Chromium removal from tannery wastewater using

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In the petroleum refining, removal of sulfur is an impor- tant step, because crude oil contains sulfur compounds that inactive the catalysts used in the refining ...

International Journal of Environmental Science and Technology


Chromium removal from tannery wastewater using Syzygium cumini bark adsorbent Md. A. Hashem1 · Md. A. Momen1 · M. Hasan1 · Md. S. Nur‑A‑Tomal1 · Md. H. R. Sheikh1 Received: 4 March 2017 / Revised: 14 November 2017 / Accepted: 9 May 2018 © Islamic Azad University (IAU) 2018

Abstract In this study, chromium removal efficiency of the prepared adsorbent from the Syzygium cumini bark is stated. After collecting, Syzygium cumini bark was sun-dried, burnt, grinded and sieved on 80 mesh. The prepared adsorbent was characterized by different techniques such as Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and energy-dispersive X-ray spectrometry (EDX). The effectiveness of adsorbent for the chromium removal efficiency was examined investigating different parameters, e.g., adsorbent dose, contact time, and relative pH. In batch-wise treatment process at optimized conditions, 75 mL chromium-containing wastewater was mixed with 3 g adsorbent, stirred for 15 min, settled, and chromium content was measured by the titrimetric method. Chromium content in the raw wastewater and filtrate was 2920.24 and 3.46 mg/L, respectively. The chromium removal efficiency was obtained 99.9%. The reduction in BOD, COD, and chloride was 97, 94, and 56%, respectively. The use of low-cost indigenous adsorbent could be an option for the chromium removal from tannery wastewater. Keywords  Tannery · Chrome-tanning wastewater · Environment · Pollution · Adsorbent

Introduction Worldwide air, water, and soil contamination from the anthropogenic activities is a common problem. Discharging or emission of solid, liquid or gaseous waste is continuously added to the environment, affecting the human health and ecosystem. Increasing urbanization and industrialization are amplified the level of trace metals especially heavy metals in the waterways (Singh et al. 2011). Certainly many methods are available for degradation process, e.g., photo catalyst, Fenton reaction, reverse osmosis, and biodegradation. Recently nanomaterials are also important for the removal of organic matter in the aqueous materials. They are used for the removal of organic matter in the aqueous materials, e.g., degradation of azo dyes with chitosan-SnO2 nanocomposite (Gupta et al. 2017), photocatalyst degradation of methyl orange, methylene blue and Editorial responsibiility: V.K. Gupta. * Md. A. Hashem [email protected] 1

Department of Leather Engineering, Khulna University of Engineering and Technology, Khulna 9203, Bangladesh

phenol (Rajendran et al. 2016), textile effluent degradation using ZnO/Ag/Mn2O3 nanocomposite (Saravanan et  al. 2015a), degradation of industrial textile effluents using ZnO/Ag/CdO nanocomposite (Saravanan et al. 2015b), textile effluent degradation using novel catalyst ZnO/γ-Mn2O3 (Saravanan et al. 2014), methylene blue degradation with ZnO/CdO composite nanorods (Saravanan et  al. 2011), textile dye degradation using ZnO/CuO nanocomposite (Saravanan et al. 2013a), degradation of methylene blue and methyl orange degradation by the photocatalytic activity of nanosized ZnO (Saravanan et al. 2013b), and degradation of textile effluents using ZnO/Ag nanocomposite (Saravanan et al. 2013c). In the petroleum refining, removal of sulfur is an important step, because crude oil contains sulfur compounds that inactive the catalysts used in the refining process, corrode the refining equipment and lead to deteriorate the air quality upon combustion, affecting public health and the ecosystem (Saleh et al. 2015). To remove sulfur compounds, e.g., dibenzothiophene and thiophenes from the petroleum products, various nanoparticles are used (Saleh and Danmaliki 2016; Danmaliki and Saleh 2017; Saleh et al. 2017). For the detection of trace-level polyaromatic hydrocarbons, Haruna et al. (2016) used hydroxylamine-reduced silver colloid.



International Journal of Environmental Science and Technology

In leather tanning, about 90% tanning industries use basic chromium sulfate as tanning agent (Aravindha et al. 2004) where the pickle pelt takes up 60% chromium and the remaining 40% chromium remained in the spent chrome liquor (Fabiani et al. 1997). Hashem et al. (2015) reported that chromium content in the wet blue spent chrome liquor ranges from 2656 to 5420 mg/L. Chromium has several oxidation states, among them, the trivalent and hexavalent state of chromium can mainly exist in the aquatic environment (Evangelou 1998). Chromium(III) is considered as an essential trace element for some metabolic function in the human body (Kalidhasan et al. 2009). However, a long-term exposure to Cr(III) is recognized to cause allergic skin reactions and cancer (Eisler 1986). It is reported that chromium(VI) can be toxic and carcinogenic (Matos et al. 2009; Yalçin and Apak 2004). Numerous researchers developed nanocomposites to remove metals from the aqueous solutions (Saleh 2015a, b). Saleh et al. (2017) has synthesized the polyamide-graphene composite adsorbent for removal of antimony(III). A good numbers of methods have been developed to remove chromium from the aqueous solutions. Chemical precipitation and electrochemical precipitation are widely used for the removal of heavy metals. Both the techniques have a significant problem in terms of disposal of the precipitated wastes (Ozdemir et al. 2005; Meunier et al. 2006); the ion exchange technique does appear to be economical (Pehlivan and Altun 2006). Of course, many attempts have been carried out to remove heavy metals with low-cost adsorbent, e.g., wood materials (Shukla et al. 2002), agricultural byproduct (Chuah et al. 2005), natural zeolite (Erdem et al. 2004), clay (Marquez et al. 2004), and eggshell and powered marble (Elabbas et al. 2016). In this study, an investigation was made to remove chromium from the wastewater using the prepared low-cost adsorbent of Syzygium cumini bark on the removal of highconcentrated chrome-tanning wastewater. The Syzygium cumini plant is available in Bangladesh, and its bark is the by-product of sawmill. The effectiveness of chromium removal was examined by investigating different parameters, e.g., adsorbent dose, contact time, pH effect.

Materials and methods Sample collection Chromium-containing wastewater was collected from the SAF Leather Industries Ltd., Jessore, Bangladesh. The


wastewater-containing chromium sample was collected in a polyethylene container, prewashed with diluted nitric acid, and immediately transported to the laboratory for the experiment.

Adsorbent preparation The Syzygium cumini bark was collected from a local Sawmill, Khulna, Bangladesh. The bark was cut into small pieces and sun-dried. The sun-dried bark was burnt at 450–550 °C under nitrogen atmosphere for 90 min in muffle furnace, cooled and grinded to make a powder using a mortar. The grinded adsorbent was sieved on 80 mesh and preserved for the experiment.

Reagents The reagents: nitric acid (Merck KGaA, Germany), sulfuric acid (Merck KGaA, Germany), perchloric acid (Merck, India), N-phenyl anthranilic acid (Merck, India), ferrous ammonium sulfate (Merck, India) and glass beads (Loba Chemie, India) were purchased from a local scientific store, Khulna, Bangladesh.

Characterization of chrome‑tanning wastewater The physicochemical properties of wastewater were measured in terms of chromium, pH, total dissolved solids (TDS), total suspended solids (TSS), electrical conductivity (EC), salinity, dissolved oxygen (DO), biological oxygen demand for 5 days ­(BOD5), and chemical oxygen demand (COD). Each measurement was taken in triplicate. Determination of chromium Chromium content in the wastewater was determined by the titrimetric method following the official methods of analysis of Society of Leather Technologist and Chemists (1996) (SLC 208). A 50 mL sample volume was taken in 500 mL conical flask. 20 mL concentrated nitric acid was added followed by 20 mL perchloric acid/sulfuric acid mixture; the flask was gently heated and boiled until the mixture had become a pure orange-red color and continued boiling for 1 min. The flask was removed from the heating source as soon as ebullition has ceased; rapidly the flask was cooled by swirling in cold water bath. Carefully, 100 mL distilled water was added with a few glass beads and boiled for 10 min to remove free chlorine. Then, 10 mL 30% (v/v) sulfuric acid was added and cooled to room temperature. The mixture was titrated with freshly prepared 0.1 N ferrous ammonium sulfate solution with six

International Journal of Environmental Science and Technology

drops of N-phenyl anthranilic acid as an indicator. The end color was indicated by a color change from the violet to green. Determination of pH pH of the spent chrome liquor and treated liquor was measured using pH (UPH-314, UNILAB, USA) meter. Before measuring pH, the meter was calibrated with standard solutions. The meter was verified after determining five samples each. Determination of TSS TSS was determined following the APHA standard method 2540 D (APHA 2012). A 10 mL sample was passed through glass fiber filter disk and dried 103–105 °C in an oven until a constant weight was obtained. Determination of TDS, EC and salinity TDS, EC and salinity were measured using conductivity meter (CT-676, BOECO, Germany). Before measuring the parameters, the meter was calibrated with standard solutions. The meter was verified after determining five samples each. Determination of DO DO was measured using the DO meter (DO-580, BOECO, Germany). Before measuring DO, the meter was calibrated with standard solutions. The meter was verified after determining five samples each. Determination of ­BOD5 BOD was determined following the APHA standard method 5210 B (APHA 2012). Dilution water was prepared placing desired volume of water in a bottle and adding phosphate buffer, magnesium sulfate, calcium chloride, and ferric chloride solutions. Before testing, pH of sample was checked. Unless pH is within the acceptable range (6.5–7.5), pH was adjusted with sulfuric acid or sodium hydroxide solution. Desired sample volume was added to 300 mL BOD bottle. Bottle was filled with enough dilution water so that insertion of stopper will displace all air, leaving no bubbles. The diluted water (blank) was also incubated as a rough check on quality of diluted water and cleanliness of incubation bottles. Initial DO was measured with DO meter (DO-580, BOECO, Germany). BOD bottle was incubated at 20 ± 1 °C. After 5 days incubation, DO was determined and calculated as ­BOD5.

Determination of COD COD was determined following the APHA standard method 5220 C (APHA 2012). Diluted wastewater sample was placed in culture tube (prewashed with 20% sulfuric acid), and potassium dichromate digested solution was added. Sulfuric acid was carefully run inside of tube so that an acid layer is formed under sample-digestion solution layer. Tube was tightly caped and inverted several times to mix completely. Tube was placed in block digester preheated to 150 °C and refluxed for 2 h behind a protective shield. Tube was cooled to room temperature and placed in test tube rack. Culture tube cap was removed and added small TFE-covered magnetic stirring bar. 0.05 to 0.10 mL (1–2 drops) ferroin indicator was added and stirred rapidly on magnetic stirrer while titrating with standardized 0.10 M ferrous ammonium sulfate. The end point was a sharp color change from blue–green to reddish brown, although the blue–green was reappeared within minutes. Similarly, a blank containing the reagents and a volume of distilled water equal to that of the sample was refluxed and titrated.

Characterization of adsorbent The surface morphology and qualitative composition of adsorbent were determined using a scanning electron microscope (JSM-6490, JOEL) equipped with a PGT energy-dispersive X-ray spectrometry (EDX). The Fourier transform infrared spectroscopy (FT-IR) studies were carried out to obtain adsorption spectrum of pure and chromium-loaded adsorbent. The FT-IR spectra were recorded using Fourier transform infrared spectrometer (FT-IR 1600, PerkinElmer) between 400 and 4000 cm−1.

Treatment of chromium‑containing wastewater Batch-wise chromium removal examination was performed with the prepared adsorbent. The scheme for the treatment of wastewater is shown in Fig. 1. Firstly, physicochemical parameters of the untreated chromium-containing wastewater were analyzed and filtered through 0.45 µm pore size filter. Secondly, 75 mL filtrate wastewater was mixed the prepared adsorbent. The adsorbent mixed wastewater was stirred over a fixed period of time, and the mixture was then allowed for settling a fixed time. After settling, the mixture was filtered through 0.45 µm pore size filter; again chromium content measurement was taken using the same procedure as described in 2.4.1.


International Journal of Environmental Science and Technology

The pseudo-second-order kinetic was analyzed based on Eq. (3):

Spent chrome liquor

t 1 t = + Qt K2 Qe Qe

Physicochemical analysis

by rearranging Eq. (3) can be written as

Mixing charcoal with chrome tanning

Qt = K2 t (Qe − Qt )


Adsorption isotherm

Filtration with 0.45 µm Physicochemical analysis Fig. 1  Schematic flow chart for the chromium removal treatment process

Process optimization The treatment process was optimized to obtain maximum removal efficiency. Tests were carried out to optimize the chromium removal parameters: adsorbent dose and contact time. The optimized conditions were established by investigating the removal efficiency of chromium.

Adsorption kinetics models Adsorption kinetics describes the rate of the adsorption process. To investigate the kinetics models of chromium ions adsorption onto Syzygium cumini bark adsorbent, pseudofirst-order and pseudo-second-order kinetic models were tested. The linear form of the pseudo-first-order kinetic model can be expressed by Eq. (1): Equation (1) can be written by rearranging


Qe − Qt = −K1 t Qe



where Qe (mg/g) is the amount of chromium adsorbed per unit mass of the adsorbent at equilibrium; Qt (mg/g) is the amount of chromium adsorbed per unit mass of the adsorbent at time t (min); K1 (per min) is the equilibrium rate constant of the pseudo-first-order model.



where K2 (g/mg/min) is the rate constant of the pseudosecond-order equation.

Stand for settling

ln(Qe − Qt ) = lnQe − K1 t


Adsorption isotherm explains the interactions between adsorbent and adsorbate. It is an important factor to determine the adsorbent capacity and optimizing adsorbent consumption. In this study, Langmuir isotherm and Freundlich isotherm were studied to explain the adsorbent characteristics of adsorbent. Langmuir model assumes the uniform energy adsorption onto the solid surface. It also designates a single-layer adsorption in the homogenous sites and the homogenous structure of adsorbent (Gimbert et al. 2008). The linearized Langmuir equation is represented by Eq. (5):

1 1 1 1 = × + Qe Ce Qm KL Qm


where Qe (mg/g) is the amount of chromium adsorbed at equilibrium; Ce (mg/L) is the equilibrium concentration chromium in solution; Qm is (mg/g) the maximum chromium adsorption capacity; KL (L/g) is the Langmuir constant related to the energy of adsorption. Data were also analyzed with the Freundlich isotherm, which can be given in its logarithmic form as following: Obtained data were also analyzed with the Freundlich isotherm. The Freundlich isotherm equation is expressed as the logarithmic Eq. (6):

ln Qe = ln kf +

1 ln Ce n


where kf is a Freundlich constant which shows the adsorption capacity of adsorbent and n is a constant which shows the greatness of relationship between the adsorbate and adsorbent.

International Journal of Environmental Science and Technology Table 1  Main characteristics of the chrome-tanning wastewater and comparison with the previous study


Transmittance (%)

Cr (mg/L) pH TDS (g/L) BOD (mg/L) COD (mg/L) EC (mS) Chloride (mg/L) Salinity (ppt)

Raw sample

Treated sample

2920.2 ± 0.7 3.9 ± 0.1 42.2 ± 0.1 3200 ± 77 4321 ± 21.2 71.9 ± 0.1 16883.7 ± 14 43.8 ± 0.1

3.46 ± 0.3 8.9 ± 0.3 48.0 ± 0.2 112 ± 3 281 ± 3.0 80.5 ± 0.4 7360.0 ± 0.1 50.8 ± 0.1

ECR (1997)

2.0 6–9 2100 250 400 1.20 600 –

Cr removal (%) This study

Elabbas et al. (2016)




Results and discussion


Characteristics of the spent chrome liquor

110 90


Pure adsorbent Cr-loaded adsorbent


70 50 30 4000 3600 3200 2800 2400 2000 1600 1200


Characteristics of the wastewater are shown in Table  1. Results indicate that wastewater had strong pollution loads because it contained higher quantities of pollutants, e.g., high chromium content, suspended solids, total dissolved solids (TDS), and strongly acidic (4.0  15 min). Thus, it was assumed that the extreme chromium removal was happened at contact time 15 min.

92 90






Contact time (min)

Fig. 6  Batch-wise chromium removal efficiency on different contact time: 5, 10, 15, 20, and 25 min; in each batch 75 mL wastewater with fixed 3 g charcoal was used

Chromium removal efficiency on adsorbent dose and relative pH changes are depicted in Fig. 5. The initial concentration of chromium (2920.24 mg/L) in the real chrome-tanning wastewater, the amount of adsorbent doses (1–6 g for every 75 mL wastewater) and contact time (15 min) were kept constant. It is clear from Fig. 5 that chromium removal efficiency was increased with increasing adsorbent dose. At adsorbent dose 3 g for 75 mL wastewater, chromium removal efficiency was 99.9%. After that, there was no changed. pH is an important parameter in adsorption because it is responsible for the protonation of metal (chromium) binding site. It was found that chromium adsorption by the Syzygium cumini bark adsorbent was a function of solution pH. At lower pH, chromium removal was obtained less than the higher pH. Chojnacka (2005) reported that at higher pH the adsorption of hydrolysis yields and precipitated chromium as colloidal

(a) -6.2

Results obtained in the treatment process with optimum conditions are represented in Table 1. The physicochemical parameters were obtained after all stages of treatments chromium, pH, TDS, BOD, COD, EC, chloride, and salinity were 3.46 mg/L, 8.9, 48.0 g/L, 112 mg/L, 281 mg/L, 80.5 mS, 7360 mg/L, and 50.8 ppt, respectively. The highest percentage of chromium removal of chromium was 99.9%. It seems that after treatment pH was within the discharged level although other parameters, e.g., TDS, EC, and salinity


8 7


y = -0.101x - 6.104 R1² = 0.997

Q t/{Qe(Qe-Q t )}

ln{(Q e-Qt)/Qe }

Treatment process efficiency

-6.6 -6.8 -7.0

y = -0.435x + 6.651 R2² = 0.923

6 5 4 3 2

-7.2 1









10 11

Contact time (min)










10 11

Contact time (min)

Fig. 7  Pseudo-first-order (a) and pseudo-second-order (b) kinetics of adsorption


International Journal of Environmental Science and Technology

(a) 0.0021






y = 8.168x - 2.882 R2² = 0.995


y = 0.011x - 0.002 R1² = 0.847


1/Q e (L/mg)



7.0 6.8 6.6



0.0003 0.0000


6.2 0.16



1/Ce (L/mg)










Fig. 8  Linearized adsorption isotherms Langmuir (a) and Freundlich (b)

were slightly increased. The reduction in BOD, COD, and chloride were 97, 94, and 56%, respectively. In batch-wise experiment higher percentage of chromium was removed from the tannery wastewater by Syzygium cumini bark adsorbent.

Adsorption kinetics In Fig.  7, the values of R12 (0.997) and R22 (0.923) were obtained for the pseudo-first order and pseudo-second order, respectively. It seems that the pseudo-second-order kinetics cannot describe the adsorption process of chromium ion onto adsorbent rather pseudo-first-order kinetic equation can, as the plot of ln(Qe − Qt) against time t, show a good liner fit (R21 = 0.997) as depicted in Fig. 7a. The pseudo-first-order model of adsorption suggests that the adsorption process follows a first-order mechanism and the rate of adsorption is proportional to the number of unoccupied sites of adsorbent. The slope range between 0 and 1 is a measure of adsorption intensity or surface heterogeneity, becoming more heterogeneous as its value gets closer to zero.

Adsorption isotherm In this work, Langmuir and Freundlich adsorption isotherm models were tested. Figure 8a, b shows the Langmuir and Freundlich adsorption isotherm models. Results indicate that the Freundlich model was well fitted with the adsorption data, as well as the correlation coefficient (R22 = 0.995) value of the Freundlich model was more suitable for the removal of chromium from the wastewater using adsorbent. The value of 1/n obtained from the Freundlich model was above 1 (1/n = 8.1675) which indicates the physical process is favorable adsorption conditions for the adsorbent, and the adsorption will be multi-layer on the heterogeneous surface.


Conclusion The present study shows that Syzygium cumini bark is very effective adsorbent for chromium removal from the real tannery wastewater. Batch-wise spent chrome liquor was treated to remove chromium from chrome-tanning wastewater. The removal efficiency of chromium at optimized condition was obtained 99.9% although others parameters were slightly increased. The reduction in biological oxygen demand, chemical oxygen demand, and chloride was 97, 94, and 56%, respectively. The investigation indicates that it was an effective technique to reduce toxic substances that will minimize pollution load from the spent chrome liquor. The study could be helpful to design the treatment of spent chrome liquor in the house prior to discharge, and the adsorbed chromium could be recovered by desorption. Acknowledgements  Authors wish to thank the related personnel for providing all facilities to conduct this research at Department of Leather Engineering, Khulna University of Engineering and Technology (KUET), Khulna 9203, Bangladesh. Authors also want to extend thanks to Prof. Dr. Md. Mominul Islam, Department of Chemistry, University of Dhaka, Dhaka 1000, Bangladesh, for laboratory support.

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