1

CITRUS FRUIT WASTE-BASED ADSORPTION TECHNOLOGY FOR THE TREATMENT OF HEAVY METAL BEARING WASTEWATER

Asma Saeed and Muhammad Iqbal T.I

Bioresource Utilization Group, Food and Biotechnology Research CentrePCSIR Laboratories Complex Lahore

What is Pollution?

Introduction of contaminants into natural environment that cause instability, disorder, harm or discomfort to the ecosystem. It may be in the form of chemical substances or energy like heat, light and noise.

ORGANIC INORGANIC

2

3

ECOSYSTEM

All organisms living in a particular area interacting with physical components like soil, water, air and sunlight

4

FOOD WEB

Food cycle depicts who eats whom in an ecological community

5

SOURCES OF ENVIRONMENTAL CONTAMINATION

AirNoiseLightWater

Water contamination is the most serious issue as it is vital for life

6

ROUTES OF WATER CONTAMINATION

Direct Discharge

Sewage

Dumping toxins

Industrial water

Indirect Discharge

Urban runoff

Agricultural runoff

7

HEAVY METALSAmong various pollutants, heavy metals impart deleterious effect on the ecosystem due to their persistent and non-biodegrable nature that ultimately led them to enter into food chain

Dangerous Substances Directive by the European Union (76/464/EEC)

Red List Grey List

1. Hg 1. Zn 2. Cu 3. Ni2. Cd 4. Cr 5. Pb 6. As7. Sb 8. Mo 9. Ti10. Sn11. Ba12. Be13. B 14. U 15. V16. Co17. Ag 18. Tl19. Se 20. Ti

GREY LIST before 1997PbCuNiCrZn

HEAVY METAL CONTAMINATION OF FRESH WATER

Electroplating (Cu, Zn, Cr, Pb, Ni)

Metal finishing (Cd, Cr, Cu, Pb, Ni, Zn, Ag)

Petroleum (Pb and Organic compounds)

Steel works (Al, Co, Cu, Ce, Ti, Ni, Cr, Mo etc)

Vehicle and aircrafts (Oils, Emulsifiers, Al, Pb)

Storage batteries (Pb, Cu, Sb)

Mining (Zn, Pb)

Pulp and Paper (Cu)

Glass, ceramics and cement (Pb, W)

Textile and Leather (Dyes, Cr)

8

WATER TREATMENT TECHNOLOGIES

Conventional technologies for heavy metal remediation include:1. Chemical precipitation2. Coagulation3. Oxidation-reduction4. Osmosis5. Reverse osmosis6. Evaporation7. Ion Exchange

10

TECHNO-ECONOMICAL CONSTRAINTS

Expensive/costlyInefficient/ineffective for the removal of

heavy metals at low concentrationHazardous/generate toxic sludge

11

BIOSORPTION-AN ALTERNATE TECHNOLOGY

Biosorption is the passive accumulation of the adsorbate e.g. metal ions, organic molecules, colour ions etc., to biologically inactive material

12

ADVANTAGES OF BIOSORPTIONBiosorption is a combination of several phenomena having several advantages:1. Cost effective2. Efficient3. Reusability in repeated cycles4. Low operational cost5. Environment-friendly6. Applicable over wide-range of physicochemical

conditions7. Non-selective work under multi-metal conditions

13

Biosorption as an Alternative Technique

Biosorption

Microbial Biomass Agro-waste Materials

Bacteria, Algae, Fungi, Yeast

Purposefully Cultured Biomass

Waste from Fermentation and Pharmaceutical

Industry

Plant Waste Biomass

Food Industry Waste

Crop Residues, Grains/Fruit Wastes

14

15

Small particles Very fragile/delicates Low mechanical strength Difficulty of separation Process can not be scaled up

Technical Limitations Towards TheirCommercial Applications

SOLUTION ?

Immobilization/Entrapment

A physical or chemical process used to fix micro-organisms on to a solid support or trap them in

a solid matrix.

16

17

Biostructural Fibrous Network as an Alternative Immobilization Matrix

Loofa Sponge Papaya Wood Palm Trunk Fibers

Process for the Production of Loofa Sponge Disc Biosorbents

M1 M2

Discs Biosorbents

LSD LSD

1 2

18

Scanning Electron Microscopy of Immobilization Process

19

20

Biowastes used as Biosorbent

Petiolar felt-sheet of Palm

Papaya wood

Black gram husk

Orange peel

Now I will discuss more about the application of citrus peel waste in the treatmentof metal contaminated water

21

Citrus Peel as a Biosorbent

wet wt dry wt Component (%) (%)

~ 6 25 - 35sugars~ 5 20 - 25cellulose & hemicellulose ~ 4 15 - 25soluble fiber (pectin) ~ 1 04 - 06flavanones (hesperidin, naringin, etc)~ 0.05 0.1 - 0.5 polymethoxylated flavones~ 0.05 0.1 - 0.3 limonoids (limonin+glucosides)~ 1 3 - 5 ash~ 1 3 - 4 protein~ 1 limonene/peel oil~ 80 water

22

Citrus Peel as a BiosorbentEffect of biomass quantityScreening and Selection

23

Citrus Peel as a BiosorbentEffect of pH Effect of Time

Optimum pH = 5.0

Time 60 min

24

Citrus Peel as a BiosorbentExperimental Equilibrium

BiosorptionLangmuir and Freundlich

Models

Metal ions Langmuir isotherm model Freundlich isotherm model qmax b r2 KF n r2 (mg g-1) (l mg-1)

Cd2+ 67.08 0.085 0.998 6.3 2.22 0.952

Pb2+ 96.32 0.101 0.996 7.26 1.94 0.975

Pb qeq = 99.05 mgg-1

Cd qeq = 68.92 mgg-1

25

FTIR Spectrum of CPW and Functional Moieties

a

b

c

Native CPW

Cd-loaded CPW

Pb-loaded CPW

-OH stretch

-CH stretch C=O stretch

26

Biosorption and Ion-Exchange SEM-EDX

Ion Exchange Equation:M+n + BHn ↔ BM + nH+

SEM-EDX of Native CPW SEM-EDX of Pb-Loaded CPW

27

PROPOSED MECHANISM OF METAL BINDING

II) Lignin moieties

I) Cellulosic moieties

III) Protein moieties

Mn2+

Mn2+

Mn2+

28

Citrus Peel as a Biosorbent

a, Maximum acceptable concentration for health reasonsb, Limits for aesthetic or consumer oriented reasonsc, Provisional value for health reasons

Metal ions

Before biosorption

(mg/L)

After biosorption

(mg/L)

Limits recommended by WHO for drinking

water (mg/L)

NEQS maximum limits for effluent

discharge (mg/L)

Cd(II)Pb(II)Cu(II)Zn(II)Cr(III)Ni(II)

10.029.9810.0410.3610.0110.06

0.001±0.0020.06±0.0150.43±0.00410.19±0.0020.78±0.0120.69±0.037

0.003a

0.01a

1.00a,b

0.1a,b

0.05c

0.07a

0.10.51.05.01.01.0

29

Fixed Bed Column Bioreactor Studies

ColumnDescription

Schematic diagram of fixed bed column bioreactor, packed with CPW designed to function as a continuous flow system for biosorption of heavy metals.

1. metal solution reservoir; 2. peristaltic pump; 3. flow control; 4. glass column reactor;5. cpw biosorbent;6. enlarged view of column

packing; 7. extension for secondary column; and 8. effluent storage.

30

Adsorption-Desorption Cycles

31

Thanks to:

University of Alaska Fairbanks, USA

University of Sheffield, UK

Forschungszentrum Karlsruhe, Germany

32

THANK YOU

33

Kinetics of Cd2+ and Pb2+ SorptionMetal ions

Experimental qeq

(mg g-1)

Pseudo-first order constants Pseudo-second order constants qeq

(mg g-1) K1

(min-1) r2 qeq

(mg g-1) K2

(g mg-1 min-1) R2

Cd2+

Pb2+

16.55

17.47

8.78

10.73

-0.052

-0.057

0.93

0.96

16.71

17.60

0.0103

0.111

0.997

0.998