removal of heavy metal in solution by modified biochar ... · pdf filesolution by modified...

Removal of heavy metal in solution by modified biochar

immobilizer

Nanjing Agricultural UniversityNanjing Agricultural University

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RongJun Bian

Institute of resource, Ecosystem and Environment of Agriculture, Nanjing Agriculture university


Nanjing Agricultural UniversityNanjing Agricultural University

� Background

� Result� Conclusion� Problems

� Materials Methods

CONTENTS

1. Background• Biochar can significantly reduce the availability of heavy metal in the soil, and

decrease Cd/Pb content in rice grain (Cui et al.,2011). Biochar could stabilize

Pb and improve soil quality in a shooting range soil (Lee, Sung Eun et al.,2011).

• The mechanism of biochar heave metal adsorption: electrostatic interactions;

biochar surface functional groups (Minori uchimiya et al.,2010).

• Immobilized alginic acid can efficiently adsorb heave metal in the water,

which can be used in wastewater treatment (Choong Jeon et al.,2001).

• The immobilization of Zoogloea ramigera in Ca-alginate adsorbed a variety of

metals, after metal adsorption was no longer effective, metal could be

recovered using NTA or concentrated acid (Sabine P. Kuhn et al.,1989).


2. Materials and methods


a. We used Ca-alginate method to immobilize biochar. The mass ratio of alginate and biochar was 1/20. The biochar-alginate bead was washed and dried for using.

b. Hitachi scanning electron microscope S-3000N was employed to observe the surface of biochar and biochar-alginate bead.

c. The sorption experiments were performed by suspending

1g powdered biochar and biochar-aglinate bead in 100ml

of metal solution shaking in a incubator at 25℃ for 4 h.

--(Different concentration of acid and alkali solution\ interferential ions \ initial

concentration\ pH\ temperature\ reaction time )

d. The final metal concentration was measured using Atomic

Absorption spectroscopy.

e. Langmuir equation: Ce/Qe=1/ (Xm*K) + Ce/Xm

f. First order Kinetic equation : Y=A*e( -k*X ) +B


3.1 The microstructure of biochar-alginate bead


3. Result

Biochar

Alginate Biochar

Transverse section

5044702975144stirred time (h)

10511051concentration(mol L-1)

NaOHH2SO4

Table 2. The time of biochar-alginate bead cracked after it was stirred in the acid and alkali solution at 180 rpm

Biochar-alginate bead had enough mechanical strength, which was stable in strong acid and alkali solution.

1-14stability to pH

0.45±0.085 mmdiameter

0.23±0.003 g cm-3bulk density

Characteristic value Physical property

Table 1. Physical property of biochar-alginate bead


3.2 physical property

(biochar-aglinate bead:1g , volume:50ml)

Adsorption capacity(mg g-1) 0.49±0.050.51±0.080.87±0.062.98±0.163.90±0.03

CaCaCaCa2+2+2+2+MgMgMgMg2+2+2+2+CdCdCdCd2+ 2+ 2+ 2+ CuCuCuCu2+2+2+2+PbPbPbPb2+2+2+2+Table 3. Adsorption capacities of various metal ions in mixed-metal solution by biochar-alginate bead(pH6)

2.35±0.085.20±0.16Cd2+

9.16±0.0211.74±0.20Cu2+

10.47±0.1313.60±0.17Pb2+

Coexisting with Ca 2+, Mg2+Ion only

Adsorption capacity (mg g-1)

Biochar-alginate bead perfered heavy metal ions to alkaline metal ions such as Ca2+ or Mg2+, so it can be used for the removal of heavy metals from ground water, which contains much more alkaline metals.

Table 4. Heave metal adsorption capacity of biochar-alginate bead with Ca2+ and Mg2+ treatment(pH6, 100mg L-1)


3.3 The influence factors to adsorption effect

3.3.1 The influence of Ca2+, mg2+

4.04.04.04.0

4.54.54.54.5

5.05.05.05.0

5.55.55.55.5

6.06.06.06.0

6.56.56.56.5

7.07.07.07.0

15151515 25252525 35353535 45454545

0.00.00.00.0

0.50.50.50.5

1.01.01.01.0

1.51.51.51.5

2.02.02.02.0

2.52.52.52.5

3.03.03.03.0

3.53.53.53.5

4.04.04.04.0

15151515 25252525 35353535 45454545Temperature(℃℃℃℃)

Cd

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

14141414

15151515

16161616

17171717

18181818

19191919

15151515 25252525 35353535 45454545Temperature(℃℃℃℃)

Pb

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

Temperature(℃℃℃℃)

Cu

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

1. The heavy metal adsorbed by biochar-alginate bead was an endothermic process since increased uptake capacity occurred as the temperature was increased.

2. The wastewater temperature of municipal wastewater ranges from 9. 6 to 31 ℃℃℃℃ and averages at (20.3 ±±±±6.0)℃℃℃℃ yearly . (Feng Ye. et al 2010)

3. The temperature of most real wastewater was higher than room temperature. (Choone Jeon. et al 2001)


3.3.2 The influence of temperature

2.02.02.02.0

2.22.22.22.2

2.42.42.42.4

2.62.62.62.6

2.82.82.82.8

3.03.03.03.0

3.23.23.23.2

3333 4444 5555 6666 7777 8888pH

Cd

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

14.014.014.014.0

14.514.514.514.5

15.015.015.015.0

15.515.515.515.5

16.016.016.016.0

16.516.516.516.5

3333 4444 5555 6666

Pb

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

pH

3.3.3 The influence of pH


1111

3333

5555

7777

9999

2222 3333 4444 5555 6666

Cu

2+ad

sorp

tio

n c

apac

ity

(mg

g-1)

pH

The adsorption capacity of heavy metal was effected by pH, and the adsorption capacity went to maximum value when pH was 6.

3.4 Kinetic process of adsorption effect

0000

1 01 01 01 0

2 02 02 02 0

3 03 03 03 0

4 04 04 04 0

5 05 05 05 0

6 06 06 06 0

7 07 07 07 0

8 08 08 08 0

9 09 09 09 0

1 0 01 0 01 0 01 0 0

0000 2 52 52 52 5 5 05 05 05 0 7 57 57 57 5 1 0 01 0 01 0 01 0 0 1 2 51 2 51 2 51 2 5 1 5 01 5 01 5 01 5 0 1 7 51 7 51 7 51 7 5 2 0 02 0 02 0 02 0 0 2 2 52 2 52 2 52 2 5 2 5 02 5 02 5 02 5 0

P b C d C u2+

Time (min)

Eq

uili

bri

um

co

nce

ntr

atio

n (

mg

L-1

)

2+ 2+

0.972y=30.275*exp(-0.036*x)+17.522Cd2+

0.994

0.992

R2First-order kinetics equation

y=75.869*exp(-0.066*x)+26.872Cu2+

y=102.022*exp(-0.078*x)+2.581Pb2+


Fig1. Adsorption kinetic changing curve

3.5 The Adsorption capaticy of heavemetal

0000

2222

4444

6666

8888

10101010

0000 1 001 001 001 00 2 002 002 002 00 3 003 003 003 00 4 004 004 004 00 5 005 005 005 00

biochar

biochar-alginate bead

Final concentration (mg L-1)

Ad

sorb

ed C

d2+

cap

acit

y (m

g g

-1)

0.978

0.974

R2 Xm(mg g-1)Langmuir equation

4.71y=x*0.67*4.71/(1+x*0.67)Biochar

8.67y=x*0.04*8.66/(1+x*0.04)Biochar-alginate bead

Fig 2. Cd2+ sorption isothermal curve


3.5.1 The adsotption capacity of Cd2+

0000

5555

10101010

15151515

20202020

25252525

30303030

35353535

0000 100100100100 200200200200 300300300300 400400400400 500500500500 600600600600 700700700700 800800800800

biochar

biochar-alginate bead


Ab

sob

edP

b2+

cap

acit

y (m

g g

-1)

0.991

0.888


32.12y=x*7.25*32.119/(1+x*7.25)Biochar


Fig 3. Pb2+ sorption Isothermal curve


3.5.2 The adsotption capacity of Pb2+

0000

3333

6666

9999

12121212

15151515

18181818

0000 100100100100 200200200200 300300300300 400400400400 500500500500 600600600600

Biochar-alginate beadBiochar

Ab

sob

edC

u2+

cap

acit

y (m

g g

-1)


0.928

0.931


8.04y=x*0.07*8.04/(1+x*0.07)Biochar


Fig 4. Cu2+ sorption Isothermal curve on biochar and biochar-alginate bead


3.5.3 The adsotption capacity of Cu2+

0

10

2030

40

50

60

7080

90

100

5 20 50 100 200 300 400

Initial concentration（（（（mg L-1））））

Ads

orpt

ion

ratio（（（（

%））））

PbCuCd


Fig 5. The adsorption ratio of heavy metal by biochar-aglinate bead in solution with different initial concentration

(biochar-aglinate bead:1g , volume:100ml)

3.6 The adsorption efficiency

Table 5. Desorption effciency of heave metal for different desorption agents


Desotption effciency(%)

0.90±0.040.78±0.010.95±0.020.2

0.81±0.010.72±0.000.94±0.030.1

0.79±0.040.14±0.010.48±0.100.01

HNO3

0.22±0.010.03±0.010.13±0.010.01Cacl2

CuPbCdConcentration(mol L-1)Desortbent

3.7 The desorption of heave metal

HNO3(0.2mol L-1) gave the best result while Cacl2 desorption efficiency was not significant.

After heave metal adsorption was no longer effiective, heave metal could be recovered by HNO3 solution.

4. Conclusion• The porous structure of biochar gave itself high internal surface, and the

ability to adsorb heave metal;

• The biochar alginate bead had enough mechanical strength, which was stable in strong acid and alkali solution;

• Biochar-alginate bead had a higher affinity to heavy metals compared to alkaline metals;

• The adsorption reaction of biochar-alginate bead was an endothermic reaction, and the uptake capacity was increased to a high temperature;

• Compare with biochar the biochar-alginate bead had higher adsorption capacity to Cd2+ and Cu2+ and its adsorption process fitted Langmuir model;

• Heavymetals on biochar-alginate bead could be desorbed effectively over 90% by HNO3(0.2mol L-1).


5. Problems• How it works in real waste water

• The mechanism of heave metal adsorption (fuctional groups, electrostatic interactions, specific surface area ? )

• How to cope with the biochar-alginate bead after it was used.(recover heave metal by concentrated acid, then the biochar used as stroma for municipal lawn or trees ?)


Biochar make the world healthy

Thanks for your attention!

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