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Carbonaceous material obtained from bark biomass as adsorbent of phenolic compounds from aqueous solutions



In this work, a novel carbonaceous material from Haematoxylum campechianum (C-HC) was obtained as an alternative adsorbent for eliminating phenol (Phen), 4-chlorophenol (4-ClPhen) and 4-nitrophenol (4-NPhen) from aqueous solutions. The carbonaceous material was prepared from bark biomass after phosphoric acid impregnation followed by thermal treatment at 500 °C for 60 min. The material was characterized by X-ray diffraction (XRD) and Scanning Electron Microscopy/​Energy dispersive X-ray Spectroscopy (SEM/EDS). The textural parameters and the point of zero charge of the C-HC adsorbent were determined as well. The results show that the carbonaceous material was obtained as a mixed graphitized/​amorphous phase. The major components of this material were carbon, oxygen, and in a minor amount, the phosphorous and sodium. The surface area, pore-volume, and mean pore diameter of this material were 181.49 m2/​g, 0.09396 cm3/​g, and 2.07 nm, respectively, with a pHpzc of 7.02. To determine the optimal conditions and the maximum adsorptive capability of the obtained C-HC material against phenolic compounds, various conditions such as the contact time (15180 min), initial adsorbate concentration (101000 mg L-1), C-HC dose (525 mg L-1) and solution pH (210) were investigated using batch experiments. The time to reach the equilibrium for 4-NPhen and 4-ClPhen was approximately 60 min, comparted to 120 min for Phen. The experimental data fit well to the pseudo-second-order kinetic model (R20.99) in all cases, and the kinetic constant of pseudo-second-order was highest for 4-NPhen (k2=0.075 g/(mg min). The experimental data of the isotherms were well fitted to Langmuir and Lui model. The maximum adsorption capacity (Qm) based on the Langmuir model was obtained for Phen (94.09 mg/​g). The dose of the C-HC and the pH of the phenolic aqueous solutions influence the sorption capacity of the carbonaceous material. The best conditions to reach the maximum adsorption of the phenolic compounds were with a dose of 20 mg/​L and at pH 2. The solubility, pKa and the dipolar moment of the phenolics affect notably the kinetic and the maximum adsorption capacity of the C-HC, considering that 4-Phen has the lowest solubility and pKa constant, and the highest dipolar moment.

M. Abatal, I. Anastopoulos, D.A. Giannakoudakis, M.T. Olguin. Journal of Environmental Chemical Engineering, 8 (3) (2020) 103784.

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