Porous cellulose microfibrils functionalized with magnetite nanostructures: Morphology controlled efficiency in...

As the demand for effective methods to remove organic dyes from water bodies continues to rise, addressing the dual challenges of biomass valorization and sustainable catalysis has become critical for the future of wastewater treatment. Despite notable advancements, the influence of the different morphologies of sono-Fenton-driven Fe₃O₄ nanoparticles (NPs) and nanorods (NRs) supported on porous cellulose microfibrils (PCMs) remain insufficiently explored. In this pioneering study, we present a novel approach to synthesizing PCMs derived from coffee pulp, a renewable biomass, thereby offering an innovative pathway to transform agricultural waste into high-value, sustainable materials. Through alkali treatment and bleaching, non-cellulosic impurities were effectively removed, yielding hydrophilic PCMs with a highly intricate macro- and microporous structure. To enhance their catalytic efficiency, Fe₃O₄NPs and NRs were successfully integrated into the PCM framework through co-precipitation and hydrothermal techniques. This process resulted in a uniform distribution of Fe₃O₄NPs (10-30 nm) and Fe₃O₄NRs (∼150 nm length and ∼ 53 nm width), significantly increasing the surface roughness and porosity of the PCMs. When tested for the degradation of Acid Blue 25 (AB 25) dye in aqueous solution, the sono-Fenton catalytic performance of PCMs@Fe₃O₄NPs and PCMs@Fe₃O₄NRs demonstrated exceptional efficiency. The combination of ultrasound, hydrogen peroxide, and PCMs@Fe₃O₄NRs achieved complete dye degradation (100 %) in 12 min, surpassing the performance of PCMs@Fe₃O₄NPs, which achieved 97 % ± 0.4 % degradation in 15 min. Kinetic studies confirmed that the degradation followed pseudo-first-order (PFO) reaction kinetics, while radical scavenging experiments identified hydroxyl radicals (^•OH) as the dominant reactive species. Furthermore, the PCMs@Fe₃O₄NRs catalyst demonstrated excellent reusability, maintaining a degradation efficiency above 98 % ± 0.3 % after five consecutive cycles, underscoring its potential as a sustainable and high-performance material for advanced wastewater treatment applications.