Application of Activated Carbon from Cocoa Pod Husk ( Theobroma cacao L.) in Used Cooking Oil

. One method for purifying used cooking oil is to utilize activated carbon derived from cocoa pod husk. Cocoa pod husk contains high cellulose, allowing it to be an absorbent material that can reduce moisture content, free fatty acids, and peroxide value in used cooking oil. This study aims to (1) determine the effect of concentration and adsorption time of cocoa pod husk activated carbon on moisture content, free fatty acids, and peroxide value of used cooking oil and (2) determine the best concentration and adsorption time of cocoa pod husk activated carbon. This study used a randomized complete factorial design consisting of two factors: concentration of cocoa pod husk activated carbon: 5%, 10%, and 15% and adsorption time: 30, 60, 90, and 120 minutes. The results after refining using cocoa pod husk activated carbon, the moisture content dropped to 0.07%- 0.28%, free fatty acid content dropped to 0.79%-1.42%, and peroxide value dropped to 32.20-32.53meq/kg. The best treatment obtained was a concentration of 15% of cocoa husk activated carbon with an adsorption time of 120 minutes, which produced used cooking oil with a moisture content of 0.08%, free fatty acids of 0.79%, and peroxide value of 32.20meq/kg.


Introduction
The increased cooking oil consumption has resulted in increased residual oil from frying, known as used cooking oil.Used cooking oil is waste cooking oil from household needs and food processing industries that have been used repeatedly and the oil has decreased in quality.The repeated frying process at high temperatures of 160-180 o C accompanied by contact with water and air, results in degradation reactions in hydrolysis, oxidation, and polymerization processes.These reactions are characterized by discoloration, increased viscosity, increased free fatty acid content, increased peroxides value, increased density, increased total polar material, high foaming properties, decreased smoke point, decreased iodine value, and reduced the degree of unsaturation of the oil [1,2].In addition, the nutritional value of fried foods will also be reduced.
Processing used cooking oil by refining is expected to solve the problem so that it can save costs but does not endanger health.The purification of used cooking oil aims to separate the products of degradation reactions, such as water, peroxides, free fatty acids, aldehydes, and ketones, from the oil.One way to improve the quality of used cooking oil is adsorption using activated carbon [4,5].
Activated carbon is a porous solid containing 85-95% carbon, produced from carboncontaining materials by heating at high temperatures.Activated carbon can absorb oil degradation products such as unwanted odors and colors and reduce peroxides and free fatty acids.Cocoa pods have great potential for being used as activated carbon.The Cocoa pod is the outer shell that covers the meat and cocoa beans with a rough, thick, and rather hard texture.As cocoa production increases, so does cocoa pod husk waste, which makes up 75% of the cocoa fruit.Cocoa pods can be utilized as animal feed, compost, or just left to pile up and decompose.Cocoa pods include lignocellulose, which contains 51.98% lignin, 21.06% hemicellulose, and 20.15% cellulose.The potential content of the cocoa fruit peel is the material for producing activated carbon [6].Based on this background, a study was conducted to purify used cooking oil with an adsorption process using activated carbon from cocoa fruit peels to improve the quality of used cooking oil.

Methods
This research was carried out in February -July 2023 at the Chemical Analysis and Food Quality Monitoring Laboratory, Food Science and Technology, Department of Agricultural Technology, Faculty of Agriculture, Hasanuddin University, Makassar.

Tools and materials
The tools used in this research were a 100-mesh sieve, porcelain cup, desiccator, mortar, analytical balance, oven, pH meter, glassware, furnace, and UV-Vis spectrophotometer.

Research design
This research design uses the Completely Randomized Factorial Design method, which consists of two factors, namely: 1.The activated carbon concentration factor consists of three levels: M1 = 5% (g/v) 2. The contact time factor consists of four levels: T1 = 30 minutes T2 = 60 minutes T3 = 90 minutes T4 = 120 minutes There were 12 treatment combinations of activated carbon concentration and contact time.Each treatment was repeated three times.

Preparation and activation of cocoa pod husk carbon
Making activated carbon from cocoa pod husks begins with drying the cocoa pod husks in the sun until dry, marked by a change in color to brownish.The dried cocoa pod husks were carbonated using a furnace at 400 o C for 15 minutes.The carbon formed is crushed and then sieved using a 100-mesh sieve.The carbon is activated by soaking it in a 10% phosphoric acid solution for 24 hours at room temperature.Then, the carbon is washed using distilled water until it is neutral.The activated carbon was dried at 105 o C for 2 hours.

Used cooking oil adsorption process
100 ml of used cooking oil was put into an Erlenmeyer flask and heated at 70 o C. 5% of activated carbon adsorbent was added and stirred for 30 minutes at 100 rpm.Then, filtering is carried out to separate the activated carbon from the used cooking oil.This series is repeated according to the experimental variables.Variable concentration of activated carbon (5%, 10%, and 15%) and variable stirring time (30, 60, 90, and 120 minutes).After that, testing is carried out.

Moisture content test (SNI 7709: 2019)
Moisture content was calculated based on the weight lost during heating in the oven.The porcelain cup was heated in an oven for 60 minutes at 105 o C, cooled in a desiccator for 15 minutes, and weighed using an analytical balance. 2 g of used cooking oil sample into a porcelain cup and then heat it in the oven for 3 hours at 105 o C. The sample was cooled in a desiccator for 15 minutes, then weighed.Ovening is carried out until the weight is constant (difference 0.0005).

Peroxide value test (SNI 7709:2019)
A total of 5 g of sample was put into an Erlenmeyer, and then 30 ml of a solvent mixture consisting of 60% glacial acetic acid and 40% chloroform was added.0.5 ml of saturated KI solution was added while shaking.The mixture was left for 2 minutes, then 30 ml of distilled water was added.0.5 ml of 1% starch was added and titrated with 0.01 N Na2S2O3 until the blue solution disappeared.The peroxide value is expressed in milliequivalents per 1000 g of oil.

Free fatty acid content test (SNI 7709: 2019)
A total of 2 g of sample was put into an Erlenmeyer.50 ml of warm 96% alcohol was added, and four drops of phenolphthalein solution were added as an indicator.The solution was titrated with 0.01 N sodium hydroxide while shaking the Erlenmeyer during the titration until a pink color was formed, lasting 30 seconds.Free fatty acids are calculated using the following formula.
Free Fatty Acid (as palmitic acid) = 25.6 x V x N W Note : V = volume of NaOH solution needed in the titration (mL) N = normality of NaOH (N) W = sample weight (g)

Data processing
This research used a completely randomized factorial design (CRD) with two factors and three replications.The data obtained were analyzed using Analysis of Variance (ANOVA), which, if the treatment had a real effect, was followed by the Duncan test using IBM SPSS Statistics 24.

Preparation and activation of cocoa peel activated carbon
The process of making activated carbon from cocoa pod skin goes through dehydration, charring, and activation.The dehydration process is done by drying in the sun until dry, marked by a color change to brownish.This drying process aims to reduce the moisture content in the skin of cocoa fruit.The charring process is carried out at a temperature of 400 o C for 15 minutes.According to Latupeirissa [7].The charring temperature of 400-600 o C causes the breakdown of organic materials into carbon and carbon formation occurs.The carbon from combustion was pulverized using a pestle and mortar to reduce the size of the carbon into powder.The resulting powder is sieved using a 100-mesh sieve to homogenize the powder size to obtain acceptable and homogeneous carbon particles.The use of H3PO4 as a chemical activator for activated carbon synthesis has the advantage of producing lignocellulosic biomass due to its ease of recovery, low environmental impact, and higher carbon yield [8]. H3PO4 can act as an activation regulator by interacting with phenolic and carbonyl groups of activated carbon, thus forming P-containing carbon species (such as C-O-P), further promoting the development of activated carbon micropores and subsequently increasing the surface area.H3PO4 also acts as a catalyst to regulate and control the texture and structural properties of activated carbon [9] 3.2 Characteristics of cocoa pod husk activated carbon

Moisture content
Moisture content is one indicator that determines the quality of active carbon.Determination of the moisture content of active carbon aims to determine the amount of water lost so that the water bound to the active carbon does not cover the pores of the active carbon.Activated carbon with high moisture content will cover the pores of the carbon so that it can reduce its adsorption power.The moisture content of activated carbon cocoa fruit skin obtained is 2.66%.Based on the results, the moisture content of cocoa fruit peel activated carbon meets the requirements of good activated carbon according to Indonesia National Standard (SNI) number 06-3730-1995, which is a maximum of 15%.

Ash content
High ash content can reduce the absorbency of activated carbon.This is because minerals have blocked the pores on the active carbon, thereby decreasing its surface area.The ash content obtained is 5.14%.Based on the results, the ash content of cocoa fruit peel activated carbon meets the requirements of good activated carbon according to Indonesia National Standard (SNI) number 06-3730-1995, which is a maximum of 10%.The percentage of ash content obtained indicates that in the activation process, the remaining minerals in the activated carbon are wasted so as not to cover the pores of the activated carbon.

Characteristics of used cooking oil before treatment
The used cooking oil used in this study before adsorption with various treatments using cocoa fruit peel activated carbon was carried out with an initial analysis of the parameters of moisture content, free fatty acids, and peroxide value.The results of this analysis depend on the samples of used cooking oil obtained depending on the ingredients fried, frying temperature, and frying time.Based on Table 1, the results obtained show that the used cooking oil samples used have exceeded the cooking oil standards set by Indonesia (SNI 7709:2019).

Moisture content
Moisture content is one of the parameters for determining the quality of cooking oil because water can cause the hydrolysis process.The hydrolysis process in cooking oil produces free fatty acids that can cause damage to cooking oil, such as changes in taste and smell color [10].The effect of activated carbon concentration on the moisture content of used cooking oil can be seen in Figure 1.The concentration of cocoa pod husk-activated carbon significantly affects the moisture content of used cooking oil (p<0.05).The addition of 5% of activated carbon concentration produced a moisture content of 0.21%.The addition of 10% and 15% activated carbon concentration reduced the moisture content to 0.20% and 0.10%.These results show that the higher the concentration of activated carbon, the lower the moisture content in used cooking oil.This indicates that the process of water adsorption in used cooking oil takes place well because more water is adsorbed.The effect of contact time on the moisture content of used cooking oil can be seen in Figure 2. Contact time significantly affects the moisture content of used cooking oil (p<0.05).The refining process with a contact time of 30 minutes resulted in a moisture content of 0.22%.Increasing the contact time to 60 minutes, 90 minutes, and 120 minutes can reduce the moisture content to 0.19%, 0.16%, and 0.11%.These results show that the longer the contact time, the lower the moisture content in used cooking oil.The longer the contact time, the lower the moisture content in used cooking oil.Because the contact time between activated carbon and used cooking oil is long, water absorption is more optimal.The effect of the interaction of activated carbon concentration and contact time can be seen in Figure 3.The interaction of activated carbon concentration and contact time significantly affected the moisture content of used cooking oil (p<0.05).The moisture content of used cooking oil after refining with the addition of activated carbon concentration (5%, 10%, and 15%) with contact time (30, 60, 90, and 120 minutes) decreased from 0.35% in the control to 0.28% -0.07%.The decrease in moisture content of used cooking oil occurs because water molecules from used cooking oil move to the surface of activated carbon and get trapped in its pores.These water molecules form hydrogen bonds with hydroxyl groups on the cellulose present in activated carbon.Hydroxyl groups on cellulose are active groups that can absorb water by forming hydrogen bonds [11].The lowest moisture content was obtained by adding active carbon, which was 15%, with a contact time of 120 minutes, namely 0.07%.The moisture content value follows SNI 7709: 2019, which requires a maximum moisture content in cooking oil of 0.3%.

Free fatty acid
Free fatty acids are fatty acids that are not bound as triglycerides.Free fatty acids are formed from the hydrolysis reaction between glycerol and water.The amount of free fatty acids formed can indicate oil deterioration.The effect of activated carbon concentration on the free fatty acids of used cooking oil can be seen in Figure 4.The concentration of activated carbon significantly influenced the free fatty acids of cooking oil (p<0.05).The addition of 5% activated carbon concentration produced 1.36% free fatty acids.The addition of 10% and 15% activated carbon concentrations reduced free fatty acids to 1.28% and 0.91%.These results show that the more activated carbon concentration is added, the fewer free fatty acids are in used cooking oil.The more concentration of active carbon is used, the surface area of active carbon also increases so that more free fatty acids can be absorbed.The effect of contact time on free fatty acids in used cooking oil can be seen in Figure 5.

Fig. 5. Effect of contact time on used cooking oil free fatty acids
Contact time significantly affects used cooking oil's free fatty acid content (p<0.05).The refining process, with a contact time of 30 minutes, produced 1.26% free fatty acids.Increasing the contact time to 60 minutes, 90 minutes, and 120 minutes can reduce the free fatty acids to 1.23%, 1.18%, and 1.05%.This shows that the longer the contact time, the lower the free fatty acid content in used cooking oil.The longer the contact time, the more free fatty acids decrease because the long contact time allows the absorption of activated carbon to be more optimal so that many free fatty acids are absorbed.qThe effect of the interaction of activated carbon concentration and adsorbent time can be seen in Figure 6.The interaction of activated carbon concentration and contact time significantly affected the free fatty acids of used cooking oil (p<0.05).The process of refining used cooking oil with a concentration of activated carbon (5%, 10%, and 15%) with contact time (30 minutes, 60 minutes, 90 minutes, and 120 minutes) was able to reduce the free fatty acid content in the control 1.56% down to 1.42% -0.79%.These results show that the higher the concentration of activated carbon and the longer the contact time, the value of free fatty acids decreases.The decrease in free fatty acids occurs because activated carbon has a hydroxyl group (-OH) present in cocoa fruit peel cellulose [12].The hydroxyl group (-OH) will bind to form hydrogen bonds with carboxyl groups (-COOH) of free fatty acids so that activated carbon can bind to free fatty acids [13].The lowest free fatty acids were obtained when adding an activated carbon concentration of 15% with a 120-minute adsorption time of 0.79%.These results do not meet the requirements of SNI 7709: 2019, which stipulates a maximum free fatty acid content of 0.3%.Active carbon cannot absorb free fatty acids that are too high in used cooking oil [14]his can cause active carbon to experience saturated conditions so that it has reached its maximum absorptive capacity.

Peroxide value
Peroxide value is one of the indicators of oil deterioration formed during primary oxidation.High peroxide value in cooking oil can cause rancidity and unpleasant flavor, thus reducing the quality of cooking oil.The effect of activated carbon concentration on the peroxide value of used cooking oil can be seen in Figure 7.The activated carbon concentration significantly affects the peroxide value of used cooking oil (p<0.05).The activated carbon concentration of 5% obtained a peroxide value of 32.49 meq/kg.Adding 10% and 15% activated carbon concentrations can reduce the peroxide value to 32.41 meq/kg and 32.27 meq/kg.These results indicate that the more activated carbon concentration is added, the more the peroxide value in used cooking oil decreases.The absorption rate is higher with an increase in activated carbon concentration.The effect of contact time on the peroxide value of used cooking oil can be seen in Figure 8. Contact time significantly affects the peroxide value of used cooking oil (p<0.05).The refining process, with a contact time of 30 minutes, produced a peroxide value of 32.45 meq/kg.Increasing the contact time to 60 minutes, 90 minutes, and 120 minutes can reduce the peroxide value to 32.40 meq/kg, 32.36 meq/kg, and 32.33 meq/kg.These results indicate that the longer the contact time, the lower the peroxide value in used cooking oil.The longer the adsorption process allows the interaction between the surface of activated carbon and peroxide to be more optimal so that the absorption of peroxide is more effective.The effect of the interaction of active carbon concentration and contact time can be seen in Figure 9.The interaction of activated carbon concentration and contact time did not significantly affect the peroxide value of used cooking oil (p>0.05).The process of refining used cooking oil with activated carbon concentration (5%, 10 %, and 15%) with contact time (30 minutes, 60 minutes, 90 minutes, and 120 minutes) was able to reduce the peroxide value in the control 34.64 meq/kg down to 32.53 meq/kg -32.20 meq/kg.These results indicate a decrease in peroxide value in used cooking oil purification results because the peroxide value in used cooking oil can be absorbed by activated carbon.The reduction in peroxide value occurs due to the interaction of hydroxyl groups (-OH) of activated carbon with free radical atoms in active peroxides.In addition, the decrease in peroxide value in used cooking oil is because used cooking oil contains polar peroxide groups, and active carbon has polar hydroxyl groups.Hence, the similarity of polarity causes active carbon to absorb peroxide value.The hydroxyl group (-OH) of activated carbon is obtained from the cellulose content of cocoa pods, which has three active hydroxyl groups (-OH) so that the adsorbate component can be bound.Three steps are involved in the process of activated charcoal absorbing peroxide value: the oxygen in cooking oil is adsorbed on the exterior of the charcoal; it travels towards the pores in the charcoal, and it is adsorbed onto the inner wall of the charcoal active [15]The lowest peroxide value was obtained by adding 15% activated carbon concentration with a 120-minute adsorption time of 32.20 meq/kg.These results do not meet the requirements of SNI 7709:2019, which stipulates a maximum free fatty acid content of 10 meq/kg.

Characteristics of used cooking oil after adsorption
Based on the test results of moisture content, free fatty acids, and peroxide value, it is known that the best treatment is the interaction treatment of activated carbon concentration of 15% and contact time of 120 minutes.The results of the parameter analysis of the lowest moisture content, lowest free fatty acids, and lowest peroxide value than other treatment interactions support this.The percentage of quality improvement of moisture content, free fatty acids, and peroxide value of used cooking oil is presented in the following The results show that the best treatment (15% of activated carbon with a contact time of 120 minutes) is only the moisture content parameter that complies with SNI 7709: 2019.Meanwhile, in the parameters of free fatty acids and peroxide value, there is an increase in oil quality, which proves that cocoa pod husk-activated carbon is able to absorb used cooking oil impurities, but the analysis results are not yet in accordance with Indonesian cooking oil standards.Therefore, a neutralization stage is needed during the preparation of used cooking oil samples to reduce free fatty acid levels and peroxide value before adsorption using activated carbon.
The percentage decrease in free fatty acids is higher than the decrease in the peroxide value of used cooking oil after purification because free fatty acids have a higher polarity than hydroperoxides, so activated carbon is more accessible to absorb than peroxide.During frying, cooking oil undergoes hydrolysis and oxidation processes that form free fatty acids and peroxides.Free fatty acids and peroxides can be bound by activated carbon because it has a high surface area and porosity.Although activated carbon can refine used cooking oil by reducing free fatty acids and peroxide value, it cannot change the chemical bonds between glycerol and carboxylic acids.In addition, activated carbon cannot remove substances covalently bonded to the carbon chain of used cooking oil, such as dimers, acid polymers, and glycerides, formed due to heating during use.Therefore, activated carbon can only improve the quality of used cooking oil but cannot restore the chemical structure like fresh oil.The used cooking oil is recommended for use as a non-food, such as biodiesel.

Conclusion
The concentration of activated carbon from cocoa pod husk and the contact time affect the cooking oil produced, reducing the moisture content, free fatty acids, and peroxide value.The best treatment of the activated carbon concentration of cocoa pod husk and contact time is an activated carbon concentration of 15% and a contact time of 120 minutes, which produces the characteristics of used cooking oil, which can produce the characteristics of used cooking oil, namely the lowest moisture content (0.07%), the lowest free fatty acids (0.79%), and the lowest peroxide value (32.20 meq/kg).
of cup and sample before drying W2 = weight of cup and sample after drying of mL of Na2S2O3 solution N = normality of Na2S2O3 G = weight of oil sample (g)

Fig. 1 .
Fig. 1.Effect of activated carbon concentration on used cooking oil moisture content

Fig. 2 .
Fig. 2. Effect of contact time on used cooking oil moisture content

Fig. 3 .
Fig. 3. Effect of the interaction of activated carbon concentration and contact time on the moisture content of used cooking oil 0

Fig. 4 .
Fig. 4. Effect of activated carbon concentration on used cooking oil free fatty acids

Fig. 7 .
Fig. 7. Effect of activated carbon concentration on peroxide value of used cooking oil

Fig. 8 .
Fig. 8. Effect of contact time on peroxide value of used cooking oil 32

Fig. 9 .
Fig. 9. Effect of adsorbent concentration interaction and contact time on peroxide value of used cooking oil

Table 1 .
Preliminary analysis of used cooking oil Effect of adsorbent concentration interaction and contact time on free fatty acid content of used cooking oil

Table 2 .
Percentage improvement of used cooking oil quality before and after adsorption