Fast g-C3N4 sonocoated activated carbon for enhanced solar photocatalytic oxidation of organic pollutants through Adsorb & Shuttle process

To solve low mass transfer in photocatalytic technology for water treatment, the combination of photoactive nanoparticles with highly adsorptive materials has been regarded as a successful approach. The optimization of photoactive particle coating in terms of dispersion on the surface of adsorbing support is the main key to reach a maximum synergism for pollutants removal. This study discusses the coating of as-prepared biomass based activated carbon by g-C3N4 using three routes, namely ball milling (AC-CN@BM), physical stirring (AC-CN@Phy) and ultrasonic assisted coating (AC-CN@US). The coating mechanisms by different processes were discussed using different characterization techniques. Ball milling based coating provides good g-C3N4 dispersion on the surface of AC, however, a partial degradation of g-C3N4 structure and a lower surface area were confirmed by FTIR, XRD and BET analysis. Physically designed sample shows a significant agglomeration of particles on the surface of AC. However, ultrasonic coating provides excellent distribution of g-C3N4 and high surface of the composite. In terms of photoactivity, AC-CN@BM exhibits the lowest adsorption and photocatalytic activity under solar light for the removal of ciprofloxacin. AC-CN@Phy showed medium performance, but less physical stability of g-C3N4 particles on AC, leading to their partial release. AC-CN@US showed the highest efficiency and stability after using; suggesting the good combination between g-C3N4 and AC, which in turn maximizes the removal of ciprofloxacin via Adsorb & shuttle process. The overall costs of composite, including the starting elements and the coating ultrasonic process are relatively low and green as compared to commonly reported routes.

Covalent Modification of Iron Phthalocyanine into Skeleton of Graphitic Carbon Nitride and Its Visible-Light-Driven Photocatalytic Reduction of Nitroaromatic Compounds

It is of great urgency to eliminate nitroaromatic compounds (NACs) in wastewater due to their high residue and toxicity. Photocatalysis reduction is considered to be an efficient technology for converting NACs to their corresponding aromatic amines. In this work, a visible-light-driven hybrid photocatalyst was synthesized by covalently doping Fe phthalocyanine (FePc) into graphitic carbon nitride skeleton. Compared to the pristine gCN, the optimized gCN-FePc-1 photocatalyst showed enhanced absorption in visible light region, which promoted photogenerated charge transfer and separation. Using p-nitrophenol (p-NP) as the model pollutant, the CN-FePc-1 effectively reduced it to p-aminophenol (p-AP), with the photocatalytic reaction rate being 18 and 3 times higher, respectively, than those of the pristine gCN and the mechanically mixed photocatalyst of gCN/FePc. Moreover, excellent photocatalytic universality for other NACs, high stability, and good reusability also were confirmed. Based on the band structure of the gCN-FePc-1 photocatalyst, a plausible mechanism was proposed to illustrate the photocatalytic reduction process of p-NP to p-AP. This study demonstrates that the covalent modification of FePc into gCN skeleton is an effective strategy to modulate the electronic structure, and the hybrid gCN-FePc is a potential visible-light-driven photocatalyst that potentially can be used for eliminating NAC contamination in wastewater.

Nanostructural catalyst: metallophthalocyanine and carbon nano-onion with enhanced visible-light photocatalytic activity towards organic pollutants

The photocatalytic studies revealed that metallophthalocyanine–carbon nano-onion nanostructural materials simultaneously exhibited a high absorption capacity and an excellent visible-light-driven photocatalytic activity towards rhodamine B.