Phenol removal from aqueous medium was studied by the batch method using novel and fully biobased solvent-cast films prepared from cellulose nanofibrils (CNFs) and in situ synthesised hydroxyapatite (HAp) by the wet-chemical precipitation method and different concentrations of HAp precursors and weight mass of CNFs. The chemical and morphological structures of as-prepared films were investigated by X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy, while their physical properties were determined by water contact angle and swelling kinetic measurements. The HAp precursor leads to a surface modification of CNFs, which increases its activity by forming differently structured, sized and distributed HAp particles, influencing the phenol adsorption kinetic and capacity. The phenol adsorption was faster and higher (~64 mg g⁻¹) in an acidic solution (pH 2) compared to the original phenol solution pH (pH 7.4, ~30 mg g⁻¹) using films with unevenly-distributed and positively-charged calcium-richer HAp particles synthesised on the CNFs’ surface, being reflected also in its higher water swelling properties, compared to their hybrid counterparts. The phenol adsorption is identified to follow pseudo-second order kinetic and intra-particle diffusion models. A highly-efficient reusing ability of the selected film with 86% adsorption capacity of the initial value at the third sequential regeneration cycle, is also confirmed. A super-hydrophilic nature of the films with high water-diffusing and transport properties, as well as low swelling, indicates their potential in the development of highly-effective adsorbents and, potentially, filter membranes for water purification.

Nanostructured bio-photocatalyst hydroxyapatite (HAp) was synthesized by a simple and productive wet chemical precipitation method to explore the photocatalytic performance of the material for degradation of Remazol Brilliant Blue R (RBBR) dye. Wet chemically synthesized nano-HAp was characterized through x-ray diffraction, Transmission electron microscope, scanning electron microscope, N₂-adsorption–desorption, thermo gravimetric analyzer, Fourier transform infrared and UV–vis absorption techniques. Photocatalytic degradation of RBBR under ultraviolet irradiation was examined and ∼80% degradation was achieved in 120 min by using nano-HAp. The photocatalytic degradation followed Parabolic Diffusion kinetics. Fast degradation kinetics and removal of RBBR dye was achieved by nano-HAp due to modification of surface entities leading to suppression of photo-generated electron-hole recombination. This makes nano-HAp a remarkable bio-photocatalyst material for removing dyes from water.