With the tremendous development of the economy and industry, the pollution of water is becoming more serious due to the excessive chemical wastes that need to remove thru reduction or oxidation reactions. Simultaneous removal of dual pollutants via photocatalytic redox reaction has been tremendously explored in the last five years due to effective decontamination of pollutants compared to a single pollutants system. In a photocatalysis mechanism, the holes in the valence band can remarkably promote the oxidation of a pollutant. At the same time, photoexcited electrons are also consumed for the reduction reaction. The synergistic between the reduction and oxidation inhibits the recombination of electron-hole pairs extending their lifetime. In this review, the binary pollutants that selectively removed via photocatalysis reduction or oxidation are classified according to heavy metal-organic pollutant (HM/OP), heavy metal-heavy metal (HM/HM) and organic-organic pollutants (OP/OP). The intrinsic between the pollutants was explained in three different mechanisms including inhibition of electron-hole recombination, ligand to metal charge transfer and electrostatic attraction. Several strategies for the enhancement of this treatment method which are designation of catalysts, pH of mixed pollutants and addition of additive were discussed. This review offers a recent perspective on the development of photocatalysis system for industrial applications. 

A review on synergistic coexisting of pollutants for efficient photocatalytic reaction in wastewater remediation.

Background The accumulation of mercury (II) ions (Hg2+) in wastewater causes critical impacts on human health and the whole environment. Methods This study report an efficient synthesis of CuCo2O4/g-C3N4 p-n heterojunction by templated growth via triblock copolymer F-127 and mesoporous silica MCM-41 for enhanced photoreduction of Hg2+. Significant Findings The 22.6 nm CuCo2O4 nanoparticles were anchored on g-C3N4 at minor content (0.5−2.0 wt. %) as observed by TEM analysis. The formed heterojunctions exhibited mesoporous surface textures with high specific surface areas. In addition, the visible-light harvesting of g-C3N4 was improved by adding CuCo2O4 due to the reduction of the bandgap energy from 2.77 to 2.17 eV. The complete visible-light photocatalytic reduction of Hg2+ utilizing 1.5 wt.% CuCo2O4-modified g-C3N4 was realized with a tremendous rate of 286.5 µmol min−1 after dose tuning at 1.5 gL−1. The enhanced catalytic presentation of this innovative CuCo2O4/g-C3N4 is denoted to the significant separation of photoinduced carriers through the p-n heterojunction's interface. The bearable photocatalytic reduction of Hg2+ for five cycles was also established for the regenerated photocatalyst.

Templated synthesis of CuCo2O4-modified g-C3N4 heterojunctions for enhanced photoreduction of Hg2+ under visible light

The accumulation of mercury (II) ions (Hg2+) in wastewater causes critical impacts on human health and the whole environment. This study report an efficient synthesis of CuCo2O4/g-C3N4 p-n heterojunction by templated growth via triblock copolymer F-127 and mesoporous silica MCM-41 for enhanced photoreduction of Hg2+. The 22.6 nm CuCo2O4 nanoparticles were anchored on g-C3N4 at minor content (0.5−2.0 wt. %) as observed by TEM analysis. The formed heterojunctions exhibited mesoporous surface textures with high specific surface areas. In addition, the visible-light harvesting of g-C3N4 was improved by adding CuCo2O4 due to the reduction of the bandgap energy from 2.77 to 2.17 eV. The complete visible-light photocatalytic reduction of Hg2+ utilizing 1.5 wt.% CuCo2O4-modified g-C3N4 was realized with a tremendous rate of 286.5 µmol min−1 after dose tuning at 1.5 gL−1. The enhanced catalytic presentation of this innovative CuCo2O4/g-C3N4 is denoted to the significant separation of photoinduced carriers through the p-n heterojunction's interface. The bearable photocatalytic reduction of Hg2+ for five cycles was also established for the regenerated photocatalyst. 

One-step hydrothermal synthesis of BiVO4/TiO2/RGO composite with effective photocatalytic performance for the degradation of ciprofloxacin

Mg-doped TiO2 nanorods-SrTiO3 heterojunction composites for efficient visible-light photocatalytic degradation of basic yellow 28

In this work, the performance of photocatalytic Cr(VI) reduction and As(III) oxidation in single and co-existing systems was systematically evaluated. The results exhibited that by employing Ni/N-codoped SnO2/Fe2O3 nanocomposites, the simultaneous photocatalytic redox conversion of Cr(VI) and As(III) were remarkably accelerated under visible light irradiation. The highest efficiency of Cr(VI) reduction and As(III) oxidation was found to be 99 and 96% with recyclability of 96.1 and 93.7% after five cycles over 8Ni/N-codoped SnO2/Fe2O3 nanocomposite under 90 min irradiation in the co-existing system, respectively. These findings open a new path to design high-performance photocatalysts for the synergetic photocatalytic redox conversation and removal of Cr(VI) and As(III) under visible light irradiation.

Javad Didari

Papers

Ni-N codoped SnO2/Fe2O3 nanocomposite as advanced bifunctional photocatalyst for simultaneous photocatalytic redox conversion of Cr(VI) and As(III)