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• A highly adsorptive magnetic biochar was prepared using K 2 FeO 4 in one-step. • Oxygen containing groups were simultaneously introduced with single phase ɤ-Fe 2 O 3. • In situ generation of oxygen containing groups benefited to capturing ɤ-Fe 2 O 3. • Both ɤ-Fe 2 O 3 and biochar matrix contributed to adsorption of Cr(VI). • The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability. Magnetic biochar was usually prepared using ferrous and ferric compounds as precursor of magnetic medium. Ferrate, which could be an internal oxidative modifier, was less explored for preparing magnetic biochar. Here, a magnetic biochar was prepared through K 2 FeO 4 -promoted pyrolysis of pomelo peel for adsorption of hexavalent chromium. Oxygen-containing groups and single phase ɤ-Fe 2 O 3 were simultaneously introduced into biochar matrix at 300 °C. The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability at 45 °C, outperformed the best magnetic biochar with 142.86 mg/g maximum adsorption capability at 40 °C in the literature. Moreover, a good magnetism was obtained, facilitating separation of the magnetic biochar from aqueous solution by a magnet. The removal of hexavalent chromium was contributed to the hybrid adsorption of ɤ-Fe 2 O 3 and biochar matrix by reduction, electrostatic interaction and complexation. This method was attractive, required neither extra modifiers nor multiple operations for preparation of highly adsorptive magnetic biochar. [ABSTRACT FROM AUTHOR]

Highlights • Coir fiber cellulose was effectively isolated and purified by multiple treatments. • Coir CNFs were prepared by mild TEMPO-mediated oxidation and ultrasonication. • Coir CNFs had been applied for effective property-reinforcement of PVA based films. Abstract Coconut waste husks were effectively utilized in this study as a promising cellulose source for production of purified coir cellulose (PCC) after multiple treatments, e.g., ultrasonic-assisted solvent immersion, alkaline treatment, bleaching, etc. As to upgrade the self-value of coir cellulose based products and further broaden their applications in light of biorefinery, coir cellulose nanofibrils (CCNF) with an average diameter of 5.6 ± 1.5 nm were prepared by selection of a milder TEMPO-mediated oxidation system (TEMPO/NaClO/NaClO 2 , pH = 4.8) accompanied by subsequent ultrasonic treatment. The cellulose nanofibrils were comprehensively characterized in terms of their functional groups, crystallinity, morphology, and thermal stability. The potential reinforcement of CCNFs as a filler for biodegradable PVA based films was investigated and the main properties including tensile strength, elongation at break, and thermal stability of CCNF/PVA composite films were significantly enhanced especially when 3% of CCNF (based on dry film weight) was applied. [ABSTRACT FROM AUTHOR]

• Fenton oxidation was first applied for presice modification of biochar. • Incorporating iron into biochar matrix through pyrolysis was of great importance. • A considerable number of oxygen containing groups were introduced. • Great increase of adsorption capability was obtained for Cr (VI) and MB. • Fenton oxidation leaded to increase of saturation magnetization. Fenton modification, involving iron-promoted pyrolysis followed by H 2 O 2 oxidation, was first employed to improve the adsorptive and magnetic capabilities of biochar. Modified biochars were prepared from rubber tree bark and coconut shell through iron-promoted pyrolysis and subsequent H 2 O 2 oxidation, and their adsorption behaviors toward Cr (VI) and MB were evaluated in aqueous solution. The modified biochars pyrolyzed at 300 and 400 ˚C displayed much higher adsorption capabilities than corresponding pristine biochars for Cr (VI) and MB, respectively, ascribing to introduction of COOH, C O and C–O groups by Fenton oxidation. More importantly, saturation magnetization could be enhanced by transforming nonmagnetic iron oxides into γ-Fe 2 O 3 through H 2 O 2 oxidation. The removal of Cr (VI) and MB could be primarily contributed to the adsorption of biochar matrix by reduction/hydrogen bonding/cation exchange/electrostatic interaction and hydrogen bonding/cation exchange/electrostatic interaction, respectively. This would provide a novel and efficient strategy for making highly adsorptive magnetic biochar. [ABSTRACT FROM AUTHOR]