Hot water treatment effect in the elephant grass ashes calcinated at different temperatures

Abstract

In recent years, agro-industrial residues have focused attention in the scientific community as a new source of pozzolans. In Brazil, for example, one of the wastes generated from agro-industrial activities comes from elephant grass that is cultivated as biomass for energy cogeneration. This study evaluated the effect of hot water treatment on the crystalline structure of elephant grass ashes calcinated in two different temperature (700 and 900°C). To study the chemical structure and the composition of the ashes the X-ray fluorescence (XRF) and X-ray diffractions (XRD) analyses were carried out. The results achieved in the present work shown that, elephant grass ashes meet the ASTM C-618 standard, for the minimum sum content of the silica (SiO2), aluminum (Al2O3) and iron (Fe2O3) oxides, of 50% to be considered as a pozzolanic material. The presence of an amorphous phase has been detected in all XRD patterns. The ashes calcinated at 700°C showed lower crystallinity and the treatment with hot water decreased crystallite size, i.e., the material became more amorphous. On the other hand, the ashes calcinated at 900°C, less reactive, had a lower content of K2O. Therefore, the hot water treatment was effective to reduce the potassium content in the ashes. Additionally, it contributed to reduce the crystallite size of silica in the ash calcinated at 700°C, while the effect is contrary to the ash calcinated at 900°C.

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“…The polynomial models exhibit a curved shape of response, the second-order polynomials function is used as provided in Equation (2), where y is the measured response, X i and X j are the coded values of independent variables, i and j denote the linear and quadratic equations coefficients, respectively, β o is the y-intercept at X 1 = X 2 = 0, k is the number of independent variables and ∈ is the error [ 66 , 67 ]. …”

A Review on the Application of Lignocellulosic Biomass Ash in Cement-Based Composites

“…The SiO2 content and ignition loss were 56.4% and 1.6%, respectively. Nakanishi et al [159] increased the calcination temperature of EGA from 700 °C to 900 °C and found that the silica content increased from 50% to 70%. Table 20 shows the main chemical components of EGA.…”

“…Cordeiro et al [158] found that the SiO 2 content in EGA gradually increased with the increase of calcination temperature, and the loss on ignition gradually decreased, reaching the optimal value at 800 • C. The SiO 2 content and ignition loss were 56.4% and 1.6%, respectively. Nakanishi et al [159] increased the calcination temperature of EGA from 700 • C to 900 • C and found that the silica content increased from 50% to 70%. Frias et al [142] confirmed through XRD that there were a large number of amorphous phases in EGA, which gave EGA pozzolanic properties.…”