Preparation and characterization of silica based xerogel and aerogel composites

Silica xerogels and aerogels were synthesized from TEOS, volcanic tuff and groundnut hull ash by sol-gel method in this study. Various properties of the materials were investigated with XRD, FTIR, FESEM, N2 adsorption-desorption isotherms, TGA, thermal conductivity, density and contact angle measurements. When compared to silica xerogels, it was specified that silica aerogels had higher surface area, pore volume, thermal stability, and lower density and thermal conductivity. To examine effects of PEG and carbon black addition on the properties of the materials, silica xerogel and aerogel composites were prepared. The addition of PEG and carbon black has synergistic effects on the properties of the materials especially their porous structure. Additionally, hydrophilic structure of the materials was converted to hydrophobic structure through surface modification of the materials using TMCS. Among the materials, silica xerogels obtained from low-cost volcanic tuff under ambient pressure drying (surface area: 195 m2/g and density: 0.037 g/cm3) were evaluated as an adsorbent for MB adsorption. In this process in which Taguchi optimization method was used, maximum MB removal and adsorption capacity was determined as 96.18% and 51.967 mg/g, respectively at optimum experimental conditions (time: 60 min, concentration: 20 mg/L, adsorbent dose: 0.0016 g/mL, temperature: 40°C ve pH: 5). After 5 adsorption-desorption cycle, it was observed that silica xerogel could be used with efficiency of 70% for MB adsorption. And also, utilization of silica xerogels synthesized from volcanic tuff as carrier materials for antibacterial applications was examined. Antibacterial activity of ε-poly-l-lysine capped linezolid loaded silica xerogels against E. coli (Gram-negative) was investigated by spread plate method at different concentrations. It was seen that silica xerogel and linezolid had no antibacterial activity separately; however, ε-poly-l-lysine capped linezolid loaded silica xerogels with the concentration of as low as 0.220 μg/mL inhibited E. coli growth. It is thought that usage of low-cost silica xerogels as carrier material in this new designed systems will provide advantage to extend the spectrum of existing antibiotics instead production of new antibiotics for decreasing bacterial diseases.