Construction of green, sustainable, and versatile hybrid catalyst using Pd-loaded carboxymethyl cellulose-activated carbon beads for efficient reduction of environmental pollutants

Water/wastewater treatment is crucial for protecting the ecosystem and ensuring the adequate use of freshwater resources due to the depletion of water resources worldwide. Freshwater resources is at risk due to the presence of toxic pollutants such as nitroaromatics and organic dyes, which contribute to water pollution. Thus, the removal of these pollutants is of great importance to human health. In this study, we developed an innovative hybrid catalyst by decorating palladium nanoparticles onto carboxymethyl cellulose-activated carbon hydrogel beads (Pd@NaCMC/AC), which serve as the support material (NaCMC/AC), and characterized its structure using FTIR, XRD, EDS, FE-SEM, and TEM analyses. Then, its performance was assessed against reduction of nitro-aromatics (4-nitro-o-phenylenediamine (4-PDA), 2-nitroaniline (2-NA), 4-nitrophenol (4-NP), and 4-nitroaniline (4-NA)), organic dyes (methyl orange (MO), methylene blue (MB), and rhodamine B (RhB)), as well as mixed pollutants. Pd@NaCMC/AC efficiently reduced 4-PDA, 2-NA, 4-NP, and 4-NA in 52, 40, 90, and 48 s, respectively, with corresponding rate constants of 0.018, 0.032, 0.014, and 0.030 s-1. Additionally, MO was reduced with rate constant of in 30 s with 0.024 s-1 and RhB in-80 s with 0.025 s-1, while MB was removed instantly. Pd@NaCMC/AC also exhibited good performance against the mixed 4-NP+MB pollutant, successfully reducing both contaminants. Moreover, for the 2-NA reduction catalyzed by Pd@NaCMC/AC, the activation energy was determined to be 20.095 kj/mol. The Pd@NaCMC/AC demonstrated good recyclability, maintaining its performance over six cycles.