Purifying agent for purifying soil or ground water, process for producing the same, and method for purifying soil or ground water using the same

Abstract

A purifying agent for purifying soil or ground water which comprises a water suspension containing iron composite particles comprising α-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 μm, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight, and polyaspartic acid or a salt thereof. The purifying agent is capable of decomposing aliphatic organohalogen compounds or aromatic organohalogen compounds contained in the soil or ground water in an efficient, continuous and economical manner.

1 .- 7 . (canceled) 
     
     
         8 . A process for producing a purifying agent for purifying soil or ground water, comprising:
 heat-reducing goethite particles having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.06 to 1.00% by weight and an S content of 2200 to 5500 ppm or hematite particles having an average major axis diameter of 0.05 to 0.50 μm, an Al content of 0.07 to 1.13% by weight and an S content of 2400 to 8000 ppm, at a temperature of 350 to 600° C. to produce iron particles;   forming a surface oxidation layer at the surface of the iron particles in a gas phase and then transferring the resultant particles into water, or transferring the iron particles into water and then forming a surface oxidation layer at the surface of the iron particles in the water to form a water suspension containing iron composite particles;   adding an aqueous solution of polyaspartic acid or a salt thereof to the water suspension such that a concentration of the polyaspartic acid or salt thereof is 5 to 50% by weight based on the weight of the iron composite particles; and   mixing and stirring the resultant mixture.   
     
     
         9 . A method for purifying soil or ground water, comprising:
 treating the soil contaminated with organohalogen compounds or the ground water contaminated with organohalogen compounds with a purifying agent comprising a water suspension containing iron composite particles comprising α-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 μm, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight; and polyaspartic acid or a salt thereof.   
     
     
         10 . A method for purifying soil or ground water, comprising:
 directly injecting a purifying agent comprising a water suspension containing iron composite particles comprising α-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 μm, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight; and polyaspartic acid or a salt thereof into the soil contaminated with organohalogen compounds or the ground water contaminated with organohalogen compounds at the in-situ position.   
     
     
         11 . A method according to  claim 9 , wherein the purifying agent further comprises as an additional component, sodium hydrogen caronate, sodium sulfate or a mixture thereof. 
     
     
         12 . A method according to  claim 9 , wherein said iron composite particles have a ratio of a diffraction intensity D 110  of (110) plane of α-Fe to a sum of a diffraction intensity D 311  of (311) plane of magnetite and the diffraction intensity D 110  (D 110 /(D 311 +D 110 )) of 0.30 to 0.95. 
     
     
         13 . A method according to  claim 9 , wherein said iron composite particles have a saturation magnetization value of 85 to 190 Am 2 /kg, and a crystallite size of (110) plane of α-Fe of 200 to 400 Å. 
     
     
         14 . A method according to  claim 9 , wherein said iron composite particles contained in the purifying agent are present in an amount of 10 to 30% by weight based on the weight of the purifying agent, and said polyaspartic acid or salt thereof is present in an amount of 5 to 50% by weight based on the weight of the iron composite particles. 
     
     
         15 . A method for purifying soil or ground water, comprising:
 treating the soil contaminated with organohalogen compounds or the ground water contaminated with organohalogen compounds with a dilute purifying agent comprising a water suspension containing iron composite particles comprising α-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 μm, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight; and polyaspartic acid or a salt thereof,   wherein the amount of the iron composite particles (as a solid content) in the purifying agent is 0.1 to 200 g/L.   
     
     
         16 . A method according to  claim 15 , wherein the purifying agent further comprising as an additional component, sodium hydrogen carbonate, sodium sulfate or a mixture thereof,
 the amount of sodium hydrogen carbonate, sodium sulfate or a mixture thereof (as a solid content) in the purifying agent being 0.01 to 1.0% by weight.   
     
     
         17 . A method for purifying soil or ground water, comprising:
 directly injecting a dilute purifying agent comprising a water suspension containing iron composite particles comprising α-Fe and magnetite, and having an average particle diameter of 0.05 to 0.50 μm, an S content of 3500 to 10000 ppm and an Al content of 0.10 to 1.50% by weight; and polyaspartic acid or a salt thereof,   wherein the amount of the iron composite particles (as a solid content) in the purifying agent is 0.1 to 200 g/L into the soil contaminated with organohalogen compounds or the ground water contaminated with organohalogen compounds at the in-situ position.