Prodigious catalytic activity towards reduction of 4-hydroxynitrobenzene sodium salt using one-pot synthesized ZnO-Pd nanobolts

4-Hydroxynitrobenzene sodium salt (4-HNBS) is primarily used to manufacture pesticides, p-aminophenol, paracetamol, and dye intermediates. However, it is released into aquatic systems, which can cause severe health issues in humans. Therefore, novel approaches for detoxifying excessive 4-HNBS must be devised using ultralow amounts of cost-effective catalysts with high reduction efficiencies. To that end, an innovative one-pot, sustainable, and cost-effective method was developed in this study to synthesize ZnO–Pd nanobolt catalysts. The nanobolts were characterized using UV–vis spectroscopy, dynamic light scattering analysis, X-ray diffractometry, field-emission scanning electron microscopy, transmission electron microscopy (TEM), and energy-dispersive X-ray spectroscopy (EDS). TEM images indicated that the nanobolts were 13.8–66.6-nm-thick and that they had a 44.5-nm-diameter central hole. The EDS results suggested that the weight percentages of Zn, O, and Pd were 37.12 %, 23.63 %, and 39.24 %, respectively. This is the first report on the catalytic conversion of 4-HNBS into 4-hydroxyaniline sodium salt (4-HAS), whereas previous studies have mainly focused on converting small amounts of 4-hydroxynitrobenzene (4-HNB) into 4-HAS using high catalyst concentrations. Additionally, the reusability of the catalyst was studied to prevent the problems encountered in large-scale remediation. The synthesized nanobolts exhibited outstanding catalytic properties for converting 4-HNBS to 4-HAS. The rate constant k was estimated to be 0.068 min⁻¹ from the linear plot of ln(C/C₀) versus the conversion time. Notably, the nanobolts achieved 99 % reduction of 0.125 mM 4-HNBS after only 30 min of incubation.