Development of PSA@PS-TiO2 nanocomposite photocatalyst: structure, mechanism, and application using response surface designs and molecular modeling.

Using periwinkle shell ash (PSA) and polystyrene (PS), a new-fangled PSA@PS-TiO2 photocatalyst was fabricated. The morphological images of all the samples studied using a high-resolution transmission electron microscope (HR-TEM) showed a size distribution of 50-200 nm for all samples. The SEM-EDX showed that the membrane substrate of PS was well dispersed, confirming the presence of anatase/rutile phases of TiO2, and Ti and O2 were the major composites. Given the very rough surface morphology (atomic force microscopy (AFM)) due to PSA, the main crystal phases (XRD) of TiO2 (rutile and anatase), low bandgap (UVDRS), and beneficial functional groups (FTIR-ATR), the 2.5 wt.% of PSA@PS-TiO2 exhibited better photocatalytic efficiency for methyl orange degradation. The photocatalyst, pH, and initial concentration were investigated and the PSA@PS-TiO2 was reused for five cycles with the same efficiency. Regression modeling predicted 98% efficiency and computational modeling showed a nucleophilic initial attack initiated by a nitro group. Therefore, PSA@PS-TiO2 nanocomposite is an industrially promising photocatalyst for treating azo dyes, particularly, methyl orange from an aqueous solution.

Particulate matter exposure and non-cancerous inhalation health risk assessment of major dumpsites of Oerri metropolis, Nigeria.

Numerous particulates are released from the dumpsites in Owerri metropolis and later dispersed to other areas in the environment where they cause adverse health challenges to the inhabitants. To analyze the PM concentration, field measurements were carried out at seven major dumpsites in the Owerri Metropolis. Estimates of the possible health risks as the result of exposure to airborne particulate matter (PM2.5, PM10, etc.) were performed using the US Environmental Protection Agency human health risk assessment framework. A scenario assessment approach in which normal exposure and worst-case scenario were adopted for acute and chronic exposure periods for infants, children, and adults. The concentrations of PM 2.5 which ranged from 122.30-501.76 µg/m3 at the dumpsites exceeded the WHO 24hr annual mean maximum exposure limit. The Nigerian National Ambient Air Quality Standard allowable limit for PM10 was exceeded by most of the dumpsites. Hazard quotient > 1 was exceeded for PM 2.5 by nearly all dumpsites and is likely to cause health challenges. The results showed that under monthly conditions, both PM2.5 and PM10 concentration levels at the dumpsites have the potential to cause adverse health effects when for infants, children, and adults on acute or chronic bases. Actions should be taken to regulate such PM exposure and to raise public awareness for the inhabitants of the affected areas. In conclusion, regular monitoring is therefore needed to decrease the ambient particulate matter (PM) concentrations in the study area.