Modified CaO Catalyst from Golden Snail Shell (Pomacea canaliculata) for Transesterification Reaction of Used Cooking Oil

Calcium oxide (CaO) shows catalytic activity because its strength, low solubility in methanol, and excessive. It can be found in golden snail shell (Pomacea canaliculata. The CaO/fly ash catalyst was applied in transesterification reaction of used cooking oil. There were three catalysts obtained, which were golden snail shell calcined (CK), 75% golden snail shell calcined modified by 25% fly ash (CKFA), and by 25% fly ash leached (CKFAL). Result showed that after the golden snail shell was calcined at 900  ̊C, it produced 93.94% Ca (OH)2. Modified CaO catalyst from golden snail shell and fly ash were active to convert used cooking oil become biodiesel.


INTRODUCTION
Biodiesel is a methyl ester made from vegetable or animal oils by trans-esterification process (Knothe, 2000). Biodiesel has been selected as an alternative fuel because it is renewable, biodegradable, non-toxic, and its physical and chemical similarity to conventional diesel fuel (Basumatary, 2013;Lotero et al., 2005). Besides, the use of biodiesel as a fuel can decrease pollutants such as CO2, SO2, CO, and HC gas (Anonymous, 2012;Endalew, Kiros, & Zanzi, 2011;Huang, Zhou, & Lin, 2012).
Vegetable oil has a big potency as a biodiesel. The main contents of vegetable oils are triacylglycerol which has three esters or fatty acid chains (acyl functional group) attached on glycerol functional group (Endalew et al., 2011;Issariyakul & Dalai, 2014). Used cooking oil is waste material derived from palm oil. The used cooking oil is an easy to get materials in reducing the cost of biodiesel production. The high free fatty acids (FFA) content in used cooking oil was reduced through the esterification reaction using acid catalyst (usually sulfuric acid, hydrochloric acid, and sulfonic acid) (Moecke et al., 2016;Ullah, Bustam, & Man, 2015).
CaO catalyst from natural materials such as limestone has better performance than catalyst from Calcium Hydroxide and Calcium Carbonate in converting biodiesel from palm oil. Biodiesel yield obtained by using CaO from limestone, Ca(OH)2, and CaCO3 were 89.98%, 85.15%, and 78.71% sequentially (Widayat, Satriadi, Syaiful, Khaibar, & Almakhi, 2017). Besides, the CaO source is not only from natural material but also from food material waste such as crab shell, egg shell, fish bone, and golden snail shell.
The use of golden snail shells as catalysts of trans-eterification reactions has been investigated by Ong et al. (Ong et al., 2014). The study stated that golden snail shells have the potential as a catalyst for biodiesel production. Prastyo, et al. used the golden snail shells to convert palm oil and maximum biodiesel yield obtained was 94.43% (Prasetyo, Margaretha, Ayucitra, & Ismadji, 2011).
Golden snail shell contains calcium carbonate, which was converted through the calcination process to gain CaO (Nopriansyah, Baehaki, & Nopianti, 2016;Prasetyo et al., 2011). The catalytic activities of CaO catalyst could be increased by adding supporting material. This study used fly ash as CaO catalyst support. Fly ash is a by-product of coal combustion consisting of micro particulates. The high amount of SiO2 and Al2O3 in fly ash is an affordable catalyst support material (Chakraborty, Bepari, & Banerjee, 2010;Jain, Khatri, & Rani, 2011). According to Jain et al. reported dispersion of fly ash on CaO catalyst increases catalytic activity due to increase the base strength (OH content) catalyst. Enggawati and Ediati modified the CaO catalyst from egg shell with fly ash to catalyze transesterification reaction of Nyamplung oil (Enggawati & Ediati, 2013). Furthermore, Rodiah and Ediati synthesized CaO catalysts from dolomite modified with leaching and non-leaching fly ash. The study reported that CaO catalyst supported by fly ash was able to convert refined palm oil to biodiesel (Rodiah & Ediati, 2015).
This research investigate the synthesis of catalysts from golden snail shells (Pomacea canaliculata) modified with fly ash to convert used cooking oil into biodiesel. Fly ash is treated differently to observe the catalyst activity.

Materials and Tools
The tools used in this study such as beaker glass, porcelain dish, measuring glass, filter paper, dropping pipette, magnetic stirrer, mortar agate, analytical balance, oven, muffle furnace, glass funnel, triple neck flask, condenser. X-Ray Diffractometer is used to charcterize the catalysts.
Golden snail shells were collected from Pelajau village, Banyuasin, South Sumatera. The fly ash was obtained from PT. Bukit Asam Persero (Tbk) Tanjung Enim, South Sumatera. Then, the used cooking oil was collected from street vendors around campus of UIN Raden Fatah Palembang and methanol p.a and n-hexane p.a. were purchased from Merck and aquades. Rodiah, et. al.

Preparation of Catalysts
Preparation of golden snail shell Golden snail shells were washed using clean water, and then crushed. The shells were dried for 24 hours at 110˚C, then calcined at 900˚C for 2 hours. The calcined golden snail shells were mashed with agate to get powder.

Preparation of Fly Ash
Fly ash washed using hot water at beaker glass while stirring for 30 minutes, this procedure was repeated 3 times. The deposited mixture was filtered, then dried at 100˚C for 24 hours. The powder obtained is called FA.
The fly ash was leached with a 10% hydrochloric acid solution (25:1 (mL /g), while stirring at 80˚C for 1 hour. The precipitate was washed with distilled water for about 3 times then filtered. The precipitate was dried at 100˚C for 24 hours. The powder obtained was fly ash leaching (FAL).
Preparation of golden snail shell catalyst/fly ash Two beaker glass which contained of 75% (m/m) of calcined snail shells were added 200 mL aquadest for each and stirred until homogeneous. Then, the first beaker glass added by 25% (m/m) FA, and the other added by 25% FAL. The mixtures stirred at 70˚C, pH 12.1 for 4 hours then left for 24 hours. The precipitate obtained was dried for 20 hours at 100˚C, then calcined at 800˚C for 2 hours.

Characterization of Catalysts
The crystal structure of catalysts was confirmed by Philips X-pert XRD Powder Diffractometer using CuKα radiation with an angle range of 2θ = 20-100˚ at scanning speed of 1˚/min.

Transesterification Reaction
The transesterification reaction was carried out in a 250 mL three neck flask equipped with a condenser and magnetic stirrer. The reaction conditions were 3% of the catalyst (by weight of oil), 1:30 of the ratio oil: methanol (m/m), at 65 ˚C for 2 hours with the mixing speed of 1200 rpm. The biodiesel obtained was added n-hexane to dissolve main product. n-Hexane was separated from the product using rotary evaporator. Biodiesel obtained was analyzed by Gas Chromatography to determine biodiesel yield.

RESULT AND DISCUSSION
CaO from golden snail shells was gained after calcinating at 900˚C for 2 hours. The Calcination process serves to activate the catalyst because during calcination at high temperatures, the carbonate group decomposes to CaO (Eqs. 1) which plays an important role in trans-esterification reactions (Aransiola, Ojumu, Oyekola, Madzimbamuto, & Ikhu-Omoregbe, 2014;Ilgen, 2011;Shajaratun Nur et al., 2014). Etuk et al. reported that the main content in golden snail shell ash was 61.95% of CaO. Rodiah, et. al.

Modified CaO Catalyst from Golden Snail Shell (Pomacea canaliculata) for Transesterification Reaction of Used Cooking Oil
Al-Kimia | Volume 8 Nomor 1 2020 86 This study produced three types of catalysts with different compositions, see Table 1. The catalysts were re-calcined to reactivate the CaO catalyst which had been changed to Ca(OH)2 after being dissolved into water in the preparation process (Eqs 2). Reactions that occur according to the following equation 2. The presence of Ca(OH)2 was confirmed by an X-Ray Diffraction (XRD) spectrophotometer ( In this study, fly ash was used as a source of SiO2 which was dispersed on CaO catalyst from golden snail shells. The presence of SiO2 on the surface of the CaO catalyst affects the content of Ca(OH)2. This is caused by the reaction between Ca(OH)2 and SiO2, thereby reducing the levels of Ca(OH)2 on each catalyst.
Dispersion of SiO2 (fly ash) on CaO (dolomite) influenced catalyst crystallinity. CaO was initially crystalline, but after adding SiO2 to the surface of CaO, the catalyst crystallinity decreased. SiO2 dispersion from fly ash on CaO from dolomite causes the catalyst to be amorphous (Rodiah & Ediati, 2015). The catalyst phase was confirmed by an XRD spectrophotometer.
The diffractogram of calcined golden snail shell (CK) is shown in Figure 1. Diffractogram of CK catalyst showed peaks that appeared at 2θ = 28.64°; 34.13°; 47.26°; 50.99°; and 54.44° which was the peak of CaO. Then new peak appeared at 2θ = 17.95° and 47.26° showed the presence of Ca(OH)2. This peak shows the occurrence of hydration during activation of the catalyst (Prasetyo et al., 2011).  , 2011). CK catalyst diffractogram did not show the appearance of the characteristic peak of CaCO3, which means that CaCO3 was fully converted into CaO and Ca(OH)2 in the calcination process. Figure 2 is a comparison of the diffraction patterns of the three catalysts, namely CK, CKFAL, and CKFA. There were several peaks appears such as CaO peaks from golden snail shells, and quartz peaks (SiO2), mulit (Al2O3.SiO2), and hematite (Fe2O3) were from fly ash. Peak at 2θ = 28.78°; 34.06°; 47.33°; 50.85°; and 53.9° was the peak of CaO on CKFAL catalyst whereas in CKFA catalyst, the characteristics of CaO appeared at 2θ = 28.71°; 34.13°; 47.26°; 50.79°; and 53.9°. In addition, the new peaks at 2θ = 29.45°; 32.84°; and 2θ = 29.39° were the peak of mulit (Al2O3.SiO2) from each CKFAL and CKFA catalyst respectively. Then peak at 2θ = Rodiah, et. al.
After the calcination process, the water content in the dicalcium silicate hydrate evaporated and obtained dicalcium silicate. Dicalcium silicate has a Si-O-H bond which was expected to increase the basicity of the catalyst (Chakraborty et al., 2010).
The used cooking oil in this study contained 0.63% FFA which was classified as low level, so that it can be directly used in the trans-esterification reaction without going through esterification. In this study, the trans-esterification reaction was catalyzed by three catalysts: CK, CKFA, and CKFAL. The mass of biodiesel from the reaction with CK, CKFA, and CKFAL catalysts was 20.43 grams, 18.62 grams and 19.89 grams, respectively (See Table 3). From these results indicate that the CK catalyst showed better activity compared to other catalysts in this research. Dispersion of fly ash on CaO catalyst affected catalyst activity. Catalysts dispersed with leaching fly ash had better activity than catalysts dispersed with non-leaching fly ash. This can be caused by the active site of the catalyst being higher after dilutting of fly ash in acid solution. Leaching process aimed to dissolve of metal impurities which covered the active site of the catalyst. The more active sites of the catalyst base, the higher of the catalyst activity. Thus the conversion of biodiesel increased because the transesterification reaction depends on the number of active sites of the base (Ilgen, 2011).
On the other hands, CK catalysts were more active than CKFA and CKFAL catalysts. According to Rodiah and Ediati, dispersion of fly ash on the surface of CaO can cover the active side of the catalyst, thereby causing a decrease in catalytic activity (Rodiah & Ediati, 2015). Therefore, the main key to increasing the modified catalytic activity of CaO was to maintain the CaO side during the modification process. However, the difference between the mass of biodiesel generated from the use of CK catalysts (20.4309 grams) and CKFAL (19.8990 grams) was quite small. This showed that leaching fly ash can be used as CaO catalyst support from a potential golden snail shell. In addition, the density of biodiesel (Table 4) with the use of CKFAL catalyst were closer to the characteristics of biodiesel Rodiah, et. al.

CONCLUSIONS
In this study the CK, CKFA, and CKFAL catalysts were successfully prepared which were used to catalyze the trans-esterification reaction of used cooking oil into biodiesel. The CK catalyst produces a higher mass than the reaction catalyzed by the CKFA and CKFAL catalysts. But the mass of biodiesel obtained from catalysis with CKFAL and CK catalysts did not have a significant difference. Biodiesel density obtained from the reaction catalyzed by CKFAL was close to the standard biodiesel density which was 0.8295 g/cm3.