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Defect engineering of semiconductor photocatalysts is considered as an evolving strategy to adjust their physiochemical properties and boost photoreactivity of the materials.

Dolomite calcination is one of process steps to prepare calcined dolomite for raw materials in magnesium production. Calcination of dolomite involves heating the raw material at sufficient temperature in order to release the carbon dioxide from its carbonate minerals. This process is commonly conducted in a rotary kiln. There have been a number of calcination studies in a laboratory scale, but the study of dolomite calcination in a larger scale is very scarce. This research is aimed to study the performance of dolomite calcination in a bench-scale rotary kiln with 500 gram of feed. The effect of various parameters, including temperatures, feed rate, rotating frequency, and particle size were examined. The temperature of rotary kiln was varied between 700 and 1000 °C, while the particle size of dolomite was varied between 0.149 – 0.297 mm and up to 10 – 15 mm. The temperature distribution inside the rotary kiln was also measured. It is obtained that a conversion of 92% was attained at operation temperature of 1000 °C, which is at a higher temperature compared to the laboratory scale, where a conversion of 100% was obtained at 900 °C. This imply that the effect of heat transfer also plays important role in the calcination of dolomite especially at a larger scale.

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A review on the effect of fly ash characteristics and their variations on the synthesis of fly ash based geopolymer AIP Conference Proceedings 1887, 020041 (2017); 10.1063/1.5003524The effect of slag addition on strength development of Class C fly ash geopolymer concrete at normal temperature AIP Conference Proceedings 1887, 020030 (2017); 10.1063/1.5003513Early age compressive strength, porosity, and sorptivity of concrete using peat water to produce and cure concrete AIP Conference Proceedings 1887, 020027 (2017) Abstract. 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..

The combustion of biomass for energy generation is practiced in an increasing scale in Indonesia as the country heads towards the long-term national energy mix targeted by 2025. However, biomass combustion is prone to operational problems caused by the generally low-melting nature of biomass ashes. This work discusses the effects of co-combusting coal with POEFB (palm oil empty fruit bunch) and bamboo with respect to the thermomechanical behavior of the produced ashes. Coal is observed to increase the ash fusion temperatures (AFT) of neat and combined POEFB and bamboo ashes by as much as 300 °C. Aluminosilicate minerals in the coal combine with potassium in the biomass during co-combustion, producing high-melting K-aluminosilicates. A linear correlation is identified between measured AFT and ash liquidus temperatures estimated by FactSage thermochemistry calculation software, enabling the prediction of AFT of coal-biomass co-combustion systems.