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Transactions on Engineering and Computing Sciences - Vol. 12, No. 3
Publication Date: June 25, 2024
DOI:10.14738/tecs.123.16957.
Douglas, R. K., Lawrence, C. A., & Ebiundu, K. (2024). Pristine Plantain Peels Biochar and Effect of Weathering on Polycyclic Aromatic
Hydrocarbon Biodegradation in Crude Oil-Contaminated Soils. Transactions on Engineering and Computing Sciences, 12(3). 64-72.
Services for Science and Education – United Kingdom
Pristine Plantain Peels Biochar and Effect of Weathering on
Polycyclic Aromatic Hydrocarbon Biodegradation in Crude Oil- Contaminated Soils
Douglas, R. K.
Department of Chemical Engineering Niger Delta University,
Wilberforce Island, Nigeria
Lawrence, C. A.
Department of Chemical Engineering Niger Delta University,
Wilberforce Island, Nigeria
Ebiundu, K.
Department of Chemical Engineering Niger Delta University,
Wilberforce Island, Nigeria
ABSTRACT
The current research compared the potential of an agricultural waste-plantain
peels derived biochar and weathering for the remediation of polycyclic aromatic
hydrocarbons (PAHs) contaminated soil at laboratory scale. PAHs concentrations
ranged from 0.245 to 348.04 mg/kg for the control sample (concentrations
obtained without amendment after 4 day incubation period). Benzo(a)pyrene had
the least concentration, while Chrysene has the highest concentration. Under
weathering conditions, the sum concentration of PAHs was observed to be 694.213,
687.892, and 670.866 mg/kg after 30, 60, and 90 days experiment, respectively.
More PAHs concentration degradation was observed with the PPB amendment
option. That is, with PPB amendment option, the sum concentration of PAHs
obtained were 649.743, 634.532, and 550.369 mg/kg after 30, 60, and 90 day
experiment, respectively. Furthermore, first-order kinetics was used to determine
the kinetics of PAHs degradation, which was applied on both the weathering and the
PPB amendment options. With weathering, PAHs degradation rate constant (K)
increased with decreasing PAHs concentrations; which shows that PAHs
degradation in contaminated soil is slow under the influence of weathering. With
PPB amendment option, the K value decreased between K30 and K60 with decreasing
PAHs concentrations, which implies faster degradation of PAHs. However, reverse
was the case between K60 and K90. This shows slow degradation of PAHs. Results
suggest that the PPB option is promising for the restoration and/or reclamation of
soil polluted with PAHs.
Keywords: Soil, Hydrocarbons, Weathering, Biochar, Biodegradation, Kinetics
INTRODUCTION
Environmental contamination is currently a critical challenge globally, and a serious threat to
human and environment health [1]. According to [2], crude oil exploration and exploitation
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Douglas, R. K., Lawrence, C. A., & Ebiundu, K. (2024). Pristine Plantain Peels Biochar and Effect of Weathering on Polycyclic Aromatic Hydrocarbon
Biodegradation in Crude Oil-Contaminated Soils. Transactions on Engineering and Computing Sciences, 12(3). 64-72.
URL: http://dx.doi.org/10.14738/tecs.123.16957
activities, accidental spills, sabotage etc, are critical issues accountable for environmental
pollution and degradation from petroleum hydrocarbons (PHCs) and its derivatives. Crude oil
is a complex mixture-comprising aliphatic and aromatic hydrocarbon compounds, and traces
of heterocyclic compounds-comprising sulphur, nitrogen, oxygen; which are acknowledged
environmental contaminants [3; 4]. PHC compounds are generally toxic, and impacts negatively
on soil’s physicochemical properties [5]. PHC induced pollution is a grave environmental
problem due its immobilization and consequent buildup nature in the environment [6]; and is
severely impacting the ecosystems wellbeing and humans [5; 7]. It was reported that the micro- organisms population in the soil was greatly depends on the level of PHC concentration [8].
Crude oil also contains potentially toxic elements (PTEs) including silver, Ag; titanium, Ti;
arsenic, As; nickel, Ni; cobalt, Co; lead, Pb; manganese, Mn; copper, Cu; iron, Fe; zinc, Zn;
cadmium, Cd; magnesium, Mg; chromium, Cr; amongst others [9]. Soil contamination by PTEs
has attracted substantial ecological concern due to their toxicity and bioaccumulation. Nigeria
has been ranked largest natural gas reserve and the second largest oil reserve in Africa. In the
Niger Delta region of Nigeria (Ogoni land in Rivers State), [10] reported that crude oil pollution
has deeply affected soil, air, and water quality criteria and thus posing a serious threat to both
human health and the environment. This is same in the other crude oil producing states,
especially, Bayelsa, Delta, Akwa Ibom, and Ondo states in the region. The devastating
environmental pollution and degradation and associated impacts in the Niger Delta, Nigeria are
primarily due oil theft; oil bunkering; artisanal (illegal) refining of crude oil in Nigeria; technical
or operational error; un-serviced oil infrastructure; and hazardous waste management. Thus,
there is need for contaminated land management in the region; which is the responsibility of
the Environment Unit at the Department of Petroleum Resources (DPR), and the National Oil
Spill Detection and Response Agency (NOSDRA). DPR is responsible for managing legacy sites
and NOSDRA is responsible for the detection and management of emerging oil spills [11; 12;
13]. However, Nigeria lacks the necessary funds and the expertise to handle these critical issues
of environmental pollution and degradation caused by the activities of the oil and gas industries
in the Niger Delta region. Therefore, there is need to develop simple, cost-effective, low-carbon,
and sustainable means and/ or methods (e.g., bioremediation by agricultural waste) to address
the issues of PHCs-contaminated soils and/or land sites in the laboratory first, and later take
the laboratory to the field to address this alarming and devastating problem of land pollution
and degradation in the region.
Remediation of PHCs-contaminated land sites has become a global concern due to the negative
effects of PHCs on the environment (soil, water, and air) and human health. Considerable efforts
have been dedicated to developing simple adoptable methods for the remediation of PHCs- contaminated soils and/or land sites. Currently used PHCs-contaminated soil remediation
methods include excavation, burning (i.e., physical, chemical approaches); chemical (detergent,
surfactant, degreaser), phytoremediation (the use of plants), and biological (bioremediation)
[5; 14]. However, there are shortcomings associated with existing remediation techniques. For
instance, thermal desorption is costly and prone to secondary pollution [15].
Contaminated soil remediation by phytoremediation is the application of plants to remove
and/or mitigate contaminants in the environment [16]. This technique has been proven
effective for the remediation of environmental contaminants including petroleum products,
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Transactions on Engineering and Computing Sciences (TECS) Vol 12, Issue 3, June - 2024
Services for Science and Education – United Kingdom
and heavy metals. However, plant for phytoremediation should tolerate both the climatic and
soil conditions of the prevailing polluted environment [5]. According to [17], for a plant to be
fit for the phytoremediation of contaminated soils, such plant should have the potential to
accumulate the extracted contaminant; should be tolerant enough not only to survive in the
contaminated environment, but also adsorb contaminants into their shoots; be able to grow
rapidly with the capacity to accumulate possible toxins; and be easily harvested and simply
disposed.
Bioremediation by the use of agricultural wastes have been reported cost-effective and a simple
approach for contaminated soil remediation [18; 19]. Consequently, the current research aims
to assess the potential of pristine plantain peels-based biochar (PPB); which might constitutes
environment pollution if not properly dispose of for PAHs biodegradation in crude oil- contaminated soil. Furthermore, the specific objective was to compare the biochar induced
degradation with the effect of weathering.
MATERIALS AND METHODS
Soil Sample Collection
1kg pristine soil sample was collected from the Niger Delta University, Department of
Agricultural and Environmental Engineering Research Farm, Amassoma, Bayelsa State, Nigeria.
The sampling site has no history of hydrocarbon pollution. A subsurface soil sample was
collected from top 0-20cm layer using a hand trowel and taken with polythene bags to the
laboratory. Pristine soil was sieved using 4 mm sieve, and analyzed for hydrocarbon
contamination.
Plantain Peel Collection and Biochar Preparation
A bounce of plantain (fresh) was bought from Swali Ultra-Modern Market (SAM), Bayelsa State,
Nigeria. The plantains were peeled to obtain the peels. The peels were sliced to smaller pieces
and sun dried at ambient condition for 2-3 days. The dried plantain peels were packaged and
taken to the Reaction Kinetics laboratory, Department of Chemical Engineering, Niger Delta
University, Wilberforce Island, Amassoma, Bayelsa State, Nigeria for the production of plantain
peel derived biochar (PPB). The PPB was produced at low-temperature (T = 300oC) at the Niger
Delta University Chemical Engineering Laboratory using a furnace.
Experimental Design
Two (n = 2) soil microcosms (labelled A and C) were set up using 2k soil, and spiked with 250ml
crude oil. The two soil samples were allowed to equilibrate at laboratory conditions for 4 days.
Sample A was amended with 500g PPB, while Sample C was kept as a control (i.e., no
amendment was added to it). All the microcosms were mixed manually to obtain homogenous
samples and kept in the laboratory at laboratory conditions. The soil moisture was adjusted
twice a week by adding deionized water to mimic ambient conditions. Sample B (i.e., the control
sample) was taken for petroleum hydrocarbon analysis by gas chromatography coupled with
mass spectrometry (GC-MS) after the 4 day incubation period. Samples A and B were further
subjected to hydrocarbon analysis by GC-MS at thirty day time intervals (i.e., 30 days, 60 days
and for 90 days) to determine the effect of the amendment option (PPB) on the concentration
of polycyclic aromatic hydrocarbons (PAHs). Furthermore, the influence of weathering and /or
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Douglas, R. K., Lawrence, C. A., & Ebiundu, K. (2024). Pristine Plantain Peels Biochar and Effect of Weathering on Polycyclic Aromatic Hydrocarbon
Biodegradation in Crude Oil-Contaminated Soils. Transactions on Engineering and Computing Sciences, 12(3). 64-72.
URL: http://dx.doi.org/10.14738/tecs.123.16957
aging on the concentration of PAHs in crude oil contaminated soil was investigate at each of the
hydrocarbon concentration measurement time.
PAHs Analysis by GC-MS
A Buchi Speed Extractor E-916 (BUCHI Labortechnik AG, Flawil, Switzerland) was applied to
carry out the hydrocarbon extraction process. It functions by 20 mL steel cells; with each cell
filled with a bed of diatomaceous earth and 10g of sample diluted with quartz. The extraction
solvent was hexane/dichloromethane 9:1 v/v mixture. To carry out the hydrocarbon
extraction, each cell was held at 50oC and 50 bar for 5 min, washed with fresh solvent for 3 min
and washed again with nitrogen for 3 additional minutes. The process was repeated for 10
times for each cell. The extract obtained was concentrated to below 10 mL by a 40oC bath under
nitrogen flow. Pure hexane was used to wash the vials and raise the volume to 10 mL. An Agilent
7820A GC using an MSD5977E mass selection detector (MSD) operating in split mode was used
for analysis of the extracts. The column was an Agilent HP5 MS30 m, 0.25 mm, 0.25 mm column;
using thermal gradient of 40oC (isothermal for 2 min) with a ramp of 7oC/min up to 270oC;
Tamp of 15oC/min up to 320oC; 320oC isotherm for 10 min; and “SCAN” mode (mass from 50 to
600).
RESULTS AND DISCUSSION
Effect of Weathering and Biochar Enhanced Hydrocarbon Degradation
The current study evaluated the effects of weathering and/or aging; and amendment on PAHs
concentrations in crude oil contaminated soils at laboratory scale. Three separate scenarios for
PAHs were considered in the current study-remediation by weathering and /or aging; PPB
enhanced degradation. The amendment option performed better than degradation due
weathering. This was considered in 13 PAHs present in the contaminated soil analyzed. The
PAHs concentrations ranged from 0.245 to 348.04 mg/kg for the control sample (that is, the
concentrations obtained without amendment for 4 day). The Benzo(a)pyrene had the least
concentration (that is 0.245 mg/kg), while Chrysene has the highest concentration value
(348.04 mg/kg). These concentrations were reduced to 347.469 mg/kg, 346.892 mg/kg, and
339.689 mg/kg after 30 day, 60 day, and 90 day, respectively. Expectedly, more hydrocarbons
(PAHs) concentration degradation and /or reduction was observed in the amendment option.
That is, for PPB, the control concentration reduced to 340.473 mg/kg after 30 day, 336.897
mg/kg after 60 day, and 334.278 mg/kg after 90 day. The results are presented in Table 4.1
below. From the results obtained, PPB amendment option performed better than the
weathering and /or aging option.
Table 4.1: Results for weathering and biochar-enhanced biodegradation of PAHs in
crude oil contaminated soils at laboratory scale.
Hydrocarbon Weathering of PAHs at Different Time
Intervals (in days)
Amendment: PPB
PAHs (mg/kg) T, 4d T, 30d T, 60d T, 90d T, 30d T, 60d T, 90d
Acenaphthylene 35.089 34.149 32.792 30. 875 29.56 27.859 26.415
Acenaphthene 6.987 6.406 6.024 5.786 4.954 4.274 4.022
Fluorene 0.735 0.701 0.668 0.579 0.516 0.468 0.397
Phenanthrene 77.018 76.615 74.872 72.286 69.135 67.451 65.941
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Services for Science and Education – United Kingdom
Fluoranthene 70.021 69.871 68.924 67.051 63.142 61.587 59.082
Pyrene 82.978 82.396 82.020 80.486 75.421 73.847 71.206
Benz(a)anthracene 69.987 69.562 69.187 68.012 60.659 57.451 56.012
Chrysene 348.04 347.469 346.892 339.689 340.473 336.897 334.278
Benzo(k)fluoranthene 5.861 5.443 5.117 4.877 4.976 4.107 3.814
Benzo(a)pyrene 0.245 0.218 0.194 0.172 0.104 0.097 0.054
Indeno (1, 2, 3-c, d)
pyrene
0.578 0.536 0.497 0.387 0.309 0.196 0.105
Dibenz (a, h)
anthracene
0.296 0.260 0.203 0.198 0.107 0.089 0.062
Benzo (g, h, i) pyrylene 0.624 0.587 0.502 0.468 0.387 0.209 0.187
Summation (Ʃ) of PAHs 698.459 694.213 687.892 670.866 649.743 634.532 550.369
PPB = Plantain peel derived biochar.
PAHs concentrations decrease was experienced in the two options evaluated. Faster
degradation of PAHs was achieved with PPB, while least PAHs concentrations decrease was
achieved via the effect of weathering and/or aging. This of course was expected as it is a natural
condition which is solely depended on soil microorganisms and environmental conditions.
Removal efficiency (%) of the two options were investigated for PAHs in contaminated soils.
Results show that PPB option outperformed that of weathering and/or aging. While the removal
efficiency of PPB was 6.97, 9.15, and 21.2 % after 30, 60, and 90-day laboratory experiment,
respectively; that of weathering (W) was 0.61, 1.51, and 3.95% after 30, 60, and 90-day
laboratory experiment, respectively. From the literature review investigated for contaminated
soil bioremediation, no study yet on the application of PPB for the bioremediation and
weathering and/or aging of PAHs in contaminated soils.
Furthermore, first-order kinetics was used to determine the kinetics of PAHs bioremediation in
this study. The equation of the first-order kinetics is as follows:
Ct = C0. exp(-kt) (1)
where Ct represents the contaminant’s concentration at time t (mg/kg), k is the first-order
kinetic constant (day-1), C0 represents the initial concentration (mg/kg) of the contaminant, and
t is the time (day). The degradation constant (K) for the three (2) different hydrocarbon
degradation options were calculated for the different time intervals (that is, t = 30, 60, and 90
days) considered in the study.
Table 4.2: Kinetics results for petroleum hydrocarbon degradation by weathering (W);
and by plantain peel based (PPB) biochar.
Degradation time Means of degradation Kinetics results
K30 W 0.00020
K60 W 0.00025
K90 W 0.00045
K30 PPB 0.00241
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Douglas, R. K., Lawrence, C. A., & Ebiundu, K. (2024). Pristine Plantain Peels Biochar and Effect of Weathering on Polycyclic Aromatic Hydrocarbon
Biodegradation in Crude Oil-Contaminated Soils. Transactions on Engineering and Computing Sciences, 12(3). 64-72.
URL: http://dx.doi.org/10.14738/tecs.123.16957
K60 PPB 0.00159
K90 PPB 0.00265
W = weathering; PPB = as defined at the foot of Table 4.1.
Option 1: this approach assessed the impact of weathering on PAHs degradation in crude oil
contaminated soils. In this case, the K values (that is K30 after thirty days, K60 after sixty days,
and K90 after ninety days) does not decrease; rather an increase was observed (Table 4.2). The
results indicate that PAHs degradation in contaminated soil cannot be fast under the influence
of weathering and/or aging. Results support the findings of [20].
Option 2: this remediation option evaluated the impact of PPB on PAHs degradation in crude
oil contaminated soils. In this bioremediation option, a decrease in K value was observed from
K30 to K60 only. This shows that with PPB biochar, PAHs degradation in contaminated soil is
faster. This also support the results of [20]. In contrast, the K value increased between K60 and
K90. This means that with PPB amendment, the reduction of PAHs in polluted soil was slow
between this period. The break in PAHs concentration reduction observed at 60 day of
bioremediation needs further investigation in the course of time.
Furthermore, the study carried out regression analysis to evaluate the relationships that existed
between the various approaches considered for the level PAHs degradation in contaminated
soils. The results for the respective plots are presented in figures 4.1 and 4.2 below. A good
relationship existed between the two remediation options. This is shown by the R-square values
of 0.999 and 0.996 for PAHs concentration after 30-day PPB enhanced degradation versus
weathering enhanced degradation of PAHs after day 30-day experiment; and 0.996 for PAHs
concentration after 60-day PPB enhanced degradation versus weathering enhanced
degradation of PAHs after day 60-day experiment;
Figure 4.1: A plot of regression analysis showing the relationship that existed between PPB
amendments and weathering for PAHs in crude oil contaminated soil after 30 day.
Y= 0.9771x - 2.1899
R2 = 0.9991
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400
PAHs concentration (mg/kg) after 30
day remediation with PPB
Weathered concentrations of PAHs (mg/kg) after 30 day
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Transactions on Engineering and Computing Sciences (TECS) Vol 12, Issue 3, June - 2024
Services for Science and Education – United Kingdom
Figure 4.2: A plot of regression analysis showing the relationship that existed between PPB
amendments and weathering for PAHs in crude oil contaminated soil after 60 day.
CONCLUSION
Industrial and technological advancements have impacted positively on human well-beings
globally. However, their operational activities have impacted negatively on the environment
(soil, water, and air) causing environmental pollution and degradation. Thus, there is need for
appropriate redial actions. Consequently, the current research compared the efficacy of an
agricultural waste-plantain peels derived biochar and weathering (a natural process) for the
remediation of organic pollutant-polycyclic aromatic hydrocarbons (PAHs) contaminated soil
at laboratory scale.
The PAHs concentrations ranged from 0.245 to 348.04 mg/kg for the control sample (that is,
the concentrations obtained without amendment after 4-day incubation period).
Benzo(a)pyrene had the least concentration, while Chrysene has the highest concentration.
Under weathering conditions, the sum concentration of PAHs was observed to be 694.213,
687.892, and 670.866 mg/kg after 30, 60, and 90 days experiment, respectively. Expectedly,
more hydrocarbons (PAHs) concentration degradation and /or reduction was observed in the
amendment option. That is, with PPB amendment option, the sum concentration of PAHs
obtained were 649.743, 634.532, and 550.369 mg/kg after 30, 60, and 90-day experiment,
respectively.
Furthermore, first-order kinetics was used to determine the kinetics of PAHs bioremediation in
this study. This was applied on both the weathering and the PPB amendment options. During
weathering of PAHs, the degradation rate constant (K) increased with decreasing PAHs
concentrations. This shows that PAHs degradation in contaminated soil is slow under the
influence of weathering. In the case of the PPB amendment option, the K value decreased
between K30 and K60 with decreasing PAHs concentrations, which implies faster degradation of
PAHs. However, reverse was the case between K60 and K90. This shows slow degradation of
Y = 1.051x - 4.4921
R2 = 0.9964
0
50
100
150
200
250
300
350
400
0 50 100 150 200 250 300 350 400
PAHs concentration (mg/kg) after 60
day remediation with PPB
Weathered concentration of PAHs (mg/kg) after 60 day
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Douglas, R. K., Lawrence, C. A., & Ebiundu, K. (2024). Pristine Plantain Peels Biochar and Effect of Weathering on Polycyclic Aromatic Hydrocarbon
Biodegradation in Crude Oil-Contaminated Soils. Transactions on Engineering and Computing Sciences, 12(3). 64-72.
URL: http://dx.doi.org/10.14738/tecs.123.16957
PAHs. Consequently, this is the best option for the restoration and/or reclamation of soil
polluted with PAHs. However, further research is needed to cover more time intervals.
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