Analysis of Optimum Temperature and Calcination Time in the Production of CaO Using Seashells Waste as CaCO3 Source

Seashells waste is abundant in coastal area, especially in the locations where fisheries are a major occupation. This abundant resource of seashells opens a new opportunity further utilization. Seashells waste is a source of CaCO3, which may be converted into CaO via the calcination process. This study analyzed the characteristics of the CaO produced via calcination process at different temperature and calcination time. The calcination process was carried out at a temperature of 800°C, 900°C, and 1000°C with variation of 2, 3, and 4 hours in time. The Fourier transform infrared spectroscopy (FTIR) result showed that the spectrum of 2513 cm-1 as an indication of the C-H group containing CaO appearing after calcination. The FTIR results suggest that the calcination time did not gave major alteration to the functional groups. The results of X-ray diffraction (XRD) analysis showed that CaO laid at the angle of 58.1o and 64.6o. Scanning Electron Microscopy–Energy Dispersive X-Ray Spectroscopy (SEM-EDS) results showed that the most significant compositional outcome after the calcination process was Ca and O at all temperatures and calcination times. All calcined seashells showed rough surface and irregular shape particles. The result of a Thermogravimetric analysis (TGA) suggested that the highest mass alteration occurred at a temperature of 800°C with 78 mins of calcination time.

INTRODUCTION carbonate, and when calcined above 700ºC, it turns into CaO (Sirisomboonchai et al., 2015). The benefit of seashells as a raw material in the production of CaO is a carrier for heterogeneous catalysts that can reduce the biodiesel production costs as well as the amount of seashells waste (Hadiyanto et al., 2016). Seashells have characteristics of 98% CaCO 3 , 0.79% MgCO 3 , and 0.15% SrCO 3 (Sirisomboonchai et al., 2015). There is also a high Ca content in the seashell waste as a source of CO 2 absorption (Huang et al., 2018).
According to Kaplan (1998), the seashells consist mostly of CaCO 3 (95-99% CaCO 3 ), but when heated to a specific temperature, it produced a single metal oxide CaO. Referring to Kwon et al. (2004), seashell waste is an effective reagent that can remove phosphorus from wastewater. Calcination temperature and time played important role in the characteristics of the produced compounds (Ramasamy et al., 2016). When heated to temperatures higher than 750-800°C, the seashells can turn into good calcium oxide (Nordin et al., 2015). Through a thermal decomposition process known as calcination, the CaCO 3 becomes CaO used in industry and everyday practices such as water and sewage treatment, glass production, construction materials, agriculture, and others (Lin et al., 2011;Mohamed et al., 2012).
Seashell waste is abundant in Tanjung Baru Beach, Karawang, Jawa barat, Indonesia. The utilization of this waste has not been explored yet, especially as a calcium carbonate source (CaCO 3 ) to produce solid CaO which may be utilized further. This study was aimed at utilizing seashell waste as the source of calcium carbonate to produce solid CaO at various temperatures and period of calcination as well as to characterize the produced compounds. This research was expected that the obtained CaO will be environmentally friendly and can be used in various fields.

Source and pretreatment of seashells waste
The seashells were taken from Tanjung Baru, Karawang, Jawa Barat, Indonesia, about 38 km from the University of Singaperbangsa Karawang. The seashells were sorted into large ones and used in the research. The obtained seashells were then cleaned by using tap water and dried under the sun (Kadir et al., 2020;Wang et al., 2019). After drying, the process was repeated by using NaOH 10% (Pudak Scientific, Indonesia) and Aquadest (Shagufta Laboratory, Indonesia) to remove the impurities that still clung to the shells (Tang et al., 2011). After the double cleansing, seashells were laid under the sun until dry (Titah et al., 2018a). The cleaned and dried seashells were ground to obtain the powder form. The seashells powder were then dried in a DHG 9053A oven (Zenithlab, USA) for twenty-four hours at 105°C (Kaewdaeng et al., 2017). The oven samples were sieved with a size of 100 mesh to obtain homogeneous powder. The homogenous powder was then subjected to the calcination process (Abutu et al., 2019).

Analysis of the optimum temperature and calcination time for CaO production
In the calcination process, total of 20 grams of powder were stored in a desiccator to obtain stable balance (

Characterization of produced compounds after calcination
The characterization and analysis of the sample were carried out based on the functional group analysis using the Fourier Transform Infrared Spectroscopy

Characterization using FTIR
On the basis of Figure 1, the IR spectrum of seashell powder before and after calcined showed diff erent transmittance and functional group. Several diff erent peaks appeared after calcination. Some peaks did not appear in the uptake of seashell powder before calcination but appeared on the spectrum after calcination. Before calcination, an absorption band appears at the wave number 3429.43 cm -1. After calcination, several wavenumbers around 3400 cm -1 belong to the O-H group vibrational absorption bands from Ca(OH) 2 due to forming the O-H group attached to the calcium atom (Suryaputra et al., 2013).
In the seashell powder, before calcination, the IR spectrum shows the absorption band change at the wavenumber of 1475.54 cm -1 and a sharp peak appearing. In contrast, the peaks are widened after calcination. The wavenumber belongs to the C-O vibration in the carbonate functional group of CaCO 3 . The absorption band on the shell powder after calcination at several time variations in general. The absorption pattern was not much diff erent, even though there were diff erences in the absorption intensity. However, the temperature variation was suffi cient to aff ect the IR spectrum results, shown by the widening of the spectrum peaks by the increasing of the calcination temperature (Brites et al., 2018). This indication is pointing that CaCO 3 has changed into CaO due to the heating process.
The CaO was detected at the absorption band of 2513.25 cm -1 which is a characteristic of the peak of the C-H functional group. The samples that have CaO showed the C-H stretching vibrations. It can also be seen that the presence of CaO was indicated by the appearance of the absorption band at a wavelength of 709.80 cm -1 . This absorption band is a fi ngerprint that indicates the presence of CaO bonds, as mentioned by Raizada et al. (2017). The FTIR results indicated that the calcination time did not aff ect the functional group of seashells. On the other hand, the increasing of calcination temperature showed an alteration to the IR spectrum. Figure 2 showed the XRD characterization patterns of seashells, before and after the calcination process. The results displayed the

Characterization using TGA analysis
The TGA analysis results showed a signifi cant change in mass begins to occur around temperatures of 780°C. This mass decrease indicates the decomposition of CaCO 3 to CaO due to the release of CO 2 compounds (Bazargan et al., 2015). The temperature of 800.5°C and calcination period of 78 minutes gave the highest mass changes for the seashells. After passing the temperature around 900°C, it appears that the mass change curve was relatively constant. The curve indicates that above temperatures of 900°C to 1200°C, there is no change in the CaO compound (Dümichen et al., 2015).

CONCLUSIONS
FTIR analysis of calcined seashells with variations in time (2-4 hours) and temperature (800-1000°C) produced a similar spectrum (2513.25 cm -1 ) which belongs to the characteristic of the peaks of the C-H group containing calcium oxide (CaO). The absorption band appearance at a wavelength of 709.80 cm -1 was a fi ngerprint indicating the presence of CaO bonds. The FTIR spectrum indicated that the calcination time did not aff ect the production of CaO. The XRD characterization showed a similar pattern, indicating that the calcination time and temperature did not aff ect the cementitious component. The SEM-EDX analysis showed that the higher the calcination temperature, the lower the calcium content, with similar irregular particles. The results of the TGA analysis showed that after passing the temperatures of 900°C the mass change curve seemed to be relatively constant, with 800.5°C giving the highest mass diff erences.