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Effect of aging process on adsorption of diethyl phthalate in soils
amended with bamboo biochar
Xiaokai Zhang
, Ajit K. Sarmah
, Nanthi S. Bolan
, Lizhi He
, Xiaoming Lin
, Lei Che
Caixian Tang
, Hailong Wang
Key Laboratory of Soil Contamination Bioremediation of Zhejiang Province, Zhejiang A & F University, Lin’an, Hangzhou, Zhejiang 311300, China
School of Environmental and Resource Sciences, Zhejiang A & F University, Lin’an, Hangzhou, Zhejiang 311300, China
Department of Civil and Environmental Engineering, Faculty of Engineering, University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
Centre for Environmental Risk Assessment and Remediation (CERAR), University of South Australia, South Australia 5095, Australia
Guangdong Dazhong Agriculture Science Co. Ltd., Hongmei Town, Dongguan, Guangdong 523169, China
School of Engineering, Huzhou University, Huzhou, Zhejiang 313000, China
Centre for AgriBioscience, La Trobe University, Kingsbury Drive, Melbourne, Victoria 3086, Australia
Biochar amendment significantly enhanced the soil adsorption of diethyl phthalate (DEP).
Aging can reduce the DEP adsorption to soils treated with biochar.
The reduction was greater under the alternating wet and dry than that under constantly moist aging process.
Soil organic carbon content can strongly affect the aging process of biochar.
article info
Article history:
Received 1 January 2015
Received in revised form 9 May 2015
Accepted 13 May 2015
Available online 23 May 2015
Aged biochar
Diethyl phthalate
Soil contamination
Biochar is a carbonaceous sorbent and can be used as a potential material to reduce the bioavailability of
organic pollutants in contaminated soils. In the present study, the adsorption and desorption of diethyl
phthalate (DEP) onto soils amended with bamboo biochar was investigated with a special focus on the
effect of biochar application rates and aging conditions on the adsorption capacity of the soils. Biochar
amendment significantly enhanced the soil adsorption of DEP that increased with increasing application
rates of biochar. However, the adsorption capacity decreased by two aging processes (alternating wet and
dry, and constantly moist). In the soil with low organic carbon (OC) content, the addition of 0.5% biochar
(without aging) increased the adsorption by nearly 98 times compared to the control, and exhibited the
highest adsorption capacity among all the treatments. In the soil with high OC content, the adsorption
capacity in the treatment of 0.5% biochar without aging was 3.5 and 3 times greater than those of the
treatments of biochar aged by alternating wet and dry, and constantly moist, respectively. Moreover, con-
stantly moist resulted in a greater adsorption capacity than alternating wet and dry treatments regardless
of biochar addition. This study revealed that biochar application enhanced soil sorption of DEP, however,
the enhancement of the adsorption capacity was dependent on the soil organic carbon levels, and aging
processes of biochar.
Ó2015 Elsevier Ltd. All rights reserved.
1. Introduction
Biochar is a carbon-rich solid product produced from the pyrol-
ysis of biomass residues. Application of biochar to soil can improve
soil properties (Verheijen et al., 2010). As a recalcitrant carbon-rich
material, the application of biochar to soil has great potential to
mitigate greenhouse gas emission and sequester carbon
(Lehmann, 2007). Past studies have shown that biochar application
to soils can decrease the bioavailability of heavy metals and
organic pollutants in contaminated soils (Beesley et al., 2011;
Zhang et al., 2013). For example, Yang and Sheng (2003) observed
that the particulates produced from burning wheat and rice resi-
dues were 400–2500 times more effective than soil in sorbing
diuron over the concentration range of 0–6 mg L
in water. High
0045-6535/Ó2015 Elsevier Ltd. All rights reserved.
Corresponding authors at: Key Laboratory of Soil Contamination Bioremedia-
tion of Zhejiang Province, Zhejiang A & F University, Lin’an, Hangzhou, Zhejiang
311300, China.
E-mail addresses: (L. He),
(H. Wang).
Chemosphere 142 (2016) 28–34
Contents lists available at ScienceDirect
journal homepage:
specific surface areas and microporous structure make biochar a
sorbent for the adsorption of a range of organic and inorganic
chemicals. When biochar is applied to the soil, it undergoes a range
of biogeochemical interactions and their properties are likely to
change with time in soil, a process commonly referred to as ‘‘ag-
ing’’ and biochar properties may change during the process of
aging (Kookana, 2010). The process of aging can be either abiotic
or biotic which can lead to changes in the sorption characteristics
of the sorbent. For example, the presence of some metallic ions
(e.g. Cu
and Ag
) and organic compounds with higher hydropho-
bicity and/or high molecular size can significantly alter surface
chemistry and pore network structure of biochar (Chen et al.,
2007; Wang et al., 2006). Also, aging processes may introduce
functional groups (i.e. carboxylic) to biochar surfaces, thereby
impacting its adsorption properties (Qian et al., 2015).
Phthalate acid esters (PAEs) are a class of organic compounds
widely used as plasticizers to improve the properties of plastics
(He et al., 2015; Fang et al., 2010). Surveys showed worldwide
production of PAEs is approximately 6 million tons per year
and a large amount of these compounds are released into the
air, sediment, natural water, wastewater, and soils (Bauer and
Herrmann, 1997; Mackintosh et al., 2006; Shailaja et al.,
2007). Recent years have witnessed widespread urbanization
around the world, causing a rapid expansion of the peri-urban
interface in many cities, especially in Asia (Zeng et al., 2008).
In many peri-urban areas in Asia (i.e., in China), land use has
been transformed from rice-based to vegetable-based systems
(Wang et al., 2013). Therefore, there is likely to be a greater
demand for plastic greenhouses and plastic mulch to grow veg-
etable crops to cope with the increasing demands. The PAEs in
the plastic greenhouses, plastic mulch and fertilizers can be
potentially released to the soil, resulting in unwanted conse-
quences of soil contamination. In recent years, high levels of
PAEs contaminated agricultural soils have already been detected
in the Pearl River Delta and northeast China (Xu et al., 2008;
Zeng et al., 2008).
Diethyl phthalate (DEP) is one of the most frequently used
phthalates possessing high aqueous solubility and is toxic at high
exposure levels as well as at low doses for a prolonged period
and it may accumulate in the soil and enter the human food chain
(Yang et al., 2005; Sun et al., 2012). Both the higher concentrations
of DEP and exposure to lower concentrations for a longer period of
time could impact human health (Sun et al., 2012). Therefore, it is
essential to find an effective way to remediate the soils contami-
nated with this pollutant.
In our previous study, we suggested that biochar can be used as
a sorbent to reduce the bioavailability of DEP in the contaminated
soils (Zhang et al., 2014). However, aging process may change the
adsorption capacity of biochar. Recently, most studies were
focused on the effect of constantly moist aging process on biochar’
adsorption capacity. Generally, the alternating wet and dry process
is more relevant to the field conditions. The objective of this study
was therefore to assess the effect of different aging processes on
the adsorption capacity of DEP to the soils amended with bamboo
biochar. We hypothesized that different aging processes altered
the adsorption ability of biochar for DEP.
2. Materials and methods
2.1. Chemicals, soils and biochar
Analytical standard of diethyl phthalate with a purity P99.5%
was obtained from Shanghai Lingfeng Chemical Reagent
(Shanghai, China). Stock solution of 400 mg L
DEP was prepared
in methanol and used for analytical purposes. High Performance
Liquid Chromatography (HPLC) grade of acetonitrile was obtained
from Tedia (Fairfield, Ohio, USA). Other chemicals were of analyti-
cal grade.
Two soils differing in organic carbon (OC) contents were col-
lected in November 2012 from a vegetable garden in the suburb
of Lin’an near Hu Tangxia village, in Hangzhou, China. The soil sam-
ples were collected from the surface with a depth of 0–0.2 m. After
air-drying, the soils were passed through a 2 mm sieve. Selected
physicochemical properties of soils are shown in Table 1.
Bamboo used to produce biochar was oven dried at 80 °C for
24 h. The stainless steel vessel was constantly purged with dry
nitrogen gas at 3.5 L min
and the vessel was heated over 3 h to
a final hold temperature of 820 °C. Physicochemical properties of
biochar are shown in Table 2.
2.2. Aging treatments
On the basis of our preliminary investigation, the application
rates of bamboo biochar were set at 0.1% and 0.5% (w/w) of soil
weight. Soils were mixed with biochars using a soil mixer and were
directly used in the sorption and desorption experiments. An addi-
tional set of samples, after adjusting the water content of soil to
about 70% of maximum water-holding capacity, were equilibrated
at 25 ± 1 °C for 30 d to evaluate the effect of aging. The samples
were checked daily for water loss by weighing, and appropriate
amount of deionized water was added to compensate for water
loss when required. Other well-mixed samples were incubated
under the same conditions and aging time, and added to compen-
sate for water loss every 10 d (alternating wet and dry).
2.3. Adsorption and desorption experiments
Sorption of DEP by the bamboo biochar was measured by the
batch equilibration technique following an earlier protocol (Yu
et al., 2006). Briefly, 4 g each of the treated soils was weighed onto
a glass centrifuge tube (40 mL) with Teflon-lined screw cap and
20 mL of 0.01 M CaCl
(the CaCl
was used to maintain the ionic
strength), containing 250 mg L
of NaN
to inhibit microbial activ-
ity, was added to obtain an initial solution concentration of 2, 4, 6,
8, and 10 mg L
of DEP (Yu et al., 2006; Wang et al., 2010).
Triplicate samples were prepared for each treatment. For the com-
parative assessment between different biochar treatments under
similar conditions, an equilibrium contact time of 24 h was found
to be adequate for the purposes of this study. Tubes were shaken
for 24 h, centrifuged at 2191 g for 10 min (Wang et al., 2010),
and the supernatant was analyzed for DEP concentrations using
High Performance Liquid Chromatography and UV detection. The
Table 1
Selected properties of soils (0–0.2 m).
Soils Organic carbon (OC) (g kg
) Total N(g kg
) pH Electrical conductivity
(dS m
) Clay (%) Silt (%) Sand (%)
Low OC soil 3.5 0.3 5.83 0.31 16.9 44.4 38.7
High OC soil 22 2.0 6.04 0.24 16.4 45.0 38.6
Electrical conductivity was measured in 1:5 water.
X. Zhang et al. / Chemosphere 142 (2016) 28–34 29
sorbed amount C
(mg kg
) was estimated by the mass difference
between the initial and final concentration as follows:
where C
is the initial solute concentration (mg L
); C
(mg L
the equilibrium solution concentration, V
is the solute volume (L);
and m
is the soil mass (kg), respectively.
Those samples with the highest sorption loading were used for
desorption experiments (Yu et al., 2006). After 24 h of equilibra-
tion, the tubes were centrifuged and 10 mL of the supernatant in
each tube was taken out for analysis. Another 10 mL of 0.01 M
(containing a concentration of 250 mg L
) was added
into each tube, shaken for 24 h, centrifuged, and the supernatants
were collected to analyze the DEP concentrations in the aqueous
phase as described above. The desorption process was repeated
four times and the supernatants were collected as separate four
desorption aliquots. The sorbed amount C
(mg kg
) in the desorp-
tion experiments was estimated as follows:
where C
is the initial sorbed concentration (mg L
), C
is the half
percent of the initial solute concentration (mg L
); C
(mg L
the equilibrium solution concentration, V
is the solute volume
(L); and m
is the soil mass (kg) (Yu et al., 2006).
To estimate the adsorption capacity for the biochar in the trea-
ted soil, K
was estimated by assuming that the adsorption of
biochar and soil organic matter has an additive effect.
f;amended soil
where K
f;amended soil
, and K
are the adsorption coeffi-
cients of amended soil, biochar, and soil, respectively; f
the fraction of the amended soil (Wang et al., 2010).
2.4. Chemical analysis
The concentration of DEP was measured using a reverse-phase
ACQUITY ultra performance liquid chromatography (UPLC) cou-
pled with a PDA detector. To determine DEP concentrations in
the equilibrium solution, the collected supernatant was passed
through a 0.45-
m Whatman and separation was carried out on
Column (1.0 100 mm, 1.7
Waters, Milford, Massachusetts, USA). The isocratic mobile phase
consisted of 45% water and 55% acetonitrile and at a flow rate of
0.1 mL min
. The injection volume was fixed at 1
L. The UV
wavelength for detection of DEP was 225 nm and the retention
time for DEP in the UPLC system was 5.0 min.
2.5. Data analysis and sorption modeling
The adsorption and desorption isotherms of DEP in the soils
with or without biochar were modeled using the Freundlich equa-
tion: C
where C
and C
are the equilibrium sorbed and
aqueous phase concentrations respectively, K
the Freundlich sorption coefficient and N(dimensionless) is the
measure of sorption non-linearity (N= 1 represents a linear iso-
therm). K
was quantified by the empirical Freundlich equation in
the log transformation form: LogC
= logK
and Nis the
exponent indicative of sorption mechanism associated with the
sorbent and sorbate interactions. The K
values and Nvalues in
the Freundlich equation are used for the comparison between the
sorbents. The larger value for K
indicates a larger adsorption
capacity of the sorbent. However, the larger value for Nindicates
a larger change in effectiveness over different equilibrium concen-
trations. When N> 1, the change in adsorbed concentration is
greater than the change in the solute concentration. A larger N
value indicates a stronger adsorption capacity of the sorbent with-
out reducing the K
value (Liu et al., 2007). The sorption–desorption
apparent hysteresis index (H) was determined by the equation:
where, the hysteresis index (H) can be used to quantify
the degree of apparent hysteresis.
3. Result and discussion
3.1. Effect of soil organic carbon content and biochar on adsorption
Fig. 1 illustrates the sorption of DEP in all fresh biochar treated
soils. Biochar addition to soil significantly enhanced the sorption of
DEP, and the sorption capacity of the biochar-amended soils
increased with an increase in biochar content. The results of this
study show that the sorption data over the entire range of DEP con-
centrations were well described (R
P0.95) by the Freundlich
equation, and the sorption parameters are summarized in Tables
3 and 4. It can be observed that Nvalues for all biochar-amended
soils were generally smaller than those for the unamended soils,
indicating a decrease in the degree of isotherm linearity with bio-
char amendment. Because of the observed variability in
non-linearity as indicated by Nvalues, K
could be used to make
a comparison of sorption affinities among the biochar-amended
soils. The K
values in Tables 3 and 4 show that bamboo bio-
char has a high affinity to DEP. Previous studies showed that the
high surface area of biochar affected its adsorption ability
(Ahmad et al., 2014; Zhang et al., 2013). It can be found that bam-
boo biochar in this study has a high surface area (276 m
which contributes to its high adsorption capacity. In addition, the
interactions between DEP molecules and surface functional
groups of biochar could potentially contribute to the sorption pro-
cess (Ahmad et al., 2014). Another possible mechanism may be
that the bamboo biochar has a high amount of amorphous carbon,
thereby supporting the formation of micropores and increasing the
sorption capacity (Haghseresht et al., 1999). This is mainly due to
the high lignin content of bamboo which contributes to the high
content of aromatic carbon of biochar (Cesarino et al., 2012;
Deshpande et al., 2000).
In the biochar-unamended soils, the adsorption capacity of soils
for DEP correlated well with the OC content of soils (i.e., the soil
with low OC content exhibited lower values of K
as compared to
the soil with high OC content). Generally, the clay minerals and
OC content of soil affect soil’s adsorption capacity of organic pollu-
tants. The two soils used in this study have similar clay, silt and
sand contents, pH and electrical conductivity but differ in the OC
content by 6-fold (Table 1). Previous study demonstrated that soil
organic carbon was responsible for partitioning and sorption of the
organic pollutants in soil (Wang et al., 2010). Therefore, this study
Table 2
Physico-chemical characteristics of the biochar used.
Samples N (%) C (%) H (%) O (%) H/C O/C C/N Organic carbon (%) pH SSA
) Ash content (%) Electrical conductivity
(dS m
Biochar 0.57 76.69 1.59 21.15 0.25 0.37 157 75.42 10.80 276 5.51 1.54
SSA: specific surface area.
Electrical conductivity was measured in 1:5 water.
30 X. Zhang et al. / Chemosphere 142 (2016) 28–34
indicates that the soil organic matter strongly affect the adsorption
capacity of DEP by the soils.
The addition of biochar at 0.1% and 0.5% dose rates significantly
enhanced the adsorption of DEP in both soils with low and high OC
content. This suggests that the presence of even small amounts of
biochar can strongly dominate the sorption of an organic compound
in soils (Zhang et al., 2014). Tables 3 and 4 show that the K
for DEP at the two application rates were about 16, nearly 98 times
higher than that of the control for the soil with low OC, and approx-
imately 4 and 10 times higher for the soil with high OC content. The
results thus demonstrate that biochar is more effective to enhance
the adsorption ability for soils with low carbon content than soils
with high OC content. This further suggests that the biochars exhib-
ited higher sorptivity to DEP than the soils with indigenous soil
organic carbon. Yu et al. (2009) reported that soils amended with
1.0% of Eucalyptus-derived biochars reduced the uptake of chlor-
pyrifos and carbofuran by Spring onion (Allium cepa). In the present
study, we observed that biochar had a strong adsorption capacity
for DEP, and this may effectively reduce the bioavailability of DEP
in soils and reduce the plant uptake.
It is important to note that for soils amended with biochar at 0.5%,
the K
values showed an opposite trend with the low OC soil exhibit-
ing a higher sorption capacity than the high OC soil. In addition, after
the application of biochar, the extent of increase in the adsorption
capacity on DEP of all the low OC content soil treatments was higher
than all the high OC content soil treatments. This may be attributed
to the attenuation of DEP adsorption of biochar by soil-derived dis-
solved organic carbon (DOC) that blocks the pores of biochars,
thereby reducing the overall accessibility to the sorption sites
(Zhang et al., 2010; Pignatello, 2013). However, Yang et al. (2013)
Fig. 1. Effect of bamboo biochar (BB) treatments on the adsorption (Ads.) and desorption (Des.) of diethyl phthalate (DEP) in soils (A: soil with low organic carbon; B: soil with
high organic carbon). Symbols are measured data and the lines are Freundlich model fits.
Table 3
Effect of bamboo biochar (BB) on parameters for the adsorption and desorption of diethyl phthalate in soil with low organic carbon.
Adsorption parameters Desorption parameters H
LS 0.46 ± 0.03 0.97 0.95 0.67 ± 0.02 1.04 0.96 0.93
LS + 0.1% BB 7.56 ± 0.03 7110 0.26 0.99 10.33 ± 0.09 0.03 0.99 8.67
LS + 0.1% AWD BB 3.84 ± 0.04 3411 0.57 0.97 8.99 ± 0.11 0.10 0.98 5.70
LS + 0.1% CM BB 5.23 ± 0.01 4779 0.35 0.99 9.50 ± 0.13 0.05 0.95 7.00
LS + 0.5% BB 45.02 ± 0.35 8914 0.67 0.99 44.90 ± 0.003 0.004 0.96 168
LS + 0.5% AWD BB 35.53 ± 0.31 7020 0.57 1 42.84 ± 0.04 0.005 0.98 114
LS + 0.5% CM BB 36.23 ± 0.22 7156 0.62 0.95 42.96 ± 0.12 0.007 0.98 89
LS is the soil with low organic carbon; AWD is alternating wet and dry aging process; CM is constantly moist aging process.
was calculated from Eq. (3) given in the text.
Table 4
Effect of bamboo biochar (BB) on parameters for the adsorption and desorption of diethyl phthalate in soil with high organic carbon.
Adsorption parameters Desorption parameters H
HS 2.12 ± 0.19 0.85 0.95 8.24 ± 0.13 0.31 0.93 2.74
HS + 0.1% BB 8.17 ± 0.02 5959 0.48 0.99 13.50 ± 0.06 0.11 0.94 4.36
HS + 0.1% AWD BB 4.51 ± 0.02 2528 0.69 0.96 10.24 ± 0.09 0.23 0.96 3.00
HS + 0.1% CM BB 5.14 ± 0.15 3115 0.59 1 11.42 ± 0.39 0.17 0.92 3.47
HS + 0.5% BB 21.88 ± 0.11 3936 0.80 0.98 39.79 ± 0.06 0.02 0.97 40.00
HS + 0.5% AWD BB 6.27 ± 0.03 859 0.71 1 20.19 ± 0.27 0.04 0.94 17.75
HS + 0.5% CM BB 7.10 ± 0.04 1017 0.62 0.99 20.99 ± 0.15 0.02 0.98 31.00
HS is the soil with high organic carbon; AWD is alternating wet and dry aging process; CM is constantly moist aging process.
was calculated from Eq. (3) given in the text.
X. Zhang et al. / Chemosphere 142 (2016) 28–34 31
showed that low DOC concentrations in soil enhanced but high DOC
concentrations decreased the sorption of DEP. Future research may
be warranted to examine the mechanisms contributing to the effect
of DOC on the adsorption of DEP in biochar-amended soil.
3.2. Effect of aging on adsorption
Upon the application of biochar to the soil, a range of biogeo-
chemical interactions can take place. One such process is aging of
biochar which will eventually affect the sorptive ability of biochar
for organic contaminants. The high specific surface area and micro-
porosity of biochar may change with time after biochar is applied
to soils (Zhang et al., 2010). In this study, we evaluated the effect
on the soils’ adsorption affinity for DEP of incubating
biochar-amended soils for 30-d under alternating wet and dry
and constantly moist conditions.
Like the other treatments, sorption isotherms of the aged treat-
ments were well described by the Freundlich model (R
(Fig. 2;Tables 3 and 4). There was a marked decrease in the K
ues for the aged samples especially for the soil with high OC con-
tent as compared with the fresh biochar-amended soils. For
example, the K
value of the high OC soil freshly added with 0.5%
biochar was approximately 3.5 and 3 times higher than those of
the biochar-amended soil aged with alternating wet and dry, and
constantly moist, respectively. The results indicate that aging pro-
cess decreases the overall sorption of DEP in the biochar-amended
soils. This decrease may be attributed to the increased association
of DOC with biochar surfaces over time, resulting in the occupation
or blocking biochar sorption sites (Zhang et al., 2010), and thereby
making them less available to absorb DEP. The unique surface
characteristics of biochar make fresh biochar a very efficient sor-
bent for organic compounds, whereas after aging, these properties
change probably due to surface interactions such as surface cover-
age, pore blockage, and surface oxidation (Huang et al., 2003;
Cornelissen et al., 2004). In a previous study, Lou et al. (2012)
observed that aging resulted in reduced pentachlorophenol sorp-
tion in a soil amended with biochar. In contrast, after aging, the
DEP sorption capacity of the 0.5% biochar-amended low OC content
soil did not markedly change as compared to fresh biochar
amended soil. The lack of a significant effect may be due to the
much lower OC content (3.5 g kg
) in this soil, and hence the
30-d aging incubation did not result in enough additional coating
of biochar particles by DOC.
In this study, we have noted that aging also tend to decrease the
sorption capacity of DEP in the soils without biochar addition
(Table 5), although the effect is not significant. The results are con-
sistent with the finding of Yang et al. (2008) that aging of soil
resulted in a reduction in pyrethroid sorption. As we discussed
above, soil OC content can strongly affect its adsorption on the
organic pollutants. Therefore, the most likely reason of our result
might be that aging process decreased the content or sorption sites
of organic matter in the soils.
3.3. Effect of different aging conditions on adsorption
Previous studies had mainly focused on the effect of constantly
moist aging condition on biochar’s adsorption capacity (Yang et al.,
2008; Zhang et al., 2010). Under natural conditions, the irregular
rainfall and the often warm, dry climate generate rapid drying of
surface soils which can be treated as an alternating wet and dry
aging condition. Therefore, the study on the effect of alternating
wet and dry aging condition on biochar’s adsorption capacity is
more appropriate to direct the biochar application measures.
The sorption capacities of DEP to the aged biochar at different
aging conditions are shown in Fig. 2, and Tables 3 and 4. The sorp-
tion capacity of DEP varied between the aging treatments. The K
values followed an order of constantly moist > alternating wet
and dry. As discussed above, soil DOC can block the sorption sites
of biochar, which may result in the reduction of biochars adsorp-
tion capacity. Numerous studies have shown that both alternating
wet and dry, and constantly moist aging conditions can enhance
DOC concentration in soil (Lundquist et al., 1999; Zhang et al.,
2010), and the soil organic carbon mineralization rate determines
the DOC concentrations in the soil. For instance, Zengin et al.
(2008) demonstrated that constantly moist condition significantly
enhanced the carbon mineralization of soil. However, dry-wet
cycles increased moderate C mineralization compared with a con-
tinuously moist soil (Yemadje et al., 2014). In our study, the
organic carbon content of the high OC soil decreased from
22 g kg
to 19.5 g kg
for alternating wet and dry aged soil, and
down to 20.5 g kg
for constantly moist aged soil. After aging,
the organic carbon contents of the low OC soil also showed the
same decreasing trend. This lends further support to the argument
that the alternating wet and dry aging condition is more effective
for soil organic carbon mineralization, and thus increases DOC con-
centration. We postulate that the difference in K
values between
the aging conditions may be attributed to the differences in the
extent of blocking of sorption sites of biochar by DOC between
these two different aging conditions.
Fig. 2. Effect of aging processes (AWD: alternating wet and dry aging; CM: constantly moist aging) on the adsorption (Ads.) of diethyl phthalate (DEP) on bamboo biochar (BB)
in soils (A: soil with low organic carbon; B: soil with high organic carbon). Symbols are measured data and the lines are Freundlich model fits.
32 X. Zhang et al. / Chemosphere 142 (2016) 28–34
3.4. Effect of biochar treated and untreated soil on desorption
In this study, the sorption and desorption isotherms were com-
pared to assess the degree of reversibility of sorption reaction.
Desorption isotherms were well described by the Freundlich model
(see Fig. 1), with R
P0.92, and the desorption parameters are
summarized in Tables 3–5. The highly nonlinear sorption isotherm
and relatively flat desorption isotherm suggest that sorption/des-
orption of DEP in the soils were consistently hysteretic (Fig. 1).
The hysteresis index (H) was used to quantify the degree of appar-
ent hysteresis. Tables 2 and 3 show the Hvalues for all treatments.
The Hvalue of the original low OC soil was 0.93, indicating a min-
imal desorption hysteresis. As the OC content and the dose of bio-
char in the soil increased, the value of Halso increased. This is
mainly due to irreversible binding or sequestration of DEP on bio-
char or certain components of soil organic matter (Bhandari et al.,
Compared to the untreated control, the soils amended with bio-
char appeared to be more hysteretic for the desorption of DEP. For
the low OC soil, addition of 0.5% biochar enhanced the Hvalue by
more than 180-fold, leading to the highest adsorption capacity.
Therefore, the application of biochar markedly reduced the
bioavailability and bioaccessibility of organic pollutants in soil
(Yu et al., 2006).
Similar to the K
value, the Hvalues were higher in all the fresh
biochar-treated soils than the aged samples, and followed an order
of fresh biochar-treated soil > biochar-treated soil aged with con-
stantly moist > biochar-treated soil aged with alternating wet
and dry. All the aging treatments displayed a tendency to more
easily desorb the DEP into the soil again. However, the degree of
desorption hysteresis was quite different between the two aging
conditions. Compared with the alternating wet and dry cycles,
the constantly moist treatments showed a higher desorption hys-
teresis. However, the underlying mechanism of this difference is
not understood and needs further investigation.
In this study, the strong sorption followed by weak desorption
of DEP in biochar-amended soils indicates that biochar sequesters
DEP in soil. Even though desorption of DEP in the biochar-amended
soils shows consistent hysteresis, the experiments were conducted
in short term under laboratory conditions. Whether sorbed DEP
will release into the soil again is an issue that requires further
investigation. The long-term environmental fate of biochar and
DEP in contaminated soils has not been studied under realistic field
conditions. This aspect warrants some investigations given the
possibility of DEP release in case of extreme weather events such
as heavy rainfall extending for days.
4. Conclusions
The sorption capacity of DEP onto soils increased with soil OC
content and rates of biochar addition. It is generally accepted that
the higher adsorption capacity of DEP to biochar reduces the
bioavailability of DEP commonly released to agriculture soils during
vegetable cultivation and other management practices. The amount
of DEP adsorbed onto the biochar-amended soil decreased after dif-
ferent aging processes with the adsorption capacity of
biochar-amended soil following the order of without aging > aged
with constantly moist > aged with alternating wet and dry. The
low OC soil amended with 0.5% biochar showed the highest adsorp-
tion capacity and weakest desorption capacity. A decreased number
of effective sorption sites of biochar for DEP adsorption by high soil
DOC may explain why the high OC soil with 0.5% biochar had lower
adsorption compared with the low OC soil with the same treatment.
The application of biochars to DEP-contaminated soils may thus be
expected to change many ecotoxicological processes of DEP,
thereby reducing both bioavailability and subsequent risk of enter-
ing the food chain. However, how the different aging processes
affect the characteristics of biochar could not be ascertained.
Therefore, more work is needed to investigate the mechanisms on
how different aging conditions changes biochar properties and
their impact on sorption and desorption behavior of DEP.
This work was financially supported by the National Natural
Science Foundation of China (41271337), Zhejiang Provincial
Natural Science Foundation (Z15D010001), the Foreign Experts
Introduction Funds of the State Administration of Foreign Experts
Affairs of China (W20143300031), the Special Funding for the
Introduced Innovative R&D Team of Dongguan (2014607101003),
and Zhejiang A & F University Research and Development Fund
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HS 2.12 ± 0.19 0.85 0.95 8.24 ± 0.13 0.31 0.93
HS AWD 1.99 ± 0.09 0.70 0.99 7.75 ± 0.09 0.17 0.92
HS CM 2.02 ± 0.06 0.78 0.97 7.86 ± 0.04 0.16 0.98
LS 0.46 ± 0.03 0.97 0.95 0.67 ± 0.02 1.04 0.96
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LS CM 0.45 ± 0.03 0.87 0.96 0.64 ± 0.09 0.66 0.96
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34 X. Zhang et al. / Chemosphere 142 (2016) 28–34
... Possible ways to prepare biochar. The results are taken from the following references Wei et al. (2015), Kim et al. (2016), Kupryianchyk et al. (2016), Zhang et al. (2016), Li et al. (2019a), Regkouzas and Diamadopoulos (2019), Taskin et al. (2019), Kumar et al. (2021), and Liu et al. (2021). low density, abundant functional groups (aromatic and heterocyclic carbons such as C=N, COOH, OH), high water holding capacity, high specific surface area and adsorption capacity (Czekała et al., 2016;Du et al., 2019a;Simiele et al., 2020;Tu et al., 2020;Li et al., 2021a;Gonzaga et al., 2022). ...
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Phytoremediation is one of the cheapest and most widely used technologies for stabilizing and extracting pollutants from contaminated sites. Recently, a variety of solutions, such as the use of different elements, compost, nanoparticles, microorganisms, etc., have been explored for improving and accelerating the phytoremediation process. Biochar has also gained attention for its affordability, abundance, ability to improve soil structure and plant morpho-physiology and biochemistry, lack of environmental hazards, etc. As a first step, this study aimed to provide an overview of biochar's properties, and operation by identifying the method of production and examining the differences between different types of biochar. Following that, by examining various factors that pollute the environment, the influence of different types of biochar on phytoremediation efficiency was explored. Also, in this study, an attempt has been made to examine the effect of the combination of biochar with other factors in improving the phytoremediation of pollutants, as well as the use of the residues of phytoremediation for the production of biochar, so that future research can be planned based on the results obtained.
... The process of biochar aging is a natural one. When applied to the soil, the biochar undergoes a series of biochemical interactions such as surface oxidation, mineral dissolution, and mechanical breakage [275,276]. The biochar aging process disrupts its role as a soil conditioner because various surface characteristics of biochar are altered through different biotic and abiotic factors. ...
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This literature review explores the assessment of biochar quality and its impact on soil properties using diffuse reflectance spectroscopy. Biochar, a product of biomass pyrolysis, is recognized for its positive effects on soil fertility and carbon sequestration. This review emphasizes the need for systematic research on biochar stability and highlights the potential of diffuse reflectance spectroscopy for analyzing soil–biochar interactions. Biochar acts as a soil conditioner, improving physical, chemical, and biological properties and enhancing soil fertility and crop yield. Furthermore, it aids in mitigating climate change by sequestering carbon dioxide. However, the long-term behavior of biochar and its interactions with various factors require further field research for optimal utilization, as the aging process of biochar in soil is complex, involving physical, chemical, and biological interactions that influence its impact on the agroecosystem. This review also emphasizes the importance of studying the interaction between biochar and soil microbes, as it plays a crucial role in enhancing soil fertility and plant resistance to pathogens. However, research on this interaction is limited. VIS-NIR spectroscopy is a valuable tool for monitoring biochar application to soil. Nevertheless, controversial results highlight the intricate interactions between biochar, soil, and environmental conditions.
... Contrarily, several research have revealed that the ageing process might cause a decrease in the ability of BC to adsorb contaminants. For instance, Zhang et al. (2016) showed that when BC ages, soil-dissolved organic debris blocks the pores, limiting its capacity to sorb contaminants. Future research is required to determine how NB impacts the retention and adsorption of heavy metals throughout time because the ageing process is complex . ...
Growing demand for foods for billions of hungry mouths is imitating high-yielding crop production which needs the application of an enormous amount of chemicals. Several human activities in recent years for societal development are also on the front foot. These agricultural activities coupled with non-systematic societal development create serious environmental pollution. Many technologies have been developed by impregnating biochar with hydrogel composites, as a sorbent to remove pollutants from water and soil. Biochar is a stable carbon-dominant material with porous structure, high surface area, developed pore structure, and low cost, which ensure its applicability as a porous absorbent. Agricultural waste biomass can be successfully converted into biochar by pyrolysis or thermochemical conversion technique. On the other hand, hydrogels are three-dimensional hydrophilic polymer molecules that can accommodate a significant fraction of fluids in their swelling form. Due to its unique bio-degradability, biocompatibility, and water retention properties, hydrogels are used as a carrier of biochar-based compounds to remediate environmental pollution. The formation of the biochar hydrogel composite systems could synergistically improve the inherent property of the sorbent system for the removal of contaminants. The most beneficial use of hydrogel-biochar nanocomposites is to remove the organic contaminant and toxic elements including chromium, arsenic, mercury, and lead in the aquatic environment via simultaneous adsorption and degradation. Most importantly, these composites contribute to waste management, climate change mitigation, and improving soil fertility. Water contaminants like phenol, dyes, and pharmaceutical hazardous compounds are effectively degraded by biochar-supported photocatalysts. In this chapter, an overview of current progress in the preparation of biochar-loaded hydrogel composites system is provided along with the potential application for removing the unwanted environmental threat. Herein, the chapter begins with a fundamental environmental contaminant and their effect on social ecosystem. We provide the basic information regarding practical information of biochar-based nanocomposites in the treatment of environmental contaminants.KeywordsBiodegradabilityBio-compatibilityEnvironmental contaminantHeavy metalPorous structureSurface areaWater treatment
... Contrarily, several research have revealed that the ageing process might cause a decrease in the ability of BC to adsorb contaminants. For instance, Zhang et al. (2016) showed that when BC ages, soil-dissolved organic debris blocks the pores, limiting its capacity to sorb contaminants. Future research is required to determine how NB impacts the retention and adsorption of heavy metals throughout time because the ageing process is complex . ...
Biochar is a solid carbonaceous pyrolyzed product prepared from various lignocellulosic biomass (agriculture and crop residues), sewage sludge, waste products obtained from different sources, litters, animal manures, etc., under limited oxygen conditions. In recent times, biochar applications in soil remediation, removal of hazardous organic and inorganic contaminants, wastewater treatment, electrode material, catalysis, etc., have drawn worldwide curiosity because of its unique properties. Instead of having unique properties, biochar application range is still limited due to its heterogeneous surface functionality, low porosity, and less adsorption capacity. The physicochemical properties of carbonaceous materials can be improved through various physical and chemical techniques, and biochar may be a better carbonaceous material due to its inexpensive and easy production process. Among physical modification techniques, steam activation is an environmentally and economically sustainable easy modification technique free from the use of any chemicals. With the advancement of nanotechnology, nanoscale engineering of biochar has captured care from scientific societies due to its nano-sized fabrication with excellent physical, chemical, and surface properties. Various mechanochemical techniques such as ball milling, microwave irradiation, and magnetic modification are vastly used for the nanoscale fabrication of biochar materials. Nanoscale engineering further increases the stability and efficiency of raw biochar material over physical modification techniques. This chapter includes steam activation used for physical activation of biochar as well as three selected mechanochemical techniques, viz. ball milling, microwave irradiation, and magnetic modification used for nanoscale modification of biochar along with their application in various fields. Biochar modification and its fabrication into nanoscale form is not only a novel approach but also provides a more advanced and efficient waste management technique.KeywordsBall millingMagnetic modificationsMicrowave irradiationModification of biocharNano-biochar materialsSteam activation
... Contrarily, several research have revealed that the ageing process might cause a decrease in the ability of BC to adsorb contaminants. For instance, Zhang et al. (2016) showed that when BC ages, soil-dissolved organic debris blocks the pores, limiting its capacity to sorb contaminants. Future research is required to determine how NB impacts the retention and adsorption of heavy metals throughout time because the ageing process is complex . ...
Dyes are extensively used in textile, leather accessories, paper, paint, printing, furniture, food, and plastic products. Release of untreated dyes causes adverse effects on environment. Different physical and biological treatments are inefficient to treat dyes. In this regard, photocatalysis using nanoparticles has emerged as an efficient method for degradation of the dyes. TiO2, Fe2O3, and ZnO under UV or sunlight exposure are used as nano-photocatalysts. These nano-photocatalysts have potential to convert toxic pollutants into simpler end products such as CO2 and H2O without generation of secondary pollutants. Photocatalytic degradation of dyes is mainly affected by concentration of dye, amount of photocatalyst, intensity of irradiated light, time of irradiation, and effect of dissolved oxygen and pH. Biochar has emerged as an eco-friendly, cost-effective, and multi-functional product prepared from thermo-chemical conversion of different biomass-based wastes. Physico-chemical properties of biochar enable it to support various light-active components with easy isolation and recovery of catalyst. Incorporation of biochar with nano-photocatalyst provides enhanced porosity, specific surface area, number of active sites, chemical stability, charge separation, and photocatalytic efficiency. The present chapter focuses on fundamentals of photocatalytic process, synthesis of biochar supported nano-photocatalysts, their application for removal of dyes, mechanism involved, and future prospects.KeywordsBiocharDyesNanoparticlesNano-photocatalystPhotocatalysis
... At the same aging time with different levels of bamboo charcoal addition, at 28 days of aging, the concentration of diuron was found to be higher in corn plants in the groups treated with the additional levels of 0.1% and 0.5% bamboo charcoal than in the groups treated without the addition of bamboo charcoal, while the opposite was true for the biomass. Zhang et al. (2016) found that the adsorption capacity of biochar decreased as the aging time of biochar increased. Therefore, some of the adsorbed diuron may be desorbed out of the biochar after aging for some time and thus absorbed by the corn plant, increasing the diuron content in the plant, at which time the toxic effect of diuron inhibits the growth of the corn plant. ...
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Purpose In this study, the adsorption behavior of diuron in a typical black soil and its bioavailability to crops and earthworms were investigated by adsorption and incubation experiments, combined with biochar amendment and aging time. Methods In this study, the adsorption of diuron, and its uptake by corn and earthworms were investigated in black soil with 0.1–5% (w/w) bamboo charcoal. Results Uptake of diuron by corns was reduced by 45% in black soil aged for 0 day in 0.1–5% biochar-amended soil, the concentration of diuron in both roots and stems of corn plants tended to decrease with the increase of aging time, and the enrichment coefficient of diuron in corn also tended to decrease in 0.1–5% biochar-amended soil. When aging time was 0 day and the biochar amendment in black soil was 0.1–5%, the accumulation concentration of diuron in earthworms decreased by 63%; the bioconcentration coefficient of diuron in earthworms in black soil with different levels of biochar decreased continuously with the increase of aging time. Conclusion Biochar is an efficient adsorbent for diuron and could significantly reduce the uptake of diuron by plants and earthworms from contaminated soil. Significant correlations indicated that regression analyses could be constructed between the bioconcentration factor and sorption coefficients to predict the bioavailability of diuron residues in soil to corns and earthworms. Biochar amendment could be used as an option to immobilize diuron in soil and protect non-target organisms from diuron contamination.
... The current study aims to investigate the collaborative degradation of plasticizers in flooded soil using MBC and naturally occurring field microorganisms. Diethyl phthalate (DP) was selected as the model PAEs for this investigation since it is one of the most widely utilized PAEs in comparison to other plasticizer types and has been found in numerous contaminated fields [25]. A multidisciplinary approach was employed to characterize the metabolic processes involved in DP degradation. ...
There has been growing concern over the release of plasticizers from plastic products, and the high levels of plasticizers in the environment have led to a threat to ecological security. Although some plasticizers may naturally degrade, their slow removal and prolonged life cycle remain challenges. To address this, this study explored a unique hybrid strategy using native field microorganisms and magnetic biochar (MBC) to support the upstream degradation of plasticizers. Diethyl phthalate (DP) was used as the test subject. The study found that MBC treatment led to high level of total organic carbon (TOC) and various organic products, demonstrating the degradation of DP. Analysis of the hybrid metagenomic model showed that several species of Pseudomonas can degrade downstream phenylmethanal and Pseudomonas nitroreducens has the ability to cooperate well with MBC due to its iron receptor and transporter. Additionally, a Pigmentiphaga species was found to have the ability to fully mineralize DP. Analysis of the Pigmentiphaga pangenome revealed that genes related to DP biodegradation were shared by members of this genus. Although some members of Pseudomonas is known to be pathogenic, the species identified in the study may not be harmful as they lack virulence factors. The study provides evidence regarding the cooperation between native biodegraders and MBC in mineralizing plasticizers, offering a new solution for removing phthalate plasticizers from soil and surface water.
The use of biochar–mineral composites has been rapidly developed, supplying numerous benefits to environmental applications including soil and water remediation, specifically assisting in wastewater treatment. They offer an advantageous diversity of shapes, micro- and nanosized particles, and functional groups. Therefore, biochar–minerals are used to absorb, retain, and degrade toxic metals and emerging organic contaminants. Moreover, environmental microorganisms can improve their performance in a synergic way. Current knowledge in nanotechnology and biotechnology enables new approaches for developing and using biochar–mineral composites. This chapter describes how researchers have taken advantage of these new tools. Also, the authors aim to highlight those examples of biochar–mineral-based composites that demonstrate multifunctional performance and a remarkable capacity to solve current environmental issues.
Environmental pollution and food safety have become key public health issues to be addressed in China. Since they are closely related to the green development of agriculture, it is of great practical significance to elucidate the intrinsic relationships between green development of agriculture, environmental regulation and residents’ health. Based on the panel data of the Yangtze River Economic Belt from 2011 to 2020, this study investigates the impacts of environmental regulation and green development of agriculture on residents’ health and the influencing mechanism by applying fixed effects method, mediating effectsmethod and the spatial Dubin method. Results show that the use of chemical fertilizers, pesticides and agricultural films is harmful to residents’ health; environmental regulation has a negative correlation with the green development of agriculture and affect residents’ health through mediating effects; the green development of agriculture has negative spillover effects on residents’ health, indicating that purchasing finished products instead of producing locally reduces the input of production factors such as chemical fertilizers and pesticides and transfers health risks associated with agricultural production activities to neighboring areas. Intensifying command-and-control environmental regulation will induce the expansion of hidden economic activities and harm local residents’ health, while intensifying market-incentive environmental regulation will lead to the ‘Pollution Haven’ phenomenon because of the ‘race to the bottom’, in government and is harmful to the health of residents in neighboring areas. Therefore, it is necessary to formulate reasonable and feasible policies and strengthen the control and prevention of agricultural pollution to enhance green development of agriculture and improve residents’ health.
Innovative nanostructured materials, such as nanobiochar (NB), have provided a sustainable solution to a number of contemporary concerns. Biochar technology and nanobiotechnology could lead to the development of carbon-based nanomaterials, such as biochar-based nanocomposites, which could revolutionise research in this sector. In recent years, NB has arisen as a technique to improve the biochar’s physical, chemical, and structural properties and so overcome its limits. Researchers’ curiosity about NB’s amazing development in recent years has been piqued due to its potential for expansion in a range of applications. As a result, it is a good choice for soil amendment, pollutant remediation, and wastewater treatment. NB’s proclivity for polluting soil and water, in addition to its benefits, has been a source of concern. To acquire a comprehensive image of the geochemical transport behaviour of NB and the possible risk of contaminant adsorption onto NB carried in the environment, it is essential to comprehend the reactivity potential of NB. Although NB can successfully adsorb micropollutants, it, like other adsorbents, will get saturated over time, necessitating NB regeneration to maintain system effectiveness and long-term use. The environmental and biological toxic effects of NB should also be thoroughly explored before large-scale industrial or environmental applications. In a nutshell, this chapter covers the most state-of-the-art information on regeneration, reactivity, and toxicity, as well as challenges that need to be addressed in the future research. The main takeaways from this chapter are the necessity of understanding NB’s behaviour, transport cycle, and potential risk of pollutant adsorption onto NB being released into the environment. One of the primary challenges to overcome for the successful application of NB in the environment is the absence of characterization methods, poor yields, a lack of ecotoxicological data, and the requirement for cost–benefit analyses and life-cycle assessments for innumerable applications.KeywordsBiotoxicityEngineered nanomaterials (ENMs)NanobiocharReactivityRecovery
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Phthalic acid esters have been used as plasticizers in numerous products and classified as endocrine-disrupting compounds. As China is one of the largest consumers of phthalic acid esters, some human activities may lead to the accumulation of phthalic acid esters in soil and result in contamination. Therefore, it is necessary for us to understand the current contamination status and to identify appropriate remediation technologies. Here, we reviewed the potential sources, distribution, and contamination status of phthalic acid esters in soil. We then described the ecological effect and human risk of phthalic acid esters and finally provided technologies to remediate phthalic acid esters. We found that (1) the application of plastic agricultural films, municipal biosolids, agricultural chemicals, and wastewater irrigation have been identified as the main sources for phthalic acid ester contamination in agricultural soil; (2) the distribution of phthalic acid esters in soils is determined by factors such as anthropogenic behaviors, soil type, properties of phthalic acid esters, seasonal variation, etc.; (3) the concentrations of phthalic acid esters in soil in most regions of China are exceeding the recommended values of soil cleanup guidelines used by the US Environmental Protection Agency (US EPA), causing phthalic acid ester in soils to contaminate vegetables; (4) phthalic acid esters are toxic to soil microbes and enzymes; and (5) phthalic acid ester-contaminated soil can be remedied by degradation, phytoremediation, and adsorption.
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Purpose Fresh biochar was shown to effectively reduce concentrations of heavy metal in soil, but the influences of the aging processes of biochar and competitions from other elements are warranted to precisely evaluate the long-term effect of biochar. This work investigated the effects of water washing, oxidation, and coexistence of aluminum (Al) on cadmium (Cd) adsorption by biochars and oxidized biochars. Materials and methods The Cd adsorption and the competitive adsorption of Cd and Al to rice straw-derived biochars, before and after oxidation by HNO3/H2SO4, were investigated. Meanwhile, the structural characteristics and surface charges of primary and oxidized biochars, with and without Cd loading, were analyzed by scanning electron microscopy, fourier-transform infrared spectroscopy, and zeta potential. Results and discussion The adsorption of Cd onto fresh biochars was dominated by surface complexation of oxygen-containing functional groups via esterification reactions, which was regulated by solution pH. Oxidization (aging) introduced carboxylic functional groups to biochar surfaces, which served as additional binding sites for Cd. The Cd binding to biochars was significantly affected by the coexistence of Al via acidification and competition for adsorption sites. Conclusions The biochars exhibited high sorption capacities of Cd in soil, but soil acidification led to a counteractive of biochar’s liming effect and a reduction of Cd-binding sites; thus, the long-term effect of biochar for heavy metal immobilization should be paid more attention in acidic soil.
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Diethyl phthalate (DEP) is one of the most commonly used plasticizers as well as a soil contaminant. Using biochar to remediate soils contaminated with DEP can potentially reduce the bioavailability of DEP and improve soil properties. Therefore, a laboratory study was conducted to evaluate the effect of biochar on soil adsorption and desorption of DEP. Two surface soils (0-20 cm) with contrasting organic carbon (OC) contents were collected from a vegetable garden. Biochars were derived from bamboo (BB) and rice straw (SB) that were pyrolyzed at 350 and 650 A degrees C. Biochars were added to two types of soil at rates of 0.1 and 0.5 % (w/w). A batch equilibration method was used to measure DEP adsorption-desorption in biochar treated and untreated soils at 25 A degrees C. The adsorption and desorption isotherms of DEP in the soils with or without biochar were evaluated using the Freundlich model. The biochar treatments significantly enhanced the soil adsorption of DEP. Compared to the untreated low organic matter soil, the soils treated with 0.5 % 650BB increased the adsorption by more than 19,000 times. For the straw biochar treated soils, the increase of DEP adsorption followed the order 350SB > 650SB. However, for the bamboo biochars, the order was 650BB > 350BB. Bamboo biochars were more effective than the straw biochars in improving soils' adsorption capacity and reducing the desorption ability of DEP. Adding biochar to soil can significantly enhance soil's adsorption capacity on DEP. The 650BB amended soil showed the highest adsorption capacity for DEP. The native soil OC contents had significant effects on the soils' sorption capacity treated with 650BB, whereas they had negligible effects on the other biochar treatments. The sorption capacity was affected by many factors such as the feedstock materials and pyrolysis temperature of biochars, the pH value of biochar, and the soil organic carbon levels.
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Lignin, after cellulose, is the second most abundant biopolymer on Earth, accounting for 30% of the organic carbon in the biosphere. It is considered an important evolutionary adaptation of plants during their transition from the aquatic environment to land, since it bestowed the early tracheophytes with physical support to stand upright and enabled long-distance transport of water and solutes by waterproofing the vascular tissue. Although essential for plant growth and development, lignin is the major plant cell wall component responsible for biomass recalcitrance to industrial processing. The fact that lignin is a non-linear aromatic polymer built with chemically diverse and poorly reactive linkages and a variety of monomer units precludes the ability of any single enzyme to properly recognize and degrade it. Consequently, the use of lignocellulosic feedstock as a renewable and sustainable resource for the production of biofuels and bio-based materials will depend on the identification and characterization of the factors that determine plant biomass recalcitrance, especially the highly complex phenolic polymer lignin. Here, we summarize the current knowledge regarding lignin metabolism in plants, its effect on biomass recalcitrance and the emergent strategies to modify biomass recalcitrance through metabolic engineering of the lignin pathway. In addition, the potential use of sugarcane as a second-generation biofuel crop and the advances in lignin-related studies in sugarcane are discussed.
Black carbon (charcoal, char, soot, biochar) in its raw state can be a strong adsorbent of organic compounds. This chapter reviews and presents new evidence that during weathering in soil, the surface activity of black carbon becomes reduced by deposition of natural organic matter from the surrounding soil matrix on its surfaces. This can rapidly lead to as much as a two-order-of-magnitude decline in the distribution coefficient of the contaminant and a sharp decline in the N2 B.E.T. specific surface area of the black carbon in the mixture. Humic substances suppress sorption by competing for sorption sites and, at cryogenic temperatures, by blocking pore entrances. The competitive effect increases with adsorbate molecular size due to size exclusion (steric) constraints that allow smaller molecules greater access to interior surfaces. It may also increase to the extent adsorbate and humics undergo common interactions with the surface, such as H-bonding. Weathering of black carbon must be taken into accounted in contaminant fate models and in strategies involving the use of black carbon for crop enhancement or soil stabilization. © 2013 Zhejiang University Press and Springer Science+Business Media Dordrecht. All rights are reserved.