Enhanced solar water disinfection using ZnO supported photocatalysts.

Nano-structured ZnO photocatalysts on cellulose and polyester supports were developed for enhancing solar water disinfection (SODIS). The photocatalysts were fabricated by a two-step hydrothermal method, in which ZnO nanoparticles were synthesized and deposited on a cellulose or polyester support as a seed layer, followed by the growth of one-dimensional ZnO nanorods on the seed layer in a liquid bath containing zinc nitrate and hexamethylenetetramine as sources of precursors. The morphologies and phase compositions of the synthesized ZnO nanorods from different growth conditions were investigated with field emission scanning electron microscope and X-ray diffraction (XRD), respectively. The crystallinity size of the ZnO nanorods was in the range of 17-30 nm and increased with the precursor concentration. The XRD patterns also revealed that higher growth solution concentrations led to higher intensity of XRD peaks, indicating higher crystallinity. Additionally, to test for SODIS enhancement, experiments using 200-mL transparent polyethylene bags as SODIS reactors, with ZnO photocatalysts inside, and water samples containing 106 CFU of Escherichia Coli were conducted in a laboratory UVA setup. The photocatalyst with a polyester support resulted in a 15% higher disinfection efficiency than that of the one with a cellulose support. Moreover, a field test of enhanced SODIS was conducted in actual sunlight, using specially designed SODIS reactors containing ZnO photocatalysts with a polyester support. Nearly total disinfection (97-98% efficiency) was achieved within the first 15 min of every test. The treated water was also tested for zinc contents, which could be released from the photocatalysts, by ICP-OES. The results were lower than 2 mg/L.

Safety and durability of low-density polyethylene bags in solar water disinfection applications.

Solar water disinfection (SODIS) is a simple point-of-use process that uses sunlight to disinfect water for drinking. Polyethylene terephthalate (PET) bottles are typically used as water containers for SODIS, but a new SODIS container design has recently been developed with low-density polyethylene (LDPE) bags and can overcome the drawbacks of PET bottles. Two nesting layers of LDPE bags are used in the new design: the inner layer containing the water to be disinfected and the outer one creating air insulation to minimize heat loss from the water to the surroundings. This work investigated the degradation of LDPE bags used in the new design in actual SODIS conditions over a period of 12 weeks. The degradation of the LDPE bags was investigated weekly using a scanning electron microscope, Fourier transform infrared spectroscopy, ultraviolet-visible spectrophotometer, and tensile strength tester. It was found that the LDPE bags gradually degraded under the sunlight due to photo-oxidation reactions, especially in the outer bags, which were directly exposed to the sun and surroundings, leading to the reduction of light transmittance (by 11% at 300 nm) and tensile strength (by 33%). In addition, possible leaching of organic compounds into the water contained in the inner bags was examined using gas chromatography-mass spectrometer. 2,4-Di-tert-butylphenol was found in some SODIS water samples as well as the as-received water samples, in the concentration range of 1-4 µg/L, which passes the Environmental Protection Agency Drinking Water Guidance on Disinfection By-Products.

A 5,7-dimethoxyflavone/hydroxypropyl-ß-cyclodextrin inclusion complex with anti-butyrylcholinesterase activity.

This study aimed to improve the water solubility of 5,7-dimethoxyflavone (5,7-DMF) isolated from Kaempferia parviflora by complexation with 2-hydroxypropyl-ß-cyclodextrin (HPß-CD). The phase solubility profile of 5,7-DMF in the presence of HPß-CD was classified as AL-type and indicated a 1:1 mole ratio. Differential scanning colorimetry, X-ray diffraction, NMR and SEM analyses supported the formation of a 5,7-DMF/HPß-CD inclusion complex involving the A ring of 5,7-DMF inside the HPß-CD cavity. This is the first example of CD inclusion with the A ring of non-hydroxyl flavones. The stability and binding constants of the complexes were determined using the phase solubility and UV-vis absorption spectroscopy, respectively. The water solubility of 5,7-DMF was increased 361.8-fold by complexation with HPß-CD and overcame the precipitation problem observed in aqueous buffers, such as during in vitro anti-butyrylcholinesterase activity assays. The 1:1 mole ratio of the 5,7-DMF/HPß-CD complex showed a 2.7-fold higher butyrylcholinesterase inhibitory activity (in terms of the IC50 value) compared to the non-complexed compound.