NITRATE REMOVAL BY MODIFIED LIGNOCELLULOSE

M.Sc. (Tech.) Anni Keränen, Dr. Tiina Leiviskä, Prof. Osmo Hormi, Prof. Juha Tanskanen

University of Oulu, FINLAND

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26 June, 2014Anni Keränen, M.Sc. (Tech.)

A FEW WORDS ABOUT OULU

• located 500 km (310 miles) north of capital Helsinki

• 194 000 inhabitants

• University of Oulu• founded in 1958, 3rd largest in Finland • 16 000 students, 3 000 staff members• focus areas

• biosciences and health• information technology• cultural identity and interaction• environment, natural resources and materials

• arctic expertise• Chemical Process Engineering

research group

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Anni Keränen, M.Sc. (Tech.)

CONTENTSNITRATE REMOVAL BY MODIFIED LIGNOCELLULOSE

• Hazards of nitrate pollution in waterways• Nitrate removal methods• Modified lignocellulose • Results of sorption studies

• synthetic solutions• industrial wastewaters

• Chemical resistance of resin• Future plans

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Anni Keränen, M.Sc. (Tech.)

NITRATE POLLUTION

• sources: agriculture, sewage, explosives in mining• problems:

drinking water: formation of carcinogens, fatal to infants water systems: eutrophication

• removal methods biological/chemical treatment electrodialysis reverse osmosis adsorption ion exchange

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Anni Keränen, M.Sc. (Tech.)

NO3-

AIMS AND OBJECTIVES

• biobased platform for anion exchanger preparation (OH-groups)

• lignocellulose + chemical modification

quaternary anion exchanger• what’s new: application of resins in industrial processes

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Anni Keränen, M.Sc. (Tech.)

1. Chemical modification of lignocellulose2. Sorption studies on synthetic and industrial wastewaters3. Desorption and reuse4. Chemical resistance5. Disposal of used resin6. Development of modification method

CHEMICAL MODIFICATION

• pine sawdust, pine, spruce and birch bark and peat • particle size 90—250 µm• chemical modification enables anion sorption

epichlorohydrin, triethylamine, ethylenediamine and N,N-dimethylformamide

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Anni Keränen, M.Sc. (Tech.)

Fig. 1. Schematic presentation of the synthesis of modified lignocellulose.Source: Xu et al., Carbohyd. Polym. 82 (2010), 1212—1218.

PREPARED RESINS

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Anni Keränen, M.Sc. (Tech.)

• 2 g of lignocellulose yielded 8—12 g of resin(mass increase 300—500%)

• increased porosity surface area increased about 1.7—4.9-fold

• nitrogen content increased from ~1% to ~9%

• positive surface charge quaternary ammonium groups

Fig. 2. FESEM micrographs of untreated pine sawdust (above) and quaternized pine sawdust (below) at 1000x magnification.

before

after

RESULTSSYNTHETIC SOLUTIONS — NITRATE

• over 80% nitrate reductions from 30 mg N/l (typical in mining ww)

• maximum binding capacity 30 mg N/g (fig. 3) • efficient sorption at pH 3—10 (fig. 4)

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Fig. 3. Maximum nitrate binding capacity. Commercial anion exchange resin, Amberjet 4200 Cl, as a reference. Resin dose 4 g/l.

Anni Keränen, M.Sc. (Tech.)

Fig. 4. Effect of pH on nitrate sorption. Initially 30 mg N/l. Resin dose 3 g/l.

Fig. 4. Effect of pH on nitrate sorption. Initially 30 mg N/l. Resin dose 3 g/l.

0 2 4 6 8 100

20

40

60

80

100

NO

3-N

red

ucti

on [

%]

Initial pH

mod. pine sawdust mod. birch bark mod. spruce bark mod. peat mod. pine bark

0 50 100 150 200 250 300 3500

5

10

15

20

25

30

Sorp

tion

cap

acit

y [m

g/g]

Initial NO3-N concentration [mg/ l]

mod. pine sawdust mod. pine bark mod. birch bark mod. spruce bark mod. peat Amberjet 4200 Cl

RESULTSSYNTHETIC SOLUTIONS — NITRATE

• wide temperature range for mod. pine sawdust: 5—70°C applicable for both cold mining ww and warm industrial

ww

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Anni Keränen, M.Sc. (Tech.)

Fig. 5. (a) Nitrate sorption capacity at 5–40°C and (b) comparison of sorption capacities at 5–70°C at 250 mg N/l. Resin dose 3 g/l.

0 100 200 300 400 5000

5

10

15

20

25

30

NO

3-N

sor

ptio

n ca

paci

ty [

mg/

g]

Initial NO3-N concentration [mg/ l]

a

5°C 23°C 40°C

250 mg N/ l

0 20 40 60 8020

22

24

26

[mg/

g]

Temperature [C]

b

RESULTSOTHER ANIONS

• sulphate, phosphate• anionic metals

• vanadate• chromate• arsenate

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AsO43

-

CrO42-SO4

2-

PO43-

VO43-

Anni Keränen, M.Sc. (Tech.)

Fig. 6. Effect of resin dosage on vanadium removal from industrial wastewater. Initially 50.4 mg V/l.

• high affinity for vanadium(V) (fig. 6)• sorption capacities

130 mg V/g for synthetic solution 103 mg V/g for industrial wastewater (initial conc. 50.4 mg V/l)

• uptake of sulphate and phosphate

etc.

MINING WASTEWATERS

• ongoing sorption tests with mining wastewater• batch tests

• effects of dose, contact time and temperature • column test series

• 3 sorption-desorption cycles, maintenance cycle,3 sorption-desorption cycles, maintenance cycle,2 sorption-desorption cycles

• contaminants:• nitrate (9 mg N/l)• sulphate (8000 mg/l)• Sb, As, Ni, V, Cr, Zn,…

• sorption of cations?

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Anni Keränen, M.Sc. (Tech.)

Fig. 7. Column apparatus for tests on mining wastewater.

CHEMICAL RESISTANCE OF RESIN

• in real processes, ion exchange resins require maintenance

• removal of accumulated impurities and foulantsby acids or disinfectants

• modified pine sawdust exhibited good resistance towards acids

• some physical degradation with H2O2 was observed

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HCl

H2O2

H2SO4

Anni Keränen, M.Sc. (Tech.)

FUTURE PLANS

• alternative modification method• less hazardous chemicals, cost-efficient process

• disposal of used resin

Publications

Keränen A., Leiviskä T., Gao B.-Y., Hormi O., & Tanskanen J. (2013). Preparation of novel anion exchangers from pine sawdust and bark, spruce bark, birch bark and peat for the removal of nitrate. Chem. Eng. Sci., 98, 59–68.

Keränen A., Leiviskä T., Hormi O., & Tanskanen J. (under review) Removal of nitrate by modified pine sawdust: Effects of temperature and co-existing anions.

Leiviskä T., Keränen A., Vainionpää N., Al Amir J., Hormi O. & Tanskanen J. (accepted) Vanadium removal from aqueous solution and real wastewater using quaternized pine sawdust. IWA World Water Congress & Exhibition, Lisbon, Portugal, September 21–26, 2014.

Funding: Maa- ja vesitekniikan tuki ry and the Maj and Tor Nessling Foundation

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Anni Keränen, M.Sc. (Tech.)

WATER RESEARCH IN THE CHEMICAL PROCESS ENGINEERING

RESEARCH GROUP• coagulation and flocculation (1), adsorption, ion

exchange (2)• total surface charge (3), zeta potential (4)• dissolved air flotation (5)• TOC, BOD, UV absorbancy

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