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« Fer le propre, ça ne coûte pas grand chose ! »

Article publié le 8 janvier 2009

« Fer le propre, ça ne coûte pas grand chose ! »

En voilà une très bonne idée ! Pour un peu, ce serait presque la pierre philosophale des cleantech, ou comment faire du propre à partir du sale. C’est un article de The Economist qui nous raconte comment une équipe de recherche sino-américaine a réussi à utiliser la ferraille, celle qui finit dans les décharges ou dans la nature et dont on ne sait jamais quoi faire, pour dépolluer l’eau usée émanant des industries les plus lourdes (pharmacie, pétrochimie, textile).
C’est un enjeu majeur pour nos sociétés qui consomment de l’eau en quantité, à titre d’exemple, il faut environ un litre d’eau pour produire une calorie d’aliment, et chaque américain consomme en moyenne 600 litres d’eau par jour.
La technique imaginée par Wei-Xian Zhang, de l’Université Lehigh en Pennsylvanie, et Luming Ma de la Tongji University à Shanghai, est simple à comprendre en plus d’être « propre ». On utilisait déjà de la poudre de fer pour retraiter les eaux industrielles. Mais personne n’avait songé à utiliser de la ferraille en quantité pour procéder à la dépollution de ces eaux. Au lieu de faire circuler l’eau usée dans une série de réservoirs contenant des agents chimiques dépolluants, l’idée est de faire passer les eaux usées à travers la ferraille. Les agents chimiques des eaux usées sont alors attirés par le fer, échangent des électrons qui rendent ces mêmes agents dégradables (le fer s’oxyde à ce moment-là), donc nettoyables plus facilement.
L’avantage de cette technique réside évidemment dans son coût : la ferraille ne coûte presque rien, et on la trouve en quantité dans les pays en développement. En Chine par exemple, le kilo de ferraille coûte 0,2 dollars, contre plus de 100 dollars pour un kilo de nano-particules de fer. Le calcul est vite fait ! La ferraille peut être utilisée 2 ans avant de perdre ses qualités, mais peut également être amélioré par un traitement au chlorure de cuivre, qui rend le prix du fer à peine plus cher de 0,05 dollars par kilo.
Les résultats sont épatants, avec un taux de dégradation du nitrogène de 13 à 85%, de 44% à 64% pour le phosphore et de 52% à 80% pour les colorants et teintures. Une première unité de retraitement expérimentale traite déjà 60 000 mètres cubes d’eau à Shanghaï, une ville où les industries polluantes sont légion. Plusieurs municipalités chinoises ont donc invité les Dr. Wang et Ma à venir concevoir d’autres unités de ce type.
Une très belle idée, particulièrement pour les pays en développement, peut-être pourrait-on également y songer en Europe ?


Eau Déchets Pollution

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36 votes

votez :
par Georgia (IP:xxx.xx1.156.19) le 8 janvier 2009 à 14H51

Très bonne nouvelle ! :-) Sait-on si ce traitement permet également de nettoyer l’eau de d’autres particules problématiques chez nous, comme les molécules de médicaments (antidépresseurs notamment) ou les hormones féminines des contraceptifs qui se retrouvent dans nos eaux via les urines ?

votez :
par zelectron (IP:xxx.xx6.203.169) le 8 janvier 2009 à 18H49

On utilisait il y a qqs années du perchlorure de fer en très gdes qtés pour traiter les eaux usées, ce n’est plus le cas aujourd’hui ?

votez :
(IP:xxx.xx3.65.100) le 10 janvier 2009 à 12H26

Le concept semble séduisant, mais où sont passés les polluants (plomb des peintures, métaux lourds, huiles,...) qui recouvraient toutes ces ferrailles ? Dans l’eau qu’ils sont sensés traiter ? Les chinois sont des magiciens. Ce genre de nouveauté nous permettra de consommer toujours plus de médicaments, produits chimiques, vêtements potentiellement toxiques,.....en ayant bonne conscience.

votez :
par manceifreecno1977 (IP:xxx.xx6.50.24) le 29 juillet 2013 à 02H54

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votez :
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