Amine-Cross-Linked Lignin-Based Polymer: Modification

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Amine-crosslinked lignin-based polymer: Modification, characterization and flocculating performance in humic acid coagulation Ruihua Li, Baoyu Gao, Shenglei Sun, Qinyan Yue, Meng Li, Xudan Yang, Wuchang Song, and Ruibao Jia ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.5b00844 • Publication Date (Web): 19 Oct 2015 Downloaded from http://pubs.acs.org on October 24, 2015

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ACS Sustainable Chemistry & Engineering

Amine-crosslinked lignin-based polymer: Modification, characterization and flocculating performance in humic acid coagulation Ruihua Lia, Baoyu Gaoa,*, Shenglei Suna, Qinyan Yuea, Meng Lia, Xudan Yanga, Wuchang Songb, Ruibao Jiab a

Shandong Key Laboratory of Water Pollution Control and Resource Reuse,

School of Environmental Science and Engineering, Shandong University, No.27 Shanda South Road, Jinan 250100, Shandong, People's Republic of China b

Jinan Water and Wastewater Monitoring Center, Jinan 250033, Shandong, People's Republic of China

Abstract: In this study, a lignin-based flocculant (LNF) was synthetized by grafting amine groups into alkali lignin containing in papermaking sludge. Characterization of LNF, such as FTIR, zeta potential, cationic degree, viscosity and molecular weight, showed that the product was a cationic polymer with high solubility. LNF was used with aluminum sulfate (AS) and polyaluminum chloride (PAC) in humic acid coagulation to demonstrate its efficiency. Coagulation behavior and floc properties of LNF+PAC and LNF+AS dual-coagulant were comparatively evaluated. Results showed that the coagulation aid effect of LNF was independent of aluminum species. Addition of LNF could enhance humic acid removal efficiency and floc properties including size, strength and fractal dimension significantly. The effect of solution pH on coagulation processes was also studied. Dual-coagulants showed the same variation trend with that of aluminum-based coagulants but enhanced coagulation * Tel.: +86 531 88366771; fax: +86 531 88364513 E-mail address: [email protected]; [email protected] 1

ACS Paragon Plus Environment


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performance during the investigative pH range. Flocs formed at pH 9 and pH 5 achieved maximum floc size in AS and PAC coagulation systems, respectively. Fractal dimension was relatively high at pH 7-9 due to the sweeping effect of aluminum hydrolysates. Overall, LNF brought in charge neutralization and absorption bridging effect and played a positive role in coagulation processes. Keywords: Lignin-based polymer; Papermaking sludge; Flocculating efficiency; Fractal dimension; Flocculating mechanism

Introduction

As a principal renewable biomass, lignin makes up 15-40 percent of the dry matter of woody plants 1. Technical or industrial lignin is also generated in significant amounts as a by-product of chemical pulping annually. About 2% of it is commercially utilized for the production of dispersing agent or adhesive. The rest is used to produce heat, steam or power by landfill, combustion and bio-compost processes, which easily causing secondary pollution 2

. Lignin composes of aromatic rings with methoxyl and hydroxyl groups as well as

propanoid chains, which providing the possibilities of producing value-added products 3.To date, however, the valuable chemical properties and functionality of lignin are to some extent stuck in laboratory-scale system and have not yet been fully realized compared with cellulose and hemicellulose

1, 4

. Currently, a few studies on feasible modification of lignin and

subsequent application have been reported, such as porous sphere adsorbents for the removal of heavy metals 5, flexible polyurethane foams as the materials of packaging

6

and a

UV-absorbent copolymer in coating manufacture 7. Nevertheless, these products were 2


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synthesized by commercial lignin and restricted to its molecular structure, which impeding their development and application.

Recently, there is a growing interest in the development of water treatment agent by utilizing

industrial

and

agricultural

waste

lignin

as

eco-friendly

materials.

Coagulation/flocculation followed by sedimentation/flotation processes are considered to be the most common and economically feasible way to remove natural organic matter (NOM) 8. Among them, hydrophilic fraction and the low molar mass compounds are limited to be efficiently removed by traditional coagulants compared with hydrophobic fraction and high molar mass ones 9. Thus, enhanced and newly-developed coagulant aids with relatively high efficiency and low cost have been suggested. Previous studies reported the preparation of flocculant recycling disposal lignin as raw materials, eg., hydrolyzed cornstalk-based flocculant 10, gum ghatti-based hydrogels 11, lignin-acrylamide neutral water treatment agent (LA)

12

, which also have drawbacks including poor solubility and high cost (vacuum

operation).There are still rare references regarding to the preparation of lignin-based cationic flocculant made from pulping sludge and its application in the treatment of low-molecular-weight matters polluted water. In this study, alkali lignin was extracted from alkaline pulping sludge 13 and reacted with epichlorohydrin,

N,N-dimethylformamide

and

ethylenediamine

to

prepare

amine

groups-impregnated lignin-based cationic flocculant (LNF), with the feature of highly cationic degree, easy operation and good solubility. Its physicochemical properties were determined by Fourier transformation infrared spectrum (FTIR), scanning electron microscope (SEM), element analysis, molecule weight and zeta potential. Then LNF was used 3



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as coagulant aid with polyaluminum chloride (PAC) and aluminum sulfate (AS) to demonstrate its efficiency. As a good model of the low molar mass compounds, humic acid solution was selected for investigation

14

. The effect of LNF addition on the properties of

Al(Ш) coagulated flocs, such as floc size, fractal dimension, breakage and subsequent regrowth potential under different conditions were used to measure the degree of flocculation 15

. Comparative evaluation of LNF and neutral pulping sludge-based flocculant

12

was also

made to illustrate its advantages. In addition, the relationship of coagulation mechanisms and coagulation behavior as well as flocs properties were analyzed in detail.

Experimental Section

Materials

The chemicals used in this study were all supplied by Sinopharm Chemical Reagent Co., Ltd., including AlCl3·6H2O, HCl, Na2CO3, NaOH, epichlorohydrin, N,N-dimethylformamide, ethylenediamine, triethylamine. These reagents were all of analytical grade. AS stock solution was prepared by directly dissolving Al2(SO4)3·18H2O into deionized water. PAC, which B value ([OH-]/[Al3+] mole ratio) of 2.0, was prepared by adding predetermined amount of Na2CO3 solution to AlCl3·6H2O solution dropwise and the mixture was stirred until no sediment existing 16. The product was diluted to the final Al concentration of 10.0 g/L and kept more than 24 h before use. The dosage of coagulant was calculated as Al content (mg/L). Dried pulping sludge used in this study was obtained from an alkaline papermaking mill in Shandong Province, China. The content of lignin was approx. 45 wt.% 13. Its mean molecular

4


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weight and zeta potential was approx. 1000 Da and -32.0 mV, respectively. The monomer structure was listed as follows:

Water sample was synthesized by humic acid stock solution, which were prepared based on previous reported methods 17. Humic acid with the mean molecular weight of 2735 Da was purchased from Aladdin Industrial Corporation, Shanghai, China. Physicochemical parameters of raw water were listed as follows: Dissolved Organic Carbon (DOC) = 4.200 ± 0.150 mg/L, UV254 absorbance = 0.285 ± 0.010 cm-1, pH = 8.10 ± 0.05, zeta potential = -15.0 ± 1.7 mV.

Experimental methods

Lignin modifications. The synthetic experiment of LNF (Figure 1) was conducted as follows: i) Dried sludge (5.0 g) was added into 0.01 mol/L NaOH solution and then centrifuged at the speed of 8000 rpm for 10 min to obtain supernatant. After adjusting pH to 7-8, collected supernatant was transferred into three-neck round bottom flask; ii) About 8 ml of epichlorohydrin and 8 ml of N,N-dimethylformamide were added and then the solution was reacted for 1 h, followed by adding 2 ml of ethylenediamine for the further reaction. After 1 h, triethylamine (6 ml) was then added and reacted for another 2 h. The system was stirred continuously and temperature was controlled at 60-70 ºC; iii) After the reaction, the product was extracted with acetone, washed with ethanol and finally dried at 50 ºC.

5



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Figure 1. Synthetic route of LNF. The preparation of Lignin-acrylamide polymer (LA) was listed as follows: with N2 inlet, a certain amount of K2S2O8 was added and then reacted for 15 min, followed by adding acrylamide at 70 ºC. After 3 h reaction, the mixture was extracted with acetone. The detailed method was based on Rong et al. 18. In this study, LNF and LA were prepared into a solution of 1.0 g/L and stored at 4 ºC before use.

Coagulation protocol. Standard jar trials were operated on the scale of 1.0 L using a program-controlled jar tester (ZR4-6, Zhongrun Water Industry Technology Development Co. Ltd., China) at the room temperature of 20 ± 2 ºC. Running programs of dual-coagulation were i) adding Al-based coagulants and LNF into raw water with a 30 s interval during rapid mixing of 200 rpm (1.5 min) ; ii) slow stirring (40 rpm) for 15 min; iii) natural sedimentation for 30 min.

Floc dynamics. The dynamic floc sizes distribution was on-line monitored by a particle size analyzer (Mastersizer 2000, Malvern Inc., UK). The whole coagulation process contained three regions including floc formation region for 15 min (slow stirring of 40 rpm), breakage 6


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region for 5 min and re-growth region for another 15 min (slow stirring of 40 rpm) 17. The shear rate during breakage region was set as 200 rpm.

Analytical methods

Physicochemical characterization. Unreacted lignin (UL) was obtained by alkaline-acid treatment and its properties were contrastively studied by the following techniques

13

.

Functional groups in UL and LNF were evaluated by FTIR technique using Perkin-Elmer “Spectrum BX” spectrometer ranging from 4000 to 400 cm-1 with a 1.0 cm-1 resolution. Molecule weight was determined by gel chromatography (using Waters 1515 gel chromatography apparatus, US) and 0.1 mol/L of NaNO3 was used as the mobile phase. Digital viscometer (NDJ-5S, Shanghai, China) was used to measure the viscosity of LNF. Zeta potential experiments were performed via Zetasizer 3000HSa, Malvern Instruments, UK.

Coagulated effluent quality analysis. Zeta potential measurement was conducted at the end of slow stirring without dilution. After precipitation, upper 200 ml of water sample was collected for the turbidity (via Portable turbidimeter 2100P, Hach, US). Collected samples filtered through a 0.45 µm fiber membrane were used to test DOC (with TOC analyzer, Shimadzu, Japan) and UV254 (using Precision Scientific Instrument Co. Ltd., Shanghai, China).

Floc measurement. The dynamic floc sizes distribution was on-line monitored by a particle size analyzer (Mastersizer 2000, Malvern Inc., UK). The whole coagulation process contained three regions including floc formation region for 15 min (slow stirring of 40 rpm), breakage region for 5 min and re-growth region for another 15 min (slow stirring of 40 rpm) 7



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17

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. The stirring rate during breakage region was set as 200 rpm.

Floc size was defined as the mean value of median volumetric diameter (d50) during the balance state of floc formation region. As the representative of floc strength and anti-shear ability, floc strength factor (Sf) was calculated by Eq. (1) 19.

Sf =

d (2) × 100 d (1)

(1)

Where d(1) is the average floc size in steady-state region and d(2) is the floc size at the end of breakage period.

Fractal dimension (Df) which described how an object occupied space could be used to characterize the compactness of an aggregate, with loose aggregates having a low fractal dimension and more compact ones having a higher fractal dimension. In this regime, a plot of log-scattering intensity vs. log-wave number would give a straight line with a gradient of - Df 20

.

Results and discussion

Physical and chemical analysis of LNF

FTIR spectra of UL and LNF were shown in Figure 2a. For FTIR spectrum of UL, there was a broad band located in 3348 cm-1, which was attributed to O-H stretching of hydrogen-bonded hydroxyl groups and considered as active site. The peaks at 1715 and 1654 cm-1 were stretching vibration of carbonyl group and contraction vibration of C=C separately. The remaining characteristic peaks were around 840 and 1213 cm-1, which was ascribed as 8


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the overtone of aromatic cyclic groups and C-O, respectively. For LNF, the width of the same band (around 3396 cm-1) narrowed and sharpened in LNF. The peaks at 1617 and 1036 cm-1 were corresponded to the bending vibration of N-H and stretching vibration of C-O-C

21-22

.

Compared with UL, the increased zeta potential of LNF during the investigated pH range indicated that quaternary ammonium functional groups were incorporated onto the structure of UL. These findings were in agreement with the reported work shown in Baidas et al. 23. In addition, molecule weight of LNF changed to approx. 510 KDa after addition polymerization and that of UL was 850-1170 Da. Cationic degree of LNF was 23.3 ± 1.4 % 24. The viscosity of 1 g/L LNF solution was 1.106 mPa•s under the rotate speed of 60 rpm at 25 oC, therefore it could be dissolved quickly in water. -15

40

(b)

(a)

LNF

UL

-20

zeta potential (mV)

30

1654 1715 3348

-25

20 -30

zeta potential (mV)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


10 -35 1036

3396 1617

UL LNF

0 0

500

1000

1500

2000

2500

3000

3500

4000

4500

2

3

4

5

6

-1

7

8

9

10

-40 11

pH

Wavenumbers (cm )

Figure 2. FTIR spectrum (a) and zeta potential (b) of LNF and UL.

The above results could conclude that UL successfully took amine cross-linking reactions and the amine groups-impregnated cationic polymer was produced.

Flocculating activity under different conditions

The changes of residual turbidity, DOC removal ratio along with zeta potential at different coagulant and flocculant dosages were shown in Figure 3. The trends of coagulation 9



efficiencies as a function of aluminum-based coagulants dosages were the same: with the increase of coagulant dosages, residual turbidity firstly decreased and then stayed the same; DOC removal ratios raised significantly when the dosages were less than 5.0 mg/L and then maintained a slight growth. There were also no differences in the change of zeta potentials under pH conditions of raw water, which was related with the theories of hydrolyzed Al 25-26

. But the correlation coefficient (R2) of DOC removal ratio vs. zeta potential in

species

PAC coagulation was 0.8945 and much larger than that of AS coagulation (0.8308). In other words, more organic colloid-Al flocs were formed by charge neutralization effect in the case of dosing PAC, whereas sweeping was the foremost mechanism in AS coagulation. Residual turbidity was much larger at lower dosage. Because under these conditions, the fewer Al hydrolysates as well as the stronger electrostatic repulsive interaction between charged Al species and colloid particles led to the relatively lower turbidity removal efficiency. Meanwhile, parts of the flocs were small and suspended in the supernatant. These ones could not be wiped off by natural sedimentation. As a result, residual turbidity at the dosage of 1 mg/L was even higher than that of raw water. 4.0

65

(I-a)

Soultion pH= 8.10 ± 0.05

3.5

(I-b)

60

(I-c)

5

55

AS AS+1.00 mg/L LNF AS+2.00 mg/L LNF AS+3.00 mg/L LNF

2.5 2.0 1.5

0

50 45 40


35 30

1.0 25 0.5

zeta potential (mV)

3.0

DOC removal ratio (%)

Residual turbidity (NTU)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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-5

-10


-15

20 15

0.0 0

2

4

6

AS dosage (mg/L)

8

10

12

0

2

4

6

8

10

12

AS dosage (mg/L)

10


-20 0

2

4

6

AS dosage (mg/L)

8

10

12

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4.0

65

(II-a)

Soultion pH= 8.10 ± 0.05

3.5

(II-b)

60

(II-c)

5

55

PAC PAC+1.00 mg/L LNF PAC+2.00 mg/L LNF PAC+3.00 mg/L LNF

2.5 2.0 1.5

0

50 45 40 35


30

1.0 25 0.5

zeta potential (mV)


3.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


-5

-10


-15

20 15

0.0 0

2

4

6

8

10

12

-20 0

PAC dosage (mg/L)

2

4

6

8

10

12

0

2

4

6

8

10

PAC dosage (mg/L)

PAC dosage (mg/L)

Figure 3. Residual turbidity (a), DOC removal ratio (b) and zeta potential (c) vs. different coagulant dosage of AS (I) and PAC (II).

In the case of dosing LNF, coagulation performance showed an obvious improvement including the removal of turbidity and humic acid. The model of coagulation mechanisms during the coagulation process was shown in Figure 4

26

. As for LNF, negatively charged

complexes could be adsorbed by quaternary ammonium cationic groups due to the electrostatic driving forces

27-28

. So this cationic polymer could adsorb the electronegative

micro flocs formed by aluminum-based coagulants and then relieve inter repulsion between destabilized flocs. When coagulants were overdosed, zeta potential exceeded isoelectric point and repulsion accordingly enhanced. But LNF chains could reach the surface of micro flocs and act as bridges between them, and tend to favor an extended structure. Additionally, OH groups existing in the LNF could also involve hydrogen bonding of NOM and consequently enhance its removal efficiency

29

. In a word, LNF offered charge neutralization and

absorption bridging effect and thus enhanced coagulation efficiency.

11


12


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Figure 4. Coagulation mechanisms during the coagulation processes. Solution pH condition is a key index influencing coagulation effectiveness 30. To verify its influence and the application range of LNF, coagulation with various pH was conducted at aluminum-based coagulants dosage of 5 mg/L and LNF dosage of 2.0 mg/L. As illustrated in Figure 5, the appropriate pH condition was the same 6 in AS and PAC coagulations separately, which was consistent with the report of O’Melia 31. Residual turbidity did not show obvious difference. Under acid conditions, major Al species hydrolyzed to positive charged complex ions, such as Al3+, Al(OH)2+, Al(OH)2+ or [Al13O4(OH)24]7+ (Al13 for PAC). When pH exceed 7, aluminum transformed into Al(OH)3 and Al(OH)4− in the presence of OH−

25, 32

and zeta

potential was extremely negative, resulting in the poorer humic acid destabilization. The addition of LNF played a significant role in DOC removal under alkaline conditions both in PAC and AS coagulation. The reason was that NOM carboxyl groups-aluminum hydroxide complexes expected to be more charged at pH of 7-9 and hence more easily be absorbed and complexed by LNF. As a result, the addition of LNF increased DOC removal ratio by 2-10% compared with single aluminum-based coagulation.

12


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3.0

65

(I-a) 5 mg/L AS 5 mg/L AS+ 2.0 mg/L LNF

1.5

8

(I-c)

5 mg/L AS 5 mg/L AS+ 2.0 mg/L LNF

6 55

zeta potential (mV)

2.0


60



10

(I-b)

2.5

50

45

4 2 0 -2 -4

1.0

-6

40 0.5 4

5

6

7

8

-8

9

4

5

6

pH

7

8

9

4

6

1.0

9

(II-c) 5.0 mg/L PAC 5.0 mg/L PAC+ 2.0 mg/L LNF

6 4

55

zeta potential (mV)

1.5

8

60


2.0

8

10

(II-b) 5.0 mg/L PAC 5.0 mg/L PAC+ 2.0 mg/L LNF

7

pH

65

(II-a) 2.5

5

pH

3.0


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


50

45

40

0 -2 -4 -6

5.0 mg/L PAC 5.0 mg/L PAC+ 2.0 mg/L LNF

0.5

2

-8

0.0

-10 4

5

6

7

8

9

4

5

6

pH

7

8

9

pH

4

5

6

7

8

9

pH

Figure 5. Residual turbidity (a), DOC removal ratio (b) and zeta potential (c) vs. various pH in the AS (I) and PAC (II) coagulation.

Effect of LNF addition on flocs properties

Floc size. The profiles of floc size at steady stage were shown in Figure 6. Floc size increased with coagulant dosage first and then presented downtrend at the large dosage. LNF could enhance floc size significantly. As reported above, there were more flocs formed by charge neutralization with the effect of PAC. Previous studies reported that flocs formed by sweeping and bridging usually had open structure and possibly with larger floc sizes. By contrast, charge neutralization created tighter and more condensed flocs with lower size 33. As a result, floc sizes coagulated by AS were larger than those of PAC under the pH of raw water, especially at the low dosage. Under high coagulants dosage conditions, the collisions between humic acid and coagulants were completed in short time. The tails of flocs with open and loose structure were easily broken during too long slow stir phase. A certain amount of flocs size was easily congregate at the smaller volume and lowered floc size accordingly. On the 13



other hand, the higher coagulants dosage, the larger absolute value of zeta potential and the stronger the repulsion between flocs, which caused the lower collision efficiency. 500

500

(a)

Solution pH= 8.10 ± 0.05

400

400

350

350

300 250 200


150 100

(b)

450

Floc size (µm)

Floc size (µm)

450

300 250 200 150


100

50

50

0 0

2

4

6

8

10

0

12

0

2

4

AS dosage (mg/L)

550

6

8

10

12

PAC dosage (mg/L)

600

600

(c)

550

500

(d)

500


450

450

400

Floc size (µm)

Floc size (µm)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

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350 300 250

400 350 300 250

200

200

150

150

100

100

5 mg/L PAC 5 mg/L PAC+ 2.0 mg/L LNF

50

50 0

0 4

5

6

7

8

9

4

5

6

7

8

9

pH

pH

Figure 6. Floc sizes under different coagulant dosages (a-b) and pH (c-d) conditions.

Solution pH also had a significant influence on flocs formation. The size of flocs coagulated by AS rose with pH and achieved the maximum at pH 9, whereas in the case of PAC, floc size achieved the peak at pH 5 and decreased during the pH range of 6-8 and then increased at pH 9. In the case of AS, the coagulation mechanism changed from charge neutralization to enmeshment sweeping with the increase of pH due to the formation of hydrolysates. As for PAC, collision efficiency and floc formation were co-affected by inter forces and coagulation mechanisms. Under acid conditions, the protonation of humic substances enhanced, leading to less hydrophilic and easier to destabilize

34

. Repulsion

between flocs which was drawn from absolute value of zeta potential was also weaker. Under 14


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alkaline conditions, stronger electrostatic repulsion under these conditions also hindered further formation of flocs.

After dosing LNF, it could rapidly absorb the negative charge on the surface of aluminum salts coagulated flocs. Meanwhile, its chains acted as flocculant bridging the colloids together and hence further aggregate. Bridging flocculation had been proved as the most effective mechanism on improving floc size 35. As displayed in Figure 6, floc size under various pH conditions in dual-coagulation demonstrated the same tendency with that of single metal salts coagulation. In other words, the performance of LNF in enhancing floc size was slightly independent on pH, which ensured its potential application in treating a wide range of water types.

Floc strength. Floc strength factor as a function of coagulant dosages were illustrated in Table 1. Irreversible breakage was unavoidable in actual water treatment works, especially in regions of high shear rate, which meant that flocs should have resistibility to high shear force. At the coagulant dosage of 1 mg/L, relatively large Sf was achieved because of the much smaller floc size, which was proved in the previous research

20

. During the range of 3-11

mg/L, floc Sf also raise with the coagulant dosage. The resistibility of flocs showed some indications of the internal bonding structure: there was a positive correlation between floc strength and the number/strength of inter bonds

36

. Hence, when coagulants dosage was

limited, fewer bonds formed between flocs would produce weaker ones. Stronger flocs were formed in PAC+LNF system with the weaker electric repulsion at lower coagulants dosage. Yukselen and Gregory also reported that higher molecular weight polymers should give stronger flocs, either as a result of polymer bridging or ‘electrostatic patch’ effects 15


37

.


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However, during the dosage range of 7-11 mg/L, electric repulsion between aluminum-based flocs was weaker. After dosing LNF, polymer chains were easily broken, which leading to the reduction of floc Sf. But floc sizes in PAC+LNF coagulation during breakage and re-growth stage were still larger than those in PAC system.

Table 1 Floc Sf by PAC and PAC+LNF under different coagulant dose conditions (pH= 8.10 ± 0.05). Dosage (mg Al/L)

1

3

5

7

9

11

AS

30.54±0.28 29.90±0.35 30.98±0.45 34.86±0.42 39.33±0.27 42.53±0.38

AS+2.0 mg/L LNF

35.89±0.91 31.65±0.29 31.69±0.25 33.74±0.30 37.93±0.43 41.88±0.74

PAC

33.67±0.26 29.20±0.28 26.54±0.34 36.52±0.32 39.75±0.35 43.05±0.32

PAC+2.0 mg/L LNF

27.62±0.15 30.08±0.61 32.77±0.16 34.40±0.21 36.95±0.54 38.48±0.13

Fractal dimension. The factors influencing Df of flocs including coagulation stages, coagulants species and doses along with pH were studied (Figure 7-8). During growth region, collision of coagulants/flocculants with colloids, destabilization of humic acid and aggregation of destabilized micro flocs proceeded successively till achieving the balance between the formation and breakage of flocs

29

. Therewith flocs with the relatively stable

structure as well as larger Df value were formed gradually. In the period of breakage, weak points existed between flocs or on the surface of flocs were broken and more stable flocs were formed, more compact flocs would be reformed. As a whole, Df value was in the order of breakage period > regrowth period > growth period.

16


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2.70

2.70


(I-a)

(I-b)

2.65

AS+ 2.0 mg/L LNF

2.65

2.60 2.60

2.50

Df

Df

2.55

2.45

2.55

2.50

AS dosage (mg/L) 1 3 5 7 9 11

2.40

AS dosage (mg/L) 1 3 5 7 9 11

2.45

2.35 5

10

15

20

25

30

2.40

35

5

10

15

20

25

30

35

Time (min)

Time (min) 2.80

2.80

(II-a)

2.75

(II-b)


PAC+2.0 mg/L LNF

2.75

2.70 2.70 2.65 2.65

2.55

Df

Df

2.60

2.50

2.60 2.55

2.45

2.35

PAC dosage (mg/L) 1 3 5 7 9 11

2.50

PAC dosage (mg/L) 1 3 5 7 9 11

2.40

2.45

2.30

2.40 5

10

15

20

25

30

35

5

10

15

20

Time (min)

25

30

35

Time (min)

Figure 7. Df under different coagulant dosages during the AS (I-a), AS+LNF (I-b), PAC (II-a) and PAC+LNF (II-b) coagulation processes.

2.70

2.70 2.65

(a)

2.65

2.55 2.50

(b)

2.60

2.60

AS: 5mg/L LNF: 2.0 mg/L

2.55 2.50

2.45

2.45

2.40

2.40

Df

Df

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2.35

2.35 2.30

AS AS+LNF AS AS+LNF

2.25 2.20

2.30

steady-state region steady-state region re-growth region re-growth region

2.25 2.20

2.15

PAC PAC+LNF PAC PAC+LNF

PAC: 5mg/L LNF: 2.0 mg/L

steady-state region steady-state region re-growth region re-growth region

2.15 2.10

2.10 4

5

6

7

8

4

9

5

6

7

8

pH

pH

Figure 8. Df under various pH conditions in the AS (a) and PAC (b) coagulation.

17


9


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Coagulants types and dosages also had a significant influence on floc structure. Df increased with coagulants dosages until it achieved the maximum at AS dosage of 3 mg/L and PAC dosage of 7 mg/L and then maintained continuous decline. Df of flocs coagulated by AS was larger than that of PAC at the lower dosage, nevertheless, there existed inverse phenomenon at the higher dosage. It could be explained that structure of flocs formed by sweeping was more compact compared with other coagulation mechanisms18. Meanwhile, polymeric aluminum molecules could not completely collide with particles compared with monomer aluminum ones. Under higher dosage conditions, the stronger electrostatic repulsion between flocs swept by AS hindered the further uniting of flocs and resulted in loose and open structure.

Under different pH conditions, Df variation with time was consistent with the above results. So the mean values of Df during steady-state region and resteady-state region were selected to demonstrate the influence of pH on floc structure. Due to the sweeping effect, flocs formed under alkaline conditions achieved larger Df. The relative large Df at pH 4 was more related with the smaller absolute value of zeta potential compared with that at pH 5. During AS coagulation, Df showed a decrease at pH 9, which was related with not only inter repulsion but also the theories 20 that a relatively large floc formed by the same effect usually had a less compact structure as well as smaller Df.

The addition of LNF provided a positive effect on improving Df. Meanwhile, it varied more smooth under different pH and dosage conditions which indicating LNF was less sensitive to the variance of coagulation conditions. As for AS+LNF, Df was a little smaller than that of AS at pH 6. The reason was that flocs formed by absorption bridging usually had 18


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the extended structure with abundant chains or tails as well as lower Df

38

. Breakage of

polymer chains at high shear rates also reduced floc bridging capability during regrowth. And the values of Df during the re-growth region enhanced accordingly. Charge neutralization effect of LNF mainly played the positive role in floc reformation. Overall, LNF increased Df by 0.01-0.20 compared with single aluminum-based coagulation.

Comparative evaluation of LNF and LA

To verify the efficiency of LNF and LA, jar tests and floc measurement were conducted at aluminum-based coagulants dosage of 5 mg/L and LNF/LA dosage of 2.0 mg/L under the pH of raw water. From Table 2, humic acid removal ratios in the PAC/AS+LNF dual-coagulation were 2.3-3.7% larger than those in PAC/AS+LA system. Floc size and strength were in the order of PAC/AS+LNF > PAC/AS+LA > PAC/AS. But Df of PAC/AS+LA coagulated flocs decreased up to 0.04-0.05 compared with single Al-based coagulants. As a neutral flocculant, LA would introduce bridging effect in metal salt coagulation and achieved the formation of flocs with open structure and lower strength. The zeta potential of LA was from -0.8 to 1.1 mV, which was much smaller compared with LNF. Namely, the positive charge existing in the surface of LA was less than that of LNF. Thus charge neutralization effect offered by LA was limited, and relatively stronger repulsive forces between formative flocs hindered floc aggregation and further formation. Overall, PAC/AS+LNF dual-coagulant achieved better coagulation behavior and better floc properties compared with PAC/AS+LA dual-coagulant. Table 2 Comparative evaluation of LNF and LA in the aspect of coagulation efficiency and floc properties. 19



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Page 20 of 26

Coagulant

DOC removal efficiency (%)

Floc size (steady-state, µm)

Sf (%)

Df (steady-state)

5 mg/L AS

49.63

247.7

30.98

2.47

5 mg/L AS+ 2.0 mg/L LNF

54.12

351.1

31.69

2.49

5 mg/L AS+2.0 mg/L LA

51.89

328.5

31.45

2.41

5 mg/L PAC

38.01

256.3

26.54

2.51

5 mg/L PAC+2.0 mg/L LNF

46.66

422.6

32.77

2.54

5 mg/L PAC+ 2.0 mg/L LA

42.97

367.4

29.61

2.46

Conclusion

LNF was synthesized by introducing amine groups into alkali lignin containing in papermaking sludge and characterized as a cationic polymer. With the dosage of aluminum-based coagulants increasing, comparatively better coagulation behavior and floc characteristics were achieved. And PAC/AS+LNF dual-coagulant achieved higher humic acid removal efficiency and better floc properties compared with single coagulants as well as PAC/AS+LA dual-coagulants. Solution pH also influenced coagulation effectiveness by the variance of hydrolyzed aluminum species and the interaction with humic acid. Under acidic condition, flocs with larger size were formed in PAC system but those in AS system was relatively smaller, where charge neutralization was the foremost mechanism. Flocs formed under alkaline condition were more compact due to sweeping effect. Coagulation aid effect of LNF was relatively independent on the species of Al-hydrolysate and pH. LNF introduced charge neutralization and slight absorption bridging effect in metal salt coagulation systems.

Acknowledgements 20


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This work is supported by the Science and Technology Program for Public Wellbeing (No. 2013GS370202-004). The kind suggestions from the anonymous reviewers are greatly acknowledged.

Reference (1) Alekhina, M.; Ershova, O.; Ebert, A.; Heikkinen, S.; Sixta, H., Softwood kraft lignin for value-added applications: Fractionation and structural characterization. Ind. Crop. Prod. 2015, 66 (0), 220-228. (2) Higson, A.; Smith, C., Renewable Chemicals Factsheet: Lignin. NNFCC: 2011. (3) Azadfar, M.; Gao, A. H.; Bule, M. V.; Chen, S., Structural characterization of lignin: A potential source of antioxidants guaiacol and 4-vinylguaiacol. Int. J. Biol. Macromol. 2015, 75 (0), 58-66. (4) Qu, Y.; Luo, H.; Li, H.; Xu, J., Comparison on structural modification of industrial lignin by wet ball milling and ionic liquid pretreatment. Biotechnology Reports 2015, 6 (0), 1-7. (5) Li, Z.; Ge, Y.; Wan, L., Fabrication of a green porous lignin-based sphere for the removal of lead ions from aqueous media. J. Hazard. Mater. 2015, 285 (0), 77-83. (6) Bernardini, J.; Cinelli, P.; Anguillesi, I.; Coltelli, M.-B.; Lazzeri, A., Flexible polyurethane foams green production employing lignin or oxypropylated lignin. Eur. Polym. J. 2015, 64 (0), 147-156. (7) Liu, X.; Wang, J.; Yu, J.; Zhang, M.; Wang, C.; Xu, Y.; Chu, F., Preparation and characterization of lignin based macromonomer and its copolymers with butyl methacrylate. Int. J. Biol. Macromol. 2013, 60 (0), 309-315. 21



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(8) Semerjian, L.; Ayoub, G. M., High-pH–magnesium coagulation–flocculation in wastewater treatment. Adv. Environ. Res. 2003, 7 (2), 389-403. (9) Sillanpää, M.; Matilainen, A., Chapter 3 - NOM Removal by Coagulation. In Natural Organic Matter in Water, Sillanpää, M., Ed. Butterworth-Heinemann: 2015, pp 55-80. (10)

Fang, R.; Cheng, X.; Xu, X., Synthesis of lignin-base cationic flocculant and its

application in removing anionic azo-dyes from simulated wastewater. Bioresource Technol. 2010, 101 (19), 7323-9. (11)

Mittal, H.; Jindal, R.; Kaith, B. S.; Maity, A.; Ray, S. S., Synthesis and flocculation

properties of gum ghatti and poly(acrylamide-co-acrylonitrile) based biodegradable hydrogels. Carbohydr. Polym. 2014, 114, 321-9. (12)

Rong, H.; Gao, B.; Zhao, Y.; Sun, S.; Yang, Z.; Wang, Y.; Yue, Q.; Li, Q., Advanced

lignin-acrylamide water treatment agent by pulp and paper industrial sludge: Synthesis, properties and application. J. Environ. Sci. 2013, 25 (12), 2367-2377. (13)

García, A.; Toledano, A.; Serrano, L.; Egüés, I.; González, M.; Marín, F.; Labidi, J.,

Characterization of lignins obtained by selective precipitation. Sep. Purif. Technol. 2009, 68 (2), 193-198. (14)

Ghernaout, D.; Ghernaout, B.; Saiba, A.; Boucherit, A.; Kellil, A., Removal of

humic acids by continuous electromagnetic treatment followed by electrocoagulation in batch using aluminium electrodes. Desalination 2009, 239 (1–3), 295-308. (15)

Cockerill, A. F., Chapter 3 Elimination Reactions. In Comprehensive Chemical

Kinetics, Bamford, C. H.; Tipper, C. F. H., Eds. Elsevier: 1973, pp 163-372. (16)

Li, R.; Gao, B.; Ma, D.; Rong, H.; Sun, S.; Wang, F.; Yue, Q.; Wang, Y., Effects of 22


Page 22 of 26

Page 23 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


chlorination operating conditions on trihalomethane formation potential in polyaluminum chloride-polymer coagulated effluent. J. Hazard. Mater. 2015, 285 (0), 103-108. (17)

Li, R.; Gao, B.; Huang, X.; Dong, H.; Li, X.; Yue, Q.; Wang, Y.; Li, Q., Compound

bioflocculant and polyaluminum chloride in kaolin-humic acid coagulation: factors influencing coagulation performance and floc characteristics. Bioresource Technol. 2014, 172, 8-15. (18)

Rong, H.; Gao, B.; Dong, M.; Zhao, Y.; Sun, S.; Yanwang; Yue, Q.; Li, Q.,

Characterization of size, strength and structure of aluminum-polymer dual-coagulant flocs under different pH and hydraulic conditions. J. Hazard. Mater. 2013, 252-253, 330-7. (19)

Jarvis, P.; Jefferson, B.; Gregory, J.; Parsons, S. A., A review of floc strength and

breakage. Water Res. 2005, 39 (14), 3121-3137. (20)

Jarvis, P.; Jefferson, B.; Parsons, S. A., Breakage, Regrowth, and Fractal Nature of

Natural Organic Matter Flocs. Environ. Sci. Technol. 2005, 39 (7), 2307-2314. (21)

Sreedhar, K.; Metcalf, P. A.; Honig, J. M., Effect of a change in the carrier

concentration and disorder on the superconducting transition temperature of the La2−xSrxCu1−yNiyO4 system. Physica C: Superconductivity 1994, 227 (1–2), 160-168. (22)

Bretherick, L., Section 1 - Specific Chemicals: Elements and Compounds arranged

in formula order. In Bretherick's Handbook of Reactive Chemical Hazards (Fourth Edition), Bretherick, L., Ed. Butterworth-Heinemann: 1990, pp 1-1475. (23)

Baidas, S.; Gao, B.; Meng, X., Perchlorate removal by quaternary amine modified

reed. J. Hazard. Mater. 2011, 189 (1–2), 54-61. (24)

Gao, B.; Zhang, X.; Zhu, Y., Studies on the preparation and antibacterial properties 23



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 24 of 26

of quaternized polyethyleneimine. J. Biomat. Sci-Polym. E. 2007, 18 (5), 531-544. (25)

Gregor, J. E.; Nokes, C. J.; Fenton, E., Optimising natural organic matter removal

from low turbidity waters by controlled pH adjustment of aluminium coagulation. Water Res. 1997, 31 (12), 2949-2958. (26)

Wei, J. C.; Gao, B. Y.; Yue, Q. Y.; Wang, Y., Strength and regrowth properties of

polyferric-polymer dual-coagulant flocs in surface water treatment. J. Hazard. Mater. 2010, 175 (1-3), 949-54. (27)

Xu, X.; Gao, B.; Huang, X.; Ling, J.; Song, W.; Yue, Q., Physicochemical

characteristics of epichlorohydrin, pyridine and trimethylamine functionalized cotton stalk and its adsorption/desorption properties for perchlorate. J. Colloid Interf. Sci. 2015, 440, 219-228. (28) removal

Kong, Z.-y.; Wei, J.-f.; Li, Y.-h.; Liu, N.-n.; Zhang, H.; Zhang, Y.; Cui, L., Rapid of

Cr(VI)

ions

using

quaternary

ammonium

fibers

functioned

by

2-(dimethylamino)ethyl methacrylate and modified with 1-bromoalkanes. Chem. Eng. J. 2014, 254, 365-373. (29)

Zhao, S.; Gao, B.; Yue, Q.; Sun, S.; Song, W.; Jia, R., Influence of Enteromorpha

polysaccharides on variation of coagulation behavior, flocs properties and membrane fouling in coagulation-ultrafiltration process. J. Hazard. Mater. 2014, 285C, 294-303. (30)

Ghernaout, D., The hydrophilic/hydrophobic ratio vs. dissolved organics removal by

coagulation – A review. Journal of King Saud University - Science 2014, 26 (3), 169-180. (31)

O'Melia, C. R., Chapter 18: Fundamentals of particle stability. In Interface Science

and Technology, Gayle, N.; David, D., Eds. Elsevier: 2006, pp 317-362. 24


Page 25 of 26

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(32)

Xu, W.; Gao, B.; Yue, Q.; Wang, Y., Effect of shear force and solution pH on flocs

breakage and re-growth formed by nano-Al13 polymer. Water Res. 2010, 44 (6), 1893-1899. (33)

Lin, J.-L.; Huang, C.; Chin, C.-J. M.; Pan, J. R., Coagulation dynamics of fractal

flocs induced by enmeshment and electrostatic patch mechanisms. Water Res. 2008, 42 (17), 4457-4466. (34)

Cheng, W. P.; Chi, F. H., A study of coagulation mechanisms of polyferric sulfate

reacting with humic acid using a fluorescence-quenching method. Water Res. 2002, 36 (18), 4583-4591. (35)

Ray, D. T.; Hogg, R., Agglomerate breakage in polymer-flocculated suspensions. J.

Colloid Interf. Sci. 1987, 116 (1), 256-268. (36)

Boller, M.; Blaser, S., Particles under stress. Water Sci. Technol. 1998, 37 (10), 9-29.

(37)

Yukselen, M. A.; Gregory, J., The reversibility of floc breakage. Int. J. Miner.

Process. 2004, 73 (2-4), 251-259. (38)

Hopkins, D. C.; Ducoste, J. J., Characterizing flocculation under heterogeneous

turbulence. J. Colloid Interf. Sci. 2003, 264 (1), 184-194.

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Title: Amine-crosslinked lignin-based polymer: Modification, characterization and flocculating performance in humic acid coagulation

Authors: Ruihua Li, Baoyu Gao*, Shenglei Sun, Qinyan Yue, Meng Li, Xudan Yang, Wuchang Song, Ruibao Jia

Table of Contents Use Only

Synopsis

The biomass existing in papermaking sludge was used to sustainably synthesize amine-crosslinked lignin-based water treatment agent, which could enhance coagulation efficiency and floc properties under various conditions.

26


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Amine-Cross-Linked Lignin-Based Polymer: Modification

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