The optical band gap energy of ZnO nanorods was estimated by different methods found in literature. These nanorods were deposited onto TiO 2 covered borosilicate glass substrates by aerosol assisted chemical vapor deposition. Characterization techniques were employed to reveal the crystalline structure, surface morphology and optical properties of the sample. The analysis proved that hexagonal cross-section ZnO nanorods in the wurtzite phase were grown onto a TiO 2 buffer thin film of anatase. Variations in the components of transmittance and reflectance were associated with the development of a rough surface. Such fluctuations were correlated with the equations employed to estimate the optical band gap. The different methods indicated band gap values of 3.17 to 3.24 eV. The energy band gap of 3.24 eV agrees to that reported in the literature for ZnO nanorods. Fluorescence spectroscopy confirmed the accuracy of the mathematical predictions since an emission at 380 nm (3.26 eV) was seen.

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Adsorption stand out among other standard techniques used for water treatment because of its remarkable simplicity, easy operation, and high removal capability. Expanded graphite has been selected as a promising agent for oil spill adsorption, but its production involves the generation of corrosive remnants and massive amounts of contaminated washing waters. Although the advantageous use of the H2O2–H2SO4 mixture was described in 1978, reported works using this method are scarce. This work deals with the urgent necessity for the development of alternative chemical routes decreasing their environmental impact (based on green chemistry concepts), presenting a process for expanded graphite production using only two intercalation chemicals, reducing the consumption of sulfuric acid to only 10% and avoiding the use of strong oxidant salts (both environmentally detrimental). Three process parameters were evaluated: milling effect, peroxide concentration, and microwave expansion. Some remarkable results were obtained following this route: high specific volumes elevated oil adsorption rate exhibiting a high oil–water selectivity and rapid adsorption. Furthermore, the recycling capability was checked using up to six adsorption cycles. Results showed that milling time reduces the specimen’s expansion rate and oil adsorption capacity due to poor intercalant insertion and generation of small particle sizes.

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