28 5 2007 5 ENVIRONMENTAL SCIENCE Vol 28,No 5 May,2007 PRB ( ) 1,2 1 3 (11 300071 ; 21 300457) : ( ) (permeable reactive barrier, PRB) ( ) ( ) 98 % 100 % 80 % 90 % ; ( ) ( ) ( ) 90 % ( ) ; 28 % ( ), ( ) 98 % 75 % 77 % ; ph ph ph PRB 2, 90 % ph : ;PRB ; ; :X53 :A :025023301(2007) 0521131206 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 300071, China ; 2 College of Science, Tianjin University of Science & Technology, Tianjin 300457, 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 ], ( ) [3 6 2002 ] [7,8 600 t 1 % 2 %, ] 015 % 1 % ( ) ( ) [9 ] ( ) :2006207208 ; :2006209211 : : (1971 ),,,E2mail : ruixue0422 @163 com 3,E2mail : sunhongwen @nankai edu cn 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet
1132 28 [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 ( ) 1 000 3 mgπkg ( ) ( ) 20 h, ( 0101 molπl KCl 1 ) 1 111 Cr ( ) Cr 165 h,, 013 km 2,, ( ), Cr ( ) Cr 400 m ( ),,163 h 325 h ( 112 ) 1 molπl 115 Fe2PRB 20 2,1 PRB, 01311 m 2 Πg X ( 1 Cr ( ) 1 000 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 % 113 215 cm 15 cm 45 1 2 kg ( ml, 114 ), 10 30 mlπh 013 kgπcm 2 16 115 4 h 11 6 cm 116 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet
5 : PRB ( ) 1133 ( ) 3 000 mgπkg ( GB 7466287) ( ) : 2 4 g 25 50 ml 014 molπl KCl 5 min,, 100 % 20 h 100 ml, 10 20 ( 89 106 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, 2 015 %, ( ) 12 45 mgπkg 99 %, 205 600 KMnO 4, 15 min, 1 ml mgπkg 10 % 2 % NaNO 2 ( ) ( ) ( ) ( ), ( ) ( ) 1 ( ) 90 % 193 555mgΠkg ( ) ( ) 2 ( ) 211 ( ) 3 2 ph 1 ( ) Cr 2 O 2-7, 2, ( ) HCrO - 4 ( ) CrO 2-4 ( ph 10154 ) ( ) Cr 3 + (ph < 4) CaO (OH) 2 Cr (OH) 3 ( ) Cr (OH) - 4 (ph > ( ), 12) ( ) ( 400 mgπkg ( ) Cr (OH) 3 300 mgπkg), 5160 10 4 mgπkg, ( ) ( ) 4100 10 4 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 - 1 5160 10 4 4100 10 4 1160 10 4 10154 9310 1110 9119 8170 212 ( ) ( ) 1 000 3 mgπkg ph 3 4 h ( ) ( 120 140 mgπkg) ; ( ), 1 3 2 90 % 80 % 1 70 h 214 213 7 L ( ) 1 000 mgπl 0 120 h, ph,1 2 h 2 ph 13 ph 3 ; 2 10, 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet
1134 28 2 ( ) 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, 1 2 3 100 ma ;,, 2 3 h 1 4 5 h 1 7 000 mgπl 163 h 70 % 900 mgπl, 13 L 160 h 72 %, 325 h 5 %, 0 75 % 77 % 1, Cr Cr ( ) Cr ( ) 5160 10 4 1160 10 4 4100 10 4, mgπkg,cr ( ) 28 % ( ) 98 %, ( ) ( ) 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet
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 h ph 917 2 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 - 33 48 80 130 ph h, ( ), 2 ph 6 8 1 3 ph (10154) 118 127 123 mgπkg ( ) ph ph 018 016 110 mgπkg ( ) 3 90 % ( ) PRB 4 ph Fig 4 ph change of the soil during the remediation process [20 ] ( ) ph,, 3 : ; PRB, ph 315 410 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, ( ) 47 86 mgπl 90 %, ( ) ( ) 1 80 % PRB PRB ; PRB ( ) ph, H + 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet
1136 28 (3) (4) : Fe 0 + CrO 2-4 + 4H 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 % 80 28 % ( ), ( ) 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 : 483 490 [ 2 ] Manna M, Sanjaya K, Shekhar R Electrochemical cleaning of soil contaminated with a dichromate lixiviant [J ] Int J Miner Process, 2003,72 : 401 406 [ 3 ] Lageman R Electroreclamation : application in the Netherlands[J ] Environ Sci Technol, 1993, 27 : 2648 2650 [ 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 :1092 1099 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 : 121 140 [ 6 ] Lageman R, Clarkea R L, Pool W Electro2reclamation, a versatile soil remediation solution[j ] Eng Geol, 2005, 77 : 191 201 [ 7 ] [J ],2005, 25(1) : 10 14 [ 8 ] [J ],2005,46 : 999 1005 [ 9 ] Zhou D M, Cang L, Alshawabkeh A N, et al Pilot2scale electrokinetic treatment of a Cu contaminated red soil [ J ] Chemosphere, 2006, 63 : 964 971 [10] ( ) [J ], 2005, 14(6) : 855 859 [11] [J ],2005, 28 (4) : 27 30 [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 : 123 137 [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 : 4599 4605 [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 : 183 202 [15] Day S R, O Hannesin S F, Marsden L Geotechnical techniques for the construction of reactive barriers [ J ] J Hazard Mater, 1999, B67 : 285 297 [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 : 5469 5475 [17] Kozuh N, Stupar J, Gorenc B Reduction and oxidation processes of chromium in soil[j ] Environ Sci Technol, 2000, 34 : 112 119 [18] Buerge I J, Hug S J Influence of mineral surface on chromium ( ) reduction by iron( ) [J ] Environ Sci Technol, 1999, 33 : 4285 4291 [19] [J ],1997,17 (3) : 334 339 [20] [M] :,1998 173 174 [21] [J ],2004,23(6) : 1192 1195 1994-2007 China Academic Journal Electronic Publishing House All rights reserved http://wwwcnkinet