Synthesis of blue glass from Eichhornia crassipes in Nakhon Chai Si River

Abstract

This research aims to enhance the value of agricultural waste by synthesizing blue glass from water hyacinth harvested from the Nakhon Chai Si River basin to replace pure chemical network modifiers such as CaO and K2O. The process began with a chemical composition analysis of the water hyacinth using the EDXRF technique, which revealed significant concentrations of K2O and CaO suitable for glass formulation, along with transition metal oxides such as Fe2O3 and MnO. In preparing the blue glass, CuO concentration was varied from 0.00 to 0.50 mol%. Physical behavior studies indicated that increasing CuO content led to a continuous rise in density from 2.5467 to 2.5634 g/cm3. Conversely, the molar volume decreased from 25.1163 to 24.9901 cm3/mol, reflecting structural compaction that resulted in a more densely packed glass network. The refractive index increased in accordance with electron density. Optical absorption spectra exhibited a broad absorption band with a peak around $765\text {nm}$, attributed to the 5Eg  5T2g energy level transition, which caused the physical appearance of the glass to shift from transparent yellowish to an intense blue. This transformation was further confirmed by color measurement results in the CIE L*a*b* system. These findings highlight the potential of water hyacinth as a sustainable alternative raw material for producing functional glass with unique optical properties.