EFFECT OF H2O2 AND MnO2 AS OXIDATORS OF GOLD AND COPPER LEACH PROCESSES FROM PRINTED CIRCUIT BOARDS

In general, electronic waste management in the form 2 of printed circuit boards (printed circuit boards/PCBs) is carried out by the process of removing components and taking precious metals that are easily recycled. However, in Indonesia, the recycling process for extracting precious metals has not been much processed, even though they contain precious metals such as copper and gold. This research was conducted to find a more economical and environmentally friendly treatment process by using an oxidizer of Hydrogen Peroxide (H2O2) and Manganese Oxide (MnO2) and reducing the level of HCl used. Observation of metal leaching results using Atomic Adsroption Spectroscopy (AAS) showed the value of recovery (recovery) of gold and copper reached 59.1% and 59.8% for 0.5M HCl + 2.5% H2O2. However, the recovery value of copper has reached its optimum point at the addition of 1.5% H2O2. The use of 3% & 5% MnO2 results in recovery values of 12% and 24% for gold and copper. Observation of the cross section shows the dissolution of the copper metal from the PCB and accompanied by a change in the color of the solution from clear to green, the more concentrated the more the amount of dissolved copper metal shows the characteristic of CuCl solution. The results of the comparison of the two types of oxidizers show that H2O2 is better than MnO2 in producing higher Cu and Au metals more than 3 times

THE EFFECT OF PYROLYSIS DURATION ON THERMAL CONDUCTIVITY, STABILITY, AND VISCOSITY OF DISPERSED PCB-BASED PARTICLES IN THERMAL FLUID

Solid particles have a higher thermal conductivity compared to a fluid. Therefore, it is a common practice to disperse solid particles inside a base fluid to increase its thermal conductivity. The particle-dispersed fluid is called a thermal fluid. Thermal fluid, such as a coolant, is widely used as a heat transfer fluid. Several types of particles can be used to increase the thermal conductivity of the fluid, i.e., metallic particles, metal-oxide particles, or even carbon-based particles. In this research, a carbon-based particle was used as the dispersed particle. The particle was obtained by processing electronic waste, specifically Printed Circuit Board (PCB). The PCB was pyrolyzed for variable duration at 15, 30, and 45 minutes to increase the carbon content. After pyrolyzing, the particle was milled to reduce its size. Subsequently, the PCB particle was added to distilled water. Sodium Dodecylbenzene Sulfonate (SDBS) was added as a surfactant to increase fluid stability and prevent particle agglomeration. Thermal conductivity was improved by up to a 13% increase at the 15-minute pyrolysis. Adding SDBS surfactant also improves the thermal fluid's stability to -29,1 mV. The fluid's viscosity was slightly increased up to a maximum of 0.984 mPa.S

Comparison of wet and dry milling on carbon biomass as dispersed particle in quench medium for steel heat treatment application

Particle dispersion in the quench medium can alter its properties, particularly its thermal conductivity. Modulating the quench medium’s thermal conductivity can impact the steel’s hardness after heat treatment. In this study, micron-sized particles of carbon biomass derived from coconuts were obtained by milling the biomass via wet and dry methods. The milling duration for both methods was 10, 15, and 20 h, while the speeds were 250, 500, and 750 rpm for each duration. Particle size analysis revealed that dry milling could decrease the particle size by up to 60% from its initial size, whereas wet milling could only decrease it by up to 43%. A thermal conductivity test was conducted on the water-based quench medium supplemented with milled particles, demonstrating an increase in thermal conductivity up to 0.68 W mK ^−1 and 0.83 W mK ^−1 for dry and wet milling, respectively. All steel quenched with particle-added quench medium showed a hardness up to 21% higher than steel quenched with distilled water. The increase in hardness suggests that the cooling rate during quenching was faster because of the additional dispersed particle, determined by the quench medium’s thermal conductivity

Effect of T6 on Mechanical Properties of TiB and Sr Modified ADC12/SiC Composite Produced by Stir Casting

A study of ADC12 (Al-Si aluminium alloy) composite is conducted to obtain a more sustainable material with enhanced properties for automotive industry purpose, such as train's brake shoe and bearing application. For those kind of utilization, material with durability, good elastic modulus, thermal stability, wear resistance, and high strength properties is needed due to its exposure to high temperature and heavy continuous application. ADC 12 acts as the matrix, reinforced with 3 vf% micro-SiC with 5 wt% Mg wetting agent was fabricated by the stir casting method. The addition of 0.18 wt% Sr and 0.15 wt% TiB were expected to finer the grain morphology of the silicone eutectic phase and to acts as the grain refiner, respectively. Furthermore, T6 heat treatment was applied with aging temperature 150 °C, 170 °C, 190 °C, 210 °C, and 230 °C, following the prior 1 h 490 °C solution treatment. The results obtained in this work showed enhancement in tensile strength with the value of 213 MPa, hardness value 75 HRB, and wear resistance. These values increase up to 115 MPa for the UTS and 38 HRB for the hardness value, as the impact of the refined grains from both modifiers and heat treatment