Enhancing Ag2MoO4 catalytic activity: An investigation on synthesis, characterization, and application in catalytic ozonation reactions

Abstract

Silver molybdate (Ag2MoO4) has promising results in photocatalysis and Fenton-like reactions, but its use in catalytic ozonation and the role of its different crystalline phases remain poorly understood. The understudied metastable α-phase remains a challenge in terms of production, characterization, and catalytic properties, due to its tendency to convert to the stable β-phase. This study investigates the optimized synthesis of the α-phase using a face-centered central composite experimental design by varying PVP concentration and pH. Results revealed that significant effects of synthesis conditions on α-phase formation and optical-textural properties. Increasing pH negatively affects textural properties and crystalline phases distribution, while the interaction between PVP concentration and pH proportionally improves optical properties. The statistical analyses predicted a maximum α-phase formation of 71 % (PVP: 2.9 mmol L−1 and pH: 4.9) externally from the parameters range applied. Silver molybdate produced under pH > 4.5 showed catalytic activity to remove trimethoprim in aqueous suspensions. Moreover, particle morphology strongly influenced on the catalytic activity, with well-structured particles achieving up to 76 % removal of trimethoprim. Higher crystallinity had a greater impact on catalysts activity. Thus, strict control during α-Ag2MoO4 synthesis is crucial, emphasizing the dependence of catalytic activity on synthesis conditions.