The Pidgeon process, a silicothermic reduction of calcined dolomite under vacuum, is the dominant process to make magnesium metal. Experimental data from Morsi et al., were utilised for kinetics analysis of silicothermic reduction of calcined dolomite under argon atmosphere. A number of kinetic models were assessed to evaluate the rate-controlling step in the process. The results suggest that the reaction is controlled by the solid-state diffusion of reactants with the Jander and Ginstling-Brounshtein model providing the best representation of the process kinetics. Mass transfer effects of magnesium vapour from the surface to the bulk gas phase was also analysed. These results suggest that gas-film mass transfer is not the limiting step of the kinetics. Pore diffusion through briquettes is postulated to have some effect on the kinetics but solid-state diffusion is the major rate-limiting step

Gum rosin is an important agricultural commodity which is widely used as a raw material for various industries. However, gum rosin has low stability, crystallizes easily, and tends to oxidize. This is due to carboxyl groups and conjugated double bonds in gum rosin’s structure. Therefore, to reduce these weaknesses, it is necessary to modify the rosin compound to achieve better stability via the esterification process. This paper surveys esterification agents such as glycerol, pentaerythritol, methanol, ethylene glycol, polyethylene glycol (PEG), allyl group, and starch Rosin ester. The product is used in the manufacture of pressure-sensitive adhesives, drug delivery, solder flux for electronic devices, as a plasticizer, and as a coating agent in fertilizers. In general, the esterification reaction between alcohols and carboxylic acids is very slow without a catalyst. Heterogeneous catalysts have the advantage of controlling size, structure, spatial distribution, surface composition, thermal-chemical stability, and selectivity. Among the catalysts for gum rosin esterification are ZSM-5, Fe₃O₄, ZnO, Calcium, TiO₂, Kaolin, and Al₂O₃, among others. Different catalysts and esterification agents can produce various physical and chemical properties of rosin ester and will result in specific rosin ester products, such as glycerol ester, pentaerythritol ester, methyl ester, glycol ester, allyl ester, and acid starch-based rosin.

This paper reports a study on thermal decomposition of dolomite under CO₂-air. Calcination was carried out non-isothermally by using thermogravimetry analysis-differential scanning calorimetry (TGA-DSC) with a heating rate of 10°C/minute in an air atmosphere as well as 10 vol% CO₂ and 90 vol% air atmosphere from 25 to 950°C. In addition, a thermodynamic modeling was also carried out to simulate dolomite calcination in different level of CO₂−air atmosphere by using FactSage® 7.0. The the main constituents of typical dolomite from Gresik, East Java include MgCO₃ (magnesite), CaCO₃ (calcite), Ca(OH)₂, CaO, MgO, and less than 1% of metal impurities. Based on the kinetics analysis from TGA results, it is found that non-isothermal dolomite calcination in 10 vol% CO₂ atmosphere is occurred in a two-stage reaction; the first stage is the decomposition of magnesite at 650-740 °C with activation energy of 161.23 kJ/mol, and the second stage is the decomposition of calcite at 775-820 °C with activation energy of 162.46 kJ/mol. The magnesite decomposition is found to follow nucleation reaction mechanism of Avrami Eroveyef (A3), while calcite decomposition follows second order chemical reaction equation. Thermodynamic modeling supports these kinetic analyses. The results of this research give insight to the kinetics of dolomite decomposition in CO₂-air atmosphere.

Zeolite A has been successfully synthesized from coal fly ash by using fusion followed by hydrothermal method. This paper describes the characterization of zeolite A. The effects of hydrothermal time, Si/Al molar ratio, and alkalinity in the converting coal fly ash to zeolite A were also investigated. The coal fly ash was obtained from a local power plant at East Java, Indonesia and contained major oxides such as SiO₂ (18.60 wt%), Al₂O₃ (7.18 wt%), Fe₂O₃ (40.20 wt%), CaO (25.20 wt%). The fusion hydrothermal method consists of the following steps: pre-treatment, fusion of coal fly ash with sodium hydroxide, aging, and hydrothermal process. The synthesized material was characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscope (SEM), Fourier Transform Infrared (FTIR), and specific surface area analytical method. The results show that the products contain zeolite A as the major phase, while the highest specific surface area of zeolite A is 37.121 m²/g. It implies that zeolite A as a higher value added product can be obtained from a solid waste/by-product of power plant, which has wide range applications, including for ion exchange and heavy metal adsorbent from waste water.

Biomass is a potential alternative fuel in Indonesia and other tropical countries. Combustion of biomass produces ash that may contain various beneficial compounds, including potassium. Potassium recovered from the biomass ash can be used as the raw material for producing fertilizer solution, thus reducing Indonesia’s dependence on fertilizer import. This study aims to assess the feasibility of potassium recovery from the ashes of oil palm empty fruit bunch (OEFB), banana peel, and corncob. The biomass ash samples are prepared by the following steps: drying, fixed-bed carbonization, and ashing. Single-stage batch extractions are carried out at 80 °C for 4 hours using demineralized water. The ash to solvent mass ratios used is 1:4, 1:5, 1:6, and 1:8, respectively. Measured ash content on dry basis is 10.75% for banana peel, 2.60% for OEFB, and 1.67% for corncob. Banana peel and OEFB ash extracts contain potassium exceeding the national standard for fertilizer solution, which is set at 30,000 ppm of equivalent K₂O. The highest potassium yield with respect to total potassium content in the ash is obtained from corncob ash within the ash to solvent ratio of 1:8, with the potassium yield of 62.29%. By contrast, banana peel ash extraction at ash to solvent ratio of 1:4 results in the lowest potassium yield of 21.41%.

Geopolymer is an environmentally attractive Portland cement substitute, owing to its lower carbon footprint and its ability to consume various aluminosilicate waste materials as its precursors. This work describes the development of geopolymer formulation based on biomass-coal ash blends, which is predicted to be the prevalent type of waste when biomass-based thermal energy production becomes mainstream in Indonesia. The ash blends contain an ASTM Class F coal fly ash (FA), rice husk ash (RHA), and coconut shell ash (CSA). A mixture of Na2SiO3 and concentrated KOH is used as the activator solution. A preliminary experiment identified the appropriate activator/ash mass ratio to be 2.0, while the activator Na2SiO3/KOH ratio varies from 0.8 to 2.0 with increasing ash blend Si/Al ratio. Both non-blended FA and CSA are able to produce geopolymer mortars with 7-day compressive strength exceeding the Indonesian national SNI 15-2049-2004 standard minimum value of 2.0 MPa stipulated for Portland cement mortars. Ash blends have to be formulated with a maximum RHA content of approximately 50 %-mass to yield satisfactory 7-day strength. No optimum ash blend composition is identified within the simplex ternary ash blend compositional region. The strength decreases with Si/Al ratio of the ash blends due to increasing amount of unreacted silicate raw materials at the end of the geopolymer hardening period. Overall, it is confirmed that CSA and blended RHA are feasible raw materials for geopolymer production..