A solar evaporator fabricated from corncob waste for the desalination of seawater and removal of oil/herbicides from contaminated water.

Corncob (CC) based solar evaporators were employed to desalinize seawater brought from the Vallarta coast in Mexico. The pure CC produced an evaporation-rate and evaporation-efficiency of 0.63 kg m-2 h-1 and 38.4%, respectively, under natural solar light. Later, the CC was coated with carbonized CC (CCCE evaporator) or was coated with graphene (CCGE evaporator). Those evaporators were used for the desalination of seawater and obtained higher evaporation rates of 1.59-1.67 kg m-2 h-1, and higher evaporation efficiencies of 92-94% (under natural solar light). The desalination experiments were repeated under artificial solar light and the evaporation-rates/evaporation-efficiencies slightly decreased to 1.43-1.52 kg m-2 h-1/88-92%. The surface analysis of the evaporators by FTIR, XPS and Raman revealed that the CCGE evaporator had on its surface a lower content of defects and a higher amount of OH groups than the CCCE evaporator. Therefore, the CCGE evaporator had higher evaporation-rates/evaporation-efficiencies in comparison with the CCCE evaporator. Furthermore, we purified water contaminated with three different herbicides (fomesafen, 2-6 dichlorobenzamide and 4-chlorophenol at 30 ppm) by evaporation and using natural solar light. Interestingly, the CCCE and CCGE evaporators also removed the herbicides by physical adsorption with efficiencies of 12-22.5%. Moreover, the CCGE evaporator removed vegetable oil from contaminated water by adsorption and its maximum adsorption capacity was 1.72 g/g. Overall, our results demonstrated that the corncob-based evaporators studied here are a low-cost alternative to obtain clean water under natural solar light and this one was more effective for the desalination of seawater than the artificial sunlight (Xe lamp).

Electroless controllable growth of ZnO films and their morphology-dependent antimicrobial properties.

An electroless deposition process was used to synthesize with a controlled morphology, polycrystalline ZnO on glass substrates as antimicrobial coatings. The influence of deposition temperature (Tdep) on the physicochemical and antimicrobial properties of the ZnO films was analyzed. The results indicated that a change in deposition temperature greatly affected the morphology and the degree of crystallinity of the films. Scanning electron microscope images show that the film surface is porous at a deposition temperature of 40 and 50 °C, whereas hexagonal-plate shaped morphology predominated at 60 °C and finally at 70 and 80 °C the films consisted of rod-like particles. The films showed good transparency in the visible region. All ZnO films presented notable antimicrobial activity against the gram-negative bacteria Escherichia coli (E. coli) and the gram-positive Staphylococcus aureus (S. aureus). It was found that the antimicrobial efficiency is strongly dependent on morphology and structural properties. The best antimicrobial performance was recorded for the films consisting of rod-like morphology with a high degree of crystallinity. The procedure used in this investigation is strongly recommended for the development of functional surfaces.