ALBERT

Notes: A visible-light active TiO2−xSx in rutile structure has been synthesized by means of a mechanochemical method. The method is composed of two steps: the first is grinding the mixture of sulfur and TiO2, and the second is calcining the ground sample at 673 K in an inert gas flow. XPS analysis confirms that sulfur has been successfully doped into TiO2. The calcined sample under irradiation of visible light with wave-length over 510 nm has shown good performance for NO gas destruction, suggesting its high photograph-reactivity.

Notes: Grinding lanthanum oxide (La2O3) with Al2O3 was conducted to investigate their mechanochemical reactions to form lanthanum aluminate (LaAlO3) powder using a planetary ball mill. Grinding for 120 min allowed us to obtain single-phase LaAlO3 with a large surface area when transition alumina was used, whereas no formation of LaAlO3 was achieved when α-Al2O3 was used. The mechanochemical process can be applied to synthesize other rare-earth (RE) aluminates (REAlO3) from mixtures of a rare-earth oxide and transition alumina.

Notes: Mechanochemical reaction between ammonium fluoride (NH4F) and gallium fluoride trihydrate (GaF3·3H2O) at a ratio of 3:1 is conducted by grinding the mixture at room temperature using a planetrary ball mill. A single phase of ammonium hexafluorogallate ((NH4)3GaF6) is obtained as a product of the reaction. Other alkali hexafluorogallates (K3GaF6, Na3GaF6, and Li3GaF6) also can be synthesized by grinding constituent components (AF and GaF3·3H2O) under proper grinding conditions. A reaction mechanism related to the dissolution of alkali fluorides in water is suggested.

Notes: A powder mixture of lanthanum oxide (La2O3) and lanthanum fluoride (LaF3) was ground by a planetary ball-mill to investigate the mechanochemical reaction forming lanthanum oxyfluoride (LaOF) at room temperature. The grinding enables us to form LaOF monophase, and the reaction proceeds with an increase in grinding time, whereas the crystallite size of LaOF formed is about 15–20 nm irrespective of the grinding time. Other rare-earth oxyfluorides (R–OF, R = Pr, Nd, Sm, Gd) can be synthesized by grinding the constituent components (R2O3 and RF3).

Notes: TiO〈sub〉2〈/sub〉(1-.ZrO〈sub〉2〈/sub〉. (.=- 0.2, 0.4, 0.6 and 0.8) composite powders having a homogeneous distribution and nanocrystalline were successfully synthesized by sol-gel process using titanium iso-propoxide as precursor. The particle sizes of TiO〈sub〉2〈/sub〉-ZrO〈sub〉2〈/sub〉 powders calcined at 600°C were measured ranging from 10nm to 19nm by XRD and TEM. For the comparison of photocatalytic activity, TiO〈sub〉2〈/sub〉-ZrO〈sub〉2〈/sub〉 composite powders were tested in the degradation of phenol and the photoreduction of inorganic pollutants. The degradation of phenol increased with increase the content of anatase TiO〈sub〉2〈/sub〉 phase

Notes: As the extension of mineral processing, recycling metals from wastes is very importantfor a sustainable society. We have been working on mechanochemistry and its engineeringapplications. One of the applications is to recover and separate useful components from differentkinds of wastes emitted in our society. When a waste sample is subjected to grinding in air so calledmechanical treatment, it changes its structure to disordered system, resulting in chemical reactionswith other substances when it takes over the certain level of energy. Depending on the existingstates of target elements in the wastes, mechanical activation and mechanochemical (MC) reactioncan be applied for the recycling of useful compositions and a process based on MC treatment hasbeen developed.We will report several examples from our research experiences at the conference. The firstexample is to recover rare earths from fluorescent powders in waste lamps. The waste is firstlysubjected to dry grinding to cause amorphization of their structures. This amorphization makes itpossible to dissolve the rare earths from the waste at high yield by leaching with mild acid solutionat room temperature. Similar phenomenon can be seen in the case of ITO (indium tin oxide) scrapwhen it is ground, followed by leaching with acid solution. In this case, dry grinding the scrapinduces disordering the In2O3 in the scrap, leading to high dissolution of In2O3 by leaching withweak acid solution at room temperature. The presence of alumina (α-Al2O3) in the scrap plays asignificant role to the amorphization. Another advanced waste processing is to recover molybdenum(Mo), vanadium (V) and nickel (Ni) sulphide in catalysts in oil refineries. The processing is basedon MC reactions between the sulphides and additives. That is, the sulphides are subjected to drygrinding with additives such as CaO, MnO2 and Na2CO3 to transform them into molybdate andvanadate. Subsequent water leaching allows us to recover Mo and V from the ground product.Other successful example is dry grinding metals or their oxides with polyvinyl chloride (PVC) totransform into chlorides, which dissolve easily in water at ambient condition. The waste processingdescribed above is now in the investigation on industrial applications, and this is a great expectationin the field of industries which emit such waste materials

Notes: It is legally demanded that the wastes containing asbestos should be change to harmlesssubstances completely due to the harmful effects of asbestos fiber on health. The purpose of presentresearch was to construct a safe, reliable and facile technique by using mechano-chemical reaction,which is a non-combustion process and operated in a closed system. It was confirmed that theneedle crystal of chrysotile asbestos was changed perfectly to amorphous state after grinding byusing a planetary ball mill. Furthermore, these products could be remade to useful materials byaddition of soil which consists of inorganic materials based on CaO and so one. After the obtainedfine powders were mixed with water, pressed and held under the humid condition, the stablehydrates were found in these products after XRD analysis. These inorganic compounds were muchuseful as a new raw material for cement-like

Notes: Abstract Dry grinding of Ca(OH)2-P2O5 and CaO-Ca(OH)2-P2O5 mixtures was conducted by a planetary ball mill to investigate the mechanochemical solid-phase reaction for the synthesis of hydroxyapatite (Ca10(PO4)6(OH)2, HAp). HAp was synthesized by grinding of the two sets of mixtures. The formation of HAp from the Ca(OH)2-P2O5 mixture was more advantageous than that from the CaO-Ca(OH)2-P2O5 one. This synthesis reaction from the former mixture was almost completed within 30 min of grinding. The presence and amount of H2O contained in the starting mixtures played a key role to promote the formation of HAp. Especially, in the former mixture, the prolonged grinding assisted the solid-phase reaction of the intermediate DCPD and Ca(OH)2 to produce HAp more effectively.