Preparation, characterization, and application of nano-silica from agricultural wastes in cement mortar

This work aimed to prepare and characterize nano-silica (SiO2) from agricultural waste (palm ash) through a leaching treatment process using citric acid (C6H8O7). These waste materials (if present in large quantities) could lead to environmental issues, since palm waste materials are burned in a furnace at 700 ? for 5 h. The produced palm ash (PA) was treated with different concentrations of citric acid solution (1-5%). Subsequently, the PA was crushed for 1 h in a ball-milling machine to minimize particle size and enhance reactivity for the leaching process. The pure extracted silica balls were then milled for 2 h. The results showed that silica could be extracted from PA using citric acid leaching treatment under the optimum extraction conditions with a solution temperature of 70 ?, a 1 h reaction time, and a concentration of 4% citric acid. The purity of the extracted silica was greater than 92%, and the average particle size was 80 nm. Various techniques (X-ray fluorescence, X-ray diffraction, particle size analyzer, atomic force microscopy, the Brunauer-Emmett-Teller method, and scanning electron microscopy) were used to detect the compositions, structures, particles distribution, surface area, and morphology of the prepared palm ash nano-silica (PANS). The PANS can be used as admixtures to enhance the mechanical properties of cement mortar. The results showed a 31% and 29% improvement in compressive and tensile strengths, respectively, under optimum conditions, and a weight of 6% and 10%, respectively, at 28 days of age. To the best of our knowledge, no work has previously prepared nano-silica from PA for use in cement mortars.

Automated summary

This study aimed to prepare and characterize nano-silica from agricultural waste (palm ash) using a leaching treatment process. The extracted silica from palm ash showed a purity above 92% and an average particle size of 80 nm. The prepared palm ash nano-silica (PANS) can be used as admixtures to enhance the mechanical properties of cement mortar, with significant improvements in compressive and tensile strengths.