The escalating demand of REY in various industrial applications becomes an important issue nowadays. REY has prominent evidence to improve material properties such as high electropositive and good conductivity. In addition REY can be classified as one of renewable and clean energy resources. Due to the increasing demand of REY, exploration of alternative sources such as red mud, spent catalyst, and coal fly ash has been conducted. Coal fly ash is one of the promising alternative sources of REY in regarding to the low radioactive material concentration. The conventional method to recover REY from coal fly ash using inorganic acids produces harmful by-product to the environment. In this research, two steps experimental methods were conducted. The first step was silicate digestion which was performed using sodium hydroxide 8 M in which REY is concentrated, with solid to liquid ratio of 1:4 and temperature of 90°C for 120 minutes. The second step was leaching the REY using citric acid. The variables studied were pH, temperature and solid to liquid ratio. The optimum condition was at the temperature of 90°C, pH 1.7 and solid to liquid ratio (15%) for each element. The maximum recovery for each elements are 77.33% Lanthanum (La), 83.47 % Cerium (Ce), 88.78% Dysprosium (Dy) and 55% Neodymium(Nd). In addition, temperature does not have any significant efect at pH 3.8.
Triggered by the concept of sustainability, the use of natural dyes in batik fabric processing has increased recently. To inhibit fungus growth on batik fabric colored with natural dyes, either clove oil or formaldehyde was added as an antifungal agent. To increase the stability of the interaction between the antifungal agent and the batik fabric, chitosan was used as a crosslinker. A modified version of the standard tests American Association of Textile Chemists and Colorists (AATCC) 30 and Response Surface Methodology (RSM) was applied as the characterization method. The results showed that the growth percentage of fungi in Batik treated with either clove oil or formaldehyde was much lower than that in the control sample. Growth of Aspergillus niger could be prevented by about 32% using clove oil and 94% using formaldehyde. The optimal condition was obtained with 1% chitosan as a crosslinking reagent, 15.91 ppm of formaldehyde, and 60-min immersion time, with absorbance intensity of formaldehyde crosslinking solution and fungus growth areas being 0.159 and 2.47%, respectively.
In five years, from 2015 to 2020, the need of coal in Indonesia is doubled to 166.2 million tonnes and increasing up to 2050 as stated in the Indonesian Energy Mix policy. Generally, coal is used in the coal-fired power plan. After the combustion, there are some residual materials such as mineral matter, fly ash and bottom ash (FABA) listed as hazardous materials due to the toxicity and metal contents. Referring to the amount of coal consumption in 2020, the fly ash and bottom ash will be of about 19.92 million tonnes. The utilization of FABA is then become a must thing to do. One of the alternatives is rare earth element (REE) extraction. Indonesian coal contains sufficient amount of REE to extract that is concentrated in the FABA to the value of more than 400 ppm. Regarding to the REE mode of occurrence that is mostly concentrated in the glass form or amorphous silicate, this study was conducted in order to observe the effect of sodium hydroxide to breakage the amorphous silicate structure. In order to obtain the amorphous silicate, magnetic separator was applied. Based on the XRF analysis, the non-magnetic fly ash (amorphous silicate of glass form) contained major elements of SiO2, Al2O3, Fe2O3, CaO, MgO and the rest were minor and trace elements such as Na2O, K2O, Cr2O3, MnO, SrO and P2O5. The particle size of the amorphous silicate is less than < 38 μm (- 400 mesh). To run the experiments, sodium hydroxide was used as the reagent with varied concentrations of 6 M, 8 M and 10 M. Other variables were temperature of 28 0C (room temperature), 60 0C and 90 0C and residence time of 2, 4, and 6 hour. Based on the results analysis, the amorphous silicate was decomposed to the most of about 22 % at 90 0C of temperature, 10 M of sodium hydroxide concentration, and 6 hour of residence time.
Along with the decrease of metal resources in the natural ores, urban mine comes up as an alternative with two aspects of both resource and environmental protection due to recycle. Broken printed circuit boards (PCBs) as one of the urban mine resources contains valuable metals, such as, Au, Ag, and Ti, with high concentration, however, it has not been seriously managed in some developing countries, such as Indonesia. Focusing on gold extraction, safer leaching agent using thiosulphate has been applied in this study and scrutinized the optimum leaching conditions with respond surface methodology. Temperature and concentration of thiosulphate were varied and designed in accordance with three factorial. Leaching time was set for two hours and the shaking speed of waterbath was set at fixed value of 200 rpm. In order to quantify the final concentration of gold in the solution, Atomic Absorption Spectroscopy (AAS) was applied for all samples. Response Surface Method (RSM) is utilized to know the optimum result of Au extracted. The result shows that the optimum result of Au extracted by using ammonium tiosulphate is 0.5114 mg/L respectively with correlative equation as follow; Gold Concentration = 0, 127+0, 00268*T+0, 66*C-0, 000021*T2+1, 74*C2- 0, 0038*T.C. With T = temperature (°C) and C = thiosulphate concentration (M) The obtained R2 is 0.94 and the p-value is 0.037 showing the significance of the variable correlation in the equation.
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