New insights into method development and characterization of amorphous silica from wheat straw

Amorphous silica, a specialised silicate adsorbent is extensively extracted from agricultural residues for application in various environmental domains. Wheat straws are a rich source of silica that have earlier been overlooked however demand for value addition. The study presents an innovative approach to extracting silica from wheat straw and standardising the extraction process to produce clean product. The sodium silicate solution and the amorphous silica synthesis were obtained by modifying the template mediated sol–gel method. Optimum temperature, concentration and pH were identified for the cleaner production of silica with maximum yield and favourable adsorbent characteristics. The crystallographic properties analysed by the X-Ray Diffraction revealed the amorphous nature of silica extracted from ash at 650 °C for 4 h. The structure of phytolith present in the wheat straw was observed in the form of articulated elongate undulate epidermal phytolith under scanning electron microscopy. The Energy Dispersive X-ray spectrum exhibited higher amount of silica (Si %) of 70.10% with a minimal percentage of potassium (9.96%). The sharp bend at 1025 cm−1 is attributed to the siloxane (Si–O-Si) vibrations in Fourier transform infrared spectroscopic graph of amorphous silica. The specific surface area measurements of amorphous silica showed type II isotherm curve with a hysteresis of H3 type. The optimum conditions derived to produce amorphous silica were 3 M NaOH and 3 M H2SO4 at pH 9

Thermochemical characterisation of hydrochar from agricultural waste and its efficiency as a supplement with solid fuel

Circular approaches to revalorise waste biomass from agriculture and food production sectors are crucial for developing a sustainable bioenergy strategy. For instance, while the demand for edible mushroom cultivation has increased globally, the production generates a substantial amount of waste biomass, known as Spent Mushroom Substrate (MS). Thermochemical biomass conversion technologies such as hydrothermal carbonisation offers a robust strategy to produce “hydrochar” from the wet biomass and can be used downstream for various environmental applications. In this study, we assess the feasibility of MS-derived hydrochar for energy application, specifically as a blend with coal. The key parameters for the hydrochar production such as temperature, time and moisture content were optimised (205 °C, 3.65 h, and 73.18 %, respectively) using a statistical tool “Response Surface Methodology (RSM)” to obtain a carbon material with higher yield and calorific value. The hydrochar from MS exhibited an acidic pH (4.42), increased fixed carbon content (23.7 %), reduced sulphur content (0.26 %), coarser porous surface, enhanced oxygenated functional groups (hydroxyl, carboxyl and ketonic) and the formation of minerals like Sodium Carbonate (NaCO3), whewellite (CaC2O4·H2O) and gypsum (CaSO4). Combustion behaviour of hydrochar was also assessed using calorimetry and thermogravimetry, specifically to test different coal and hydrochar blends on the feasibility of using hydrochar as a supplement to conventional solid fuels. Our results suggest that a blend of 20 % hydrochar with 80 % coal as an ideal blending ratio (with a calorific value of 27.65 MJ kg−1) highlighting the use of hydrochar as supplement with conventional fuel like coal.</p