Sustainable ZnO synthesis from skim latex serum wastewater for efficient dye degradation and enhanced rubber vulcanization

This study presents a sustainable approach for synthesizing zinc oxide (ZnO) using skim latex serum, a wastewater from concentrated latex manufacturing. Utilizing biomolecules in the serum as capping and stabilizing agents, ZnO yield increases 25-fold through a precipitation method. The resulting ZnO features a unique flower-like morphology, observed by field-emission scanning electron microscopy, with particle size controllable by adjusting serum content. Higher serum levels result in smaller and more uniform ZnO structures, as the serum enhances nucleation while simultaneously impeding particle growth. For the first time, a reaction mechanism is proposed for ZnO synthesis from skim latex serum wastewater, identifying the plausible pathways through a serum-based precipitation method, and elucidating the role of serum constituents and NaOH in morphology control. This flower-like ZnO shows effective photocatalytic activity, degrading dyes through the pseudo-zero-order kinetic process, and demonstrates recyclability. Furthermore, it functions as an activator in rubber vulcanization. Rubber vulcanizates prepared with the synthesized ZnO show curing and mechanical properties comparable to those prepared with commercial ZnO. Fourier-transform infrared spectroscopy confirms the formation of zinc-stearate with monodentate coordination upon reaction with stearic acid at 144 °C, consistent with the behavior of commercial ZnO. This dual functionality as both a photocatalyst and a vulcanization activator underscores the potential of flower-like ZnO as an alternative for conventional ZnO. The process contributes to Sustainable Development Goal 6 by valorizing industrial wastewater, and exemplifying a circular economy. Overall, this work integrates environmental stewardship with high-performance applications in environmental remediation and rubber technology.