This study reports the base-catalyzed aqueous sol-gel synthesis of zinc oxide nanoparticles. The solution was primarily comprised of zinc nitrate hexahydrate as a metal precursor, isopropyl alcohol and water as solvents, and glycerin as a stabilizing agent. The effect of calcination temperature on the structure and morphology of the prepared nanoparticles was investigated by varying the calcination temperature from 500 to 900 °C. The X-ray diffraction analysis, infrared spectroscopy, thermogravimetric analysis, and field emission scanning electron microscopy were employed to determine the crystal structure, surface functional groups, thermal stability, and surface morphology of the nanoparticles. The particle size was found to be directly proportional to the calcination temperature.

Treatment of the contaminated aqueous solutions to improve their quality is indispensible for their reuse resulting in an emergent challenge to develop facile, nontoxic and less energy consuming techniques to purify water. Present study is therefore aimed at the synthesis of an adsorbent using agricultural waste i.e. coconut shell. The charcoal obtained from coconut shell was modified by acid activation and manganese doping following a simple chemical route. The products were characterized by scanning electron microscopy, energy dispersive X-ray analysis and infrared spectroscopy. Preliminary studies were carried out to compare the adsorption potential of acid modified coconut shell charcoal (AMCSC) and manganese doped coconut shell charcoal (MDCSC) for the removal of chromium (VI) and iron (III) from aqueous solutions. Various physicochemical parameters such as adsorbent dosage, initial metal ions concentration and pH were studied. MDCSC was found to be a better adsorbent for metals as compared to AMCSC and removed chromium more efficiently than iron from synthetic solutions i.e. 56.10% at optimum conditions i.e. 0.6 g/L adsorbent dosage, 10 mg/L initial metal ions concentration and pH = 3. The effect of adsorbents on color and conductivity of the aqueous solutions was also noted; slight variation in color of all the aqueous solutions with a maximum of 91.67% removal was observed.

Background This study is aimed to synthesize nanosize zinc oxide by acid catalyzed sol–gel process using zinc nitrate hexahydrate as precursor, aqueous isopropanol as solvent and glycerin for making polyol system. The polyol mediated procedure was employed in combination with calcination induced synthesis of nanoparticles of numerous sizes obtained with the variation in calcination temperature from 500 to 900 ℃. The crystal structure of the prepared samples was characterized by X-ray diffraction analysis (XRD). Infrared spectroscopy (IR) was used to identify the surface hydroxyl groups. Thermal stability was confirmed by differential scanning calorimetry-thermogravimetric analysis (DSC-TGA) whereas field emission scanning electron microscopy (FESEM) was used to study the surface morphology of nanoparticles. Results Results revealed the formation of hexagonal wurtzite structure of irregular shaped nanoparticles having size ranging from 50–100 nm. However, the particles combined to form agglomerates of 200–400 nm with the rise in calcination temperature. Conclusions These results indicate that nanosize zinc oxide can be synthesized successfully by a simple process comprising of glycerin as a low-cost, non-toxic and eco-friendly polyol followed by calcination at ambient temperatures.

Background This study is aimed to synthesize zinc oxide nanoparticles by acid catalyzed sol-gel process using zinc nitrate hexahydrate as precursor, aqueous isopropanol as solvent and glycerin as stabilizing agent. The optimum conditions for preparing the sol were kept at pH 1 and 70 ºC temperature with constant stirring for two hours. The gel obtained after drying the sol was calcined at various temperatures i.e. 500 ºC, 700 ºC and 900 ºC. The crystal structure of the samples was characterized by X-ray diffraction analysis (XRD). Thermal stability was confirmed by differential scanning calorimetry-thermogravimetric analysis (DSC-TGA). Infrared spectroscopy (IR) was employed to identify the surface hydroxyl groups whereas field emission scanning electron microscopy (FESEM) was used to study the surface morphology of nanoparticles. Results Results revealed the formation of hexagonal wurtzite structure of nanoparticles of size below 100 nm having flake-like morphology with a substantial increase in size of flakes with the increasing calcination temperature. Conclusions These results indicate that zinc oxide nanoflakes can be synthesized successfully by a simple, feasible and environment friendly process.