Pd@Na-CMC/g-C3N4: A nanostructured catalyst system based on sodium carboxymethyl cellulose/graphitic carbon nitride hydrogel beads and its performance in the treatment of organic and inorganic pollutants in water

The chemical reduction of organic or inorganic water contaminants is very important for both human health and pollution control. However, challenges still persist in preparing catalysts for chemical reduction, and there is a need for the development of inexpensive, easily synthesized, and effective catalyst systems. In this study, we have synthesized a new palladium nanocatalyst supported on the composite hydrogel beads composed of sodium carboxymethyl cellulose (Na-CMC) and graphitic carbon nitride (g-C3N4). The Pd@Na-CMC/g-C3N4 composite was fully characterized using FE-SEM, XRD, BET, EDS, TEM, and EDS mapping analysis, confirming its successful preparation at the nano-scale. Pd@Na-CMC/g-C3N4 was utilized to reduce various nitroaromatics such as 4-nitrophenol (4-NP), 2-nitrophenol (2-NA), 4-nitroaniline (4-NA), 4-nitro-o-phenylenediamine (4-NPDA), and organic dyes including methylene blue (MB), methyl orange (MO), Rhodamine B (RhB), as well as potassium hexacyanoferrate(III) (K3[Fe(CN)6]), which is the inorganic contaminant. While Pd@Na-CMC/g-C3N4 completely reduced nitroaromatics within 65-120 sat 1 x 10-4 M concentration, organic dyes within 0-60 sat 1 x 10-5 M concentration, and K3[Fe(CN)6] within 90 s at 0.002 M concentration in water at room temperature. Rate constant values (kapp) of 4-NP, 2-NA, 4-NA, 4-NPDA, MO, RhB, and K3[Fe(CN)6] were calculated to be 0.0085 s-1, 0.012 s-1, 0.016 s-1, 0.01 s-1, 0.013 s-1, 0.021 s-1, and 0.015 s-1, respectively. Additionally, the Pd@NaCMC/g-C3N4 displayed high stability and even after four consecutive runs, it was able to reduce 4-NP and MO without any significant loss in its performance.