Comparison of natural corn cob and carbon corn cob in the purification of used cooking oil with shaker operation

The research aims to determine the adsorption ability and modeling of adsorption kinetics to purify used cooking oil using natural and carbonized corn cob adsorbent, which is economical, efficient, and sustainable due to its low price, renewability, and simplicity. Samples of used cooking oil were taken as much as 100 ml with an adsorbent mass of 3 g and particle size of 50 mesh and stirred using a shaker. Based on the results, it was found that the effect of carbonization was able to reduce the turbidity of used cooking oil, whereas for the use of natural corn cob adsorbent, at 20 minutes, turbidity of 59.0 NTU was obtained and 45.2 NTU was obtained after the adsorption process for 5 hours, while for the use of corn cob carbon adsorbent, a turbidity of 62.8 NTU was obtained for the same adsorbent size and 39.8 NTU was obtained after the adsorption process for 5 hours. Chemical interaction trends were also obtained, as shown in the second-order pseudo graph with coefficient of determination (R2) values close to 1 using natural corn cob and corn cob carbon adsorbents, namely 0.9965 and 0.9959.


Introduction
Used cooking oil that has been used repeatedly is not suitable for reuse because it can pose a health risk to humans [1].Continued usage of waste cooking oil can increases the likelihood it will cause cardiovascular diseases, liver disorders, and cancer risk [2].Cooking oil that is heated for a long time will increase the amount of hydrocarbons in the oil, making it unsafe to use for consumption [3].Waste cooking oil is often discarded without further processing and has a high content of free fatty acids (FFA).It is important to process cooking oil properly, as continued use without proper processing can increase the risk of developing cancer and can lead to death [4].Used cooking oil can also cause environmental damage if disposed of directly into the environment.
Used cooking oil can be reused and processed into biodiesel [5].The management of waste vegetable oil in food factories has always been an environmental issue, so converting used cooking oil into biodiesel can provide a solution to reduce this environmental impact.The use of biodiesel from used cooking oil can also reduce assembly costs, as the majority of biodiesel production costs generally come from raw material costs, reaching 70-95% [6].Before being used as biodiesel, used cooking oil needs to undergo a purification process to meet set standards [7].Purification process of waste cooking oil that will be used to make biodiesel could be done physically through the adsorption method aimed at reducing the content of free fatty acids [8].Out of the several effluent treatment techniques, adsorption is mostly chosen because it is sustanainable and has inexpensive operational costs [9].Adsorption has a simple process design, low equipment costs, and cheap adsorbents.In addition, the adsorption process is also environmentally friendly [10].
Adsorbent selection is the key to success in adsorption methods.Adsorbent uses can come from agricultural and industrial solid waste [11].Agricultural waste can be converted and added value as a natural adsorbent.Natural adsorbents are cheap, environmentally friendly, and easily obtained [12].Some organic materials considered agricultural waste, such as soybean, corn, wheat, and sugarcane, have been tested and proven to be used as adsorbents in the cooking oil purification process [13].
Bio-sorption the dye out of the water solvent has become a major focus in the treatment of agricultural waste.Most materials show good capability, are renewable, no cost, ubiquitous, and enviromentally friendly [14].Corn cobs are an interesting agricultural waste to be used as an adsorbent [15].Corn cobs have potential as a local resource that is easy to find and practical to use in experiments, given their abundant and widespread carbon content.Carbon can be obtained from corn cobs through pyrolysis process [16].Corn cobs contain cellulose, hemicellulose, and lignin [15].The structure of corn cobs consists of components such as lignin 6%, hemicellulose 36%, and cellulose 41%.Corn cobs have a carbon content level that reaches 80.5%, while the ash content is low [17].
An alternative methods for treating biomass and waste is pyrolysis [18].One form of thermochemical conversion of biomass through pyrolysis is known as carbonization [19].The adsorption process can be carried out through steps such as mixing cooking oil with adsorbents, conduct stirring, filtering, and performing the purification process [20].Through this stirring process, the adsorbent will adhere which allows for interaction [21].
A factor to determine the effectiveness regarding sorption is kinetics of adsorption [22].Basically, adsorption kinetics indicate the absorption speed of the solute and adsorbate dwell time [23].The kinetics of adsorption is the rate at which a liquid is adsorbed by an adsorbent over a given period.It requires the use of the first-order pseudo equation and the second-order pseudo equation to derive the kinetics of adsorption [24].This is a model that can be used to identify the presence or absence of chemical reactions during the adsorption process [25].Therefore, this study aims to see effect of adsorption ability, as well as modeling of adsorption kinetics on adsorbents from natural corn cobs and those that have undergone shaker carbonization.

Materials and tools
This research uses corn cob as adsorbent and waste cooking oil to be purified.Equipment used includes aluminum foil, shaker (SWB-B Biobase), turbidimeter, beaker glass, cutter, measuring cup, ball mill, digital scale, pyrolysis reactor, and sieve.

Procedure
This research consists of two stages, namely purification of waste cooking oil uses natural and carbon corn cob adsorbent.In this study, corn cobs were cleaned first with water to reduce impurities in the corn cobs.The preparation of corn cob carbon adsorbent was carried out by carbonization method using a pyrolysis reactor at 500oC for 30 minutes.The resulting charcoal was crushed using ball mill and sieved with a 50 mesh sieve.The process of purification of cooking oil was carried out using 100 ml of cooking oil which was put into a beaker.The sample added as much as 3 grams of natural corn cob adsorbent with 50 mesh adsorbent size.The sample mixture was put into a shaker (SWB-B Biobase) and then set at a speed of 100 rpm.Turbidity measurements using a turbidimeter sampled every 20 minutes for 5 hours by taking 5 ml.The same thing was also done for corn cob carbon adsorbent.The same thing was also done for corn cob carbon adsorbent.Smaller particle size will increase the surface area, while suitable surface functional groups will increase the adsorption ability [26].In general, as the particle size gets smaller and the specific surface area gets larger, their amount sorption sites and pollutant sorption capacity will also increase [27].The purpose of sieving is to make the carbon more homogeneous in size and have a wider surface.Figure 3 shows the relationship of time to cooking oil turbidity using natural corn cob and corn cob carbon adsorbents in shaker operation.This study used adsorbents with a mass of 3 grams, 50 mesh size on natural corn cob and corn cob carbon.At 5 hours at every 20-minute interval, the turbidity of the cooking oil was measured.122 NTU is the initial process turbidity value.The use of natural corn cob adsorbent for 20 minutes resulted in a turbidity of 59.0 NTU, and after 5 hours of adsorption, the turbidity became 45.2 NTU.Meanwhile, the use of corn cob carbon adsorbent, for 20 minutes produced a turbidity of 62.8 NTU, and after 5 hours of adsorption, the turbidity became 39.8 NTU.

A B C
Based on Figure 3, the type of adsorbent has an impact on the turbidity of cooking oil.The data shows that corn cob carbon is more effective in reducing the turbidity of cooking oil than natural corn cob adsorbent.These findings support the theory that carbon-based adsorbents are effective in removing pollutants because their strong interactions, abundant pore arragement, and surface area are spesific [28].

Figure 4. Decrease in Total Used Cooking Oil Turbidity
Figure 4 the results obtained from the study using samples of cooking oil without adsorbents and using adsorbents natural corn cob and corn cob carbon.For corn cob natural, the total turbidity reduction was 76.8 NTU, while corn cob carbon obtained a total turbidity reduction of 82.2 NTU.Based on the study's results, the natural corn cob adsorbent and corn cob carbon have the potential and sustainability to purify used cooking oil in the adsorption process with shaker operation.Corn cob carbon has the best ability to purify used cooking oil in adsorption, with the most carbon composition in shaker operation.
Analysis of adsorption kinetics provides data about performance regarding adsorbents used, rate of adsorption, as well as mass transfer mechanisms [29].The study used first-order pseudo (1) and secondorder pseudo (2) modeling equations.First Order Pseudo Equation Model [30] : Second Order Pseudo Equation Model [30] : The data of log(q1-q2) dan t are plotted on a graph to obtain the values of k, qecalc, dan R 2 .To obtain the value of qt, the following equation ( 3 Figure 5 is the first-order pseudo modeling of the cooking oil purification using natural and carbon corn cob adsorbents.The first-order pseudo model supposes adsorption speed in line with available vacant sites to be governed maily by diffusion-controlled physically adsorbed by processes.This situation may exist at high dose concentrations of pollutants after the chemical activated sorption sites are all occupied [32].Based on Figure 5, the coefficient of determination (R 2 ) value of using natural corn cob is 0.268.Similarly, the R 2 value for the use of corn cob carbon is 0.384.The purpose of stirring is to increase the effectiveness of adsorbent concentration and produce a homogeneous mixture with varying particle sizes [21].

Figure 6. Second-order pseudo modeling of the used cooking oil purification uses natural and carbon corn cob adsorbents
Figure 6 is a second-order pseudo modeling of cooking oil purification using natural and carbon corn cob adsorbents.In the context of pseudo kinetic models of the second order, this assumes adsorption effectiveness increases with the amount a sites available and without depending on the adsorbate's starting concentration [33].
Based on Figure 6, the R 2 value of using natural corn cob is 0.9965.In contrast, the R 2 value on the use of corn cob carbon is 0.9959.The closer to 1, the higher the value of determination, indicating a better level of accuracy [21].Figure 7a and Figure 7b are the characteristics of cooking oil before and after purification.Waste cooking oil can be purified by an adsorption process so that the changes can be seen [34].Biological adsorbents derived from carbon-containing materials play a role in purifying or separating parts in the liquid or gas phase.These adsorbents are solids employed to adsorb specific phases of fluid or adsorbate components [35].From Figure 7a, it is evident that the waste cooking oil has a high level of turbidity, indicated by the dark brown color.After going through the adsorption process for 5 hours, the color changes to light brown, as shown in Figure 7b.

Conclusion
An adsorbent that could serve to purify waste cooking oil was corn cob.Based on the study's results, the absorption kinetics increased rapidly from the beginning of the adsorption time to reach equilibrium at 240 minutes to 300 minutes.The effect of carbonization could decrease the turbidity level of waste cooking oil, while the natural corn cob with 100 rpm stirring speed obtained a total turbidity reduction of 76.8In contrast, for corn cob carbon, it increases by 82.2 NTU.From this research, it is obtained that the pseudo second order graph showed the trend of chemical interaction, the coefficient of determination (R 2 ) values were close to 1 in the use of corn cob natural adsorbent and corn cob carbon, namely 0.9965 and 0.9959, respectively.Using corn cobs is considered a sustainability measure for reuse by utilizing corn cob waste to create value.

Figure 3 .
Figure 3. Relationship between the time and the turbidity of waste cooking oil on natural corn cob and corn cob carbon adsorbents in shaker operation

Figure 5 .
Figure 5. First order pseudo modeling of the used cooking oil purification uses natural and carbon corn cob adsorbents

Figure 7b .
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