Author(s)

N. E. Quaranta, G. G. Pelozo, A. Cesari, A. A. Cristóbal

Abstract

The aim of this work is to study ashes from the combustion of sunflower husks in order to determine their environmental suitability for reuse as a structural filler or as an aggregate in clay mixtures for the manufacture of ceramics. Various characterization techniques were used, such as optical and electronic microscopy, X-ray electron dispersive analysis, X-ray diffraction, analysis of particle size distribution, soluble solids, conductivity, pH, leaching test and ecotoxicity, among others. The results of chemical analysis show that the main elements are Mg, Ca, and P. The conductivity and pH values after 2h of stirring in distilled water are 17.11 mS and 11.46, respectively. Results from analysis of the leaching test determine that none of the measured values in the ashes exceed the limits established by law 24051 (Argentina) on hazardous waste. Regarding the ecotoxicity analysis, it is observed that sunflower husk ashes inhibit the growth of seedlings at the studied concentrations. It can be concluded that it is not convenient to use the ashes as soil filler because it would produce alkaline soil, transferring a large amount of electrolytes, and producing negative effects on the development of many species that need acid or slightly alkaline soil. From the experimental results and the analysis of the equilibrium diagrams of the major oxides of clay-waste mixtures, the theoretical sintering temperature was determined. It shows that it is feasible to incorporate up to 20% of this waste material holding sintering temperatures commonly used in the ceramic industry (1050°C). For higher percentages, the sintering temperatures of the compact bodies increase, making incorporation difficult and costly.

Keywords

sunflower husk ashes, soils, ceramics