Solar-Assisted Paraquat Removal Using Coconut-Waste-Derived Biofiber/Carbon/TiO2 Composites

Although TiO2/carbon composites and cellulose-supported TiO2 materials have been investigated for pollutant removal, the integration of distinct fractions of coconut biomass into a single fiber-based hybrid architecture remains comparatively underexplored, particularly for solar-assisted paraquat (PQT) removal. In this study, coir fibers from coconut mesocarp were modified with trichlorovinylsilane (TClVS), impregnated with oxidized carbonaceous material (OxCM) obtained from carbonized coconut endocarp, and subsequently loaded with titanium-containing particles to produce CF/TClVS-OxCM-TiO2. The materials were characterized by ATR-FTIR, solid-state UV–Vis spectroscopy, thermogravimetric analysis, SEM, and EDS. OxCM exhibited oxygen-containing functionalities and lower thermal stability than the original carbon, while remaining distinguishable from graphite-derived graphene oxide. The final composite showed increased surface roughness, detectable Si and Ti signals, and a decrease in the C/O mass ratio from 2.23 ± 0.44 to 0.77 ± 0.33. Under dark conditions, apparent PQT removal reached 32.81 ± 2.64% after 6 h and 47.27 ± 2.85% after 72 h. Direct solar exposure without material produced approximately 7.8% removal after 6 h, whereas the irradiated hybrid system yielded an apparent residual PQT concentration of 3.43 ± 0.06 ppm. After correction for the irradiated control, material-associated removal was approximately 58.5%, with an operationally estimated additional irradiation-associated contribution of 25.7 percentage points relative to dark adsorption. These findings demonstrate the feasibility of integrating complementary coconut biomass fractions into a multifunctional hybrid material and provide preliminary evidence of enhanced apparent PQT removal under natural sunlight.