 of pH, 3 hours of time operation, 0.9 liter/minute of flow rate and 0.75 of organic/aqueous solutions ratio.

Andesite stone is usually used for split stone material in the concrete making. However, its availability is decreasing. Lampung province has natural resources that can be used for coarse aggregate materials to substitute andesite stone. These natural materials include limestone, feldspar stone, basalt, granite, and slags from iron processing waste. Therefore, a research on optimizing natural materials in Lampung to substitute andesite stone for concrete making is required. This research used laboratory experiment method. The research activities included making cubical object samples of 150 x 150 x 150 mm with material composition referring to a standard of K.200 and w/c 0.61. Concrete making by using varying types of aggregates (basalt, limestone, slag) and aggregate sizes (A = 5-15 mm, B = 15-25 mm, and 25-50 mm) was followed by compressive strength test. The results showed that the obtained optimal compressive strengths for basalt were 24.47 MPa for 50-150 mm aggregate sizes, 21.2 MPa for 15-25 mm aggregate sizes, and 20.7 MPa for 25-50 mm aggregate sizes. These results of basalt compressive strength values were higher than the same result for andesite (19.69 MPa for 50-150 mm aggregate sizes), slag (22.72 MPa for 50-150 mm aggregate sizes), and limestone (19.69 Mpa for 50-150 mm aggregate sizes). These results indicated that basalt, limestone, and slag aggregates were good enough to substitute andesite as materials for concrete making. Therefore, natural resources in Lampung can be optimized as construction materials in concrete making.