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Abstrak :
Inhibition is one of the mechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims to investigate the inhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on the corrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafel extrapolation and linear polarization techniques. The study reveals that BPTU acts as an excellent anodic inhibitor for low carbon steel in a HCl solution. The protective efficiency of the compound was found to be more than 97% even at higher temperatures. The study demonstrated that BPTU gets adsorbed on the steel surface, following Temkin?s adsorption isotherm and the inhibition is controlled by a chemisorption mechanism. The investigation shows that the results obtained from the Tafel extrapolation and linear polarization techniques for the corrosion of mild steel in HCl medium were in good agreement. The influence of temperatures and concentrations of BPTU on the corrosion of low carbon steel are also examined in the present work.

Abstrak :
Inhibition is one of the mechanisms used for mitigating the metallic corrosion, particularly in an acid environment. The present work aims to investigate the inhibiting effect of N-benzyl-N/-phenyl thiourea (BPTU) on the corrosion of low carbon steel in a 0.1 M hydrochloric acid (HCl) solution using a Tafel extrapolation and linear polarization techniques. The study reveals that BPTU acts as an excellent anodic inhibitor for low carbon steel in a HCl solution. The protective efficiency of the compound was found to be more than 97% even at higher temperatures. The study demonstrated that BPTU gets adsorbed on the steel surface, following Temkin’s adsorption isotherm and the inhibition is controlled by a chemisorption mechanism. The investigation shows that the results obtained from the Tafel extrapolation and linear polarization techniques for the corrosion of mild steel in HCl medium were in good agreement. The influence of temperatures and concentrations of BPTU on the corrosion of low carbon steel are also examined in the present work.

Abstrak :
ABSTRAK
Bijih nikel laterit banyak tersedia di Indonesia bagian timur, seperti Pulau Sulawesi dan kepulauan Maluku termasuk pulau-pulau kecil di sekitarnya. Faktanya, sejauh ini bijih nikel kadar rendah tipe limonit belum diproses karena kandungan nikelnya sangat rendah. Dalam tesis ini kami membahas hasil terbaru pada efek scale-up dari pengolahan bijih nikel kadar rendah melalui pendekatan hidrometalurgi. Proses ini dipilih karena kandungan magnesium yang rendah dalam bijih dan konsumsi energi yang minimal selama pemprosesan. Proses yang dipilih yaitu pelindian atmosferik. Variabel-variabel proses yang dipelajari adalah persen pelarut, temperatur proses, waktu pelindian, ukuran mesh dan efek scaleup. Karakterisasi residu dipelajari dengan menggunakan SEM, XRD dan XRF. Sementara hasil proses pelindian dalam bentuk larutan dianalisis menggunakan AAS untuk menentukan fraksi elemen terlarut. Hasil penelitian saat ini menunjukkan bahwa pelindian bijih nikel kadar rendah jalur hidrometalurgi menggunakan 37% asam klorida pekat telah mengekstraksi Ni dan Fe dari bijih dengan hasil 76,7% dan 75,8%. Hal ini dicapai pada kondisi proses berikut: temperatur optimum 90oC, 200 mesh dan kecepatan pengadukan 300 rpm. Selanjutnya, pada saat bahan baku tersebut ditingkatkan hingga 100 gram limonit, hasil tersebut menurun menjadi 55% dan 65 %. Selanjutnya, terjadi penurunan hingga sekitar 45% ketika bahan baku ditingkatkan dua kali lipat menjadi 200 gram limonit.

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Abstract
The laterite nickel ores are abundantly available in the eastern part of Indonesia island like Sulawesi and Maluku islands including many small islands around them. The fact that nickel ores called limonite have not been processed so far due to the nickel content is very low. In this thesis, we discussed our recent works on the effects of scaling up of processing for low grade nickel ores through a hydrometallurgical approach. This was selected due to the low magnesium content in the ores and minimum energy consumption during processing. The selected process is the atmospheric leaching. Processing variables which were studied including the optimum percentage of solvent, processing temperatures, leaching time, mesh sizing and the scale-up effects. Characterization of the residue was studied using SEM, XRD and XRF. While the materials which deposited in the leaching filtrate were analyzed using AAS to determine the fraction of dissolved elements. Results of current recearch work showed that leaching of low grade nickel ore using a hydrometallurgical route using 37% concentrated hydrochloric acids have resulted extracted materials of Ni and Fe with extraction yields 76.7% and 75.8% respectivelly. This was obtained at the following processing conditions: optimum temperature 90°C; 200 mesh and the stirring speed of 300 rpm. Further to this, when the feedstock was scaled up to 100 grams limonite, the yields were decreased to 55 % and 65 % for Ni and Fe respectively. A further decreased to about 45 % occurred when the feedstock was doubled to 200 grams limonite.

Abstrak :
Perkembangan teknologi serta penggunaannya yang pesat membuat meningkatnya jumlah limbah elektronik global, salah satunya adalah limbah printed circuit board PCB . Limbah PCB dipersiapkan dengan mengominusi hingga ukuran partikel 1-2 cm2. Limbah yang telah dikominusi dilindi dengan menggunakan campuran asam klorida 0,5 M dan hidrogen peroksida 0,4 M sebagai pelarut dan hasilnya diuji Atomic Absorption Spectrophotometer AAS. Hasil analisis pelindian menunjukan peningkatan kadar emas mencapai 33,24 dan tembaga mencapai 24,60 . Hasil pelindian diadsorpsi dengan karbon aktif dengan variasi konsentrasi 10, 20, 25, 30, dan 50 g/L. Hasil adsorpsi dianalisis dengan AAS dan menunjukan peningkatan kadar emas mencapai 99,1 pada konsentrasi karbon aktif 50 g/L.

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Advancement in technology and the increasing of its demand increase the amount of electronic waste especially printed circuit board PCB . Waste PCB was comminuted to particle size of 1 2 cm2. Comminuted waste PCB was leached in the mixture of 0,5 M hydrochloric acid and 0,4 M hydrogen peroxide as lixiviants and the result was tested using Atomic Absorption Spectrophotometer AAS. The result showed that the gold recovery is 33.24 and copper 24.60 . Adsorption was done using activated carbon with the concentration of 10, 20, 25, 30, and 50 g L. The filtrate then was tested using AAS and showed that 99.1 of gold was recovered in the adsorption using 50 g L activated carbon.

Abstrak :
Pada penelitian ini dibuat formulasi pembersih toilet berbahan dasar asam klorida (HCl) pada rentang variasi konsentrasi 37% (12 M) hingga 1 M dan asam sitrat (HOC(CH2CO2H)2) pada rentang variasi konsentrasi 5 M hingga 1 M yang ditambahkan surfaktan kokamida dietanolamina (CDEA) dengan metode pengadukan pada suhu ruang. Formulasi pembersih toilet yang dibuat dilakukan karakterisasi dengan Fourier Transform Infrared (FT-IR), uji antibakteri, diuji stabilitas fisiknya secara visual dan uji penilaian kualitas kinerjanya secara visual dalam membersihkan noda pada keramik kamar mandi. Hasil uji antibakteri menunjukkan sampel yang dapat menghasilkan zona hambatan pada bakteri gram negatif E. coli dan bakteri gram positif S. aureus adalah surfaktan CDEA serta cairan pembersih toilet berbahan dasar HCl pada konsentrasi 7 M, 10 M, dan pekat 37%. Diameter zona hambatan pembersih toilet HCl terhadap E. coli berada pada rentang 52-96 mm, sedangkan untuk pembersih toilet asam sitrat pada rentang 64-91 mm. Diameter zona hambatan pembersih toilet HCl terhadap S. aureus berada pada rentang 56-80 mm, sedangkan pembersih toilet asam sitrat tidak menghasilkan zona hambatan. Hasil uji stabilitas fisik formula pembersih toilet selama 2 (dua) minggu menunjukkan bahwa volume fase terpisah formula pembersih toilet berbahan dasar HCl kecuali pada konsentrasi 1 M, semua mengalami peningkatan volume dari hari ke-2 hingga hari terakhir pengamatan. Sedangkan volume fase terpisah formula pembersih toilet berbahan dasar asam sitrat kecuali pada konsentrasi 1 M, semua mengalami penurunan volume dari hari ke-2 hingga hari terakhir pengamatan. Berdasarkan uji aplikasi penilaian kualitas kinerja pembersih toilet berbahan dasar HCl maupun asam sitrat menunjukkan efektivitas kemampuan menghilangkan noda dan kerak pada keramik yang semakin baik seiring meningkatnya konsentrasi senyawa asam yang digunakan. ......In this study, a formulation of toilet cleaner was made using hydrochloric acid (HCl) with concentration ranging from 37% to 1 M, and citric acid with concentrations ranging from 5 M to 1 M, both added with cocamide DEA (CDEA) surfactant using stirring method at room temperature. The formulated toilet cleaner was characterized using FT-IR, tested for antibacterial activity, visually assessed for physical stability, and visually evaluated for its performance in removing stains on bathroom ceramic tiles. The antibacterial test results showed that the samples capable of producing inhibition zones against gram-negative bacteria E. coli and gram-positive bacteria S. aureus were the CDEA surfactant and the toilet cleaner with hydrochloric acid at concentrations of 7 M, 10 M, and concentrated 37%. The diameter of the inhibition zone of the HCl toilet cleaner against E. coli ranged from 52 to 96 mm, while for the citric acid toilet cleaner, it ranged from 64 to 91 mm. The diameter of the inhibition zone of the HCl toilet cleaner against S. aureus ranged from 56 to 80 mm, while the citric acid toilet cleaner did not produce any inhibition zones. The results of the physical stability test of the toilet cleaner formula showed that the separated phase volume of the hydrochloric acid-based toilet cleaner, except at a concentration of 1 M, increased from day 2 until the last day of observation. On the other hand, the separated phase volume of the citric acid-based toilet cleaner, except at a concentration of 1 M, decreased from day 2 until the last day of observation. Based on the evaluation of the performance quality of the hydrochloric acid and citric acid-based toilet cleaners, the results showed that the effectiveness in removing stains and scale on toilet ceramics improved with increasing concentration of the acid compounds used.

Abstrak :
Since inhibition is the simplest mechanism used for mitigating the corrosion of metals and alloys, particularly in acidic environments, the present work aims to investigate the inhibiting effect of N-benzyl-N?-phenyl thiourea (BPTU) and N-cyclohexyl-N?-phenyl thiourea (CPTU) on mild steel corrosion in 0.1M HCl medium using the Tafel extrapolation technique. Tafel experiments were conducted with ±250 mV vs. rest potential (RP) in steps of 20 mV from the cathodic side for recording the corrosion currents, and then, the Tafel plot of potential vs. current was drawn for determining the corrosion current density (icorr). The linear polarization method was also used for validating the Tafel results. It was performed by polarizing the specimen with ±20 mV vs. RP in steps of 5 mV, and the corrosion currents were noted. The plot of potential vs. current was drawn for calculating icorr. The study reveals that both BPTU and CPTU act as anodic inhibitors for mild steel in the HCl medium, and good inhibition efficiency (>97%) was evidenced from both the compounds even at elevated temperatures. The study also reveals that the investigated compounds get adsorbed quickly on the steel surface, following Temkin’s adsorption isotherm. The kinetic parameters obtained from the study indicated that the inhibition was governed by a chemisorption mechanism and the presence of inhibitors substantially reduced the metal dissolution in the studied temperature range. The investigation shows that there was a good correlation between the Tafel extrapolation and linear polarization results.

Abstrak :
Baterai lithium ion merupakan jenis baterai yang paling sering digunakan sebagai sumber energi pada telepon genggam. Jumlah limbah baterai lithium ion diperkirakan mencapai 200 - 500 ton per tahun. Dalam satu baterai lithium ion, terdapat 5 - 20 kandungan logam Co. Salah satu cara untuk memperoleh kembali sebuah logam berharga dari limbah adalah proses leaching yang kemudian dilanjutkan dengan ekstraksi. Limbah baterai Lithium-Ion akan dikarakterisasi menggunakan EDX dan AAS, hasilnya menunjukkan bahwa terdapat kandungan logam Co dalam bentuk LiCoO2 pada katoda. Proses leaching dilakukan dengan menggunakan asam klorida 4 M pada suhu 80°C dan waktu reaksi 1 jam. Logam Co akan diekstraksi dari larutan hasil leaching dengan kondisi optimal pada pH antara 5,0 - 6,0 menggunakan ekstraktan Cyanex 272 0,7 M dalam fasa membran, konsentrasi stripping acid H2SO4 sebesar 0,1 M, dan kecepatan pengadukan 1500 rpm. ......Lithium ion batteries are the most common type to be used as energy source in mobile phone. The amount of lithium ion battery wastes is approximated by 200 ndash 500 ton year. In one lithium ion battery, there are 5 ndash 20 of cobalt metal, depend on the manufacturer. One of the way to recover a valuable metal from waste is leaching process then continued with extraction. Spent lithium ion batteries will be characterized with EDX and AAS, the result will show the amount of cobalt metal with form of LiCoO2 in the cathode. Leaching process is done with hydrochloric acid 4 M, temperature 80°C, and stirring time 1 hour. Cobalt metal will be extracted from leaching liquor with optimum condition pH between 5.0 ndash 6.0 using Cyanex 272 0.7 M in membrane phase as extractant, stripping acid concentration H2SO4 is 0.1 M, and stirring speed of 1500 rpm.

Abstrak :
Light rare earth metals (LREM) banyak dimanfaatkan sebagai bahan baku katalis, keramik dan gelas mutakhir, paduan logam, material poles, dan lain-lain. Terak dari hasil samping pengecoran gold crude bullion memiliki kandungan LREM dalam jumlah yang signifikan. Dengan demikian terak gold crude bullion dapat dimanfaatkan sebagai bahan baku LREM. Kandungan LREM dalam terak gold crude bullion dapat ditingkatkan dengan proses pencucian air dan dilanjutkan dengan proses pelindian asam. Proses pencucian air dilakukan untuk meningkatkan kandungan LREM, menghilangkan kandungan Na, dan menurunkan nilai pH terak. Proses pencucian air mampu meningkatkan kandungan LREM hingga 55 kali dari kandungan sebelumnya, serta menurunkan nilai pH terak dari pH 13 menjadi pH 10 yang akan bermanfaat pada proses pelindian asam. Proses pelindian asam dilakukan dengan menggunakan asam klorida (HCl) sebagai larutan pelindi. Proses pelindian asam dilakukan pada rentang konsentrasi HCl 0,5 – 2,0 M, suhu proses 25 – 70°C, waktu pelindian 15 – 120 menit, serta rasio solid-liquid 1/10, ukuran partikel -74 μm, dan kecepatan pengadukan 300 rpm. Hasil dari proses pelindian asam memberikan persen ekstraksi hingga 76,62% untuk La, 76,56% untuk Ce, 76,77% untuk Pr, dan 76,66% untuk Nd pada konsentrasi HCl 1,5 M, suhu proses 55°C, serta waktu pelindian 120 menit. ......Light rare earth metals (LREM) are widely used as raw materials for catalysts, advanced ceramics and glasses, metal alloys, polishing materials, and others. Slag as a by-product from gold crude bullion casting process contains a significant LREM composition. Thus, gold crude bullion slag could be used as LREM raw materials. The LREM composition in gold crude bullion slag can be increased by water washing process followed by an acid leaching process. The water washing process is carried out to increase the LREM content, removing Na content, and reduce the pH value of the slag. The water washing process could increase the LREM content up to 55 times from the previous content and reduce the pH value of the slag from pH 13 to pH 10 which will be useful in the acid leaching process. The acid leaching process is carried out using hydrochloric acid (HCl) as the leachate solution. The acid leaching process is carried out in a HCl concentration of 0.5 - 2.0 M HCl, a process temperature of 25 - 70 ° C, a leaching time of 15 - 120 minutes, a solid-liquid ratio of 1/10, a particle size of -74 μm, and the stirring speed. 300 rpm. The results from the acid leaching process gave an extraction percentage of up to 76,62% for La, 76,56% for Ce, 76,77% for Pr, and 76,66% for Nd at a concentration of 1.5 M HCl, a process temperature of 55 ° C, and a leaching time of 120 minutes.

Abstrak :
Nikel sebagai salah satu logam strategis dan sangat berguna memiliki banyak manfaat untuk bidang industri berupa pembuatan baja (stainless steel), superalloy, otomotif, baterai, dan electroplating. Indonesia menjadi salah satu negara di dunia untuk dengan cadangan maupun sumber daya nikel laterit terbanyak. Pengolahan bijih laterit dapat menggunakan dua metode, yaitu pirometalurgi dan hidrometalurgi. Sebagian besar pengolahan bijih laterit di Indonesia menggunakan metode pirometalurgi. Tujuan penelitian ini adalah mempelajari perilaku elektrokimia pelindian bijih nikel laterit dengan metode OCP, EIS, dan LP menggunakan asam klorida dengan konsentrasi 1M, 2M, 4M dan 6M, dan menghubungkan hasil metode OCP, EIS, dan LP terhadap perilaku nikel laterit yang dilakukan pelindian. Metodologi yang digunakan, yaitu preparasi asam klorida, preparasi sampel dengan pemotongan, metalografi, dan preparasi sampel studi elektrokimia. Karakterisasi sampel dengan SEM, EDAX, dan petrografi. Studi elektrokimia dari pelindian bijih nikel laterit dengan OCP, EIS, dan LP. Hasil pengujian karakteristik elektrokimia OCP, EIS dan LP menunjukan pelarutan konsentrasi HCl 6M menghasilkan perilaku pelarutan yang paling baik. Peningkatan konsentrasi meningkatkan nilai OCP. Nilai R2 ata Rct pada konsentrasi HCl 6M paling rendah dengan nilai 523,07 Ω. Hasil LP menunjukan peristiwa pasivasi pada setiap konsentrasi pelarutan. Laju pelarutan semakin besar dengan peningkatan konsentrasi. Laju pelarutan tertinggi pada konsentrasi HCl 6M sebesar 9,55 mm/year. Peningkatan konsentrasi HCl menyebabkan pemecahan lapisan pasif pada permukaan yang dapat dilihat dari kurva Nyquist, nilai R2 semakin rendah, nilai Q1 semakin tinggi dan nilai N semakin rendah. Ketiga pengujian elektrokimia menunjukan semakin tinggi konsentrasi maka semakin besar laju pelarutan dan pemecahan lapisan pasif pada permukaan. ......Nickel as one of the strategic metals has many benefits for the industrial sector in the form of steel (stainless steel), superalloy, automotive, battery, and electroplating. Indonesia is one of the countries in the world with the largest reserves and resources of nickel laterite. Lateritic nickel ore processing can use two methods, that is pirometallurgical and hydrometallurgical. Most of the processing of lateritic nickel ore in Indonesia uses the pirometallurgical. The purpose of this study was to study the electrochemical behavior of leaching of lateritic nickel ore with the OCP, EIS, and LP methods with 1M, 2M, 4M and 6M concentrations of chloric acid. The methodology used in this research is preparation of chloric acid solution, preparation samples by cutting, metallography, and preparation of electrochemical study samples. Characterization of laterite ore samples with SEM, EDAX, and petrography. Electrochemical study of dissolution lateritic nickel ore with OCP, EIS, and LP. The test results of the electrochemical characteristics of OCP, EIS and LP showed that dissolution at the 6M HCl concentration produced the best dissolution behavior. The increasing concentration increased the value of OCP. The value of R2 or Rct at the lowest concentration of 6M HCl was 523.07 Ω. The LP results showed passivation at each dissolution concentration. The dissolution rate was greater with increasing concentration. The highest dissolution rate occurred at 6M HCl concentration of 9.55 mm/year. Increased concentration of HCl causes the breakdown of passive layer on the surface of sample which can be seen from the Nyquist curve. Electrochemical tests show that increasing concentration linear to dissolution rate and passive layer more destructive on the surface.