Comparative sorption of benzo[a]pyrene by soil and carbonaceous adsorbents

<p>Benzo[a]pyrene (BaP) is one of the most dangerous polycyclic aromatic hydrocarbon, highly persistent and toxic and its remediation by the cost-effective adsorbents are of great importance. Although various technologies have been developed to remove BaP from the environment, its sorption through solid matrixes has received increasing attention due to cost-effectiveness. Studies regarding the absorption of PAHs by soil matrix have been focused mostly on non-carcinogenic compounds comprising two or three aromatic rings, such as naphthalene and phenanthrene. However, the BaP absorption by the soil matrix and different adsorbents is not yet well explored. The present research investigates the adsorption capacity of Haplic Chernozem, granular activated carbon and biochar in relation to BaP. The Haplic Chernozem properties has following properties : clay particles content was 53.1% for particles with diameter < 0.01 mm and 32.4% for particles < 0.001 mm; pHH2O - 7.3; Corg - 129 3.7%; CaСО3 - 0.1%; exchangeable cations Ca2+ - 31.0 and Mg2+ - 4.5 cmol(+) kg−1; cation exchange capacity (CEC) - 37.1 cmol(+) kg−1. Laboratory experiments with different initial BaP concentrations in the liquid phase, and different rations of both solid and liquid phases, show that Freundlich model describes well the adsorption isotherms of BaP by the soil and both adsorbents. Moreover, the BaP isotherm sorption by the Haplic Chernozem is better illustrated by the Freundlich model than the Langmuir equation. The results reveal that the sorption capacity of the carbonaceous adsorbents at a ratio 1:20 is orders of magnitude higher (13368 ng mL<sup>-1</sup> of activated carbon and 3578 ng mL<sup>-1</sup> of biochar) than that of the soil (57.8 ng mL<sup>-1</sup>). The difference of the sorption capacity of the carbonaceous adsorbents and soil at a ratio 0.5:20 were 17-45 times. This is due to the higher pore volume and specific surface area of the carbonaceous adsorbents than soil particles, assessed through scanning electron microscopy. The results of sorption kinetics showed high sorption rates and achievement of sorption equilibrium after 1 h. Biochar adsorbed BaP more intensely than granular activated carbon. The sorption kinetic of  BaP by chernozem was compared with the adsorption kinetics by the carbonaceous adsorbents. Results indicate that the adsorption dynamic involves two steps. The first one is associated with a fast BaP adsorption on the large available surface and inside macro- and mesopores of the sorbent particles of the granular activated carbon and biochar. Then, the adsorption is followed by a slower process of BaP penetration into the microporous space, and/or redistribution into a hydrophobic fraction. Overall, the granular activated carbon and biochar are highly effective adsorbents for BaP, whereas the Haplic Chernozem has a rather limited capacity to remove BaP from contaminated solutions.  </p><p>The research was supported by RFBR, projects no. 19-29-05265 and 19-34-90185.</p>

The adsorption mechanism of water-based ink particles onto cellulosic fibers

Water-based flexographic-printed ink has attracted much attention due to the reduced emission of volatile organic compounds in the printing process. However, it is difficult to remove water-based ink particles with small particle size and high hydrophilicity because they are easily reabsorbed onto cellulosic fibers during wastepaper recycling. In this paper, the absorption mechanism of water-based ink particles onto fibers was studied by using isotherm models and adsorption dynamic kinetics models at different temperatures. The adsorption process was fitted to the Freundlich isotherm, and the adsorption behavior was spontaneous and exothermic processes with an increase of entropy. It fitted well with the pseudo-second-order rate model, and the equilibrium adsorption amounts at three temperature conditions were 2.55, 2.34, and 2.21 mg/g, respectively. The B value was 9.20 g·mg−1·min−1, and the Ea value was 15.6 kJ·mol−1. The results showed that it was easier to remove the water-based ink particles from cellulosic fibers under shorter contact time and higher operation temperature during wastepaper recycling. It would be helpful to optimize the wastepaper recycling operation and to develop a novel deinking process.

Adsorption of Methylene Blue on Prepared Charcoal from Molasses Waste

Recently, important efforts have been made in an attempt to search for the cheapest and ecofriendly alternatives adsorbents. In the present work, waste molasses from Iraqi date palm (Zahdi) had been used as a provenance to produce charcoal for the removal of methylene blue (MB) dye from water. The optimum prepared charcoal was obtained at 150 C, by increasing temperature to 175 C, the charcoal had almost converted to ash. The obtained charcoal have been inspected for properties using scanning electron microscope (SEM), atomic force microscope (AFM), porosity and surface area. Adsorption data were optimized to Langmuir and Freundlich and adsorption parameters have been evaluated. The thermodynamic parameters like a change in Gipps energy (ΔG), enthalpy (ΔH) and entropy (ΔS). The effects of increasing temperature on adsorption capacity were investigated and the results indicate that pseudo-second-order kinetics model could be presented the adsorption dynamic data. The resultant values for the heat of adsorption and the free energy indicated that adsorption of methylene blue dye is preferred at low temperatures.

Column Performance in Lead(II) Removal from Aqueous Solutions by Fixed-bed Column of Mango Wood Sawdust (Mangifera indica)

The contamination of water resources due to the exceed Pb content is becoming an environmental serious problem. Adsorption method in dynamic system using fixed bed column can be used to reduce the level of Pb in an attempt to suppress the toxic effects caused by Pb. This study aims to optimize the parameters of Pb adsorption on samples by mango wood sawdust in a dynamic system. Mango wood sawdust was activated by HNO3 and ethanol then packed in a column. Optimization of adsorption parameters including adsorbent heating temperature, adsorbent mass, pH of the influen solution, and the influen flow rate. The experiment result showed that the optimum conditions of mango wood sawdust to reducing Pb in samples are adsorbent was heated at temperature 145°C, using 3 grams adsorbent packed in a column, and the influen solution at pH 7 was passed at a flow rate 1 mL/min. Adsorption capacity of mango wood sawdust in reducing Pb in samples at optimum condition is equal to 14.8 mg/g of adsorbent and types of adsorption that occurs between the adsorbent with adsorbate is chemical adsorption . Keywords: Adsorption, dynamic system, fixed-bed column, mango wood sawdust, lead metal