Journal of Earth, Environment and Health Sciences

ORIGINAL ARTICLE
Year
: 2016  |  Volume : 2  |  Issue : 1  |  Page : 15--20

Application of Palm Kernel Shell Activated Carbon for the Removal of Pollutant and Color in Palm Oil Mill Effluent Treatment


Nor Faizah Jalani, Astimar Abdul Aziz, Noorshamsiana Abdul Wahab, Wan Hasamudin Wan Hassan, Nahrul Hayawin Zainal 
 Biomass Technology Unit, Engineering and Processing Research Division, Malaysian Palm Oil Board, Ministry of Plantation Industries and Commodities, Bandar Baru Bangi, 43000 Kajang, Selangor, Malaysia

Correspondence Address:
Nor Faizah Jalani
Biomass Technology Unit, Engineering and Processing Research Division, Malaysian Palm Oil Board, Ministry of Plantation Industries and Commodities, 6, Persiaran Institusi, Bandar Baru Bangi, 43000 Kajang, Selangor
Malaysia

Abstract

Introduction: Application of palm kernel shell activated carbon (PKSAC) in reducing the pollutant in palm oil mill effluent (POME) was studied as the alternative treatment system. Aim: The objective of this study was to determine the optimum PKSAC dosage and treatment time for its capability to treat the effluent. Methods: The study was carried out in batch and continuous systems. For batch system, activated carbon dosage ranging from 1% to 15% (w/v) was added into 200 mL of POME and agitated at 160 rpm for 24-120 h treatment time. As for continuous system, POME samples were fed into 2000 mL fixed-bed glass column and run continuously for 8 h/cycle. Results: For the batch study, results showed that the PKSAC works with maximum removal of pollutant at very high dosage up to 15% (w/v) in 72 h treatment time. Meanwhile, for fixed-bed treatment, POME was fed to the column with flow rate of 15 mL/min. The initial chemical oxygen demand (COD) and color of samples were in the range of 450-910 mg/L and 3500-6500 Pt/Co, respectively, and after the treatment, the maximum COD and color removal were 75% and 76%, respectively. The PKSAC became saturated after 8 treatment cycle. Conclusion: It can be concluded that the palm-based activated carbon was able to remove the organic pollutant and color of POME in both batch and continuous adsorption treatments. Being the raw material available in the palm oil mill, the PKS can be converted into activated carbon and used as sustainable practice to treat POME.



How to cite this article:
Jalani NF, Aziz AA, Wahab NA, Hassan WH, Zainal NH. Application of Palm Kernel Shell Activated Carbon for the Removal of Pollutant and Color in Palm Oil Mill Effluent Treatment.J Earth Environ Health Sci 2016;2:15-20


How to cite this URL:
Jalani NF, Aziz AA, Wahab NA, Hassan WH, Zainal NH. Application of Palm Kernel Shell Activated Carbon for the Removal of Pollutant and Color in Palm Oil Mill Effluent Treatment. J Earth Environ Health Sci [serial online] 2016 [cited 2024 Mar 29 ];2:15-20
Available from: https://www.ijeehs.org/text.asp?2016/2/1/15/181802


Full Text

 Introduction



Palm oil is one of the important world commodities, with 85% production of world's oil palm from Indonesia and Malaysia. In 2014, it was reported that about 19.67 million metric tons of crude palm oil (CPO) produced in Malaysia. [1] Commonly, 1 metric ton CPO will generate about 2.5 m 3 of palm oil mill effluent (POME). [2] From this statistic, we can estimate that POME was abundantly generated from the mill with the volume approximately of 49.18 million m 3 /year. If this POME did not treat properly, very large volume of the organic waste will be discharged into the watercourse, hence create pollution and threat the aquatic life.

This POME contains very high organic constituent with biochemical oxygen demand (BOD) of 25,000 mg/L, chemical oxygen demand (COD) of 50,000 mg/L, as well as high total solid which about 40,500 mg/L, and these were due to its high cellulosic materials content. [2] Most of the palm oil mills treat the POME using ponding system to reduce its organic content due to its cheap cost and easy to construct. The systems need long hydraulic retention time up to 120 days and are able to reduce the BOD content down to 100 mg/L. This system needs proper monitoring and maintenance so that the system operates well. [3]

Currently, the Department of Environment of Malaysia is going to impose the final discharge limit for POME from the current BOD level of 100 mg/L down to 20 mg/L for all palm oil mills in Malaysia. [4] There are lots of new and advance technologies/systems available in the market that claims are able to reduce the organic load in the final effluent and comply with the standard requirements. The system includes ultrafiltration (UF), sequencing batch reactor, conventional activated sludge, membrane bioreactor, and coagulation treatment. [5],[6],[7] Although the POME has been treated with those stated technologies, there are still concerns for the POME that being discharged to the water stream which is brownish and sometimes blackish and still visible in water stream.

Moreover, activated carbon has been widely used to adsorb color and pollutant from the conventional and nonconventional wastewater. Activated carbon or charcoal can be derived from agricultural resources or its wastes such as banana peel and oil palm empty fruit bunch. [8],[9] Activated carbon was also tested in various applications such as dye removal from textile mill effluent, COD of coffee processing wastewater as well as decolorization of POME. [10],[11],[12]

Previous studies evaluated the adsorption capability of the prepared activated carbon using artificial pollutants such as methylene blue, phenol, Cr (IV), and copper. [13],[14],[15],[16] A few papers presented the activated carbon adsorption capability using real industrial wastewater, but only single material removal is measured in the study either color or COD. [8],[17] Most of them tested the activated carbon that prepared in laboratory scale with ideal conditions, thus gave very good physical characteristics. On the other hand, Ahmad et al. studied on the modeling of multicomponent adsorption in pretreated POME onto commercial AC for the breakthrough curve prediction. [18]

In promoting toward zero waste in oil palm industry, the palm kernel shell activated carbon (PKSAC) that produced from palm oil mill solid waste is then will be used to treat POME, the liquid waste of palm oil mill. Therefore, the objective of this study is to determine the adsorption capability of the PKSAC in treating the POME by simultaneous removal of organic pollutants (COD, tannin, and lignin) and color, via batch, continuous, and integrated treatment systems.

 Materials and Methods



Activated carbon

The palm-based charcoal was obtained from in-house technology that produced via hollow plinth carbonization furnace system. [19] Then, the charcoal was activated using commercial steam activation kiln with typical steam temperature in the range of 800-1000°C. [17] The Brunauer-Emmett-Teller surface area for this activated carbon was analyzed using accelerated surface area and porosimetry system, ASAP-2000, Micromeritics by nitrogen adsorption and gave value of 566.27 m 2 /g. This value is relatively low compared to surface area of PKSAC that produced in commercial scale as well as in other pilot system such as closed-system brick kiln. [16],[17] Before POME treatment, the activated carbon is soaked with boiled distilled water for 1 h, then rinsed with distilled water, and drained for few minutes. Then, it dried in an oven for 3 h at 100°C to ensure all water evaporate and dry the carbon. This will remove the ash that covered the pore and may reduce the carbon adsorption capability.

Palm oil mill effluent samples

The POME samples were collected from various sampling points, such as final discharge of secondary treatment pond and tertiary treatment plant, from the Malaysian Palm Oil Board, Palm Oil Mill Technology Center in Labu, Negeri Sembilan. The samples were then preserved in a refrigerator at temperature of 4°C before used in the adsorption test.

Instrumentation and analysis

The organic content of POME samples was measured in terms of COD using Hach DR/890 Colorimeter by reactor digestion method that was approved by the US Environmental Protection Agency for reporting of wastewater analysis. Tannin and lignin (measured as tannic acid) contents were also analyzed using HACH DR/890 by tyrosine method. The color of POME was measured using the same colorimeter by following APHA platinum-cobalt standard method. For image analysis, scanning electron microscope (SEM) Hitachi SN-3400 was used to identify the changes of carbon pores before and after the adsorption treatments.

Batch adsorption

Twelve Erlenmeyer flasks were filled with 200 mL of POME sample from the primary aeration pond. PKSAC was weighed into different amounts ranges from 2 to 30 g that gave dosages in the range of 1-15% w/v with respect to the samples volume. Each amount of activated carbon was added to the prepared flask, and all flasks were shaken by SK-600 shaker at 160 rpm. This high shaking speed is used to ensure that the samples and carbon will mix properly and thus maximizing the adsorption capacity. Five milliliters of the sample from each flask was collected at specific time interval between 24 and 120 h and analyzed for color, COD, and tannin-lignin. The percentages of reduction of each adsorbate (COD, color, and tannin-lignin) onto PKSAC were calculated using following the equations:

[INLINE:1]

where Co is the initial adsorbate concentration in solution and Cf is the residual concentration of the adsorbate after adsorption treatment.

Integrated tertiary treatment system and palm kernel shell activated carbon fixed-bed adsorption treatment system

POME samples from primary aeration system were further treated in the fixed-bed adsorption treatment to remove residual organic constituent and the color. POME treatment via UF membrane and chemical treatment system also was carried out before the fixed-bed treatment to enhance the organic constituent and suspended solids removal.

A laboratory-scale, column reactor called as PKSAC fixed-bed column reactor was used in this study. The glass reactor was fabricated with borosilicate glass with diameter of 64 mm, height of 590 mm, and total volume of nearly 2000 mL [Figure 1]. The column consisted of three sections: Bottom, middle, and top. In the column, the activated carbon was filled up as fixed-bed adsorbent. In this system, the POME is pumped through the bottom and flows upward through the column, contacting the media that act simultaneously as adsorbent, bacterial hosts, and filter. The flow rate of influent introduced into the reactor is 15 mL/min. Then, the treated POME leaves the reactor via overflow weirs at the top of the reactor and collected as effluent. This treatment was carried out continuously for 7-8 h/cycle. The treated effluents were collected for every hour for the analysis of COD and color.{Figure 1}

 Results



Palm oil mill effluent characteristics

The analysis of pH, color, and COD of POME samples from various sources is tabulated in [Table 1]. There is no different of pH for the secondary to tertiary treatments. As for COD and color, it reduced as the treatment goes from maturation to primary aeration and tertiary system.{Table 1}

Batch treatment

The adsorption of organic materials and color onto the PKSAC were observed at different dosages and treatment time while using the same agitation speed and sample pH. The adsorption capability measured in terms of organic pollutant reduction in the samples after treatment. The initial COD of POME before PKSAC treatment is 800 mg/L.

[Figure 2]a shows the effect of adsorbent dosages toward the adsorption uptake of pollutant in POME. It can be seen that the adsorption uptakes increases with the increase of dosages from 2 to 16 g in 120 h treatment time. As the dosages increase up to 20 g, the removal of pollutant from the POME became slower, and further increase of the adsorbent dosages above 20 g had not shown significant increment in pollutant removal rate. The maximum COD, color, and tannin-lignin removal in 120 h are 94%, 100%, and 96%, respectively, with 30 g adsorbent dosages.{Figure 2}

[Figure 2]b shows the effect of a period of treatment toward the pollutant removal by PKSAC. At 30 g dosages of the activated carbon, the optimum removal was achieved at 72 h with COD, color, and tannin-lignin removal at 85%, 92%, and 92%, respectively.

Adsorption isotherm

The adsorption isotherm is usually used to model the adsorption capacity of respective adsorbate (pollutants) and also for different types of adsorbents. The constant value describes the surface properties and affinity of the adsorbent. [20] The commonly used equation and isotherms are Langmuir and Freundlich. The Freundlich equations are derived as Equation 2 and linearized as Equation 3. As for Langmuir, the linearized equation is given by Equation 4.

[INLINE:2]

Where qe is the amount of pollutant adsorbed per gram of adsorbent at equilibrium (mg/g), Ce is the equilibrium concentration of pollutant in the solution (mg/L), Kf and n are the constants for Freundlich to indicate the adsorption capacity and intensity, respectively. These constant values can be obtained from the slope and intercept of the plot of log qe versus log Ce , while qm and KL are the Langmuir constants that can be obtained from the slope and intercept from the plots of Ce /qe versus Ce . The qm value is the maximum pollutant uptake capacity for the respective adsorbent and conditions.

It was found that color adsorption onto the PKSAC solely is best fitted into both isotherms with regression value, R2 for Freundlich and Langmuir are 0.90 and 0.95, respectively. However, Freundlich isotherm gives better R2 value than Langmuir for COD and tannin-lignin adsorption. The constants for Freundlich and Langmuir isotherms are shown in [Table 2].{Table 2}

Integrated tertiary treatment system and palm kernel shell activated carbon fixed-bed adsorption treatment system

Initial PKSAC fixed-bed adsorption treatment was carried out using samples from primary aeration treatment. After 8 treatment cycles, with the total column operation of 50 h and 4500 mL volume of POME, the activated carbon became saturated with 0% reduction of color and 8% reduction of COD [Figure 3]a. The breakthrough curve is plotted by the relationship of Cf /Co ratio with the treatment time. [Figure 3]b shows that both the breakpoint time, tb for COD and color in this fixed-bed column is at 28 h. At <28 h, the Cf /Co ratio maintained below 0.5 and then the Cf /Co ratio for color increased rapidly and reached the saturation point (Cf /Co = 1) at 49 h of column operation. This may be due to the decrement of adsorption sites that already filled with the adsorbate. Besides, the PKSAC bed still is able to adsorb COD at 49 h but reaching the saturation point with Cf /Co >0.9.{Figure 3}

After 50 h of continuous adsorption treatment, it was found that the PKSAC became saturated with impurities. This can be seen from the image analysis using SEM [Figure 4]. The pores at the surface can be clearly seen in [Figure 4]a and b showing the PKSAC surface before the adsorption treatment at ×1500 and ×5000 magnifications, respectively. In contrast, after the PKSAC has been used for continuous adsorption treatment for 50 h, the pores of the PKSAC surface were filled with impurities [Figure 4]c and d.{Figure 4}

As for various integrated systems, the highest COD and color removal was achieved through the combination of chemical and PKSAC treatment, however, the breakpoint time (when Cf /Co >0.5) only at 7 h. Compared to the combination of UF and PKSAC treatment, the color removal is comparable and the COD removal is lower but with longer breakpoint time. As for combination of primary aeration with PKSAC, it has longer tb but with lower COD and color removal rate. Among all, treatment of POME from a secondary system with PKSAC was less effective since the removal of COD and color only up to 70.1% and 56.1%, respectively, with tb = 3. The maximum COD and color removals and tb for each treatment configuration are shown in [Table 3].{Table 3}

 Discussion



Batch adsorption

As for the batch system, the adsorption uptake of color and tannin-lignin onto PKSAC is comparable while the COD uptake is lower at given dosages and treatment times. COD is measuring the organic content in POME by chemical oxidation method. These organic contents include multiple components such as sugar, carbohydrate, and protein. These complex organic substances are different in molecules sizes and mass transfer rate and may be repulsive to each other. The difference in adsorption uptake for these components is also shown by Ahmad et al. [18] The order for the adsorption uptake of pollutant in POME is color > tannin-lignin > COD.

However, from the adsorption isotherm, it showed that the adsorption of COD and tannin-lignin onto this PKSAC was not well fitted in both linearized Freundlich and Langmuir isotherms. This was because the pollutants are multicomponent and having different mass transfer rate. Lower adsorbent surface area (compared to other studies) contributes to this scenario in which colored compound adsorbed faster on the PKSAC surface rather than organic compound. Mohammed and Chong found that the sorption data for color, total suspended solids, and COD is best fitted in Redlich-Peterson since it combines features of Langmuir and Freundlich isotherms. [8] This isotherm describes the adsorption occurred in both heterogeneous and homogeneous surface on the adsorbent.

Integrated tertiary treatment system and palm kernel shell activated carbon fixed-bed adsorption treatment system

For the continuous treatment via fixed-bed adsorption of primary aerated samples, the sluggish breakthrough curve was observed for this fixed-bed column. This was due to the low surface area of PKSAC compared to the commercial activated carbon and thus gave lower adsorption site for the adsorbate. The weak driving force for mass transfers impeded the movement of the adsorbate to PKSAC surface. This made the breakthrough curve became sluggish until reached the saturation point. [13] This helps to maintain the performance of the column for pollutant and color removal and with longer treatment cycle.

As for various integrated systems, the breakpoint times for those systems were affected by the difference of initial COD and color concentration loaded into PKSAC column. Devi et al. (2008) stated that as the initial concentration increases, the driving force also increases until it achieves its saturation point. [11] After the saturation of adsorbent sites, the ratio of initial adsorbate to available adsorption sites of adsorbent reduced accordingly and hence, the pollutant uptake will also decrease. The higher adsorption rate of adsorbate onto the PKSAC also will make the adsorbent reach its saturation level fast. POME samples from primary aeration with relatively low COD and color of 800 mg/L and 3773 Pt/Co, respectively, will give longer breakpoint time.

 Conclusions



Palm-based activated carbon is able to simultaneously remove the organic pollutant (measured as COD), colored compound as well as tannin and lignin. For batch adsorption, high dosages and treatment time which up to 15% (w/v) and 72 h, respectively, are required to achieve optimum pollutant removal. Freundlich and Langmuir isotherm showed that PKSAC used in this study is well fitted for color adsorption. To make the treatment more practical for industrial application, continuous treatment in PKSAC fixed-bed column was also tested. With the PKSAC loading height to column diameter ratio of 9, the combination of primary aeration with PKSAC fixed-bed treatment was able to continuously remove the POME pollutant until it achieved the breakpoint at 28 h with 3100 mL of treated POME. It can be implied that the biomass produced from the palm oil mill, the PKS, can be used to treat the POME in a sustainable way. With the current activity on trapping the biogas from POME which can be used as fuel for the carbonization and activation of the PKS, the polishing treatment of POME using PKSAC should be economically viable. In fact from this study, results have showed that the PKSAC can be recycled up to 8 cycles in continuous treatment. Since this PKSAC has low surface area, focus also should be given to study other sustainable activation methods to enhance the adsorption capability.

Acknowledgment

The first author would like to thank the Director General of Malaysian Palm Oil Board for the financial support given to conduct this study.

Financial support and sponsorship

The internal funding was provided by the Malaysian Palm Oil Board.

Conflicts of interest

There are no conflicts of interest.

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