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This study examines the physical and chemical properties of nano-activated carbon obtained from Robusta coffee pulp. It also examines the potential use of Robusta coffee pulp biomass as a raw material for hydrogen storage. In this investigation, the dried coffee pulp samples were carbonized using the slow pyrolysis method at temperatures of 400°C and 500°C. A biochar product was obtained and activated using NaOH and ZnCl 2 solutions. The analysis results Fourier Transform Infra-Red (FTIR) suggested that both carbonization and activation processes with NaOH or ZnCl 2 solutions were unable to removed the caffeine content in coffee pulp. The Differential Calorimetric Analysis/Thermogravimetric Analysis (DSC/TGA) indicated that coffee pulp carbonization reached optimality within the temperature range of 400 to 500°C. Furthermore, the Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDS) and N 2 -adsorption isothermal analysis showed that the surface pores of activated carbon had a honeycomb-like structure with a size greater than 0.7 nm which is applicable for hydrogen storage material.

Fly ash waste is a by-product of coal burning at PLTU Nagan Raya, Aceh Province, Indonesia. Since 2017, the coal used is a mixture of 90% Kalimantan coal (sub-bituminous) and 10% local Nagan Raya coal (lignite) which is still young so that the mineral ash content is still high. Silica is among the interesting minerals to be extracted from fly ash, given its wide range of benefits. This paper describes the process of extracting silica from fly ash at the Aceh power plant through the leaching method using a chemical solution and heating for 2 and 4 hours at a temperature of 100˚C. The difference in heat treatment aimed to study the changes in properties and obtain the best method in the silica extraction process. The effect of heat treatment on silica characteristics was studied based on X Ray Diffraction (XRD) test for phase identification, Scanning Electron Microscopy (SEM) test for morphological identification, Energy Dispersive X-Ray Spectroscopy (EDS) test for mineralogy element identification, Fourier Transform Infra-Red (FTIR) test for identification of functional groups and surface chemistry, and differential calorimetric analysis/ thermogravimetric (DSC/TGA) test for identification of thermal properties. As a result, it was found that fly ash still contains unburned carbon, which significantly affects its color, and has the potential for application as a hydrogen storage material because its pore diameter structure is larger than 0.7 nm. The silica extracted from fly ash is capable of achieving a purity of up to 87% and exhibits excellent thermal stability, especially at temperatures between 120-300 °C; thus, it has the potential to be a catalyst material in the adsorption-desorption reaction of hydrogen by magnesium, although further research is still needed.