Life cycle assessment of waste printed wiring board-derived Ag photocatalyst for sustainable fermentable sugar production.

Abstract

An exploratory work involving waste printed wiring board (WPWB)-derived inexpensive silver oxide (Ag2O)-grafted silica-alumina composite photocatalyst (SAA) using quartz halogen and UVA irradiations (QHUV) (wavelength: 315 nm-1000 nm) has been revealed. The efficacy of the novel SAA photocatalyst was assessed in the synthesis of fermentable sugar (FS) by photo-hydrolysis of pure crystalline cellulose (PCC) in the QHUV-assisted batch reactor (QHUVBR), and the process parameters (5% AgNO3 doping, 7.5% catalyst concentration, 20 min PH time, and 80 °C PH temperature) were optimized using Taguchi orthogonal array design. The BET analysis of the optimal SAA catalyst possessed high surface area (27.24 m2/g), high pore volume, and pore diameter (0.042 cc/g and 13.1684 nm), respectively, whereas the XRD indicated the presence of significant crystalline phases of Ag2O. EDS mapping displayed the uniform distribution of silver active sites on silica-alumina support of the optimal SAA photocatalyst. The optimized parametric conditions in QHUVBR resulted in a maximum FS yield of 77.53% which was significantly higher compared to that achieved (34.52%) in a conventionally heated batch reactor (CHBR). Besides, the energy consumption was 75% more in CHBR (600 W) in comparison with QHUVBR (150 W), making the process energy-efficient and cost-effective. The environmental sustainability could be ascertained from the life cycle assessment (LCA) study in terms of low climate change, ionizing radiation, metal depletion, human toxicity, and other potential indicator values.