Heterostructures of silver and zinc based layered double hydroxides for pollutant removal under simulated solar light

Nitrophenols are among the most hazardous refractory pollutants showing high stability and solubility in water. This work presents heterostructures of nanoparticles of silver/zinc based layered double hydroxides as efficient photocatalysts for degrading 4nitrophenol (4-NPh), from aqueous solutions under irradiation with solar light. ZnAl-layered double hydroxides (ZnAl-LDHs) with Zn/Al = 2:1 and Zn/Al = 3:1 ratios were synthesized, characterized by XRD, FTIR, SEM and TEM and further used as precursors to form mixed oxides after calcination at 550 C. Based on the capability of the calcined LDHs to reconstruct their layered structure in aqueous media, AgNO3 solutions were used to obtain Ag nanoparticles directly on ZnAl-LDHs matrices. The calculated value of the band gap of Ag/ZnAl-LDHs was ~ 3.1 eV, revealing that these materials might successfully act as photocatalysts under solar light irradiation. The photocatalytic tests performed on the decomposition of 4-NPh aqueous solutions indicate that on Ag/ZnAl-LDH (3:1)87% of 4-NPh was degraded after 6 h under irradiation with solar light.