Remediation of engineered-nanomaterials is an up-coming major environmental concern. This study demonstrates adsorptive-remediation of cobalt oxide nanoparticles (CoO NPs) from the water. The a-cellulose-fibers were extracted from waste-paper biomass (WP-aCFs) and magnetized with Fe304 NPs (M-WP-aCFs). The XRD, FT-IR, and TGA were performed for detailed characterization of the newly developed bioadsorbent. The M-WPaCFs was then applied for adsorptive remediation of CoO NPs. The adsorptive kinetics of CoO NPs adsorption onto the M-WP-aCFs reveals the pseudo-second-order model. The various adsorption isotherm studies revealed Langmuir is a best-fit isotherm. A prominently high adsorption capacity qm (1567 mg/g) corroborated extraordinary adsorptive potential of M-WP-aCFs. Furthermore, CoO NPs were adsorbed onto M-WP-aCFs were analyzed by the XPS, VSM, and TEM. Therefore, this study gave rise WP biomass extracted and rapidly-separable nano-biocomposite of `M-WP-aCFs' with a high-capacity for CoO NPs remediation and can be further applied in remediation of several other engineered-nanomaterials.