Mercury pollution through water causes several dangerous diseases. Various efforts have been made to reduce mercury pollution. One of them is by using sorbent. Many ways to improve absorption efficiency, one of which is using magnetic sorbents. This study focused on the effect of grain size and the concentration of Mn0.25Fe2.75O4@SiO2 core-shell on mercury absorption efficiency. The synthesis of Mn0.25Fe2.75O4@SiO2 with 6 and 8 mL of TEOS was carried out through coprecipitation and sol-gel methods. The characterization using XRD, VSM, and FTIR was conducted to determine grain size, properties, and material functional groups proving that SiO2 was successfully covered on the Fe3O4 surface. The percentage of absorption was found by using the AAS instrument. Diffraction data confirmed the presence of Fe3O4 and the amorphous SiO2 phase. According to the Rietveld analysis of all samples demonstrated the particle size of Mn0.25Fe2.75O4 around 11-12 nm. The Mn0.25Fe2.75O4 core had superparamagnetic properties for magnetic separation, and the SiO2 shell could protect the core of being oxidized or dissolved under acid condition. FTIR results showed the sample had a functional group of the main components of Fe-O and SiO2 at a wavenumber of 420-507 cm-1 and 801 cm-1 (stretching) and 1078 cm-1 (bending), respectively. The results of the mercury absorption test indicated that the smaller the grain size and the higher the concentration of TEOS, the percentage of mercury uptake would increase. In addition, the absorption percentage increased with the duration of absorption time given.

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This study aims to determine the difference in learning outcomes in work and energy from students who learned using inquiry training model with merry-go-round techniques. This study was designed using a quasi-experimental design with 74 students as samples. The instrument developed was 21 questions about work and energy. The results show that the experimental class has the highest value of 85.27 compared to the control class with 77.56. The test results of the physics learning outcomes hypothesis were tcount (3,295) >ttable (1,666), indicating that there were differences in physics learning outcomes of students who studied using the inquiry training model with the merry-go-round technique than students who studied conventionally.

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