Thermochemical Conversion of Waste Glass and Mollusk Shells into an Absorbent Material for Separation of Direct Blue 15 Azo Dye from Industrial Wastewater

Abstract

The objective of the presented work was to convert waste glass and mollusk shells into a porous material for separation of the direct blue 15 azo dye from industrial wastewater. The porous glass material of specific pore size and surface area was prepared through a thermochemical reaction by reacting waste glass with mollusk shells, soda, and rock salt. The optimal reaction conditions were determined by adjusting the reaction time, reaction temperature, and relative amount of the reactants. The surface morphology, elemental composition, and functional groups of the material were studied through scanning electron microscopy (SEM), X-ray florescence spectroscopy (XRF), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FT-IR). Barrett-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) methods were used to determine the pore size distribution and surface area of the porous material. The material consisted of different types of flakes, oval-shaped particles, and granules. In addition to the functionalized char, the porous material contained Si-O-Si, Si-O-Al, and Si-OH groups. Relatively better yield and pore size distribution were obtained at a reaction temperature of 800 °C and reaction time of 90 min. The fully characterized material was used to separate the blue dye from industrial wastewater. This porous material absorbed about 2.66 mg/g blue dye from wastewater after 20 min of treatment time. The adsorption data fit the Freundlich isotherm better than the Langmuir isotherm. The correlation coefficient of Freundlich isotherm varied from 0.93 to 0.98, which was slightly higher than the correlation coefficient of Langmuir isotherm.