Analysis of Sulfate (SO 4 ) Concentration in Bittern as Raw Material for Magnesium Sulfate (MgSO 4 )

The investigation on traditional salt production had developed in the characterization of Bittern. Bittern is the dense residual liquor with specific gravity ≥ 1.28 gr/cm 3 obtained after precipitation and harvesting of NaCl salt from seawater. In this research, the measurment of sulfate in the bittern was carried out. Sulfate is one of the raw materials for MgSO 4 . The determination of sulfate concentration is using a turbidimetric method according to SNI 6989 20:2009 using a spectrophotometer at a wavelength of 420 nm. In this process the Sulfate in an acidic environment reacts with barium chloride (BaCl2) to form barium sulfate (BaSO4) crystals. The light absorbed by the barium sulfate suspension is measured with a photometer and the sulfate content is calculated by comparing the readings with the calibration curve. The results of the analysis showed that at 31 o Baume the sulfate content is 40.0 g/L, at 32 o Baume the sulfate content is 42.6 g/L, at 33 o Baume the sulfate content is 42.8 g/L. The sulfate concentration in the bittern showed a linear increase with increasing water concentration. The sulphate content of bittern with 31 o Be levels has an average value of 40.028 g/L, at 32 o Be levels the average sulphate content is 42.599 g/L and at 33 o Be levels it is 42,825 g/L.


Introduction
Bittern is a residual product from the production of salt, conventionally referred as old water. It has a form of a yellowish liquid, placed on the crystallization  with the rich content of minerals and other minor elements . Several references state that Bittern contains various minerals such as magnesium (Mg 2+), potassium (K+), sodium (Na+), chloride (Cl+) sulphate (SO42-) and other minor compounds , Aral et al. al., 2004. Faizah, et.al., 2018, also identified that there are various compounds such as magnesium sulphate (MgSO4), sodium chloride (NaCl), magnesium chloride (MgCl2), potassium chloride (KCl), calcium chloride (CaCl2).
Nowadays, bittern has begun to get a lot of attention to be identified as a cheaper source to produce minerals and reduce seawater pollution. Megawati et al. (2021) stated that the higher of o Be of the liquid being measured will make the density of the liquid is greater, which means the mineral content such as Mg, K and SO₄²ˉ will be higher. In this case, sulfate is one type of ion contained in bittern with the chemical formula SO 4 2has an atomic mass of 96.06 atomic mass units. Sulphate is composed of a central Sulphur atom surrounded by four oxygen atoms in a tetrahedron arrangement, the sulphate ion is negatively charged (Erviana et al 2018). The sulphate contained in the bittern comes from sulphur. The formation of sulphur comes from volcanic activity in the form of gas originating from the active crater of Solfatara or it can also come from hot water that flows into the sea, then settles to form sediment (Indiyati, 2002).
The sulphate will be higher linear with the o Be of seawater . In the industrial, sulphate is widely used as additional raw material in the manufacture of fertilizers multi nutrients. The usage of sulfuric acid as one of the components for fertilizers multi nutrients production serves to grow natural food (plankton) in fish ponds (Nadia et al. 2015). Sulfuric acid is one of the supporting materials that is widely used in the production of phosphoric acid which is used for the manufacture of phosphate fertilizers, pharmaceuticals and is widely used in the manufacture of detergents and paper (Hakim et al 2018). In addition, the SO 4 can also be used as raw material for Magnesium Sulphate (MgSO4) (Hapsari, 2006;Sani, 2010 Be. The increasing process is done by transferring the bittern sample from the prototype into the UTM salt house. This process is presented in Figures 1 and 2.

Sulphate Level Test on Bittern
Analysis of the sulphate level test on bittern using the turbidimetric method. As per SNI 6989 20:2009, the first step is to make a working solution using a standard sulphate solution. The standard series of working The second stage after making the calibration curve is testing the bittern sample at each different Baume scale level, by pipetting 0.1 mL of a bittern in each sample into a 10 mL volumetric flask, dissolving it with aqua bidestilata to the limit of tera, then transferring it to an Erlenmeyer 250 mL, and added 2 mL of the buffer solution stirred at a constant speed using a magnetic stirrer. During the stirring process, BaCl was added and stirred for 1 minute starting from the addition of BaCl. After stirring, the absorption rate was measured using a spectrophotometer with a wavelength of 420 nm. Calculation of sulphate levels based on SNI 6989 20:2009 as the following formula:

Level of Sulphate (MgSO₄²ˉ⁄ L ) = C x f
Note: C = Sulphate content obtained from the calibration curve (mg/L); f = Dilution factor.

Result and Discussion
Bittern is a waste obtained from the salt production process. Be is various because it is strongly influenced by climatic conditions. In addition, wind speed, air humidity and temperature also affect the speed of the evaporation process (Adira and Setiawan, 2014). The characteristics of the Baume scale can be seen from the colour of the liquid, which is the yellower means the Baume scale is higher. it can be seen in Figure 3. In contrast, the results of research by Sidik (2013) showed that the sulphate content (SO₄²ˉ) in bittern 30oBe was 73.15 g/L but in Megawati et al., (2021) with the same concentration the sulphate content value produced was 60.2g. /L. This difference in sulphate content is identified due to the different sources of seawater raw materials used in the salt production process. This results in a different sulphate content in each bittern. Considering that the sulfuric content comes from organic waste produced, including livestock waste, industrial waste, agriculture and also urban   areas. Hydrogen sulfide will be oxidized by photosynthetic bacteria to produce sulphate. The sulphate will be carried away by rainwater and groundwater to the mouth of the river and flows into the sea (Hadiarti, 2015).

Test Anova one-sample t-test
Analysis of variance (ANOVA) is a method to collect the statistical models and their associated hypotheses or other procedures used to analyze the differences among means. The Anova test hypothesis H0 indicates that the data or groups are from the same population so that they have the same expected mean and variance, while H1 indicates that the data has unequal or different variances (Marpaung 2020). The hypothetical determination of the ANOVA test is if the significance value is > 0.05 then accept H₀ and reject H₁, but if the significance value is <0.05 then accept H₁ and reject H₀   et al., (2016) which states that the concentration of bittern water has a significant influence on the mineral content in bittern, where the higher the concentration level, the higher the concentration of minerals contained in bittern, one of which is sulphate.

A further test of ANOVA
A further test is carried out in case of a significant difference in the results of the ANOVA test to find out the significant impact of sulphate concentration. The results of ANOVA shown in Table 2. Bitern 31 Be further test with 32 Be below. The P-value (2.818 x 10 -13 ) < (0.05), then H 0 is rejected and H 1 is accepted, which means that there is a difference in the average sulfate content at the concentration level of bittern 31 Be water with bittern 32 Be concentration levels.
Next, the further analysis is in the Bittern 31 Be and 33 Be shown in Table 3. Bitern 31 Be further test with bittern 33 Be below. The Pvalue (6.375 x 10 -12 ) < (0.05), then H0 is rejected and H1 is accepted, which means that there is a difference in the average sulfate content at the concentration level of bittern 31 Be water and bittern 33 Be.
The last is analysis from Bittern 32 Be and 33 Be as per Table 4. Bitern 32 Be further test with bittern 33 Be below. The P-value (6.973 x 10 -05 ) < (0.05), then H 0 is rejected and H 1 is accepted, which means that there is a difference in the average sulfate content of the 32 Be bittern water concentration with the 33 Be bittern concentration level.

Conclusion
This study concludes that the sulphate content of bittern with 31 o Be levels has an average value of 40.028 g/L, at 32 o Be levels