alexa Adsorption of Aluminum, Arsenic and Sulphate Ions from Synthetic and Real Underground Water by Marine Fouling

E-ISSN: 2252-5211

International Journal of Waste Resources

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Adsorption of Aluminum, Arsenic and Sulphate Ions from Synthetic and Real Underground Water by Marine Fouling

Saeyda A. El-Enein, Ahmed H. Mangoode, Fathy A. Elsayed and Mahmoud A. Hammad*
Chemistry Department, Faculty of Science, Menoufia University, Egypt
*Corresponding Author: Mahmoud A. Hammad, Chemistry Department, Faculty of Science, Menoufia University, Egypt, Email: [email protected]

Received Date: May 15, 2018 / Accepted Date: Jun 18, 2018 / Published Date: Jun 25, 2018

Abstract

The removal of Al3+, As3+ and SO42- ions from aqueous solution was investigated by using marine fouling. The effect of removal of adsorbent was studied in batch technique under various operating parameters such as pH, contact time, adsorbent dose, adsorbent particle size and metal ions concentration at 500 rpm and 25ºC. The maximum removal of Al3+, As3+ and SO42- was 100% at pH 5 for Al3+, pH 8 for As3+ and pH 3 for SO42- using 0.7 g for 120 min. and 45 μm of adsorbent particle size. The Langmuir and Freundlich adsorption isotherm models were under taken to analyse the equilibrium data. Langmuir isotherm showed the best fit to the equilibrium data, which gave maximum adsorption capacity for Al3+, As3+ and SO42- was 28.81, 23.58 and 34.48 mg/g, respectively. The adsorption process follows the pseudo-second-order model. This study recommended that marine fouling can be used for removal of toxic metal ions due to highly efficiently and low cost.

Keywords: Adsorption; Marine fouling; Heavy metal ions; Kinetic; Adsorption isotherm

Introduction

The presence of heavy metals in the industrial waste water causes many serious environmental problems attributed to their toxicity and their non-biodegradable properties [1-3]. The non-biodegradable heavy metals tend to accumulate in living organisms causing several diseases that affect the kidney, nervous, hematopoietic and gastrointestinal systems of humans [4-8]. The pollution problems arise from heavy metal ions makes the removal of heavy metals from wastewater important [9]. The conventional methods for removing heavy metals from wastewater involve precipitation technique, membrane processes, electrolytic recovery, liquid-liquid extraction, ion exchange, photocatalyst ultrafiltration and adsorption [2,3,10-12]. Most of these processes have significant disadvantages such as need for high energy and costly process, low efficiency, production of high amounts of sludge, sludge disposal problems, high levels of trace elements, high cost of specialty chemicals, and reclamation processes [13-15]. Among these various techniques, the adsorption technique with the selection of suitable adsorbents is considered one of the most effective and economical techniques used to remove heavy metals from water [16-19]. Some of natural materials that are available in large quantities or certain waste from agricultural and manufacture operations may have potential to be used as low-cost adsorbents, as they represent unused resources, widely available and are environment friendly to remove heavy metals from wastewater [20,21]. This work aimed to use marine fouling as a cheap and natural adsorbent for removing toxic heavy metal ions as arsenic, aluminum and sulphate from real and synthetic wastewater. Studying various parameters at 500 rpm and 25ºC such as pH, variable concentration of metal ions, adsorbent dosage, adsorbent particle size and contact time. Also, the isotherm and kinetic models were applied.

Material and Methods

Chemicals and instruments

Chemicals used are Aldrich products while NaOH and HCl solutions are standard solutions. Stock solutions of Al3+, As3+ and SO42- of 1000 mg/L were prepared by dissolving an accurate amount of analytical grade reagents aluminum chloride AlCl3, sodium arsenite NaAsO2 and sodium sulphate Na2SO4 in deionized water, respectively. Using 1.0 M HCl and 1.0 M NaOH to adjust the pH of solutions in range of 1-9, the value of pH of solutions resulted was detected by a pH meter (WTW-inolab, Germany). Using the atomic absorption spectrophotometer (AAS) (Perkin Elmer 503), the concentration of metal ions in aqueous solutions was detected by using a calibration curve prepared with standard metal ions solutions.

Adsorbent purification

Marine fouling was collected from The Eastern Harbour of Alexandria. The whole quantity was washed many times with hydrogen peroxide (H2O2) and distilled water (1:1) in order to remove impurities till the pH of washed water become 7. The pure sample was dried in an oven at 70°C for 24h and then crushed well and sieved to get a uniform particle size (45 μm).

Adsorbent characterization

The adsorbent was characterized by Fourier Transform infrared spectrophotometer (FTIR system-BX 0.8009) was used in the range 500-4000 cm-1 to assign surface functional groups of the studied adsorbent. The spectrum exhibits bands at 3428, 2924, 1789, 1486, 860 and 711 cm-1 assignable to ʋ(OH), ʋ(CH), ʋ(C=C), ʋ(CH), ʋ(C–Si) and ʋ(C-Cl), respectively (Figure 1).

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Figure 1: FTIR spectrum of marine fouling

Batch adsorption study

Experiments of batch adsorption were under taken to assessment the effect of different adsorption parameters such as pH, contact time, dosage of adsorbent, adsorbent particle size and metal ions initial concentration on the adsorption capacity of marine fouling to remove Al3+, As3+ and SO42- ions.

pH of Solution Effect

The pH-effect on removing ions of heavy metals by marine fouling was investigated by modification of the initial pH (1-9) for a volume of 50 ml of metal aqueous solution at concentration of 5 mg/L for Al3+ and SO42-, and concentration of 3 mg/L for As3+. The pH-value of was modified with 1.0 M HCl and 1.0 M NaOH in presence of 0.5 g of marine fouling. The mixture was shaken at room temperature (25°C) magnetically at 500 rpm for 60 min. The suspension was filtered off then the un-adsorbed residual of metal ion in the filtrates was measured by AAS.

Adsorbent Dosage Effect

Various adsorbent dosages of (0.1-1 g) were added to a series of flasks composed all of them of 50 mL of metal aqueous solution of 5 mg/L for Al3+ and SO42- and 3 mg/L for As3+ which is adjusted to the optimal pH . The mixtures of suspension were magnetically shaken at 500 rpm for 60 min. at room temperature (25°C).

Contact Time Effect

Experiments were done on a series of solutions composed each of them of 50 ml of metal ion solution of 5 mg/L for Al3+ and SO42- and 3 mg/L for As3+ and adjusted to the optimal pH then the optimal dose of marine fouling was added to each of these solutions. The mixtures of solutions were magnetically shaken at room temperature (25°C) at 500 rpm for various times of (5-120) min.

Initial Metals Ions Concentrations Effect

Concentrations of metal ions in the range of 3-25 mg/L were added in different conical flasks containing 50 ml of each concentration. The optimal conditions of pH of solution, contact time and dosage of the adsorbent were under taken to the experiments.

Effect of Particle Size

Three different particle sizes of adsorbent (average diameter of 45,125 and 500 μm) were added to three flasks all of them consisted of 50 mL of metal aqueous solution of 5 mg/L for Al3+ and SO42- and 3 mg/L for As3+. The optimal conditions of pH of solution, contact time and dosage of the adsorbent were under taken to the experiments.

After each experiment, the solution mixtures were filtered off by using 0.45 μm filter paper and the un-adsorbed concentrations in the filtrates of heavy metal ions were measured using Atomic Absorption Spectrophotometer (AAS).

The removed percentage of metal ions (R %) was calculated from equation:

image(1)

Where C0 is the metal ion initial concentration (mg/L) before adsorption and Ce is the metal ion concentration (mg/L) at equilibrium.

The adsorbed amount of metal ion (qt at time t) per unit mass of the adsorbent (M) was estimated by using the following equation:

image(2)

Ct is the metal ion concentration (mg/L) after time t min., V is the initial metal ion volume in liter and M the mass adsorbent in gram

The mass balance equation was used to determine the adsorption capacity (qe):

image(3)

Kinetic Analysis

The adsorption kinetics was obtained by determining adsorptive uptake of heavy metals at different time intervals from the aqueous metal solution. The pseudo-first-order and pseudo-second-order equations are suited to the kinetic models of the heavy metals adsorption onto marine fouling. Each model gave linearity when plotted that indicates if the model suitably described the process adsorption or not. The equation of pseudo-first-order is expressed generally by equation (4) [22,23].

image(4)

Where qe and qt are the capacities of sorption at equilibrium and at time t, respectively (mg.g-1) and k1 is the rate constant of pseudo-first order sorption (L.min-1).

The pseudo- second-order equation is expressed generally by equation (5) [24,25].

image(5)

Since k2 is the rate constant of the pseudo second order sorption (g.mg-1.min-1).

Adsorption isotherm experiments

The data of initial metal ions concentrations was able to be studied by adsorption isotherm studies. The Langmuir and Freundlich isotherms models were fitted to the results.

Equation (6) is applied to obtain the linear form of Langmuir isotherm:

image(6)

Where KL is Langmuir equilibrium constant (L.mg-1), and qmax (mg.g-1) is the adsorption monolayer capacity. A dimensionless constant separation factor (RL) can be used to characterize Langmuir isotherm [26,27].

image(7)

Where Co is the highest initial concentration of the solute. The type of the isotherm and the nature of the adsorption process either to be unfavourable (RL<0), linear (RL=1), favourable (0<RL<1) or irreversible (RL=0) can be assigned by the value of separation factor (RL).

However, the linear freundlich isotherm equation form is obtained by:

image(8)

Where KF (L.g-1) is adsorption isotherm constant for Freundlich that refers to the multilayer adsorption capacity, image is the intensity of adsorption. The value of image(indicative of favourability when (0.1<1/ n<1) [28].

Results and Discussion

The effect of different parameters on the removal efficiency of marine fouling for metal ions is discussed as following:

Effect of pH on adsorption of metal ions

The removal of metal Al3+, As3+ ions and SO42- ion is examined at different pH ranged from 1-9. Figure 2 illustrate the effect of pH on the removal percentages of Al3+, As3+ and SO42- ions by marine fouling. The data refers to the removal percentage of Al3+ and As3+ increases with increasing pH, where the maximum removal percentage of Al3+ was 97% at (pH=5) and 90% at (pH=8) for As3+ ions. The metal species, M(III); Al(III) and As(III), are present in forms of M3+, M(OH)2+, M(OH)3(S), etc. in water. At lower pH the metal removal decreased due to the competition between H+ (at higher H+ concentration) and metal cation against the negative adsorption sites on the adsorbent surface. In addition, reduction attraction between metal cation and adsorbents is due to positive charge of sorbents’ surface. However, with increasing pH values, the negative charge on the surface of adsorbent increases, which provides electrostatic interactions that are favourable for adsorbing cationic species [29]. However, the data shows that the adsorption of Al3+ ions starts decrease at pH>5 due to formation of soluble hydroxide cation Al (OH)+2 and Al(OH)2+ [30]. While, the adsorption of As3+ ions decrease at pH>8 as arsenic exists as oxyanion) H2AsO3-, HAsO3-2 and AsO3-3) in that pH range resulting in repulsion between this oxyanion and the negative charge on the adsorbent surface [31].

international-journal-waste-resources-percentage

Figure 2: Effect of pH on removal percentage of Al3+, As3+ and SO42- ions. Initial Concentration of metal ions: 5 ppm for Al3+ and SO42 and 3ppm for As3+; volume of solution: 50 ml; adsorbent dosage 0.5 g; contact time 1h; particlesize 45 μm.

The removal of SO42- group reaches its maximum at pH 3.0 (100%) due to the degree of surface protonation was high and so surface offers maximum positive charge for the adsorption of sulfate. Lower removal at pH <3.0 was due to the competition of Cl- ions (added externally to adjust the pH in the form of HCl) with sulfate for the adsorbent sites. The degree of surface protonation decreased and the removal also decreased at pH >3.0 [32,33].

Effect of adsorbent dosage on adsorption of metals ions

The adsorption of Al3+, As3+ and SO42- ions onto marine fouling is examined at over a range from (0.1-1 g) of adsorbent dosage. The obtained data in Figure 3 illustrate that the removal percentage of metal ions increase with increasing adsorbent dosage, where the maximum removal of Al3+ and As3+ ions was 100% at 0.7 g, while it reached 100% at 0.3 g for SO42- ions . This is attributed to increase the surface area of the adsorbent, which increases the number of binding sites for the same liquid volume and thus the total amount of removal of metal ions are increased [34,35].

international-journal-waste-resources-dosage

Figure 3: Adsorbent dosage effect on removal percentage of Al3+, As3+ and SO42- ions. Initial Concentration of metal ions: 5 ppm for Al3+ and SO42 and 3ppm for As3+; volume of solution: 50 ml; pH: Al3+=5, As3+=8, SO42-=3; contact time 1h; particle size 45 μm.

Effect of contact time on adsorption of metal ions

The effect of contact time on the adsorption percentage of Al3+, As3+ and SO42- ions onto marine fouling was examined at different times ranged from 5-120 min. Figure 4 refers to the effect of contact time at removal percentages of Al3+, As3+ and SO42- ions by marine fouling. The data recorded removal percentage of 97.83%, 79.31 % and 85.32 % for Al+3, As+3 and SO42- ions respectively during the first 20 min, this is in agreement with earlier reports where fast metal ions adsorption take place from (10-20 min) [36,37]. The percentage of metal ions removal reached 100% within 30 min for Al+3 and 60 min for As+3 and SO42-. The observed increase in percentage of the removal of heavy metal ions as the contact time increase, clarified that during the initial stage of sorption, a large number of vacant surface sites are available for adsorption. After some time, the remaining vacant surface sites are difficult to be occupied as a result of saturation [38].

international-journal-waste-resources-percentage

Figure 4: Effect of contact time on removal percentage of Al3+, As3+ and SO42- ions. Initial Concentration: 5 ppm for Al3+ and SO42 and 3ppm for As3+; volume of solution: 50 ml; pH: Al3+=5, As3+=8, SO42-=3; adsorbent dose 0.7 g; particle size 45 μm.

Effect of initial heavy metal ion concentration on adsorption of metals ions

The effect of varying initial metal ions concentration on the adsorption of Al3+, As3+ and SO42- ions onto marine fouling was under taken in a range from (3-25 mg/l), (Figure 5). The results revealed a decrease in adsorption with increasing concentration of the heavy metal ions. This is due to the occupancy of the available adsorption sites and thus the adsorption is not as efficient as in the start [39]. The higher adsorption value of Al+3 and SO42- is 100% at initial concentration (Cₒ=5 mg/L) and it is 100% at initial concentration (Cₒ=3 mg/L) for As+3.

international-journal-waste-resources-concentration

Figure 5: Effect of initial metal ion concentration on removal percentage of Al3+, As3+ and SO42- ions. Volume of solution: 50 ml; pH: Al3+=5, As3+=8, SO42-=3; contact time 1h; adsorbent dose 0.7 g; particle size 45 μm.

The Effect of adsorbent particle size on the removal of Al3+, As3+ and SO42- ions from aqueous solution was carried out using three different particle sizes (average diameters of 45, 125 and 500 μm). The results in Figure 6 indicates that with decreasing particle size, the removal increased from 50% to 100% for Al3+, from 40% to 100% for As3+ and from 51% to 100% for SO42-. These might be due to the fact that the smaller particles offer larger surface areas and greater numbers of adsorption sites [40].

international-journal-waste-resources-metal

Figure 6: Particle size effect on removal percentage of Al3+, As3+ and SO42- ions. Initial Concentration of metal ions: 5 ppm for Al3+ and SO42 and 3 ppm for As3+; volume of solution: 50 ml; pH: Al3+=5, As3+=8, SO42-=3; contact time 1h; adsorbent dose 0.7 g.

Adsorption Kinetics

Adsorption is a physical-chemical process in which the mass transports the adsorbate from the fluid phase to the adsorbent surface [41]. The study of kinetics of adsorption is very important because it provides information about the mechanism of adsorption that is necessary for the efficiency of the process [42]. The adsorption kinetics was investigated at various contact time (10-120) then analysing the data enabled to know which model is better to explain adsorption of Al3+ , As3+ and SO42- ions. Figures 7 and 8 represents pseudo-firstorder model and pseudo-second-order model for the investigated ions, respectively. It is obtained by plotting ln image against time (t) min, respectively.

international-journal-waste-resources-first-order

Figure 7: Pseudo-first-order reaction model for adsorption of Al3+, As3+ and SO42- ions on to marine fouling.

international-journal-waste-resources-second-order

Figure 8: Pseudo-second-order reaction model for adsorption of Al3+, As3+ and SO42- ions on to marine fouling.

The above data displayed (Table 1) that pseudo-second-order model yields very good straight lines as compared to pseudo-first-order due to the correlation coefficient R2 of pseudo-second-order model is greater than pseudo-first-order and the theoretical values of e C pseudosecond- order model also agree very well with the experimental ones. Both facts suggest that the adsorption of Al3+, As3+ and SO42- ions on adsorbents follows the pseudo-second-order kinetic model rather than first order model. This confirms that the chemisorption process here is the predominant, which includes a sharing of electrons between the surface of the adsorbent and the adsorbate, also it is usually restricted to form just one layer of molecules on the surface although it may be followed by additional layers of physically adsorbed molecules [43].

Pseudo-first-order Parameters Al3+ As3+ SO42-
K1 (min-1) 0.108 0.043 0.079
qe cal. (mg/g) 1.061 1.992 10.26
R2 0.907 0.965 0.886
Pseudo-second-order K2 (g/mg min) 0.025 0.04 0.019
qe cal. (mg/g) 7.22 4.518 17.18
R2 0.999 0.998 0.999
Experimental qe Exp. (mg/g) 7.142 4.285 16.67

Table 1: Pseudo-first-order and Pseudo-second-order parameters for adsorption of Al3+, As3+ and SO42- ions on to marine fouling.

Adsorption isotherms

The adsorption isotherm is the mathematical model, which gives a description for the adsorbate species behaviour between liquid and solid phases [44]. Adsorption isotherm was investigated at constant temperature and at different initial metal ions concentrations (3-25 mg/L). The equilibrium data obtained for the adsorption of Al3+, As3+ and SO42- ions onto marine fouling were analysed by Langmuir and Freundlich isotherm models [45,46].

Langmuir isotherm models is based on the homogeneity of the surface, there is only an adsorption monolayer on an adsorbent. This monolayer results from the distribution of equilibrium for the metal ions between the liquid and solid phases. After formation of a single layer of the adsorbate on the adsorbent outer surface, no additional adsorption occurs [47]. Figure 9 shows Langmuir models for the investigated ions by plotting C versus Ce . The slope from the figure enabled to calculate the monolayer adsorption capacity KL while KL was obtained from intercept.

international-journal-waste-resources-langmuir

Figure 9: Model of langmuir adsorption isotherm for adsorption of Al3+, As3+ and SO42- ions on marine fouling.

Freundlich isotherm models are purely empirical and best describes the adsorption on heterogeneous surfaces. Figure 10 shows Freundlich models for the studied ions by plotting log qe versus logCe . The adsorption intensity l n was estimated from the slope which indicates both the relative distribution of energy and the heterogeneity of the adsorbent sites whereas, the intercept represented to KF .

international-journal-waste-resources-adsorption

Figure 10: Freundlich adsorption isotherm model for adsorption of Al3+, As3+ and SO42- ions on marine fouling.

Based on the obtained data Langmuir model shows (Table 2) favourability is due to image which is greater than zero and less than unity. On the other hand, Freundlish model also indicates favourability is due to image which is greater than 0.1 and less than 1. However, R2 value of Longmuir model is greater than Freundlish model, so adsorption of Al3+, As3+ and SO42- ions onto marine fouling follows Langmuir isotherm model. This suggests that the adsorption of metal ions take place on a homogeneous surface by monolayer sorption without any interaction with the adsorbed species [48].

Langmuir Parameters Al3+ As3+ SO42-
KL (L/mg) 1.669 1.159 7.435
qmax (mg/g) 28.81 23.58 34.48
RL 0.023 0.033 0.0054
R2 0.972 0.977 0.973
Freundlich KF (L/g) 17.14 11.81 28.6
1/n 0.214 0.268 0.0895
R2 0.934 0.975 0.6877

Table 2: Langmuir and Freundlich adsorption isotherm parameters for adsorption of Al3+, As3+ and SO42- ions on marine fouling.

Application on Real Underground Water

To apply the treatment method used for removing Al3+, As3+ and SO42- ions from synthetic water, underground water sample was collected from El-Meridian Hotel located in El-Haram, Giza, Egypt. The sample was passed through a 0.45 μm membrane filter. The metal ions concentration in water sample was determined by atomic absorption spectrophotometer (ASS), as Tables 3 and 4.

Adsorbent q max (mg/g) reference
Al3+ As3+ SO42-
Raw African beech sawdust 1.913 ----- ----- (Nour et al., 2013)
Groundnut Shell ----- 0.024 ----- (Haldhar et al.,2014)
Surfactant-Modified Palygorskite ----- ----- 3.24 (Dong et al., 2011)
Waste coir pith ----- ----- 0.305 (Namasivayam and Sureshkumar ., 2007)
Marine fouling 28.81 23.58 34.48 Present study

Table 3: Comparison of the maximum monolayer adsorption of Al3+, As3+ and SO4 onto various adsorbents.

adsorbent dosage (g) Ce (mg/L) Removal percentage (%)
Al3+ As3+ SO42- Al3+ As3+ SO42-
0.1 0.2 - 94.445 93.4 100 5.55
0.3 - - 85.327 100 100 14.67
0.5 - - 80.576 100 100 19.42
0.7 - - 71.452 100 100 28.54
1 - - 59.221 100 100 40.77

Table 4: Removal percentage of Al3+ , As3+ and SO42- ions from underground water by marine fouling at different adsorbent dosage, (Cₒ=3.0751, 0.3247 and 100 mg/L for Al3+, As3+ and SO42- respectively).

In the experiment, various dosages of the adsorbent in the range of (0.1-1 g) were added to a series of flasks all of them consisted of 50 mL of water sample and shacked at room temperature (25°C) at 500 rpm for 60 min at pH 7. Solution mixtures were filtered using 0.45 μm filter paper and kept for analyses.

Conclusion and Recommendation

From the obtained results, it is obvious that marine fouling is an excellent adsorbent which has a great efficiency for removing of Al3+, As3+ and SO42- ions from real underground water. Also, Marine fouling is natural, inexpensive and available, so this study provide a cost effective way for removing metal ions from polluted water.

References

Citation: El-Enein SA, Mangoode AH, Elsayed FA, Hammad MA (2018) Adsorption of Aluminum, Arsenic and Sulphate Ions from Synthetic and Real Underground Water by Marine Fouling. Int J Waste Resour 8: 345. DOI: 10.4172/2252-5211.1000345

Copyright: © 2018 El-Enein SA, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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