A functionalized waste tire rubber powders for mitigating leaching of heavy metal ions and enhancing photocatalytic properties of rubberized cement mortar

Abstract

In this study, waste tire rubber powder (R) was subjected to modification using tannic acid (TA) and ZnO to produce R-TA-ZnO composites, aiming to enhance the immobilization of heavy metal ions and improve the photocatalytic properties of rubberized cement-based materials. The characterization of R-TA-ZnO was conducted using a comprehensive range of analytical techniques, including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible-diffuse reflectance spectroscopy (UV–Vis-DRS), and other relevant methods. The findings of the study revealed that R-TA-ZnO exhibited notable hydrophilicity, surface activity, and photocatalytic properties, resulting in effective containment of the leaching of heavy metal ions. FTIR and XRD analyses confirmed the retardation of R and R-TA-ZnO. Nevertheless, the strength of the rubberized cement mortar with 5% R-TA-ZnO exceeds that of the rubberized cement mortar with 5% R (28 days) due to the interfacial bonding. The SEM and X-ray Computed Tomography (XCT) results of the rubberized cement mortar indicated that R-TA-ZnO exhibited strong binding to the cement paste, reducing both the number and size of pores. However, a high concentration of R-TA-ZnO led to the formation of larger pores, which did not contribute to the reduction of porosity. Furthermore, the rubberized mortar incorporating R-TA-ZnO displayed remarkable photocatalytic capabilities. The results of the 5-cycle degradation experiments and microscopic characterization confirmed its exceptional structural stability and reusability.