Simultaneous utilization of soju industrial waste for silica production and its residue ash as effective cationic dye adsorbent

Soju industrial waste is an important biomass resource. The present study aimed to utilize soju industrial waste for silica extraction, and residual ash (RA) as a low cost adsorbent for the removal of methylene blue (MB) from aqueous solution. A high percentage of pure amorphous nanosilica was obtained from soju industrial waste ash by the acid dissolution-precipitation process. The synthesized nanosilica and the RA were characterized well using various techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), and field-emission electron microscopy with energy dispersive spectroscopy (EDS). The amorphous nature of nanosilica and its 99% purity were confirmed by XRD and EDS profiles, respectively. Transmission electron microscopy (TEM) micrographs show the nano range (14-18 nm) of synthesized silica. The adsorption capacity of RA was evaluated as a function of initial dye concentration, pH, and contact time. The sorption equilibrium data were modeled with isotherms; the Langmuir isotherm model fits well with maximum monolayer adsorption capacity of 232.5 mg/g at 30°C. The adsorption kinetics was best fitted with the pseudo-second-order model, suggesting that chemisorption plays a significant role in the adsorption process. The results showed that soju industrial waste is a potential waste for silica extraction and that its byproducts are effective adsorbents.