Preparation of CaCO3/MgO from Bangkalan’s dolomite for raw biomaterial

Dolomite is a double salt consisting of calcium carbonate (CaCO3) and magnesium carbonate (MgO) and is one of the two forms of limestone. This dolomite can be found in the Bangkalan area, which only used as the landfill and making light stone. Existence the great potential for dolomite as a biomaterial then in this research was carried by making CaCO3/MgO from dolomite using a simple calcination method at 600°C, 700°C and 800°C for one hour. The results of the calcination then carried out of XRD characterization. From the results of XRD found that the CaCO3/MgO phase was formed optimally at a temperature of 700°C.


Introduction
Bangkalan district which is located on the island of Madura, East Java, has the potential high rock minerals in the form of Jaddih mountainous, which are carbonate bases limestone, which consists of limestone, calcite mineral and dolomite limestone. The limestone hill is a mining location carried out by local residents, which is usually used as bricks, soil fillings, plant fertilizer [1] and animal feed [2]even sold to other areas. The existence of massive exploitation by local residents, then the government transferred the function of the mining site into a tourism area. But currently, there is still illegal mining of the limestone, especially dolomite minerals. The result of dolomite mining is sold to consumers at relatively cheap prices because ordinary people do not yet know the use of dolomite material as an advanced raw material.
Advanced materials bases on dolomite are known as raw materials for biomaterials and ceramics. Dolomite as a biomaterial including functioning as antibacterial substances [3,4]that have not been studied optimally. Dolomite contains 94.5 % Ca and 5.5 % Mg [5]. Yamamoto et al report that calcination of dolomite with carbon coatings at a temperature of 400°C to 800°C produced optimum CaCO3/MgO content at temperature 700°C [3]. Furthermore, in the research of the same carried out calcination of dolomite without coating carbon at a temperature of 600°C to 800°C, the optimum CaCO3/MgO content was produced at a temperature of 800°C [6]. CaCO3/MgO showed good antibacterial activity in Staphylococcus aureus and Escherichia coli [6]. This is because CaCO3/MgO is a porous material that has adsorption ability that can damage the surface of bacterial growth to hamper [3]. Based on the above research, then the synthesis of CaCO3/MgO from natural limestone for raw biomaterial preparations with calcination temperatures of 600°C to 800 °C for one hour. Then the performer of XRD characterization to determine the phases contained in dolomite and the results of  [7]. The results of this research expected that CaCO3/MgO content from dolomite formed optimally and can be used as raw biomaterial preparation.

Materials
The material used in this research was dolomite powder, which was taken from Jaddih hill limestone, Bangkalan District, Madura, East Java. To the resulted in the fine powder used mortal and pestle tools, and the sieves of 200 mesh. The calcination process uses a type furnace is L5/11/B170.

Preparation of CaCO3/MgO
Preparation of CaCO3/MgO was carried out by refining dolomite limestone using mortal and pestle until obtained dolomite powder. After that, the powder was sieved using a 200 mesh sieve and obtained homogeneous dolomite powder. The weighed using digital balance the brand of OHAUS PA224 amounted of 5 grams. Then the dolomite powder was calcined at a temperature of 600°C, 700°C and 800°C for one hour.

Instrumentation
The result of calcination from dolomite powder was characterized using XRD type of Philips X'Pert MPD (Multi Purpose Diffractometer) system, with radiation of anode Cu 40 kV, 30 mA, wavelength CuKα 1.54056Ǻ and Bragg-Brentano optical light. The powder tested as big as 0.1 gram. Information generated from X-ray diffraction patterns in the form of a peak position (2 ), distance between fields (d) which shows the phase Miller index, diffraction (I). Each formula has a unique and different crystal structure both on a single phase and several phases. The results of the characterization of XRD are then carried out using software match, so that obtained each percentage of CaCO3 and MgO.

Result and Discussions
In phase identification and analysis of the size crystal from a simple tested needed some data from Xray diffraction. Among them are, peak position (2 ), the distance between fields (d) and diffraction intensity (I). The result of this research match for CaCO3/MgO powder at the calcination of 600°C ( Figure 1). The result of this search match shows four phases that appear in software match, among other of CaCO3 (pdf card 96-900-0969), MgO (pdf card 96-100-0054), Dolomit (96-900-1419) and CaO lime (pdf card 96-900-6699). Each phase has a different percentage, which shows the optimum level that appears in the calcined dolomite powder, which is indicated by the number of peaks that appear. In Figure 1 shows the peak that appears on dolomite powder for the Magnesium Oxide Periclase phase was identified at the diffraction angle 2Ɵ = 36. 86°

Figure 1. Match analysis results for CaCO3/MgO powder at the calcination 600°C
The highest peaks are dominated by the MgO and CaCO3 with the percentages showed in Table 1. In Table 1, shows the percentage of each phase identified by the software Match. Calcite has the highest percentage compared to the other three phases. This proves that calcite is the most dominant mineral in dolomite from the Jaddih hill. However, in the results of the calcination process, there are various impurities detected such as Table 2. calcination is required at high temperatures of 700°C and 800°C. The following results of match analysis for CaCO3/MgO powder at the calcination 700° ( Figure 2) and 800°C (Figure 3).  At the calcination 700°C, in addition to the MgO, CaCO3 and CaO phases is also impurities detected in the software Match and shown in Table 4.    Based on the three XRD test results obtained the largest CaCO3/MgO concentration on calcination 700•C with MgO of 42.3% and CaCO3 of 54.9%. By increasing the temperature of calcination, the presence of CaO element has increased, such as the calcination temperature of 800°C, which is 20.7%. The presence of impurities in the form of CaO in the powder of CaCO3/MgO then it is possible to reduce its potential as an antibacterial activity.

Conclusion
In this research, calcination was done at dolomite with a temperature of 600°C to 800°C. After XRD characterization, we can know the largest concentration of CaCO3 and MgO with calcination of