En-Chin Su

Sustainable hydrogen production from electroplating wastewater over a solar light responsive photocatalyst

An environmentally friendly and sustainable photocatalytic hydrogen production system was successfully developed using ethylenediaminetetraacetic acid (EDTA) found in the wastewater from electroplating plants as the photo-excited hole scavenger and a solar light responsive multi-junction material as the photocatalyst. Additionally, a facile method of metal removal was established to increase the photocatalytic hydrogen production efficiency. The influences of the metal concentration, pH of the electroplating wastewater, and the photocatalyst concentration on the efficacy of hydrogen production were studied in detail. The results show that before metal removal, the unchelated metal ions and/or the metal–EDTA chelates block the active sites of the photocatalyst, resulting in suppressed adsorptions of H+ ions and/or H2O, which results in negligible hydrogen production efficiency. Through the metal removal process developed in this study, most of the metals could be removed and most of the EDTA could be retained. The removal efficiencies of copper, nickel, and zinc ions were all higher than 90%, facilitating better reaction between the liberated EDTA molecules and the photo-excited holes, improved charge separation, and enhanced hydrogen production efficiency. The system showed economically optimal hydrogen production when the reaction pH was maintained at pH = 6 and the photocatalyst concentration was maintained at 2 g L−1 under simulated sunlight irradiation.

Photocatalytic conversion of ethylenediaminetetraacetic acid dissolved in real electroplating wastewater to hydrogen in a solar light-responsive system

A sustainable and multifunctional photocatalysis-based technology has been established herein for simultaneous hydrogen generation and oxidation of ethylenediaminetetraacetic acid (EDTA) in real electroplating wastewater. When the photocatalyst concentration was 4 g/L and electroplating wastewater pH was 6, optimal adsorptions of EDTA2-, H+, and H2O were observed, while hydrogen generation efficiency reached 305 µmol/(h g). Owing to EDTA oxidation and occupation of the active sites of the photocatalyst by Ni ions or Ni-EDTA chelates, the charge separation and adsorptions of H+ and H2O decreased, reducing hydrogen generation efficiency with time. The lower EDTA and Ni concentrations in treated wastewater showed that photocatalytic conversion of EDTA in real electroplating wastewater to enhance hydrogen generation efficiency can be a practical alternative energy production technology. This study provided a novel idea to enhance the value of electroplating wastewater, to build a hydrogen generation route with no consumption of a valuable resource, and to reduce EDTA and Ni concentrations in electroplating wastewater.

Tailored Pt/TiO2 Photocatalyst with Controllable Phase Prepared via a Modified Sol–Gel Process for Dye Degradation

Pt/TiO2 photocatalysts with controllable phase were successfully prepared by controlling the hydrolysis pH values during the sol-gel process followed by Pt photodeposition. The effect of different phases of TiO2 coated with Pt on the catalytic properties and the photocatalytic activities were also investigated. The characterization results of the synthesis of TiO2 under neutral/alkaline and acidic conditions during the hydrolysis step revealed the facile formation of the anatase phase and the brookite/rutile phase, respectively. Pt/TiO2 photocatalysts prepared at hydrolysis pH values of 2, 7, and 10 had different TiO2 phase compositions, but the main crystalline sizes of the photocatalysts were all close to 6 nm. The Pt/TiO2 particles prepared at various hydrolysis pH values were all spheroidal. The PL results indicated that the anatase/rutile junction of a Pt/TiO2 sample had a lower recombination rate than did the anatase phase of Pt/TiO2 owing to the longer recombination pathway. However, the anatase phase of Pt/TiO2 exhibited better degradation ability than the anatase/rutile junction of Pt/TiO2, and the degradation rate decreased with a decrease in the anatase composition of TiO2, indicating that anatase composition in the Pt/TiO2 system played an important role of enhancing the photocatalytic degradation of Acid Red 1 dye.