Effectiveness of Activated Biochar from Rubber (Hevea
brasiliensis) Seed Shells and Epicarp As an Amelioration Material Against Pesticide Residues in The Soil
Sumihar Hutapea1, Ellen Lumisar Panggabean1, Tumpal HS Siregar2, Andi Wijaya2
1. Medan Area University, Agricultural Faculty, Department of Agrotechnology,. Jl. Kolam No. 1 Medan Estate, Medan 20223, Indonesia.
2. Indonesian Rubber Research Institute (IRRI), Sungei Putih Research Center. Galang-Deli Serdang, Po Box 1415, Medan 20001, Indonesia.
Abstract
Producing environment-friendly technology is important to improve the quality of corps land and dairy products through the utilization of biomass waste as amelioration agent of pesticide residues in agricultural land. It had investigated that pesticide was widely used on holticultural land in Karo District to prevent crop failure caused by pests.
Generally, farmers used pesticide on chilies, onions or tuberous root groups and it was also expected to contaminate the products produced by the plant so that it can cause health problem. This study aimed to determine adsorption capacity in the soil using activated biochar from epicarp and rubber seed shells (Hevea brasiliensis). This experiment used two soil samples from Sukanalu and Korpri village, Karo District, North Sumatera-Indonesia. Each soil sample was equilibrated with varying concentration of cypermethrin and chlorpyrifos, i.e 3, 6, 9, and 12 ppm. Langmuir and Freundlich isotherms model were used to explain equilibrium adsorption. The result showed that from these isotherms it was evaluated that Freundlich isotherm was obeyed with adsorption capacity of cypermethrin about 1.786 mg/g (R2=0.963) for Sukanalu and 1.247 mg/g (R2=0.983) for Korpri. Adsorption capacity of chlorpyrifos about 2.529 mg/g (R2= 0.905) for Sukanalu and 5.395 mg/g (R2=0.929) for Korpri. Generally, activated biochar applied by soil sample of Korpri had bigger adsorption capacity than soil sample of Sukanalu. Adsorption mechanism of pesticide residue was integrated by clay of soil structure, organic material, and pH value.
Keywords : Hevea brasiliensis, activated biochar, cypermethrin, chlorpyrifos, adsorption capacity
1. INTRODUCTION
As the product of photosynthesis from carbon dioxide and water, biomass is the only renewable resource available for both energy and chemical feedstock production. Among different utilization method of biomass, this study focus on biochar, which is the solid product of pyrolysis. At moderately high temperature in an inert atmosphere, pyrolysis thermally decomposes the carbohydrate structure of biomass into carbonaceous solid residue (biochar), and condensable and non condensable vapors of various molecular weight compounds.
Biochar is a value added product, which can be used for many purpose (Lee, et al., 2013).
Recently, the application of biochar to soil is drawing greater attention for sustainable soil quality improvement and carbon sequestration (Lehmann et al., 2006; Woolf et al., 2010;
Sohi, 2012). In the soil, biochar increases the capacity of the soil holding water and nutrients, reducing the need for fertilizers. Many small and field test reported increases in the plant growth and crop productivity after mixing biochar with the soil (Jeffery et al., 2011). Biochar also reduces the emission of other greenhouse gases from the soil, such as N2O and CH4 (Van Zweiten et al., 2009). More importantly, biochar can directly store the carbon for a sufficiently long time due to its strong resistance to biological decomposition (Preston and Schmidt, 2006; Liang et al., 2008).
For global warming prevention, it is important to study the sequestration mechanism of carbon in soil of farmland where biochar and composts are used. By using biochar carbonized with biomass materials such as waste wood, bamboo, and agricultural materials in farmland, carbon storage in the soil for long period is expected. As the soil properties are improved and soil microorganisms concentration increase with the addition of charcoal to the soil, the plant growth promotion in the farmland is also expected.
Growth stimulation of the spinach in the farmland used with the charcoal and the composts was observed. The aggregation of the soil in farmland was developed by using the biochar and the composts. It was suggested that the soil was aggregated with microorganisms proliferated on the surface of the aggregate in the soil (Shuji, et al., 2013).
The role agrochemical in modern agriculture is continuously evolving, and their contribution to crop protection continues to increase. Linking science and policy is a cornerstone of the work of both the regulatory authorities and industry. Pesticide are widely used in producing food and feed. Their residues may remain in small amounts in or on agricultural produce and processed food. To ensure the safety of food, most governments regulate the maximum level of each permitted pesticide residue (Byung-Youl, 2001).
In principle, all chemicals, including pesticides, which are introduced into the environment are gradually recycled within and between the bio-, geo-, atmo-, and hydro- spheric systems. The rate at which pesticides are moved and dissipated is closely related to the physico-chemical parameters of the chemical itself and surrounding environmental conditions. The latter factors include application time and dose, land use patterns and target crops. Factors related to climate and weather include temperature, rainfall, evapo-transpiration rates and wind velocity. Parameters related to soil are run-off characteristics, organic carbon content, texture, hydraulic characteristics and pH (Byung-Youl, 2001).
The experiment about effectivity of activated biochar from rubber seed shells and epicarp wastes (Hevea brasiliensis) as a amelioration material towards pesticide residues in the soil aimed to determine the adsorption capacity of cypermethrin and chlorpyrifos residue using the Langmuir and Freundlich isotherm models.
2. MATERIALS AND METHODS
A series of experiments on adsorption of pesticide residues in some soil samples was carried out in July and August 2016. The soil sample was obtained from Sukanalu and Korpri village, Karo District, North Sumatra-Indonesia. The series experiments consist of manufacturing activated biochar and test of adsorption isotherm of pesticide residues in the soil.
2.1. Preparation and manufacturing activated biochar
Rubber seed shell and epicarp wastes were obtained from experimental field of Sungei Putih, Galang-Deli Serdang. The properties of biochar were studied from rubber seed shells and epicarp waste. The reactor was made of metal with a diameter of 57 cm and a height of 120 cm for carbonization. After carbonization, biochar was placed inside an electrically-
heated furnace. In each test, 100-400 g of sample was heated from room temperature to 800oC and maintained for at least two hour to allow sufficient time for complete pyrolysis. A detailed description of process and analytical methods has been presented elsewhere (Hutapea, 2015).
2.2. Test and analysis adsorption of pesticide residues in the soil
For laboratory study the inert soil samples were collected from the 0 to 15 cm soil depth and ground to pass through a 2 mm sieve. These soil samples were stored in plastic bags at room temperature. The standard methods were used to determine physicochemical properties of the soil.
Residue pesticides adsorption isotherms were determined according to the procedure of Muktamar (2015). Fifty gram of soil sample was equilibrated with 20 ml of varying concentrations of cypermethrin and chlorpyrifos in 0.01 M CaCl2 solution in erlenmeyer. The concentrations of the solutions were 3, 6, 9, 12 ppm. Then soil sample was incubated for a week.
Analysis of pesticide residues in soil used the QuEChERS (quick, easy, cheap, rugged, and safe) method using a single-step buffered acetonitrile (MeCN) extraction and salting out liquid-liquid partitioning from the water in the sample with MgSO4. Dispersive-solid-phase extraction (dispersive-SPE) cleanup was done to remove organic acids, excess water, and other components with a combination of primary secondary amine (PSA) sorbent and MgSO4; then the extracts were analyzed by mass spectrometry (MS) techniques after a chromatographic analytical separation (AOAC, 2007).
Calculation of residual concentration using the formula:
2.3. Langmuir isotherm model
This model deals with monolayer and homogeneous adsorption because the adsorbed layer is one molecule in thickness, with adsorption occurring at fixed sites, which are identical and equivalent. Linear form of this model is given in Equation (1):
Ce/(x/m) = 1/ab + 1/a Ce……….. (1)
Where Ce is the equilibrium concentration of pesticides in solution and x/m is the amount of pesticides residue in soil, a is the monolayer adsorption capacity, and b is Langmuir isotherm which was not obeyed by adsorption of pesticides residue (cypermethrin and chlorpyrifos).
2.4. Freundlich isotherm model
Freundlich isotherm is related to the non-ideal and reversible adsorption, not limited to monolayer formation. Therefore is applied to multilayer adsorption, with non-uniform distribution of adsorption heat and affinities over the heterogeneous surface. Linear form of this model is given as in Equation (2).
Log (x/m) = log k + 1/n log Ce ………. (2)
Where k is multilayer adsorption capacity and n is adsorption intensity. The parameters of both models are shown in Table 2.
3. RESULTS AND DISCUSSION
Table 1 compares the characteristics of biochar in experiment with SNI standards. The biomass samples exhibit large variations in the proximate analysis, especially in the volatile matter and fixed carbon. From the carbon content and mass yield, the carbon yield
representing the amount of carbon remaining in the biochar can be calculated. Biochar have carbon yields of about 61-65% while the rest have values in the range of 65%.
Tabel 1. Characteristics of biochar compared with SNI standards
Parameters Value
Biochar SNI
standards
Moisture content (%) 3.97 Max. 15
Ash content (%) 3.78 Max. 10
Volatile matter (%) 30.91 Max. 25
Fixed carbon (%) 65.27 Min. 65
Iodium number (mg/g) 875.97 Min. 750
Benzena number (%) 25.94 Min. 25
Sumihar (2015)
The main role of biochar in the soil is the increased retention of nutrients in addition to the direct supply of nutrients. Therefore, the microscopic surface area is one of the crucial properties for biochar, which determines the capability of nutrients and water absorption.
3.1. Soil properties
The soil samples were collected from horticultural land and analyzed in order to evaluate the soil texture and pH value. Table 2 shows the results obtained from these tests. From table 2, it was noticed that the silt percentage is larger than that in the clay. Organic carbon is relatively high (4.07 and 4.22%) which reduced the adsorption of pesticides. Sorption of pesticides to soil generally increases with soil organic matter content (Tiwari and Guha, 2012).
Tabel 2. Physical and chemical soil properties Parameters Sukanalu Korpri Texture
sand (%) 62.87 59.05
silt (%) 33.41 33.50
clay (%) 3.72 7.46
pH (H2O) 5.30 5.70
Organic material
C (%) 4.07 4.22
N (%) 0.78 0.82
P-Bray (ppm) 541.00 448.00
Base saturation (%) 29.91 28.96 CEC (meq/100 g) 32.97 32.45 K-exch (meq/100 g) 6.51 5.39 Ca-exch (meq/100 g) 1.57 2.50 Mg-exch (meq/100 g) 1.31 1.63 Na-exch (meq/100 g) 0.18 0.15
The results of the analysis of both physical and chemical properties soil samples in both groups, namely Sukanalu and Korpri shown in Table 2. The soil samples Sukanalu contains 62.87% sand, 33.41% silt, and 3.72% clay. The pH value of the water is 5.30 and relatively acid. Organic matter content C includes high at 4.07%, while the organic matter content of N is very high, 0.78%. P content is obtained by extracting Bray classified as very high at 541.00 ppm. While the CEC and base saturation values obtained are respectively 32.97 meq / 100 g (high) and 29.91% (lower). The composition of cation in the soil samples Sukanalu includes K at 6.51 meq /100 g (very high), Ca at 1.57 meq /100 g (very low), Mg at 1.31 meq /100 g (moderate), and Na of 0.18 meq /100 g (low). The soil samples of Korpri
contain 59.05% of sand, 33.50% of silt and 5.7% of clay. The pH value of the water is 5.70 and the relatively acid. Organic matter content C includes high at 4.22%, while the organic matter content of N is very high, 0.82%. P content is obtained by extracting Bray classified as very high at 448.00 ppm. While the CEC and base saturation values obtained are respectively 32.45 meq /100 g (high) and 28.96% (lower). The composition of cation in the soil samples of Korpri includes K at 5.39 meq /100 g (very high), Ca at 2.50 meq /100 g (low), Mg of 1.63 meq /100 g (moderate), and Na 0.15 meq /100 g (low). In general, both the soil samples have physical and chemical properties are no different.
3.2. Cypermethrin adsorption isotherms
Tabel 3. The residual values of adsorption by activated biochar on some concentrations of cypermethrin
Sample of soil
C0 (ppm)
Ce (ppm)
Cads (ppm)
Xm/m
(mg/g) Ce/(X/m) log Ce log Xm
Sukanalu 3 1.39 1.61 0.81 1.7267 0.1430 -0.0942
6 2.08 3.92 1.96 1.0612 0.3181 0.2923
9 3.16 5.84 2.92 1.0822 0.4997 0.4654
12 4.02 7.98 3.99 1.0075 0.6042 0.6010
Korpri 3 1.13 1.87 0.94 1.2086 0.0531 -0.0292
6 1.60 4.40 2.20 0.7273 0.2041 0.3424
9 2.18 6.82 3.41 0.6393 0.3385 0.5328
12 2.63 9.37 4.69 0.5614 0.4200 0.6707
The process of absorption or adsorption by an adsorbent is influenced by many factors and patterns within specific adsorption isotherm. Factors that influence in the adsorption process, i.e the type of adsorbent, the type of substance that is absorbed, the surface area of the adsorbent, the substance concentration and temperature. Because of these factors, each adsorbent which absorbs a substance one with another substance would not have the same pattern of the adsorption isotherm (Handayani and Sulistiyono, 2009).
Table 3 shows that the greater the concentration of pesticides was, the greater the mass of pesticide was adsorbed by biochar. In concentration of 3 ppm of cypermethrin, pesticide was adsorbed by biochar about 0.81 mg/gram for Sukanalu and 0.94 mg/gram for Korpri. In concentration of 6 ppm, pesticide was adsorbed by biochar about 1.96 mg/gram for Sukanalu and 2.20 mg/gram for Korpri. In concentration of 9 ppm, pesticide was adsorbed by biochar about 2.92 mg/gram for Sukanalu and 3.41 mg/gram for Korpri. In concentration of 12 ppm, pesticide was adsorbed by biochar about 3.99 mg/gram for Sukanalu and 4.69 mg/gram for Korpri. Generally, the absorption of pesticide residues in soil samples of Korpri was larger than the soil samples of Sukanalu. This condition occured because the soil samples of Korpri have a clay structure that was larger than the soil samples of Sukanalu, so that the absorption of pesticide residues was also influenced by the structure of clay in the soil (Tu, 2001).
Figure 1. Langmuir plot for the Cypermethrin adsorption onto biochar
Figure 2. Freundlich plot for the Cypermethrin adsorption onto biochar Table 4. Equilibrium adsorption isotherm values for cypermethrin pesticide
Soil samples Isotherm Isotherm
parameters Value
Sukanalu Langmuir
a (mg/g) 4.464
b 0.224
R2 0.590
Korpri Langmuir
a (mg/g) 2.525
b 0.396
R2 0.801
Sukanalu Freundlich
k (mg/g) 1.786
n 0.688
R2 0.963
Korpri Freundlich
k (mg/g) 1.247
n 0.534
R2 0.983
The Langmuir adsorption isotherms showed that it is not linear relationship on the present results shown in Figs. 1, but the Freundlich adsorption isotherms showed linear
y = -0.224x + 1.817 R² = 0.59
y = -0.396x + 1.531 R² = 0.801 0.0
0.5 1.0 1.5 2.0
0.0 1.0 2.0 3.0 4.0 5.0
Ce/(Xm/m)
Ce
Sukanalu Korpri
y = 1.454x - 0.252 R² = 0.963 y = 1.873x - 0.096
R² = 0.983
-0.20 0.00 0.20 0.40 0.60 0.80
0.00 0.20 0.40 0.60 0.80
Log Ce/Xm
Log Ce
Sukanalu Korpri
relationship present results shown in Figs. 2. R2 of the Freundlich adsorption isotherms is larger than that in Langmuir adsorption isotherms and close to 1. It means that this Freundlich model was obeyed by adsorption of cypermethrin as shown in Figs. 2.
Adsorption tends to have n between 1 and 10. Larger value of n implies stronger interaction between the soil and the pesticides (Öztürk and Bektas, 2004). The n values were 0.688 and 0.534 for Sukanalu and Korpri respectively in Freundlich isotherm model, showing that adsorption process was unfavorable and this has to do with low percentage of the clay (3.72 and 7.46) and due to the organics material available in the horticultural soil. The multilayey capacity factor of both pesticides (k) is higher than one which shows the good interaction between the soil and the pesticides with more interaction in Sukanalu than Korpri.
The Langmuir adsorption isotherm is commonly applied to monolayer chemisorptions of gases. This isotherm is mainly applied when no strong adsorption is expected and when the adsorption surface is uniform. The Langmuir isotherm shows that adsorption will increase with increasing pesticides concentration up to a saturation point, in which all of the sites are occupied (Fig. 1) (Jodeh, et.al., 2013).
3.3. Chlorpyrifos adsorption isotherms
Tabel 5. The residual values of adsorption by activated biochar on some concentrations of chlorpyrifos
Sample of soil
C0 (ppm)
Ce (ppm)
Cads (ppm)
Xm/m
(mg/g) Ce/(Xm/m) log Ce log Xm
Sukanalu 3 1.82 1.18 0.59 3.0847 0.2601 -0.2291
6 3.06 2.94 1.47 2.0816 0.4857 0.1673
9 5.30 3.70 1.85 2.8649 0.7243 0.2671
12 7.30 4.70 2.35 3.1064 0.8633 0.3710
Korpri 3 2.03 0.97 0.49 4.1856 0.3075 -0.3143
6 3.43 2.57 1.29 2.6693 0.5353 0.1089
9 4.37 4.63 2.32 1.8877 0.6405 0.3645
12 6.57 5.43 2.72 2.4199 0.8176 0.4337
Table 3 shows that the greater the concentration of pesticides was, the greater the mass of pesticide was adsorbed by biochar. In concentration of 3 ppm of chlorpyrifos, pesticide was adsorbed by biochar about 0.59 mg/gram for Sukanalu and 0.49 mg/gram for Korpri. In concentration of 6 ppm, pesticide was adsorbed by biochar about 1.47 mg/gram for Sukanalu and 1.29 mg/gram for Korpri. In concentration of 9 ppm, pesticide was adsorbed by biochar about 1.85 mg/gram for Sukanalu and 2.32 mg/gram for Korpri. In concentration of 12 ppm, pesticide was adsorbed by biochar about 2.35 mg/gram for Sukanalu and 2.72 mg/gram for Korpri. Generally, the absorption of chlorpyrifos residues in soil was smaller than the adsorption of cypermethrin.
Figure 3. Langmuir plot for the chlorpyrifos adsorption onto biochar
Figure 4. Freundlich plot for the chlorpyrifos adsorption onto biochar Tabel 6. Equilibrium adsorption isotherm values for chlorpyrifos pesticide
Soil samples Isotherm Isotherm
parameters Value
Sukanalu Langmuir
a (mg/g) 15.15
b 0.066
R2 0.112
Korpri Langmuir
a (mg/g) 2.755
b 0.363
R2 0.494
Sukanalu Freundlich
k (mg/g) 2.529
n 1.066
R2 0.905
Korpri Freundlich
k (mg/g) 5.395
n 0.653
R2 0.929
y = 0.066x + 2.494 R² = 0.112
y = -0.363x + 4.281 R² = 0.494
0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
0.00 2.00 4.00 6.00 8.00
Ce/(Xm/m)
Ce
Sukanalu Korpri
y = 0.938x - 0.403 R² = 0.905 y = 1.531x - 0.732
R² = 0.929
-0.4 -0.3 -0.2 -0.1 0.0 0.1 0.2 0.3 0.4 0.5 0.6
0.0 0.2 0.4 0.6 0.8 1.0
Log Xm/m
Log Ce
Sukanalu Korpri
The Langmuir adsorption isotherms showed that it is not linear relationship on the present results shown in Figs. 3, but the Freundlich adsorption isotherms showed linear relationship present results shown in Figs. 4. R2 of the Freundlich adsorption isotherms is larger than that in Langmuir adsorption isotherms and close to 1. It means that this Freundlich model was obeyed by adsorption of chlorpyrifos as shown in Figs. 4.
Adsorption tends to have n between 1 and 10. Larger value of n implies stronger interaction between the soil and the pesticides (Öztürk and Bektas, 2004). The n values were 1.066 and 0.653 for Sukanalu and Korpri respectively in Freundlich isotherm model, showing that adsorption process was unfavorable and this has to do with low percentage of the clay (3.72 and 7.46) and due to the organics material available in the horticultural soil. The multilayey capacity factor of both pesticides (k) is higher than one which shows the good interaction between the soil and the pesticides with more interaction in Korpri than Sukanalu.
The Langmuir adsorption isotherm is commonly applied to monolayer chemisorptions of gases. This isotherm is mainly applied when no strong adsorption is expected and when the adsorption surface is uniform.
Generally, the effect of organic matter content in the soil into adsorption residue as the influence of soil clay content. The greater the content of organic material is, the greater the adsorption. Pesticides have the speed for different decay (half-life). The half-life of this will affect the resistance properties of the residue in the soil. The greater half-life is the longer it will stay in the soil and more difficult to be degraded. Activated biochar which has been incorporated into the soil will have different adsorption power compared to the initial state.
This is due to the possibility of activated biochar adsorb other compounds.
4. CONCLUSION
It was evaluated that Freundlich isotherm was obeyed with adsorption capacity of cypermethrin about 1.786 mg/g (R2=0.963) for Sukanalu and 1.247 mg/g (R2=0.983) for Korpri. Adsorption capacity of chlorpyrifos about 2.529 mg/g (R2= 0.905) for Sukanalu and 5.395 mg/g (R2=0.929) for Korpri. Langmuir isotherm model was not obeyed in this experiment because the result showed that R2 value was not close to 1. Generally, activated biochar applied by soil sample of Korpri had larger adsorption capacity than soil sample of Sukanalu. Adsorption mechanism of pesticide residue was integrated by clay of soil structure, organic material, and pH value.
Acknowledgement
We thank Indonesian Rubber Research Institute-Sungei Putih Research Center, University of Medan Area, Ministry of Research and Higher Education (Simlitabmas- competitive research 2016) for the financial support.
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