Alkalizing properties of biomass ash

Worldwide, the sunflower is an important agricultural crop—the seeds are used as a food source for people and animals, and as feedstock for liquid biofuel production. The biomass residues are utilised as solid biofuel for local heating systems and industrial facilities. Although the biomass ash is a tertiary product of biomass usage, it is not classed as waste—depending on the biomass type, it consists of valuable elements such as potassium, calcium, sodium, phosphorus, etc. The current study aims to investigate the alkalizing properties of biomass ash in two forms: sunflower husk ash (SHA) and sunflower husk ash granules (SHAGs). Both materials were characterized with dominant alkaline oxides, as K₂O was in the range of 15.09-17.56 wt. % and Na₂O was in the range of 4.42-6.19 wt. %. The pH measurements were carried out with an apparatus type HI-5522, while the elemental analysis of solid and liquid samples was performed using an X-ray fluorescence (XRF) apparatus type E-lite. The experiments were conducted with 30 ml of deionized water, different amounts (2 and 3 g) of SHA and SHAG, with and without stirring, at contact times of 2 and 72 hours. The investigated materials demonstrated good alkalizing properties—the pH rose from 6.8 to over 10.3 and remained stable over time, with a maximum pH of 10.96 for 3 g SHA without stirring, after 2 hours. The XRF results were similar for both materials—Na reacted with water was found to contain 37.51% SHA and 35.87% SHAG, while the dissolved K in the water was measured at 84.43% for SHA and 83.33% for SHAG. The obtained results are a prerequisite for further utilization of this by-product as a green chemical material for increasing pH, with different applications like the production of liquid fertilizers, soaps, etc., or for wastewater decontamination from heavy metals.