Novel waste processing by means of mechanochemical treatment

Qiwu Zhang, Fumio Saito

Research output: Chapter in Book/Report/Conference proceedingConference contribution

2 Citations (Scopus)

Abstract

As the extension of mineral processing, recycling metals from wastes is very important for a sustainable society. We have been working on mechanochemistry and its engineering applications. One of the applications is to recover and separate useful components from different kinds of wastes emitted in our society. When a waste sample is subjected to grinding in air so called mechanical treatment, it changes its structure to disordered system, resulting in chemical reactions with other substances when it takes over the certain level of energy. Depending on the existing states of target elements in the wastes, mechanical activation and mechanochemical (MC) reaction can be applied for the recycling of useful compositions and a process based on MC treatment has been developed. We will report several examples from our research experiences at the conference. The first example is to recover rare earths from fluorescent powders in waste lamps. The waste is firstly subjected to dry grinding to cause amorphization of their structures. This amorphization makes it possible to dissolve the rare earths from the waste at high yield by leaching with mild acid solution at room temperature. Similar phenomenon can be seen in the case of ITO (indium tin oxide) scrap when it is ground, followed by leaching with acid solution. In this case, dry grinding the scrap induces disordering the In 2O3 in the scrap, leading to high dissolution of In 2O3 by leaching with weak acid solution at room temperature. The presence of alumina (α-Al2O3) in the scrap plays a significant 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 based on MC reactions between the sulphides and additives. That is, the sulphides are subjected to dry grinding with additives such as CaO, MnO2 and Na2CO 3 to transform them into molybdate and vanadate. 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) to transform into chlorides, which dissolve easily in water at ambient condition. The waste processing described above is now in the investigation on industrial applications, and this is a great expectation in the field of industries which emit such waste materials.

Original languageEnglish
Title of host publicationSelected, peer reviewed papers from The Sixth Pacific Rim International Conference on Advanced Materials and Processing, PRICM 6
PublisherTrans Tech Publications Ltd
Pages1569-1573
Number of pages5
EditionPART 2
ISBN (Print)0878494626, 9780878494620
DOIs
Publication statusPublished - 2007 Jan 1
Event6th Pacific Rim International Conference on Advanced Materials and Processing, PRICM 6 - Jeju, Korea, Republic of
Duration: 2007 Nov 52007 Nov 9

Publication series

NameMaterials Science Forum
NumberPART 2
Volume561-565
ISSN (Print)0255-5476
ISSN (Electronic)1662-9752

Other

Other6th Pacific Rim International Conference on Advanced Materials and Processing, PRICM 6
CountryKorea, Republic of
CityJeju
Period07/11/507/11/9

Keywords

  • Dechlorination
  • Mechanochemical
  • Rare metals
  • Recycling
  • Solid-state reaction
  • Wastes

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

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