APPLICATION OF NANOZEOLITE AND ...

Amir Mohammadi* et al. International Journal Of Pharmacy & Technology

IJPT| June-2016 | Vol. 8 | Issue No.2 | 13337-13352 3337

ISSN: 0975-766X CODEN: IJPTFI

Available Online through Research Article

www.ijptonline.com APPLICATION OF NANOZEOLITE AND NANOCARBON FOR THE REMOVAL OF

HUMIC ACID FROM AQUEOUS SOLUTIONS Heshmatollah Nourmoradi

1, Afshin Ebrahimi

2, Yaghoub Hajizadeh

2, Sepideh Nemati

3, Amir Mohammadi

4*

1Department of Environmental Health Engineering, School of Health, Ilam University of Medical Sciences, Ilam, Iran.

2Department of Environmental Health Engineering, Environment Research Center, School of Health, Isfahan

University of Medical Sciences, Isfahan, Iran. 3Department of Environmental Health Engineering, School of Health,

Uromia University of Medical Sciences, Uromia, Iran. 4Department of Environmental Health Engineering, School of Health,

Shahid Sadoghi University of Medical Sciences, Yazd, Iran.

Email: [email protected]

Received on 13-05-2016 Accepted on 12-06-2016

Abstract

The reaction of humic acid with chlorine (as the most common water disinfectant) in drinking water results in

production of dangerous compounds of halo organic compounds (trihalomethanes and halo acetic acids) which are

known as carcinogen materials to human. This study aimed to remove humic acid (HA) from aqueous solutions by

surfactant-modified nanozeolite (SMNZ) and activated nanocarbon (ANC) as novel adsorbents. The results revealed

that the adsorbent types and solution pH played important roles in the humic acid removal from the aqueous solution.

The optimal conditions to remove 50 mg/L humic acid using SMNZ (as the most effective sorbent) were obtained at

agitation speed 250 rpm, contact time 2 hours, turbidity 10 NTU, pH 5 and SMNZ dosage 0.2 g/L. Also, SMNZ had an

excellent capacity of 250 mg/g. Isotherm analysis by ISOFIT software showed that the adsorption of humic acid on the

SMNZ fitted well with the Langmuir isotherm. The results indicated that SMNZ had high potential as a low-cost

sorbent for the removal of humic acid in water and wastewater treatment processes.

Key Words: Humic acids; Nanocarbon; Surfactant-modified Nanozeolite, Aqueous solution.

1. Introduction

Humic acids (HAs) as a major proportion of natural organic matter are vastly present in natural water resources.

Elimination of these compounds has become a major issue due to their precursor role in the formation of disinfection

by-products (DBPs) (1). Most humic substances including humic acid, fulvic acid and humin which account for 80%

of organic matters in dark soils are resulted from natural process of plant material decomposition (2). Chlorination is a


IJPT| June-2016 | Vol. 8 | Issue No.2 | 13337-13352 Page 13338

commonly used method for disinfection of water and wastewater due to its extremely performance and cost-

effectiveness. Chlorine can react with humic acid and produce halo organic compounds such as trihalomethanes

(THMs) and halo acetic acids (HAAs) which are known to be carcinogen and hazardous to human health (3, 4). Humic

acids are categorized as dissolved organic carbons (DOC) and with concentrations more than 5 mg/L have an impact

on water color (5). Thus, the removal of this natural matter is of great importance (4). Several techniques including

chemical coagulation, membrane separation, advanced oxidation processes, adsorption or hybrid processes have been

efficiently applied to reduce humic acid from aqueous solution (6-8). However, the cost-effectiveness and selectivity of

the method should be taken into account. Application of adsorption process with a low-cost sorbent such as zeolite

especially new absorbent of nanozeolite with high specific surface can be considered as one of the promising

alternative for HAs removal (2, 9). Nanozeolite has also showed a significant potential for tannic acid, azo dyes,

ammonium and heavy metals removal from aqueous solutions (10-12). Activated carbon also has been used as a useful

sorbent for adsorption of organic compounds and humic acids in water and wastewater treatment processes due to its

high surface. But, the cost of commercial activated carbon is relatively high (13, 14).

A typical zeolite cannot properly remove or adsorb anion species due to having anionic charges on its surface. In order

to adsorb both anions and cations, the surface must possess positively and negatively charged exchange sites,

respectively. It has been suggested that modification of nanozeolite by a cationic surfactant can increase its capacity in

adsorbing anionic compounds such as humic acids due to increasing its positive charge (15, 16). The most

conventional surfactant for surface modification of zeolites is hexadecyl trimethyl ammonium bromide (HDTMA-Br),

a quaternary amine long chain cationic surfactant that possesses a permanent positive charge (17). The aim of this

study was to investigate the most effective sorbent among NZ, SMNZ and activated nanocarbon (ANC) in the removal

of humic acid from aqueous solutions.

2. Materials and Methods

The nanozeolite and activated nanocarbon were purchased from Nanoshel LLC (Germany). Humic acid was provided

from Sigma-Aldrich Co (USA). Other chemicals (H2SO4 and NaOH, etc) and also the cationic surfactant (Hexadecyl

Trimethyl ammonium Bromide) were obtained from Merck Co (Germany).

2.1. Characteristics of the applied adsorbents

In this research, a type of clinoptilolite nanozeolite, the most abundant and inexpensive zeolite (11), and activated

nanocarbon were applied. According transmission electron microscopy (TEM) images which were taken using a 300



kV Philips CM-30 TEM, the size of nanozeolite and nanocarbon were 30-60 nm (Fig. 1.a), and <40 nm (Fig. 1.b), and

their surface area was measured using Brunaure–Emmet–Teller (BET) method. They had specific surface areas of 160

m2/g and ~40 m

2/g, respectively. Table 1 specifies the chemical compositions of used CNZ. The amounts of Al and Si

are high which gives mostly alumina-silicate structure to the nanozeolite. Purity of activated nanocarbon was more

than 98% and Fe < 0.01%, Cl < 0.01%, Zn < 0.01%, SO4 <0.01%.

Fig.1. TEM (Transmission Electron Microscopy) image of a) the nanozeolite; b) the nanocarbon.

Table 1. Chemical compositions of the used clinoptilolite nanozeolite.

Compositions

Weight

%

Compositions Weight %

SiO2 69.44 K2O 1.31

Al2O3 11.87 Na2O 0.68

Fe2O3 1.3 CaO 3.28

Ti2O 0.18 MgO 0.99

2.2. Modification of the nanozeolite

Due to having a negative charge on the surface of zeolites, they have high tendency to adsorb or exchange cations than

onions (15). To increase positive charges on their surface, they should be modified by cationic agents (16). Fig. 2

shows the optimum dosage of applied HDTMA-Br for modification of the nanozeolite. In the present work, for the

modification of CNZ, it was primarily treated with 1 molar sodium chloride solution by stirring at 150 rpm for 24

hours. Then, the CNZ was separated from the solution by a centrifuge (Sigma 3K30) at 20000 rpm until the silver-

nitrate test became negative.

The separated solid phase of CNZ was rinsed with distilled water and dried in an oven at 105˚C for 24 hours. For final

modification with optimum dosage of cationic surfactant, 10 g/L of pre-treated CNZ was contacted with different

ba



concentrations of HDTMA-Br solution, including 0.5, 1, 3, 5, 7 and 10 g/L in a shaker for 24 hours by continuously

mixing at 150 rpm. Ultimately, it was separated by centrifugal force at 20000 rpm, rinsed with distilled water and dried

in the oven at 105˚C for 24 hours (18-20). The surface charge of the CNZ before and after modification was

determined by X-ray diffraction (XRD) technique (Fig. 3).

Fig. 2. Optimal dosage of applied HDTMA-Br for modification of the nanozeolite.

(pH 0 , UV254 0 and turb 0 is the values in the solution before adsorption procesess).

Fig. 3. XRD pattern of the applied nanozeolite.

3. Design of experiments

Due to the interaction of various factors and their multiple levels, it was not possible to examine the effects of all

variables with respect to more cost and time requirement. Thus, the Taguchi method was used for experimental design.

As shown in Table 2, this mixed Taguchi design was included 6 factors in 3 levels and one factor (agitation speed) in 2

0.80

0.90

1.00

1.10

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

0 2 4 6 8 10 12

pH

/pH

0

Tu

rb/T

urb

0 ,

UV

25

4/U

V2

54

0

surfactant dosage (g /l )

UV254/UV254 0 Turb/turb 0 pH/pH 0

op

tim

al d

osa

ge

3 10 17 24 31 38 45 52 59 66 73 80

Inte

nsity (

counts

)

2Ө (o)

Before Modification

After Modification



levels. After pre-tests implementation for determination of optimum dosage of the cationic surfactant, the operation of

batch system was carried out for each desired concentration in triplicate and the average of the results was considered.

Also, final test carried out after determination of optimum condition using selected adsorbent by statistical analysis

usiing Mini Tab software, to gained efficiency removal of humic acid and specific ultraviolet absorption (SUVA254).

Table-2: Design of the adsorption experiments via mixed Taguchi method.

Number of

experiments Agitation Time Turbidity

HA

concentration

Adsorbent

dosage pH type of

adsorbent (RPM) (hr) (NTU) (ppm) (g /l)

1 100 1 2.56 25 0.05 5 ANC

2 100 1 5.29 50 0.5 7 NZ

3 100 1 10.23 100 0.8 9 SMNZ

4 100 2 5.29 50 0.5 5 SMNZ

5 100 2 10.23 100 0.2 7 ANC

6 100 2 2.56 25 0.2 9 NZ

7 100 3 2.56 25 0.8 7 NZ

8 100 3 5.29 50 0.2 9 SMNZ

9 100 3 10.23 100 0.1 5 ANC

10 250 1 10.23 100 0.5 9 NZ

11 250 1 2.56 25 0.8 5 SMNZ

12 250 1 5.29 50 0.05 7 ANC

13 250 2 10.23 100 0.2 7 SMNZ

14 250 2 2.56 25 0.1 9 ANC

15 250 2 5.29 50 0.8 5 NZ

16 250 3 5.29 50 0.2 9 ANC

17 250 3 10.23 100 0.2 5 NZ

18 250 3 2.56 25 0.5 7 SMNZ

HA: humic acid, ANC: activated nanocarbon, NZ: nanozeolite, SMNZ: surfactant modified nanozeolite

2.4. Analytical methods

Dissolved organic carbon (DOC) was analyzed, using combustion techniques (method 5310B) by TOC-VCSH analyzer

(Shimadzu, Japan). A UV-visible spectrophotometer (DR-5000, HACH-LANGE) was used to measure the UV

absorption at 254 nm wavelength in the samples (method 5910B) (21, 22). The specific ultraviolet absorption

(SUVA254) for each sample was calculated by dividing UVA254 value to DOC concentration (23). Turbidities of the

samples were measured using a EUTECH TN100 (HACH-LANGE) turbidity analyzer. The XRD pattern of the SMNZ



was obtained using an X-Ray Diffractometer to determine surface modification characteristics (Bruker, D8 Advance,

Germany (X-Ray Tube Anode: Cu, Wavelength: 1.5406 Å (Cu K), Filter: Ni).

2.5. Adsorption isotherm experiments

ISOFIT software was used to determine the adsorption isotherm patterns that primarily uses optimum condition in each

factor (21). In this study after determination of optimum condition using selected adsorbent by analysis Mini Tab

software, adsorption isotherms was done by shaking 500 mg of SMNZ (the most effective sorbent selected from

among NZ, SMNZ and ANC) in 1 liter humic acid solutions (50 mg/L) with initial concentrations ranging from 1 to 50

mg/L at pH 5 and 20±2ºC for 24 h. Then, the treated samples were instantly filtered, and the concentrations of HA in

the filtrates were determined via UV absorption method using a Dr-5000 Hach spectrophotometer.

3. Results and Discussion

3.1. Modification of the nanozeolite

To produce cationic charge on the surface of the nanozeolite and thereby to enhance its potential in adsorbing both

cationic and anionic compounds, it was modified by a cationic surfactant (HDTMA-Br). As Fig. 2 shows, with a

surfactant dosage of 7 g/L there was no significant variation in the ratio of pH / pH0 (pH: final, pH0:initial) and a

maximum removal of humic acid, and thereby turbidity was achieved. Thus, 7 g/L was considered as optimum dosage

of HDTMA-Br for modifying 10 g/L of the nanozeolite (700 mg/g). Fig. 3 illustrates the XRD patterns and surface

charge changes of the nanozeolite before and after the modification. This figure clearly shows that the nanozeolite

structure was not changed by the adsorption of HDTMA-Br, since the HDTMA-Br is adsorbed on the external surface

of the nanozeolite and it just increases the positive charges of the nanozeolite (16).

3.2. Selection of the most effective sorbent and Optimum condition

The optimal experimental conditions can be simply determined by Taguchi method. Usually, in this method, three

types of the signal-to-noise (S/N) ratio analyses including i) smaller is better, ii) nominal is the best, and iii) larger is

better (SNL) (24) are required to assess the experimental results. Since the aim of this analysis is to maximize the

pollutant removal efficiency, the S/N ratio with SNL characteristics is necessary, which is given by Eq. 1:

(1)

Where, ‘yi’ is the comparison variable in the experiment and ‘n’ is the number of experiments (24). According Fig. 4,

the optimal conditions to remove 50 mg/L humic acid using SMNZ include agitation speed 250 rpm, contact time 2



hours, turbidity 10 NTU, pH 5, SMNZ dosage 0.2 g/L and the best adsorbent SMNZ. To determine the most important

factor for humic acid removal in this study, descending delta factor ranking was used between 7 studied factors (Table

3). Type of adsorbent > pH > turbidity > adsorbent dosage > agitation > time > HA concentration;

However this relation does not mean that the latest factors are not so important or can be completely negligible in the

adsorption studies. All of the studied parameters are necessary in their optimum levels, but some have more influence

than the others on the adsorption process

Table 3. Variations in the humic acid concentration, turbidity and SUVA values under the set of experimental

conditions, and the humic acid removal eficiency of each test.

Type of

adsorbent

Dosage of

adsorbent

(g/L)

HA

concentration

(ppm)

Turbidity

(NTU)

SUVA

(l/mg.m) pH

Removal

of HA

%

Input Output

In

put

Out

put

In

put

Out

put

ANC 0.05 25 9 2.6 5.6 6.8 6.3 5 64

0.1 25 19 2.6 18 6.8 3.5 9 24

0.05 50 21 5.3 8.1 8.5 2.3 7 58

0.2 50 30 5.3 6.8 8.5 8.3 7 40

0.1 100 53 10.2 16.9 7.6 9.8 5 47

0.2 100 80 10.2 5.7 7.6 8.8 7 20

NZ 0.8 25 25 2.6 14.2 6.8 7.9 7 0

0.2 25 23 2.6 4.3 6.8 6.9 9 8

0.8 50 28 5.3 5.3 8.5 7 5 44

0.5 50 48 5.3 21 8.5 9.3 7 4

0.5 100 99 10.2 19.4 7.6 8.6 9 1

0.2 100 80 10.2 14.7 7.6 8.7 5 20

SMNZ 0.5 25 ND 2.6 1.1 6.8 0.06 7 99.9

0.8 25 1 2.6 1.3 6.8 0.07 5 96

0.5 50 2 5.3 0.8 8.5 0.3 5 96

0.2 50 32 5.3 8.1 8.5 4.6 9 36

0.8 100 31 10.2 6.2 7.6 5.1 9 69

0.2 100 50 10.2 6 7.6 6.5 7 50

ND: Not Detectable

This ranking factor indicates the differences of the highest and the lowest response values of the parameters (25).

According to the results in Table 3, the preference ordering of the studied factors could be deliver as follow:

As shown in Fig. 4a, S/N ratio for 250 rpm agitation is higher than that for 100 rpm. Thus, 250 rpm could be enough

for proper contact between SMNZ and HA. It should be noted that to reduce the number of total experiments we just

considered two levels for the agitation speed. Nevertheless, as can be seen in Table 3, within the 7 examined

parameters the agitation rank is 5, indicating its less effect than the other 4 descending factors. Generally, contact time



is an important factor in adsorption process; however, it should be optimized to the high efficiency point. In contact

time lower than the optimum, adsorption process may not be completed and higher than that, desorption of the

pollutant may be occur. In this study, an ideal contact time of 2 hours was obtained (Fig. 4b). However, it ranked fifth

throughout the 7 factors for HA removal (Table 3) which shows its low effect in the adsorption process. According to

Fig. 4c, the turbidity resulting from humic acid dissolution in optimum condition was 10.23 NTU, which was the third

important factor after type of adsorbent and pH; and resulted in a better adsorption of humic acid compared to the

lower turbidities. In a similar study, the effect of turbidity on humic acid adsorption was negligible and not measured

(6, 9). After operation of the batch system in the optimum conditions residual turbidity of 1.1 NTU was measured

which is less than the WHO guidelines (26). The pH showed to be the second important factor in the adsorption of

humic acid especially at high concentration (Table 3). In the present study to confine the number of experiments only

three levels of pH (5, 7, and 9) were introduced to the Taguchi method used for experimental design. The plot of S/N

ratio versus pH values showed a high S/N ratio at pH = 5 (Fig. 4d). However, as the applicability of this pH in the real

world is under question due to technical and cost-effectiveness point of view, further scrutiny would be necessary to

find a proper range of pH for the adsorption process. Notwithstanding, the adsorbent must have cationic charges to

efficiently adsorb the humic acid. Therefore, to increase its positive charges the acidification of the aqueous solution is

required. There are contradictory reports in literature regarding to optimum pH at which a maximum humic acid

adsorption can be achieved. This can be attributed to the adsorbent types as well as to the experimental conditions (27).

Close to neutral pH or pHZPC (zero point charge) the Van der Waals force would be the major force for organic

compound removal by modified adsorbent. However, in practice, reducing the pH down to its neutral value resulted in

an increase in the adsorption efficiency due to the increasing of positively charged layers, and thereby, prevailing the

electrostatic forces which are stronger than the Van der Waals forces. Therefore, the adsorption experiments in the

present work were conducted in acidic solution. In a study, maximum removal of arsenic by surfactant modified zeolite

was obtained in pHzpc. Because, the pollutant ions size was fit for adsorption on zeolite surface and pKa was maximum,

a negligible changes of initial pH comparing to ultimate pH was occurred (16). Our study showed that removal of

humic acid from aqueous solution needs a pH lower than pHzpc. However, in high humic acid concentration, its

removal was not significant, but, in low concentration it was removed completely.

Accessing the effects of adsorbate dose showed that the S/N ratio for 50 ppm humic acid was higher than the two other

concentrations (Fig. 4e). It means that HA with this concentration range could be properly removed in operation batch



adsorption system. Dosage of SMNZ and ANC were 0.2 g/L and 0.05 g/L, respectively (Fig. 4f and 4g). Based on the

results of a similar study, a macro scale surfactant modified zeolite with dosages of 0.5 to 1 g/L could markedly

remove arsenic from aqueous solution (28). Low dosage requirement of SMNZ could be attributed to its more

adsorption surface compared to the surfactant modified macro zeolite. As Table 3 and Fig. 4h show, the SMNZ gaining

a first rank and with a high S/N ratio was the most efficient adsorbent used in this study. Changes associated with

errors and unknown factors were 4%. Thus, the influence of uncontrolled variables in the process parameters of the

present study can be negligible. According to Table 4, the highest removal efficiency humic acid was obtained by the

surfactant modified nanozeolite which was 96% and optimum condition obtained 99%. Whereas, the ANC used in this

study could remove 64% of humic acid from the solution in the optimum condition. According to the literature, PAC

(powdered activated carbon) has shown less efficiency in the adsorption of humic substances, in which a removal of

51% has been reported (25, 29). However, due to the lack of enough positive charges, unmodified NZ could not be

able to treat pollutants containing negative charges. Thus, adsorbent selection is an important factor in the humic acid

adsorption. On the other hand, ANOVA analysis showed meaningful difference between humic acid removal capacity

and adsorbent type (Pvalue=0.004). In the present study, in optimal condition maximum adsorption capacity was

obtained 250 mg HA per gram of SMNZ, whereas, in a previous study by Lin et al (30) the maximum adsorption of

164 mg humic acid per gram of an surfactant modified Chitosan/zeolite composite was achieved (Table 4). Thus,

SMNZ in comparison with NZ, ANC and the other sorbents performs higher capacity of pollutant adsorption.

20

23

26

29

32

35

1 2 3

Time (hr)

(b)

20

23

26

29

32

35

100 250

S/N

ratio

Agitation (rpm)

(a)

20

23

26

29

32

35

38

5 7 9

pH

(d)

20

23

26

29

32

35

2.56 5.29 10.23

S/N

ratio

Turbidity (NTU)

(c)



Fig.4. Effects of process parameters on S/N ratio in the humic acid adsorption (the larger the better). Marked

points on the lines indicate optimum values for the adsorption process.

Table 4. Comparison of HA adsorption capacities in some recent adsorbent studies.

Adsorbent qm (mg/g) Reference

Surfactant modified Chitosan/zeolite composite 164 (31)

HTAB-modified zeolite synthesized from coal fly ash

126

(32)

Bi-functional resin JN-10

105 (33)

CPB-modified zeolite 92 (6)

Aminopropyl functionalized SBA-15 117

(34)

SMNZ 250 This study

3.3. Effect of adsorbents on SUVA reduction

SUVA is a suitable and easily applicable index for determination of DBPs generation potential in aqueous solution

(23). Generally, natural water resources with SUVA254 values less than 2.0 l/mg.m contain mostly hydrophilic and low

molecular weight natural organic matter. However, water resources with higher SUVA values (i.e., > 4 l/mg.m) mainly

have humic materials of higher molecular weight with hydrophobic nature (30). Such waters after chlorination may

generate higher concentrations of DBPs (35). In our study, in optimal condition SUVA value reduction of above 99%.

Whereas, the ANC the highest reduced 64% of the humic acid and performed less capability in removing the SUVA

production constitutes (Table 5). The humic acid removal by NZ was not significant as well.

20

22

24

26

28

30

32

34

0.2 0.5 0.8

SMNZ and NZ Dosage (g /l)

(f)

25

26

27

28

29

30

31

32

25 50 100

S/N

ratio

HA (mg /l)

(e)

10

15

20

25

30

35

40

NAC NZ SMNZ

Adsorbent type

(h)

20

22

24

26

28

30

32

34

0.05 0.1 0.2

S/N

ratio

NAC Dosage (g /l)

(g)



Table 5. Importance of different experimental factors in the adsorption efficiency based on Delta rank of S/N

ratios.

Level Type of

adsorbent pH Turbidity

Adsorbe

nt dose Agitation Time

HA

Concentration

1 31.83 34.7

6

24.25 29.23 24.33 24.16 26.57

2 12.43 21.9

8

25.19 23.5 29.81 29.28 28.55

3 36.95 24.4

7

31.77 28.49 - 27.77 26.09

Delta 24.52 12.7

8

7.52 5.73 5.48 5.12 2.46

Rank 1 2 3 4 5 6 7

Note: The higher the rank the less the importance.

3.4. Isotherm study

Isotherm expressions are frequently used to describe the partitioning of contaminants in environmental systems. The

humic acid adsorption equilibrium data in the experiments by SMNZ (the most effective sorbent selected from among

NZ, SMNZ and ANC) were fitted by several well-known isotherm models to evaluate the adsorbent efficiency.

Numerous studies have considered one or more of the supported isotherms in the context of water/wastewater systems.

The dual-mode isotherm reflects a recently developed model for the sorption of hydrophobic organic solutes (36). To

characterize parameter uncertainty, ISOFIT reports correlation coefficients (CORij) of the parameters and 95% linear

confidence intervals for each isotherm parameter.

The CORij between parameters Xi and Xj is a measure of linear dependence between those parameters. Its values

range from -1 to 1 with a value of zero (0) representing no correlation (37). Table 6 shows optimal parameters and

some of basic statistical outputs of the ISOFIT software for humic acid adsorption by SMNZ according to different

Isotherm models. Table 7 also summarizes the resulting parameters estimated for each isotherm, along with their linear

confidence intervals.

The software then applies these data to determine the best adsorption isotherm of the adsorbent. Isotherm with lowest

Corrected Akaike Information Criterion (AICc) value would be the best isotherm of adsorption (31). The AICc values

show that the Langmuir and Langmuir-Partition (L-P) isotherms provide the best fit of the sorption data for humic acid

by SMNZ.



Table-6. Summary of parameters estimated for humic acid adsorption by SMNZ according to different

Isotherm models.

Isotherms Parameters Estimate CIlow CIhigh

Langmuir bQ0 2 1.8 2.2

b 1.9×10-3

4.7×10-4

3.4×10-3

L-P (Langmuir-

Partition)

bQ0 2 1.8 2.3

B 1.9×10-3

4.5×10-4

3.4×10-3

Kp 1.3 n/a n/a

Freundlich Kf 2.8 1.9 3.5

(1/nf) 8.9×10-1

8.3×10-1

9.6×10-1

Toth bQ0 2.2 4.5×10-1

3.9

B -7.7×10-3

-2×10-2

8.9×10-3

nT 6.2×10-1

-2 3.7

F-P (Freundlich-

Partition)

Kf 1.9 3.2×10-1

3.6

(1/nf) 7.4×10-1

-1 2.5

Kp 1.1 -4 6.3

Linear Kp 1.8 1.7 1.8

CIlow, CIhigh: lower and upper 95% confidence bounds; Q0: (mg /g); b: (l/ g); Kf: [((mg/g)/(mg/L) ))](1/n)

; (1/nf),

(1/ng), Kp, A, B, and nT: no units

Table 7. Summary of ISOFIT data for determination of the best adsorption isotherm.

Isotherms

Multi

model

ranking

(AICc)

Correlation

between

measured and

simulated

observation

(R2

y))

Correlation

between

residual and

normality

(R2

N))

Linssen

measure of

non-linearity

(M2)

Linearity

assessment

Langmuir 24 0.997 0.763 2.5×10-3

Linear

L-Partition 24 0.997 0.759 2.6×10-3

Linear

Freundlich 25 0.997 0.892 1.3 Non- Linear

Toth 29 0.997 0.8 122 Non- Linear

F-Partition 30 0.997 0.92 639 Non- Linear

Linear 30 0.995 0.841 1.05×10-8

Linear

4. Conclusions

In this study the natural nanozeolite was modified by a cationic surfactant namely HDTMA-Br using an optimum ratio

of 700 mg/g in order to increase its positive charges. Humic acid removal potential of three adsorbent: a nanozeolite,

its modified form by a cationic surfactant and an activated nanocarbon from aqueous solutions was investigated. Their

adsorption efficiencies and optimum conditions for the pollutant removal were also evaluated and compared.


IJPT| June-2016 | Vol. 8 | Issue No.2 | 13337-13352 349

Acourding to the results obtaind, the most important parameter affecting the humic acid adsorption is the type of

adsorbent. The pH value plays the second role in the adsorption environment. An optimum SMNZ dosage of 0.2 g/L

(as the most effective sorbent among NZ, SMNZ and ANC) and a pH value of 5 cause dominant adsorption in the

laboratory scale. In the optimum conditions, it can reduce the humic acid in concentration of 50 mg/L and SUVA up to

99%. Also this new sorbent has shown an excellent capacity for humic acid removal, 250 mg/g. ISOFIT analysis

showed that humic acid adsorption on the SMNZ fits well with the the Langmuir isotherm. The results suggest that

SMNZ shows potencial as a low-cost and control material for DBPs precursors in water and wastewater treatment

processes. However, pilot plant experiments need to be carried out to verify the results and to evaluate the feasibility of

the process.

Acknowledgement

This article is the result of MSc. approved thesis with project number 389133. The authors wish to acknowledge the

Environment Research Center in Isfahan University of Medical Sciences for the financial support.

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Corresponding Author:

Amir Mohammadi*,

Email: [email protected]

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