PRB. Remediation of Chromate Contaminated Soils by Combined Technology of Electrokinetic and Iron PRB ENVIRONMENTAL SCIENCE

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1 ENVIRONMENTAL SCIENCE Vol 28,No 5 May,2007 PRB ( ) 1,2 1 3 ( ; ) : ( ) (permeable reactive barrier, PRB) ( ) ( ) 98 % 100 % 80 % 90 % ; ( ) ( ) ( ) 90 % ( ) ; 28 % ( ), ( ) 98 % 75 % 77 % ; ph ph ph PRB 2, 90 % ph : ;PRB ; ; :X53 :A : (2007) Remediation of Chromate Contaminated Soils by Combined Technology of Electrokinetic and Iron PRB ZHANG Rui2hua 1,2,SUN Hong2wen 1 (1 College of Environmental Science and Engineering, Nankai University, Tianjin , China ; 2 College of Science, Tianjin University of Science & Technology, Tianjin , China) Abstract :Remediation efficiency on artificial chromate [ Cr ( ) ] contaminated soil and a field Cr ( ) contaminated soil around industrial Cr residue ( Tianjin Tongsheng Chemical and Industrial Factory) by using electrokinetic method was studied Moreover, the electrokinetic method was combined with iron permeable reactive barrier ( PRB) and a better combination mode was found The remediation efficiency of the combined method was compared with electrokinetic method The results showed that Cr ( ) contaminated soil can be remedied effectively by electrokinetic method For artificial contaminated soil, the removal ratio of Cr ( ) reached 98 % 100 %, while the total Cr was removed about 80 % near the anode, and more than 90 % near the cathode, where the content of Cr came back to soil background The reduction of Cr ( ) to Cr ( ) occurred during the soil remediation, and more than 90 % of the residual Cr was Cr ( ) at the end of remediation More than 98 % Cr ( ) were removed, whereas only 75 % 77 % of total Cr were removed from the heavily contaminated field soil as the soil contained 28 % Cr ( ) initially Soil ph increased near the cathode and decreased near the anode, while the change of soil ph was insignificant in the middle In situ combination mode of electrokinetic and PRB is a better method that could take the full advantages of the two technologies The removal efficiency of total Cr was about 90 % at the end of the remediation, which is better than electrokinetic method especially near the anode, and had less effect on soil ph Key words :iron chips ; PRB ; electrokinetic remediation ; chromium pollution ; soil remediation 20 a [1,2 ], ( ) [ ] [7,8 600 t 1 % 2 %, ] 015 % 1 % ( ) ( ) [9 ] ( ) : ; : : : (1971 ),,,E2mail : com 3,E2mail : edu cn China Academic Journal Electronic Publishing House All rights reserved

2 [10,11 ] ( ) (11 cm 9 cm 115 cm) 115 cm ( 1 mm ) 0101 ( ) molπl KCl,, 1 ( ) VΠcm, 1 ( ) 1 (115 cm ) ( ), ( ) 80 (permeable reactive barrier, PRB) ( ) ( ) 20 a [12 16 ], PRB PRB PRB ( ) 114 ( ) ( ) K 2 Cr 2 O 7 ( ) PRB, Cr ( ) mgπkg ( ) ( ) 20 h, ( 0101 molπl KCl 1 ) Cr ( ) Cr 165 h,, 013 km 2,, ( ), Cr ( ) Cr 400 m ( ),,163 h 325 h ( 112 ) 1 molπl 115 Fe2PRB 20 2,1 PRB, m 2 Πg X ( 1 Cr ( ) DΠmax22500 XRD ) X (PW mgπkg, 115 cm 1404X ) 115 cm, 95 % ( 75 % Fe 0,22 %,, Fe 3 O 4,3 % FeO) Mn, Zn, Cu, 1 cm 1 Ca, K 1 Fig 1 Scheme of soil electrokinetic remediation reactor PRB 70 % 30 % cm 15 cm kg ( ml, 114 ), mlπh 013 kgπcm h 11 6 cm China Academic Journal Electronic Publishing House All rights reserved

3 5 : PRB ( ) 1133 ( ) mgπkg ( GB ) ( ) : 2 4 g ml 014 molπl KCl 5 min,, 100 % 20 h 100 ml, ( mgπkg) ; 2 ml KCl 2 min, 2 3, 10 h,,, 70 h ( ) 100 %, : 015 g, 1 4 h 50 h H 3 PO 4 H 2 SO 4 2 ml,, 20 h (50 70h) HNO 3,70 h (165 h) 25 ml, %, ( ) mgπkg 99 %, KMnO 4, 15 min, 1 ml mgπkg 10 % 2 % NaNO 2 ( ) ( ) ( ) ( ), ( ) ( ) 1 ( ) 90 % mgΠkg ( ) ( ) 2 ( ) 211 ( ) 3 2 ph 1 ( ) Cr 2 O 2-7, 2, ( ) HCrO - 4 ( ) CrO 2-4 ( ph ) ( ) Cr 3 + (ph < 4) CaO (OH) 2 Cr (OH) 3 ( ) Cr (OH) - 4 (ph > ( ), 12) ( ) ( 400 mgπkg ( ) Cr (OH) mgπkg), mgπkg, ( ) ( ) mgπkg 98 % 100 % : ( < 90 mgπkg) Mn ( ) ( ), ( ) ( ) 400 m ( ) [17 19 ], 3 1 ph ( ) 90 % ( ) Table 1 Chromium concentration and ph of the tested soils Πmg kg - 1 ( ) Πmg kg - 1 ( ) Πmg kg ( ) ( ) mgπkg ph 3 4 h ( ) ( mgπkg) ; ( ), % 80 % 1 70 h L ( ) mgπl h, ph,1 2 h 2 ph 13 ph 3 ; 2 10, China Academic Journal Electronic Publishing House All rights reserved

4 ( ) Fig 2 Curves of Cr ( ) and total Cr concentration in soil during the electrokinetic remediation process 3 ( )Π Fig 3 Percentage curves of Cr ( )Πtotal Cr in soil during the electrokinetic remediation process ; 214 A, ma ;,, 2 3 h h mgπl 163 h 70 % 900 mgπl, 13 L 160 h 72 %, 325 h 5 %, 0 75 % 77 % 1, Cr Cr ( ) Cr ( ) , mgπkg,cr ( ) 28 % ( ) 98 %, ( ) ( ) China Academic Journal Electronic Publishing House All rights reserved

5 : PRB ( ) 1135 ( ) ( ) 325 h ( ) 70 h ( ) 95 % [ ( ) ] [ ( ) ( ) 2 3 ( ] [ ( ) ] 100 %), 2 ( ) Cr ( ) ( ), 12 45 mgπkg, 215 Fe2PRB PRB 4 214 ph ph 1 :50 ml 4 (3 000 mgπkg) 1 ph,94 h ph 418, 3 ph,94

5 5 : PRB ( ) 1135 ( ) ( ) 325 h ( ) 70 h ( ) 95 % [ ( ) ] [ ( ) ( ) 2 3 ( ] [ ( ) ] 100 %), 2 ( ) Cr ( ) ( ), mgπkg, 215 Fe2PRB PRB ph ph 1 :50 ml 4 (3 000 mgπkg) 1 ph,94 h ph 418, 3 ph,94 h ph ph ;, ( ) ( ) ( ), H + OH - [21 ], (1) (2) : : 2H + + 2e H 2 (1) : 4OH - - 4e 2H 2 O + O 2 (2) H + OH - PRB, ph ph H + Fe2PRB OH - ph ph 130 h H + OH ph h, ( ), 2 ph ph (10154) mgπkg ( ) ph ph mgπkg ( ) 3 90 % ( ) PRB 4 ph Fig 4 ph change of the soil during the remediation process [20 ] ( ) ph,, 3 : ; PRB, ph ph = 615, ph > 8 ( ), ph ( 1 ph 4), ( ) H +,94 h (3 000 mgπkg) ph 418 OH - h 5 h ( ) ( 015 mgπl) 5 [ 400 mgπl ( ) ] 2 [1 000 mgπl ( ) ] 115 g (25,200 rπmin) 20 h, ( ) mgπl 90 %, ( ) ( ) 1 80 % PRB PRB ; PRB ( ) ph, H China Academic Journal Electronic Publishing House All rights reserved

6 (3) (4) : Fe 0 + CrO H 2 O Cr (OH) 3 + Fe (OH) 3 + 2OH - (3) xfe (OH) 3 + (1 - x) Cr (OH) 3 (4) Fe x Cr (1 - x) (OH) 3 + 3OH - ( ) ( ),, Fe 2 + ( ), PRB ( ) ( ) 1, 80 % 90 3 H 2 (1) ( ) ( ) ( ) ( ) 98 % 100 % ( ) ( ) 90 % ( ) ; ( ) 90 % % ( ), ( ) 98 % 75 % 77 % (2) ph, ph ph ph (3) PRB ( ) ( ) PRB PRB 90 %, ph ph PRB : [ 1 ] Sawada A, Morid K, Tanaka S, et al Removal of Cr (VI) from contaminated soil by electrokinetic remediation[j ] Waste Manage, 2004, 24 : [ 2 ] Manna M, Sanjaya K, Shekhar R Electrochemical cleaning of soil contaminated with a dichromate lixiviant [J ] Int J Miner Process, 2003,72 : [ 3 ] Lageman R Electroreclamation : application in the Netherlands[J ] Environ Sci Technol, 1993, 27 : [ 4 ] Ho S V, Athmer C, Sheridan P W, et al The Lasagna technology for in situ soil remediation 2 large field test [ J ] Technol, 1999, 33 : Environ Sci [ 5 ] Mattson E D, Bowman R S, Lindgren E R Electrokinetic ion transport through unsaturated soil :2 application to a heterogeneous field site[j ] J Contam Hydrol, 2002, 54 : [ 6 ] Lageman R, Clarkea R L, Pool W Electro2reclamation, a versatile soil remediation solution[j ] Eng Geol, 2005, 77 : [ 7 ] [J ],2005, 25(1) : [ 8 ] [J ],2005,46 : [ 9 ] Zhou D M, Cang L, Alshawabkeh A N, et al Pilot2scale electrokinetic treatment of a Cu contaminated red soil [ J ] Chemosphere, 2006, 63 : [10] ( ) [J ], 2005, 14(6) : [11] [J ],2005, 28 (4) : [12] Blowes D W, Ptacek C J, Benner S G, et al Treatment of inorganic contaminants using permeable reactive barriers [ J ] J Contam Hydrol, 2000, 45 : [13] Wilkin R, Su C M, Ford R, et al Chromium removal processes during groundwater remediation by a zerovalent iron permeable reactive barrier[j ] Environ Sci Technol, 2005, 39 : [14] Schafer D, Kober R, Dahmke A Competing TCE and cis2dce degradation kinetics by zero2valent iron experimental results and numerical simulation[j ] J Contam Hydrol, 2003, 65 : [15] Day S R, O Hannesin S F, Marsden L Geotechnical techniques for the construction of reactive barriers [ J ] J Hazard Mater, 1999, B67 : [16] Furukawa Y, Kim J W, Watkins J, et al Formation of Ferrihydrite and Associated Iron Corrosion Products in Permeable Reactive Barriers of Zero2Valent Iron [J ] Environ Sci Technol, 2002, 36 : [17] Kozuh N, Stupar J, Gorenc B Reduction and oxidation processes of chromium in soil[j ] Environ Sci Technol, 2000, 34 : [18] Buerge I J, Hug S J Influence of mineral surface on chromium ( ) reduction by iron( ) [J ] Environ Sci Technol, 1999, 33 : [19] [J ],1997,17 (3) : [20] [M] :, [21] [J ],2004,23(6) : China Academic Journal Electronic Publishing House All rights reserved

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