# European Journal of Sustainable Development Research

Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent
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1 Jessore University of Science and Technology, Department of Chemical Engineering, 7408 Jessore, BANGLADESH
2 Asia Arsenic Network, Arsenic Center, Jessore, BANGLADESH
* Corresponding Author
Research Article

European Journal of Sustainable Development Research, 2019 - Volume 3 Issue 1, Article No: em0065
https://doi.org/10.20897/ejosdr/3917

Published Online: 06 Oct 2018

APA 6th edition
In-text citation: (Parvin et al., 2019)
Reference: Parvin, S., Hossen, A., Rahman, W., Hossen, I., Halim, A., Biswas, B. K., & Khan, A. S. (2019). Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent. European Journal of Sustainable Development Research, 3(1), em0065. https://doi.org/10.20897/ejosdr/3917
Vancouver
In-text citation: (1), (2), (3), etc.
Reference: Parvin S, Hossen A, Rahman W, Hossen I, Halim A, Biswas BK, et al. Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent. EUR J SUSTAIN DEV RES. 2019;3(1):em0065. https://doi.org/10.20897/ejosdr/3917
AMA 10th edition
In-text citation: (1), (2), (3), etc.
Reference: Parvin S, Hossen A, Rahman W, et al. Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent. EUR J SUSTAIN DEV RES. 2019;3(1), em0065. https://doi.org/10.20897/ejosdr/3917
Chicago
In-text citation: (Parvin et al., 2019)
Reference: Parvin, Shahanaz, Afzal Hossen, Wasikur Rahman, Israfil Hossen, Abdul Halim, Biplob Kumar Biswas, and Abu Shamim Khan. "Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent". European Journal of Sustainable Development Research 2019 3 no. 1 (2019): em0065. https://doi.org/10.20897/ejosdr/3917
Harvard
In-text citation: (Parvin et al., 2019)
Reference: Parvin, S., Hossen, A., Rahman, W., Hossen, I., Halim, A., Biswas, B. K., and Khan, A. S. (2019). Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent. European Journal of Sustainable Development Research, 3(1), em0065. https://doi.org/10.20897/ejosdr/3917
MLA
In-text citation: (Parvin et al., 2019)
Reference: Parvin, Shahanaz et al. "Uptake Hazardous Dye from Wastewater Using Water Hyacinth as Bio-Adsorbent". European Journal of Sustainable Development Research, vol. 3, no. 1, 2019, em0065. https://doi.org/10.20897/ejosdr/3917
ABSTRACT
The existing study demonstrates that water hyacinth (eichhorniacrassipes) is a potential adsorbent for the removal of Congo red dye from synthetic wastewater by batch process. The experiments were conducted to study the influence of various parameters such as initial dye concentration, pH, contact time and adsorbent dosage at different operating conditions. The effect of pH and dye concentration was found to be significant and the maximum removal was detected at pH 5 and concentration 100 ppm; considered to be optimum values. The removal of Congo red was consistent initially proportional to the adsorbent dosage. The adsorption process followed Langmuir adsorption isotherm model; point out that the process supported monolayer adsorption of Congo red on the adsorbent surface. Adsorption kinetics closely followed the pseudo-second-order model and mass transfer analysis indicated better transportation of adsorbate from solution phase to solid phase. These results point out suitability of the locally available low cost adsorbents in the niche area of wastewater treatment and can be implemented in commercial dye enriched industrial effluent.
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# INTRODUCTION

In the present work, naturally available low–cost adsorbent, such as water hyacinth has been used as an adsorbent for Congo-red dye removal from aqueous solution. The consequence of the experimental parameters such as initial pH, concentration of dye, adsorbent dosage and contact time has been investigated. The outcome of the experiments was analyzed by Langmuir adsorption isotherm, mass transfer and kinetics viewpoints.

# MATERIALS AND METHODS

## Materials

Water hyacinth was collected from the local area of Jessore University of Science and Technology, Bangladesh. The chemical substances, e.g., Congo red (CR) dye, HCl and NaOH were purchased from Merck, Germany. Stock solution of Congo red was prepared by dissolving 696.665 g/mol of dye in doubled distilled water and different concentrations (25, 50,100, 200, 300, 400 and 500 ppm) of solution were made by dilution of the stock solution.

Water hyacinth was carefully washed by distilled water to remove the dirt and mud. It was then sun dried and acid washed to eliminate the soluble impurities. Then acid washed sample was dried again in an oven at 105°C for 2 hrs to leave out the moisture from it. The dried adsorbent was crushed in a micro-plant grinding machine and converted into fine powder which was stored in air tight plastic containers for further use in the whole experiment.

UV-1650 spectrophotometer (Shimadzu Co., Japan) was used to measure the concentration of solution where maximum absorbance wavelength was 450 nm. pH of the solutions were studied over the range from 4 to 8 through pH meter.

The batch experiments were run out to investigate the influence of various parameters including contact time (0 to 210 mins), pH (4 to 8), adsorbent dosages (0.5 to 5 g/L). In this study 250 ml conical flasks were used to keep 100 ml adsorbate solution of various concentrations (25, 50,100, 200, 300, 400 and 500 ppm) and known amount of adsorbent were added into each flask at different conditions which shaken continuously at a constant oscillation of 211 osc/min for 3.5 hrs. Then the solution was filtered and the remaining sample was analyzed to determine the adsorption percentage of Congo red which computed by the following equation (1):

 $\%\ Removal\ of\ CR = \frac{C_{0}{- C}_{t}}{C_{0}} \times 100\%$ (1)

where, $$C_{0}$$ is the initial concentration (mg/L) and $$C_{t}$$ is the concentration at time $$t$$. The amount of CR adsorbed per unit mass of the adsorbent, $$q_{e}$$ (mg/g) was evaluated by the following mass balance equation (2):

 $q_{e} = \frac{{(C}_{0}{- C}_{e})V}{m}$ (2)

where, $$C_{0}$$ and $$C_{e}$$ are the concentrations (mg/L) of Congo-red at initial and at equilibrium, correspondingly. $$V$$ is the volume (L) of the solution and $$m$$ is the mass of the adsorbent (g).

## Pseudosecondorder Model

Adsorption capacity of dye on the adsorbent particles was assumed proportional to the active sites of the surface. For pseudo–second order kinetic rate, the above equation is as in the following equation (3):

 $\frac{t}{q_{1}} = \frac{1}{k_{2}q_{e}^{2}} + \frac{1}{q_{e}}t$ (3)

If second–order kinetic is applied, the plot of $$t/q_{1}$$ against $$t$$ of the above equation should demonstrate a linear relationship and $$q_{e}$$ and $$k_{2}$$ can be determined from the slope and intercept.

## Intra-particle Diffusion Study

Diffusion coefficient ($$K_{\text{ip}}$$) for the intra–particle transport of CR has been calculated at initial dye concentrations and pH by employing the rate equation (4) expressed by Vadivalen and Kumar, 2005:

 $q_{t} = \varnothing + K_{\text{ip}}\sqrt{t}$ (4)

Langmuir represents the equilibrium distribution of dye molecules between the solid and liquid phases. Langmuir isotherm is valid for monolayer adsorption onto a surface containing a finite number of identical sites.

Based upon these assumptions, Langmuir represented the following equation (5):

 $q_{e} = \frac{Q_{o}K_{L}C_{e}}{1 + K_{L}C_{e}}$ (5)

Langmuir adsorption parameters were determined by transforming the Langmuir equation into linear form (6):

 $\frac{1}{q_{e}} = \frac{1}{Q_{0}} + \frac{1}{Q_{0}K_{L}C_{e}}$ (6)

where, $$C_{e}$$ is the equilibrium concentration of adsorbate (mg/L), $$q_{e}$$ is the amount of dye adsorbed per gram of the adsorbent at equilibrium (mg/g), $$Q_{0}$$ is the maximum monolayer coverage capacity (mg/g) and $$K_{L}$$ is the Langmuir isotherm constant (L/mg).

## Mass Transfer Analysis

Mass transfer analysis for adsorption of Congo red on the water hyacinth was carried out using the Mckay et al. (1981) equation (7):

 $\ln\left( \frac{C_{t}}{C_{o}} - \frac{1}{1 + MK_{\text{bq}}} \right) = \ln\left( \frac{MK_{\text{bq}}}{1 + MK_{\text{bq}}} \right) - \left( \frac{1 + MK_{\text{bq}}}{MK_{\text{bq}}} \right)\beta S_{s}t$ (7)

where, $$M$$ is the mass of the adsorbent per unit volume (g/L), $$K_{\text{bq}}$$ is the constant obtained by multiplying $$Q_{o}$$ and $$K_{L}$$ which are defined in 2.7 section, $$S_{s}$$ is the external surface area of the adsorbent per unit volume (m−1), $$\beta$$ is the mass transfer coefficient (cm/min)and $$t$$ is the contact time (min).

The plot of $$\ln\left\{ \frac{C_{t}}{C_{0}} - \frac{1}{\left( 1 + MK_{\text{bq}} \right)} \right\}$$ versus $$t$$ is carried out. The values of mass transfer coefficient, $$\beta$$ were determined graphically from the slope $$\left\{ \frac{\left( 1 + MK_{\text{bq}} \right)}{MK_{\text{bq}}} \right\}\beta S_{s}$$ of the individual plots.

# RESULTS AND DISCUSSION

## Removal Properties of CR

### Effect of pH

The removal of Congo red dye from synthetic waste water with varying pH is illustrated in Figure 1 where initial dye concentration 100 ppm and contact time 150 min.

From the figure, it can be seen that the maximum dye adsorption (87%) was obtained at pH 5 and gradual decrease in adsorption take place with increasing the value of pH. Only 58% dye adsorption take place at pH 8. This is due to the fact that, Congo red is anionic dye and at higher pH, OH- ions are plenty and it can compete with the anionic dye which accounts low adsorption. At lower pH, due to the electrostatic attraction between negative charged dye molecules and positive charged adsorbent surface higher adsorption can be observed (Aboul-Fetouh et al., 2010; Alam et al., 2014).For these reason, pH 5 was taken as optimum result for further whole experiment herein.

The result of Congo red dye removal where initial concentration 100 ppm, contact time 150 min and optimum pH 5 with varying amount of adsorbent dosages is depicted in Figure 2.

From the Figure, it can be seen that adsorption of dye increased from 69% to 85% with increasing adsorbent dose from 0.5 to 1.0 g/L. After that when we increased the adsorbent dose, the dye removal% decreased due to the fact that there might be formation of particle aggregation resulting in a decrease in the total surface area which responsible for decreasing adsorbed amount per unit mass (Khan et al., 2015). Even if the uptake of dye increased by increasing the adsorbent dose beyond a dose of 1.0 g/L, the rise of dye removal% is insignificant and capacity of adsorbent is low. Therefore, further increase of dose result the much production of sludge and wastage of material. Similar result was found from lead ion removal by bamboo based activated carbon which is reported in Khan et al., 2015. Thus 1.0 g/L of adsorbent dose was taken as an optimum dose for further experiments.

### Effect of Dye Concentration

This study was performed by changing the initial dye concentration in the range of 25 to 500 ppm (Figure 3) with optimum conditions received from previous experiments (adsorbent dose 1.0 g/L, contact time 150 min and pH 5).

The initial dye concentration provided significant driving force to overcome all mass transfer resistances of the dye between the aqueous and solid phases (Ho et al., 2005). In this study, when the initial concentration of dye increased from 25 to 100 ppm, the percentage of dye removal using water hyacinth increased from 90 to 93% and after that the removal percentages fall with increasing dye concentration. The reasons behind that, the increase of adsorption capacity might be due to the increment of driving force that is concentration gradient which causes an increased number of dye particles coming in contact with the adsorbent. On the other hand, number of available adsorption sites in adsorbent is the same for all concentrations. Thus concentration increases with the more number of dye particles but adsorbent dose remain same, therefore, dye competes with the same adsorption sites. As a result, some dye particles without being adsorbed retain in the system and decrease the removal percentage upon increases the Congo red dye concentration.

### Effect of Contact Time

Effect of contact time on the removal of dye by the water hyacinth as adsorbent is illustrated in Figure 4. It showed that the removal percentage increased (0 to 96%) with the increase in contact time (0 to 150 min). Highest removal (96%) was obtained at and above 150 min. It means that the removal rate becomes slower with time and finally a saturation stage is obtained. Similar result was discussed in Kumar and Bilal, 2018.

Pseudo second order kinetic model was studied at optimized operating conditions such as concentration 100 ppm, pH 5 and the results were described in Figure 5. The figure ($$t/q_{t}$$versus $$t$$) showed linear plot from which the value of $$q_{e}$$ and $$k_{2}$$ were calculated (Table 1). The result revealed that $$R^{2}$$ value is close to 1 and linearity of this curve indicates that the kinetic data fitted well with the pseudo second order model. Similar results were also reported in Cheng et al., 2015 to uptake CR dye via activated carbon.

Table 1. Kinetics results for adsorption of CR onto water hyacinth

 Pseudo second order Intra–particle diffusion K2 (g/mg) qe (mg/g) R2 Kip (g/mg/min1/2) Ø (mg/g) 1.77×10-3 Exp. Calc. 0.9865 0.9512 7.6938 8.77 20.12

For the intra-particle diffusion analysis, if the plot of $$q_{t}$$ versus $$t^{\frac{1}{2}}$$ gives a straight line that pass through the origin which indicates the intra-particle diffusion model contributes in the rate determining step (Ghorai and Pant 2005) but in Figure 6, this linear relationship does not pass through the origin that imply the intra-particle diffusion model was not rate controlling step.

In the present study, the plot of $$\frac{1}{q_{e}}$$ against $$\frac{1}{C_{e}}$$ gives straight line shown in Figure 7 with a slope of $$\frac{1}{Q_{0}K_{L}}$$ and intercept of $$\frac{1}{Q_{0}}$$. From the plot we can notice that the value of regression correlation co-efficient ($$R^{2}$$) is 0.9899 which is very close to 1 and indicates that the obtained data are well fitted in Langmuir isotherm model and also suggests that monolayer sorption exists under the experimental conditions.

The adsorption capacity ($$Q_{0}$$) of the adsorbent was found to be 53.76 mg/g. The adsorption capacity of the adsorbent under study is comparable to other bio-adsorbents reported in Table 2.

 Adsorbents Adsorption capacity (mg/g) Type of Dyes References Water hyacinth 53.76 Congo red Present study Water hyacinth 17.58–46.35 Methylene blue Murali and Uma, 2016 Water hyacinth root 46.15 Congo red Kumar and Bilal, 2018 Water hyacinth root 8.04 Methylene blue Soni et al., 2012 Rice Husk 4.29 Congo red Taha et al., 2014 Sugarcane bagasse 39.8 Congo red Zhang et al., 2011 Cashew nut shell 5.18 Congo red Senthil et al., 2010 Kaolin 5.44 Congo red Vimonses et al., 2009 Bagasse fly ash 11.89 Congo red Mall et al., 2005 Neem leaf powder 41.20 Congo red Bhattacharrya and Sharma, 2004

## Mass Transfer Analysis

The plot of $$\ln\left\{ \frac{C_{t}}{C_{0}} - \frac{1}{\left( 1 + MK_{\text{bq}} \right)} \right\}$$ versus $$t$$ resulted a straight line shown in Figure 8 representing the applicability of the model.

The value of mass transfer coefficient ($$\beta$$) were determined graphically from the slope $$\left\{ \left( \frac{1 + MK_{\text{bq}}}{MK_{\text{bq}}} \right)\beta S_{s} \right\}$$ of the individual plots and presented in Table 3.

Table 3. Mass transfer analysis for adsorption of congo red on water hyacinth

 Adsorbents Mass transfer constants, βs (cm/min) Correlation coefficient, R2 Water hyacinth 62.39×10-12 0.9825

The values obtained from the experimental analysis shown that the velocity of the adsorbate Congo red for transporting from bulk i.e. solution phase to solid phase was quite good (Bhattacharya et al., 2008).

# CONCLUSION

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