Vol.11 no.3 2019

Research paper : High-value materials from incineration residues of burnable garbage (N. FUKAYA et al.)−130−Synthesiology - English edition Vol.11 No.3 (2018) performance humidity control agent, a drug transfer system, or a catalyst carrier.[7]Silica obtained from molten slag mentioned in the previous subchapter has high specic surface area but does not have a pore structure. Therefore, we engaged in the synthesis of mesoporous silica for the purpose of developing technology to convert molten slag into a higher performance, higher added-value material.The chemical treatment to obtain silica with high specific surface area shown in the previous subchapter was conducted in a condition in which surfactants that acted as templates to make the pores coexisted. The white solids obtained was red at 550 °C to burn away the template, and we were able to obtain mesoporous silica with ordered nano-size pores. The specific surface area of mesoporous silica produced from molten slag was 675 m2/g and the average pore size was 9.2 nm. The electron microscope photograph of this mesoporus silica is shown in Fig. 8. The already known mesoporous silica was synthesized from highly pure and relatively expensive silicon raw materials such as colloidal silica and tetraalkoxysilane. On the other hand, molten slag was not pretreated in this technology and contained large amounts of impurities such as calcium and aluminum. We succeeded in synthesizing the material with pores and specic surface areas similar to the conventional mesoporous silica by maneuvering the reaction time and temperature and nding the condition in which self-assembly of the template surfactants progressed.Both AIST and Mitsui E&S published press releases of the results of this joint research on July 25, 2017 (Fig. 9).[8][9] We were contacted by companies of various industries including chemicals, nonferrous metals, ceramics, traders, and others, and we are now preparing for supplying test sample of silica with high specic surface area to users.4 Future prospectsThe technology developed in this research can expand the advanced use of molten slag, as it leads to wide-ranging use of silica with high specific surface area that can be made from molten slag whose current use is limited. In the future, we aim to improve the manufacturing process, work on upsizing the manufacturing scale, and try for practical utilization in a few years. Through practical realization of this technology, we hope it leads to such outcomes as added value through effective use of waste residue and resource savings through substance circulation.5 AcknowledgementThe research pertaining to the direct synthesis of organic silicon material using silica as raw material in this paper was conducted as part of the NEDO Project “Development of the manufacturing process technology for organic silicon functional chemical products” (FY 2014 up to the present).Can synthesize mesoporous silica!Collection →Disposal plantBurnable garbageMolten slagBecome silica with high specic surface area!Fig. 8 Electron microscope photograph of mesoporous silica synthesized from molten slagFig. 9 Conversion of molten slag, incineration residue of burnable garbage, into high added-value material

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