Characteristic investigations on bio-silica gel prepared from teff (Eragrostis tef) straw: effect of calcination time

Abstract

Bio-based silica gel is having many commercial significances in various sectors, such as medical, cleansing agents in industries, laboratory analysis, cosmetics, food additives, and so forth. In view of crucial requirements, this study aimed to synthesize and characterize the silica gel from Ethiopia’s primary post-harvest biomass residue, known as teff straw. The present study has been emphasized to investigate on the influence of calcination time for teff straw ash [Joshi et al 2022 Investigation of bamboo leaves as an alternative source of silica: extraction, characterization and its application as an adsorbent for methylene blue sequestration Chem. Select. 7, e202200011] preparation between 2 to 5 h. Further, the specific surface area of the resultant TSA samples was examined for preliminary understandings of processing time. By adopting the standard procedures through template-mediated sol–gel process, acquired TSA samples were subjected to treatment with NaOH to result sodium silicate solution and the amorphous silica. From the findings, it was apparent that the yield of silica gel has significantly influenced by calcination time. Accordingly, the maximum yield (90.0%) was attained at the calcination time of 4 h at 900 °C. Further, physiochemical and morphological characteristics of acquired silica gels were ascertained using sophisticated instrumental techniques such as BET, FTIR, XRD, SEM, and EDX. The XRD analysis of the crystallographic characteristics showed that the silica extracted from TSA at 900 °C for 2, 3, 4, and 5 h was found to be in amorphous state. The surface morphological studies of silica gel samples have been carried out using SEM studied. the EDX spectra showed the negligible amount of other impurities, nevertheless a larger amount of silica was found with highest purity of 99.77% e silica gel was obtained in TSA calcinated at 3 h. FTIR spectrum confirmed the presence of siloxane (Si–O–Si) vibrations of amorphous silica that are responsible for the strong bend observed at 1070 cm−1. It was found that the silica gel prepared at 3 h of calcination time had the largest specific surface area of 739.242 m2 g−1, pore volume of 0.32 cm3 g−1, and a pore diameter of 1.68 nm.