CdS quantum dots/nano-TiO2 incorporated wood as a long-term stable and easily separable photocatalytic adsorbent for efficient Cr(VI) removal

Abstract

To address chromium pollution in water resources, a novel photocatalytic adsorbent, CdS quantum dots/nano-TiO2 incorporated wood (QNIW), was synthesized for efficient removal of Cr(VI), which displayed both long-term stability and easy separability. We extensively analyzed QNIW using a range of analytical techniques to investigate its morphology, structure, optical characteristics, as well as adsorption and photocatalytic properties. The adsorption experiments revealed QNIW's remarkable capacity for Cr(VI) adsorption in the absence of light, reaching a maximum value of 482.1 mg/g calculated using the Langmuir model. This value was 8.4 times greater than that of natural wood. The outcomes of adsorption and photocatalytic experiments showcased QNIW's superior performance. Specifically, the photocatalytic reaction rate coefficient of QNIW was measured to be 0.0661 ± 0.0078 min−1 under specific conditions: UV light intensity of 500 mW/cm2, adsorbent concentration of 0.25 g/L, pH of 2, initial Cr(VI) concentration of 20 mg/L, and temperature of 20 ℃. Remarkably, this coefficient exceeded that of pure nano-TiO2 by an impressive factor of 6.2. Importantly, QNIW exhibited exceptional stability, preserving 92.2 % of its initial removal efficiency after twelve weeks storage and maintaining 83.4 % efficiency even after undergoing five consecutive adsorption–desorption cycles. Thus, this study offers valuable insights into the progress of photocatalytic adsorbents characterized by high efficiency, enduring stability, and facile separability from treated wastewater.