Microcrystalline Cellulose From Kapok Fiber (Ceiba pentandra) as Carbon Interstitial Dopant in ZnO: Physicochemical Characteristics and Photocatalytic Activity

The present work describes the facile fabrication of microcrystalline cellulose (MCC) from Kapok fiber (Ceiba pentandra) as a carbon interstitial dopant in a zinc oxide (ZnO) photocatalyst, with varying ratios. The successful integration of carbon-derived MCC into ZnO was characterized by several characterization techniques. The photocatalytic evaluations of the composites were carried out against paracetamol (PARA) in an aqueous medium using a relatively low UV-C light intensity (8 W). Under normal conditions, the carbon-doped ZnO (1:1) composite photocatalyst achieved a significant degradation percentage of ∼86%, following pseudo-first-order kinetics with a rate constant of 1.29 × 10⁻³ min⁻¹, which was 3.5 times higher than that of pristine ZnO. The improved efficiency was attributed to the outstanding separation of photoexcited charge carriers, ease of electron migration, and the presence of carbon dopant as electron mediators in the composite photocatalyst, as evidenced by band gap, photoluminescence, and x-ray photoelectron spectroscopy analyses. The main reactive species were identified to be hydroxyl radicals (•OH) and holes (h_vb⁺). The photocatalytic performance was sustained over 75% efficiency for four consecutive cycles without a regeneration step, suggesting long-term stability.