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Industrialization plays important role in the economy of developing countries, including increasing community welfare. However, the presence of poorly industries waste disposal system has negative impact to the environment. Therefore, it is necessary to overcome this problem with low-cost technology, called adsorption. In this research, silylated-montmorillonite (sMMt) has been successfully prepared as supporting material for adsorption of methylene blue by chitosan. The sMMt was characterized by FTIR, XRD, and elemental mapping techniques. The chitosan/sMMt composites were prepared through dissolution-precipitation method and produced rod-like morphology as observed by SEM. The adsorption process was carried out in a batch method by studying the pH and the adsorption contact time. The adsorption kinetic mechanism of the chitosan/sMMt nanocomposite followed pseudo-second order rather than Lagergren model indicating chemisorption predominant. The addition of silylated-montmorillonite into chitosan enhanced the methylene blue dye removal performance, which evidenced by improving Qe values by 10% compared to chitosan.

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In this work, we reported the nanostructure and optical properties of the Fe3O4 nanoparticles. The Fe3O4 have been synthesized from local iron sand Halmahera Utara by using the coprecipitation method at a temperature of 80°C and NaOH concentration of 3M. The nanoparticles were calcined at 150°C and 250°C for 4 hours consecutively, while the calcination dwelling time was 2 hours and 4 hours at a temperature of 250°C. The results show that a formation of Fe3O4 nanoparticles with a spinel crystal structure. The lattice parameter of nanoparticles decreases with an increase of calcination temperature and dwelling time due to higher thermal energy driving the atom to move closer to each other. Hence, the crystallite size of the nanoparticles increases due to the expansion process to the grain of the nanoparticles. The optical gap energy of the nanoparticles decreases due to the formation of a larger particle. It also confirms that the existence of Fe3+-O and Fe2+-O bonds in the nanoparticles which are characteristic functional group bond of Fe3O4 in the tetrahedral and octahedral sublattice. This result can prove that a higher calcination temperature and longer dwelling time can improve the nanostructure and optical properties of Fe3O4.