1
Department of Chemistry and Physics of Functional Material, University of Koblenz and
Landau, Landau, Germany
2
Institute of Leather Engineering and Technology, , University of Dhaka, Dhaka, Bangladesh
3
Department of Applied Chemistry and Chemical Engineering, University of Dhaka, Dhaka, Bangladesh
Corresponding author details:
Md Razib Hosen
Department of Chemistry and Physics of Functional Materials
University of Koblenz
Landau,Germany
Copyright: © 2019 Razib Hosen Md, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 international License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
This study had been conducted using low-cost agricultural waste to remove chromium
and other parameters from tannery effluents. Orange peel and tea waste were used as
bioadsorbent for this study; the findings were then compared with that of commercially
activated carbon. The nature of these Bio-adsorbent was examined using Fourier-transform
infrared spectrometer (FTIR) technique. The maximum adsorption capacity for tea waste
and orange peel were 11.25 mg/g and for 10.83 mg/g. Characterization of the effluents
was done both before and after treatments. The result represents the maximum removal
percentage of TDS 97.13, Turbidity 99.7, conductivity 97.5 and chromium 97.63. The order
of adsorption activated carbon> tea waste> orange peel. Tea waste has better removal
ability to remove chromium than orange peel, although in the case of conductivity and Total
dissolved solid (TDS) orange peel is better. The aim of this research involves implementation
of low cost agricultural waste for the purpose of tannery effluent treatment.
Adsorbent; Tannery effluents; Chromium
Chromium is the 7th most abundant metal on the earth, which is present in the
environment, mainly in two oxidation states Cr3+ and Cr6+ having average concentration
100 mg/kg. Chromium is commonly used in electroplating, leather tannin, metal finishing,
wood treatment [1,2]. About 107 tons of chromium is produced annually and 60-70% is
used in alloys containing stainless steel and 15% in chemical manufacturing practices,
mainly leather tannin and pigment [3,4]. Nowadays about 80-90% of international leather
production is tanned using trivalent chromium known as basic chromium sulfate [5]. One
of the major concerns of tannin industry is to dispose of chrome-containing effluent that
is produced as a by-product of chrome tannin [6]. The removal of chromium from tannery
waste water is important as most of the cases it poses a threat to the human being as well
as environment due to their non-degradability and toxic effect on the aquatic organism.
Retention of hexavalent chromium can cause skin disease, inhalation and damage of
internal organs [7,8]. In Bangladesh, less than 2 mg/l chromium concentration in the
effluent is allowed to discharge into drains [9]. Several physical and chemical processes like
chemical precipitation, reverse osmosis; ultrafiltration, ion exchange, electrochemical and
adsorption are available for the removal of chromium from tannery waste water. But these
processes are costly, generate poisonous sludge result in partial metal removal. As a result,
adsorption has become one of the alternative processes in recent years. Several studies
have been completed using bio-adsorbents like garlic peel [10], olives tone [11], Carica
papaya seed [12], Anabaena and vetiveria [13], rice husk [14], green alagy [15], maple
sawdust [16], sugar industry waste [17], red mud [18], duolite [19], sogacane [20] oriental
beech sawdust [21] cotton seed hulls [22,23] mustard seed cane [24] coconut waste [25] to
remove chromium and other heavy metal from waste water [26,27]. In this study, we used
tea waste and orange peel to remove chromium from the tannery waste water. Tea is a very
common and popular drink in Bangladesh as well as orange is also a popular fruit. So tea
waste and orange peel are available in Bangladesh with low economic value. The aim of this
study is to investigate the possible use of tea waste and orange peel in the adsorption of
chromium from the tannery waste water.
Chemical and instrumental analysis
Tea waste and orange peel both were modified by using only NaOH. An AAS flame technique at λ=357.9 nm was used for measuring chrome concentration with flame atomization model AA-7000. The functional group in bio adsorbents was identified by transforming infrared spectrophotometer (FTIR Shimadzu Corporation, model- IR prestige 21, serial no-A21004501831). Parameter such as DO, conductivity, total dissolved solid (TDS) and turbidity were measured by HACH and digital direct reading meter.
Sample collection and preparation of bio-Adsorbents
The bio-adsorbent materials orange peel and tea waste both were collected 11 February 2016 from the local market of Dhaka. After cleaning with distilled water both samples were dried at 60°C until constant mass. Then the samples were crushed into small particle of approximately sieve size ≤ 60 µm. Deionized water was used to wash the powder then oven dried at 60°C until constant mass is acquired. These final samples were preserved in an air tight bottle for further use.
Chemical modification of bio-Adsorbents.
In this study, 50 gm of each bio-adsorbents were treated with 500 ml (0.1 M) NaOH for 24 hours shaking at 120 rpm. After treatment, the modified bio-adsorbents were washed with deionized water until the pH of this solution became neutral.
Effluent samples collection
The chrome tannin and retannin effluents were collected 3rd
march 2016 from the Ruma tannery at Hazaribagh. Ndimele and
Kumolu-Johnson (2012) procedure was followed for water sampling
of the river. 5 L of plastic bottle was used to collect water. Before
sampling, 10% HNO3
was used to clean plastic bottle and rinsed well
with distilled water. To abate of metals adsorption onto the wall of the
plastic bottle 2 to 3 drops of HNO3
was added to the sample. In tannin
industry, Basic chromium sulfate was used in tannin and retannin
operation.
Procedure
At first, 20 gm of adsorbent was added to 200 ml of tannery effluent in a beaker. The solution was then stirred with magnetic for one hour and kept overnight. The solution filtered using Whatman 11 cm filter paper onto volumetric flask. After preparing all of these samples were kept at room temperature until analysis.
Adsorption studies
The percentage of adsorption was determined by the following equation.
Where, Co and Ce represent the initial concentration of the solution and the concentration of the solution after adsorption respectively. In this study, the concentration of chromium was higher in chrome tannin effluent than re-tannin. The effect of chromium concentration on adsorption was calculated using the equation below
Here, Co and Ce are the concentration of chromium at initial and equilibrium respectively, m is the weight of adsorbents in g, V is the volume of effluent in L
Characterization of chrome tannin and re-tannin
| Parameter | Tannin | Re-tannin |
| Cr concentration (mg/L) | 1526 | 1056 |
| Turbidity (NTU) | 247 | 177 |
| Conductivity (mS/sec) | 97.1 | 53.3 |
| TDS (g/L) | 54.3 | 27.3 |
| Dissolved oxygen (mg/L) | 1.67 | 2.63 |
Table 1: Characterization of chrome tannin and re-tannin effluents
Table 2: Percentage removal and Capacity of Bio-adsorbents
Figure 3: Removal percentage of chrome tannin and re-tannin
with adsorbents
Figure 4: Reduction of different parameters in chrome tannin
after treatment of adsorbents
First and second author contribute equally in this study.
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