Synthesis and Photocatalytic Activity of Ni–Fe Layered Double Hydroxide Modified Sulphur Doped Graphitic Carbon Nitride (SGCN/Ni–Fe LDH) Photocatalyst for 2,4-Dinitrophenol Degradation

In recent years, semiconductor photocatalytic process has shown a great potential as a low-cost, environmental friendly and sustainable treatment technology to align with the "zero" waste scheme in the water/wastewater industry. The ability of this advanced oxidation technology has been widely demonstrated to remove persistent organic compounds and microorganisms in water. At present, the main technical barriers that impede its commercialisation remained on the post-recovery of the catalyst particles after water treatment. This paper reviews the recent R&D progresses of engineered-photocatalysts, photoreactor systems, and the process optimizations and modellings of the photooxidation processes for water treatment. A number of potential and commercial photocatalytic reactor configurations are discussed, in particular the photocatalytic membrane reactors. The effects of key photoreactor operation parameters and water quality on the photo-process performances in terms of the mineralization and disinfection are assessed. For the first time, we describe how to utilize a multi-variables optimization approach to determine the optimum operation parameters so as to enhance process performance and photooxidation efficiency. Both photomineralization and photo-disinfection kinetics and their modellings associated with the photocatalytic water treatment process are detailed. A brief discussion on the life cycle assessment for retrofitting the photocatalytic technology as an alternative waste treatment process is presented. This paper will deliver a scientific and technical overview and useful information to scientists and engineers who work in this field.

Dispersion of exfoliated CN over the surface of exfoliated LDH composite materials, and its photocatalytic water splitting under visible-light irradiation. Exploiting the advantage of a layered architecture, layered graphitic carbon nitride (CN) and NiFe-layered double hydroxide (LDH) have been coupled in the present investigation to design a series of highly efficient novel CNLDH composites for visible light-induced photocatalytic H 2 and O 2 evolution. The syntheses of these composites were carried out using a facile weight impregnation method while varying the wt% of CN on LDH. The structural, optical, and morphological properties of these composites were characterized by various physicochemical techniques. The results indicate a tuned-in band gap energy within the range of pure LDH to pure CN. In addition, the remarkable quenching of the PL signal and prolonged photogenerated charge lifetime confirmed by TRPL spectra demonstrates the excellent photocatalytic activity of these composites. The activity could be ascribed to the dispersion of exfoliated CN over the brucite layer of LDH, in which strong energy transfer takes place in terms of charge carriers. The visible light-induced photocatalytic H 2 and O 2 evolution study resulted in an enhancement in the activity of the CNLDH10 composite with a H 2 evolution rate of 1488 μmol 2 h −1 and O 2 evolution rate of 886 μmol 2 h −1 . The high photocatalytic activities of these composites may be due to good dispersion of exfoliated CN over the brucite layer of edge-shared MO 6 octahedra, higher life time of charge carriers, low PL intensity, appropriate band gap energy and enhancement in photocurrent density.