UV-assisted synthesis of cadmium(II) diacetate dihydrate for the photocatalytic degradation of methylene blue: kinetics, pathway, and energy consumption

• Cadmium diacetate, as a liquid homogeneous photocatalyst was successfully prepared. • The prepared photocatalyst showed good properties and photocatalytic ability to degrade methylene blue dye (MB) in an aqueous medium. • By optimizing the studied variables using the prepared photocatalyst, almost 93% degradation in methylene blue dye (MB) was obtained in aqueous media. This study focuses on the UV-assisted synthesis and investigation of Cadmium(II) Diacetate dihydrate [Cd(CH 3 COO) 2 ·2H 2 O] (CdDD) it assesses its effectiveness as a liquid photocatalyst for degrading the methylene blue dye (MB). The synthesized compound was characterized using Dynamic Light Scattering (DLS), Ultraviolet–visible (UV–Vis) spectroscopy, Fourier-transform infrared spectroscopy (FT-IR), and Nuclear Magnetic Resonance (NMR) spectroscopy. Using DLS Analysis, the uniform particle size distribution of liquid CdDD was confirmed, and the mean particle size (z-average) was determined to be 101.66 nm with a Polydispersity Index (PdI) of 0.0014. Band gap energy ( E g ) of liquid CdDD is estimated to be 3.3 eV. FT-IR and NMR analyses confirm the successful formation of the desired catalyst structure. Liquid CdDD as a photocatalyst for MB degradation was evaluated and optimized. Degradation efficiency of 93 % was achieved under optimum conditions of [MB] o = 20 mg/L, [CdDD] = 10 ml/L, pH of 2, and [30 % H 2 O 2 ] = 2.5 ml. The kinetic model under optimum conditions, pseudo-first-order, was obtained, with a rate constant of 0.06232 min −1 . Also, the half-life values for concentrations of 5, 10, 20, and 40 ppm of MB dye were evaluated and obtained as 26.45, 23.9 min, 20.7 min, and 78.8 min, respectively. Furthermore, the electrical energy consumption ( E EC ) and the process evaluation criterion ( PE ) were recorded as 303.8 kWh/m 3 and 2.15 × 10 −2 , respectively, and the results were compared with related reported processes. The most significant outcome of this study is the introduction of CdDD as an effective liquid catalyst in the photodegradation of organic pollutants.