Application of an experimental design in the hydrothermal synthesis of GIS-NaP zeolite from brickwall wastes

Abstract

This article reports the results of an investigation carried out in order to obtain zeolitic material of the GIS-NaP type with high cation exchange capacity using brick waste. The hydrothermal synthesis was carried out in a stainless-steel reactor using NaOH activating solutions at concentrations of 2.0, 2.5 and 3.0 M, activation temperatures of 100, 120 and 140 ℃ and activation times of 7, 8 and 9 hours. The product obtained was characterized by X-ray Fluorescence, Scanning Electron Microscopy (SEM), X-ray Diffraction, and Cation Exchange Capacity (CEC). The results obtained showed that for the hydrothermal conversion test at 140 ℃/2 M/7 hours, GIS-NaP synthetic zeolite with a cation exchange capacity equal to 163.5 meq/100 g was obtained. The statistical analysis, applying a factorial experimental design, indicated that the main factors with a great effect on the cation exchange capacity (CEC) are the activation temperature and the interaction between it and the concentration of the activating solution, with a degree of significance of 0.049250 and 0.056631 for a confidence level of 90.82%. An empirical mathematical model was devel-oped and validated by applying ANOVA analysis that considers the interaction effects of all factors and was optimized by applying the response surface methodology.