@conference{
author = "Kragulj Isakovski, Marijana and Maletić, Snežana and Mihajlović, Marija and Petrović, Jelena and Tričković, Jelena and Apostolović, Tamara and Tubić, Aleksandra and Agbaba, Jasmina",
year = "2019",
abstract = "In this work we studied the adsorption of two structurally different organic compounds (pentachlorobenzene and alachlor) on biochar
and hydrochar obtained during different thermal carbonization processes. As biomass we used energy cropMiscanthus×giganteus and
sugar beet shreds. Both types of hydrochar were obtained at three different HTC temperatures (180, 200 and 220ºC), while the biochar
was obtained during a slow pyrolysis process at 400ºC.
Characterization of the investigated adsorbents included multi-point BET specific surface area (SSA), pore volume and elemental
analysis. The multi-point BET (Brunauer-Emmett-Teller) SSA and pore volume of the adsorbents was determined by nitrogen
adsorption at 77 K using an AutosorbiQ Surface Area Analyzer (Quantochrome Instruments, USA). Elemental analysis (C, H, N, and
S) was conducted using a Vario EL III CHNS Analyzer. The SSA for all investigated adsorbents ranged from 3.87 to 260 m2/g. Both
of the biochars had a significantly higher SSA than the hydrochar. The mesopore contents of the biochars were expressed as BJH total pore volume (cm3/g),and for the biochars obtained from sugar
beet shreds and Miscanthus were 0.016 and 0.023 cm3/g, respectively. The obtained mesopore volumes were lower compared to the
hydrochars, which shows that the porosity of the material decreased during pyrolysis at higher temperatures. The biochars originating
from sugar beet shreds and Miscanthushad micropore volumes of 0.086 and 0.1042 cm3/g, respectively. All the investigated
hydrochars originating from Miscanthushad higher pore volumes (micro- meso and total pore volume) than those obtained for
hydrochars of sugar beet shreds. Additionally, it can be noticed that the volume of micro- meso- and total pore volume for all the
investigated hydrochars increases with increasing temperature from 180°C to 220°C.
The results of the elemental analysis show that the H/C atomic ratiodecreases with increasing temperature of the HTC processto
values close to 1, indicating an increase in the aromatic structure as the temperature of the process increases. In addition, (N+O)/C
ratio, expressed as the polarity index, decreases as the temperature of the process rises, which indicates the formation of less polar
structures with increasing temperature. In order to investigate the adsorption characteristics of the adsorbents, experiments were performed in conventional batch adsorption
experiments. The background solution was 0.01 M CaCl2 in doubly distilled water with 100 mg/l NaN3 as a biocide.The amount of
adsorbent in each experiment corresponded to a sample/solution ratio that resulted in 20-80% uptake of the given organic compounds.
The procedure was as follows: flasks containing premeasured adsorbent and background solution and a certain volume of methanol
organic compoundstock solution was spiked and equilibrated at room temperature by continuous shaking for 72 h. Samples of clear
supernatant were then removed for gas-chromatographic determination of the organic compound equilibrium concentrations.
All adsorption isotherms well fitted the Freundlich model. The nonlinearity of all the isotherms ranged from 0.450 to 0.986, except for
alachlor on sugar beet shreds hydrochar at200ºC, where the value of n was 1.180. Adsorption coefficients (KF) were in the range
0.053 to 243 (μg/g)/(μg/l)n for both compounds and all adsorbents. However, direct comparison of adsorption affinities could not be
made because of their different units as a result of the nonlinearity of the adsorption isotherms. Therefore, distribution coefficients
(Kd) were calculated for three equilibrium concentrations (Ce = 0.01SW, 0.1SW and 0.5SW). Generally, in the case of both compounds,
theKd values increased in the range: hydrochar of sugar beet shreds<hydrochar of Miscanthus<biochars of sugar beet shreds and
Miscanthus. The highest adsorption affinities were obtained for biochars for both investigated compounds. The reason for the higher
adsorption affinity for both compounds on the investigated biochars may be due to higher specific surface areas.It is known that slow
pyrolysis produces biocharswith higher specific surface area, as well as a higher content of aromatic structures in relation to the
hydrochar produced by hydrothermal conversion process, which can affect the formation of additional adsorption sites on the surface
as well as increase the hydrophobicity of the adsorbent To support this fact, the logKd values obtained for the adsorbents were correlated with the atomic H/C ratios, whereby a positive trend
was observed between the aromaticity and the affinity for adsorption in the case of both investigated compound. Generally,
adsorption affinity increased with increasing aromatic structure in the adsorbents. In addition, it can be noticed that changes in logKd
with the change in the atomic H/C ratio were particularly pronounced at the low equilibrium concentrations, indicating the importance
of specific interactions such as π-π interactions in the overall adsorption mechanism. Based on the obtained results, it can be concluded that the adsorption efficiency is significantly dependent on the physico-chemical
characteristics of the investigated adsorbents, which arestrongly affected by the process and conditions during adsorbents synthesis. In
addition,both investigated adsorbents could be used for the purpose of remediationof water or sediment polluted with organic
compounds.",
journal = "17TH INTERNATIONAL CONFERENCE ON CHEMISTRY AND THE ENVIRONMENT",
title = "Adsorption of alachlor and pentachlorbenzene on biochar and hydrochar originating from Miscanthus giganteus and sugar beet shreds",
pages = "1040-1038"
}
