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Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater
Journal Pre-proof Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater Md. Abul Hashem, Mehedi Hasan, Md. Abdul Momen, Sofia Payel, Md. Sharuk NurA-Tomal PII:
S2665-9727(20)30004-0
DOI:
https://doi.org/10.1016/j.indic.2020.100022
Reference:
INDIC 100022
To appear in:
Environmental and Sustainability Indicators
Received Date: 8 November 2019 Revised Date:
6 January 2020
Accepted Date: 15 January 2020
Please cite this article as: Hashem, M.A., Hasan, M., Momen, M.A., Payel, S., Nur-A-Tomal, M.S., Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater, Environmental and Sustainability Indicators, https://doi.org/10.1016/j.indic.2020.100022. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 The Author(s). Published by Elsevier Inc.
Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater Md. Abul Hashem*, Mehedi Hasan, Md. Abdul Momen, Sofia Payel, Md. Sharuk Nur-A-Tomal Department of Leather Engineering, Khulna University of Engineering & Technology (KUET), Khulna-9203, Bangladesh
Corresponding author
: Dr. Md. Abul Hashem Associate Professor Department of Leather engineering Khulna University of Engineering & Technology Khulna-9203, Bangladesh Tel.: +88 041 774344; Fax: +88 041 774403 E-mail address: [email protected], [email protected]
1
Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater
1 2 3 4
Abstract
5
This investigation studied the utilization of water hyacinth (Eichhornia crassipes) as biochar for
6
adsorption of trivalent chromium ion. The prepared biochar has been characterized by Fourier
7
transforms infrared spectroscopy (FTIR) before and after the experiment. The trivalent chromium ion
8
adsorption efficacy on biochar was investigated considering parameters e.g., adsorbent dose,
9
interaction time, and relative pH. In the batch-wise treatment process, 70 mL chromium loaded
10
tannery wastewater was treated with prepared biochar as adsorbent, shaken for a fixed period, rested,
11
and the chromium, as well as pollution load, was measured. Chromium content in the untreated
12
wastewater and treated wastewater at optimized conditions was 3190.1 and 27.3 mg/L, respectively.
13
The chromium ion adsorption on biochar was 99%. The chloride, biochemical oxygen demand
14
(BOD), and chemical oxygen demand (COD) reduction were by 56%, 93.4%, and 92.6%,
15
respectively. The use of aquatic weed Eichhornia crassipes as biochar could be a novel economical
16
alternative to adsorb trivalent chromium ion from the tannery wastewater.
17 18
Keywords: Chromium; Biochar; Tannery; Biochemical Oxygen Demand; Chemical Oxygen Demand
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
1
37
1. Introduction
38
Conserving the environment has become a major critical issue in developing the industrial sector. The
39
abundant biomass available in the environment is being tried to utilize in producing the value-added
40
product or as remediation. The water hyacinth (Eichhornia crassipes) is a floating aquatic weed
41
abundantly available in the tropical and sub-tropical areas growing on the water surface. Recently,
42
hyacinth has been listed as one of the 100 most intrusive exotic species in the world (Jafari, 2010).
43
The water hyacinth germinates during the summer season and the hibernation time of the seeds are up
44
to 20 years (Lubovich, 2009). Studies show that hyacinth diffusion requires a 12-day time period to
45
reproduce the population with an 8% increase (APIRIS, 2005). In most tropical and sub-tropical
46
countries, the infestation of Eichhornia crassipes is a serious problem due to their rapid adaptability
47
(Van Driesche et al. 2002). This huge biomass obstructs the surface water flow, hydraulic turbine and
48
irrigation channel.
49
Chromium is discharged into the aquatic environment from anthropogenic sources like tannery
50
industries, metal finishing industries, electroplating, and so on. The contamination of water, soil or
51
sediment with chromium is a major significant concern for the environment because of the possibility
52
of entering into the food chain.
53
Tanning agent, basic chromium sulfate is used by 90% tanning industries (Arabindha et al. 2004)
54
where only 60% chromium penetrates the pickled pelt and the rest of the 40% chromium is discharged
55
with the wastewater (Fabiani et al. 1997). Hashem et al. (2015) showed that the amount of chromium
56
in the discharged chrome tanning wastewater ranged between 2656-5420 mg/L. The universal
57
oxidative states of chromium are trivalent and hexavalent. Levis et al. (1978) reported that within the
58
cell Cr(III) unites to nucleotide bases in DNA to provide genotoxic effects. A group of researchers (El-
59
Shahawi et al. 2008) showed the kinetic transformation of chromium from trivalent to hexavalent is
60
fast even in the presence of mild oxidants. Hexavalent chromium, Cr(VI) is extremely virulent and
61
may cause contact dermatitis on the skin and act as a trigger for many ailments (Bulut et al. 2009).
62
Several types of research have been tried to remove hexavalent chromium using Annona reticulate
63
Linn peel microparticles (Saranya et al. 2017), mixed-culture of bacteria (Molokwane et al. 2008),
64
metal oxide photocatalysts (Cheng et al. 2015) and some studies like eggshell and powdered marble
65
(Elabbas et al. 2016), charcoal of bone (Dahbi et al. 2002), nano carbonate-hydroxylapatite (Tang et
66
al. 2013), three-phase three-dimensional electrode reactor (Grace Pavithra et al. 2017), nano spherical
67
shell necklaces (Azzam et al. 2017) have been carried out as an attempt to remove Cr(III) from
68
aqueous solution. Most of these techniques are developed for homogenous tannery wastewater
69
treatment and rather complex procedures for industrial applications.
70
In many countries, chromium content in the spent chrome is strictly regulated e.g., the discharge level
71
of chromium is 2 mg/L for Bangladesh (ECR 1997). Therefore, chromium removal from various
72
industrial wastewater especially tannery wastewater is an important issue for environmental
73
protection. 2
74
Recently, the application of a biological substance to remove metal especially heavy metals from the
75
contaminated wastewater has become a popular emerging technique. In this technique, biomass
76
accumulates heavy metals from the wastewater through the physicochemical pathway (Hossain et al.
77
2012). Prabu et al. (2012) stated that the adsorption process has some benefits: i) a substantial amount
78
of energy saving, ii) short time process, iii) inexpensive, and iv) available widely. However, in the
79
adsorption process, some essential parameters have to be controlled.
80
The water hyacinth has been tried for biogas (Barua and Kalamdhad, 2019), biodiesel (Alagu et al.
81
2019), removal of Cr(III) (Kelley et al. 2000) and so on. But it has yet to try in tannery wastewater as
82
an adsorbent. Considering the availability of the hyacinth in Bangladesh, water hyacinth could be an
83
economical adsorbent to utilize in over 187 tanneries (EPB, 2014) in Bangladesh.
84
This investigation studied the effectiveness of Eichhornia crassipes biochar to remove pollution from
85
tannery wastewater, especially chromium, without any conditioning. Several parameters like
86
adsorbent load, interaction time, and relative pH were studied with the kinetics and thermodynamic
87
study of the process.
88 89
2. Materials and Methodology
90
2.1 Wastewater collection
91
Chromium-containing wastewater was collected from the SAF Leather Industries Ltd., Jessore,
92
Bangladesh. The wastewater was collected into a polyethylene container, pre-washed with diluted
93
nitric acid, and immediately transported to the laboratory for the experiment.
94 95
2.2 Adsorbent preparation
96
Green Eichhornia crassipes was collected from a nearby pond of the university campus, Khulna
97
University of Engineering & Technology, Khulna, Bangladesh. The root of the Eichhornia
98
crassipes was removed and the forepart was dried at the open air. Dried Eichhornia crassipes was
99
burnt at 475-500°C assuring an inert environment in a muffle furnace for 2 h. The burnt Eichhornia
100
crassipes was cooled in desiccator, ground, sieved with 80-mesh and stored for further experiment.
101 102
2.3 Reagents
103
The required reagents perchloric acid (HClO4) (Merck, India), concentrated nitric acid (HNO3)
104
(Merck KGaA, Germany), sulphuric acid (H2SO4) (Merck KGaA, Germany), glass beads (Loba
105
Chemie, India), ferrous-ammonium sulfate (Merck, India), N-phynylanthralinic acid (Merck, India)
106
were obtained from local scientific store, Khulna, Bangladesh.
107 108
2.4 FTIR study of adsorbent
109
The Fourier transform infrared spectroscopy (FTIR) study of pure adsorbent and chromium-loaded
110
adsorbent was carried out to find the relative functional group from the adsorption spectrum. The 3
111
Fourier transform infrared spectrometer (FTIR 1600, Perkin-Elmer) data spectrum was recorded
112
between 400 and 4000 cm–1 wavelength.
113 114
2.5 Laboratory analysis
115
The physicochemical analysis of wastewater was carried out regarding pH, electrical conductivity
116
(EC), chloride content, salinity, total dissolved solids (TDS), biochemical oxygen demand for 5 days
117
(BOD5), chemical oxygen demand (COD) and total suspended solids (TSS). The pH was determined
118
by using the calibrated pH meter (UPH-314, UNILAB, USA). The TS, TSS, and TDS of the initial
119
and treated wastewater were carried out following APHA-2540 D method. The EC and salinity of the
120
were measured with the conductivity meter (CT-676, BOECO, Germany). The BOD5 and COD values
121
were determined following the APHA standard method 5210 B and 5220 C (APHA 2012),
122
respectively. Chloride content was determined following the Mohr method. Triplicate measurement
123
was done for each analysis/measurement.
124 125
2.6 Chromium determination
126
The official analytical methods of the Society of Leather Technologist and Chemists (SLTC 1996)
127
was followed for chromium (Cr) determination. A 25 mL sample was taken in an Erlenmeyer flask
128
(250 mL) and mixed with HNO3 (15 mL) followed by HClO4/H2SO4 mixture (15 mL). Then, the
129
mixture was gently boiled until a pure orange-red colour; boiling was continued for one more minute.
130
After that, the flask was removed from the heating source and rapidly cooled by whirling in a cold
131
water bath. Subsequently, 75 mL distilled water was carefully added with a few glass beads (anti-
132
bumping granules) and boiled for 10 min to remove any presence of free chlorine. Slowly, 10 mL
133
30% H2SO4 was added and the mixture was cooled at 20°C. The solution was titrated with freshly
134
prepared 0.1N ferrous ammonium sulfate where N-phenyl anthranilic acid was used as an indicator.
135
The end colour was indicated by a colour change from the violet to green. Finally, the Cr was
136
calculated.
137 138
2.7 Treatment of spent chrome wastewater
139
The treatment of chromium wastewater by Eichhornia crassipes biochar was performed by following
140
the batch operation starting with the raw wastewater filtered through the filter paper (0.45 µm pore
141
size). Then, 70 mL permeate liquor was added with Eichhornia crassipes biochar; stirred for a fixed
142
period and allowed for settling. After settlement, the mixture was filtered through a filter paper (0.45
143
µm pore size) and chromium content measurement was performed following the official methods of
144
SLTC 1996. The schematic flow diagram is shown in Fig. 1.
145 146
2.7.1 Optimization process
4
147
The maximum removal efficiency was found from the optimization of the treatment process. The
148
batch-wise test was made on the chromium removal parameters: adsorbent load, relative pH, and
149
interaction time. The parameters were optimized examining chromium removal efficiency.
150 151
2.8 Kinetics analysis
152
Adsorption kinetics causes the adsorption process rate. Adsorption mechanism depends on the
153
physicochemical properties of adsorbent. Pseudo-first-order, as well as the pseudo-second-order
154
adsorption kinetics model was considered. Pseudo-first order model can be written as:
ln(Qe − Q t ) = lnQe − K1t...(i)
155 156
Equation (i) can be expressed by rearranging ln
157
Qe − Qt = − K 1 t...(ii) Qe
158
At equilibrium condition in the pseudo-first-order kinetics, Qe is the adsorbent quantity (mg/g) at time
159
t (min) with the equilibrium constant K1 (min-1).
160
The pseudo-second-order model was analyzed based on the following equation (iii): t
161
Qt
162
=
1 K 2Qe 2
+
t Qe
...(iii)
By rearranging the equation (iii) can be written Qt
163
Qe − Q t
= K 2Q e t...(iv)
164
In the equation (iv), K2 is the equilibrium constant for per mg adsorbent per min of time (t).
165
2.9 Isotherm analysis
166
The interaction of adsorbent with the adsorbate is termed as adsorption isotherm. It is a key parameter
167
to determine the adsorbent efficiency and enhancing adsorbent consumption. In this report, Langmuir
168
and Freundlich isotherm to analyze the adsorbent characteristics of Eichhornia crassipes biochar.
169
Langmuir model estimates the adsorption onto the solid surface uniformly. Also, it gives unitary layer
170
adsorption in the analogous sites and the homogenous structure of adsorbent (Gimbert et al. 2008).
171
Langmuir isotherm implies the following equation:
172
173
Qe =
Q m K LCe 1 + K LCe
By rearranging the equation (v) can be written: 5
...(v)
1
174
Qe
=
1 Ce
×
1 Qm K L
+
1 Qm
...(vi)
175
In the equation (vi), at an equilibrium condition adsorbed chromium content in the unit of mg/g is Qe
176
and Ce is the mg amount of chromium in per liter of solution. The maximum adsorption capacity of
177
biochar is symbolized by Qm (mg/g) and Langmuir constant, KL (L/g) which is associated with the
178
free energy of adsorption. Also, the data were investigated with the Freundlich isotherm model. The
179
logarithmic equation of Freundlich isotherm can be stated as: 1 n
Q e = K f Ce ...(vii)
180 181
Equation (vii) can be written as: lnQe = ln K f +
182
1 n
lnCe ...(viii)
183
In the equation (viii), Kf is the Freundlich adsorption constant, which shows the adsorption capacity of
184
Eichhornia crassipes biochar, and the relation between the adsorbate and adsorbent is represented by
185
constant n.
186 187
3. Results and Discussion
188
3.1 FTIR analysis
189
Fig. 2 represents the FTIR analysis of the pure and Cr loaded biochar dictating a fluctuation of the
190
peak intensity. The shift indicates the alteration of frequency in the functional groups of the biochar
191
due to the adsorption of chromium. A significant band shift in the region of 500 to 1500 cm-1 is due to
192
hydroxyl groups of phenols present on the adsorbent surface (Saranya et al. 2017). The wavelength
193
was shifted from around 1600 cm-1 to 1787 cm-1 due to the N-H bending vibration of amide groups.
194
The distinctive band of C–N was shifted at the peak maximum 1184 to 1205 cm-1 showing its
195
involvement in adsorption. The strong, sharp change in intensity from 3500-3700 cm-1 region
196
indicates the involvement of O-H stretching vibration. The disappearance of the peak at 1828 cm-1 is
197
due to the adsorption of Cr(III) by stretching of C=O functional group. The analysis indicates various
198
responsible functional groups e.g., O-H, C=O, N-H for the adsorption of chromium by Eichhornia
199
crassipes biochar.
200 201
3.2 Adsorbent dose and solution pH
202
Adsorbent dose and pH are the most critical factors that have a substantial effect on the chromium
203
eradication in the treatment procedure. The effect of adsorbent dose and solution pH fluctuation on
204
chromium removal efficiency are depicted in Fig. 3 and Fig. 4 respectively. In real chrome tanning
205
wastewater, initial chromium concentration was 3190.1 mg/L. The number of adsorbent dose (1 g to 5 6
206
g per 70 mL wastewater) and 15 min were kept constant for interaction time. Fig. 3 implies that with
207
increasing the adsorbent dose chromium adsorption efficiency was increased. The chromium removal
208
efficiency was 99% at an adsorbent dose of 4 g for 70 mL of wastewater. Subsequently, the chromium
209
adsorption capacity was somewhat increased with increasing the adsorbent dose.
210
Fig. 4 expresses the effect of solution pH on chromium removal efficiency. It can be seen that the
211
removal efficiency was increased with increasing the solution pH up to pH 7.7. There was a negligible
212
change in chromium removal efficiency up to pH 8.3. After that, the system was reached an
213
equilibrium condition. During adsorption of chromium on biochar, pH is accountable for the
214
promotion of the metal-binding site, especially chromium. Chonjacka (2005) showed that at higher
215
pH the hydrolysis adsorption occurs and chromium is precipitated as insoluble colloidal chromium
216
hydroxide. Supporting this remark, the experiment also showed that at higher pH, chromium removal
217
was more than it was at lower pH. Therefore, it was projected that at 4 g adsorbent dose for 70 mL
218
wastewater, maximum chromium was removed with the relative pH 8.2. It also explained that
219
Eichhornia crassipes biochar was an action of solution pH.
220 221
3.3 Interaction time
222
Interaction time is another essential parameter for chromium adsorption. Fig. 5 depicts the chromium
223
removal efficiency on interaction time. Batch wise treatment of chromium removal efficacy for 5, 10
224
and 15 min was 98.5%, 99.8%, and 99.8%, respectively and at 20 and 25 min, the removal efficiency
225
was unchanged. The metal adsorption achieved with long time duration and higher chance to form
226
metal hydroxide especially, chromium hydroxide. Fig. 5 implies that chromium adsorption capacity
227
was enhanced with the increasing contact time. It appears that after a period of time e.g., 10 min,
228
chromium adsorption reached a steady-state (99.8%). Afterwards, the chromium adsorption capacity
229
was removal efficiency was constant. Hence, it was assumed that the maximal chromium adsorption
230
occurred at 10 min.
231 232
3.4 Treatment process efficiency
233
The results of the investigation at optimized conditions represent in Table 1. After all stages of
234
treatments, the obtained physicochemical parameters pH, TDS, EC, salinity, chromium, BOD, COD,
235
and chloride were 8.3, 48.9 g/L, 80.5 mS, 50.0 ppt, 27.33 mg/L, 239 mg/L, 387 mg/L, and 8366.6
236
mg/L, respectively. The maximum chrome removal efficiency was 99.14%. The pH seemed within
237
the discharge level after treatment although other parameters e.g. TDS, EC, and salinity were
238
somewhat bigger. The chloride, BOD, and COD reduction were 56%, 93.4%, and 92.6%,
239
respectively.
240
The comparison with the previous studies is depicted in Table 2. In this present study, comparatively
241
less interaction time was required than previous studies to obtain maximum chromium removal
7
242
efficiency. The Eichhornia crassipes biochar is a better choice for pollution removal from tannery
243
wastewater.
244 245
3.5 Adsorption kinetics analysis
246
Fig. 6 represents the pseudo-first-order and pseudo-second-order adsorption kinetics with their
247
correlation coefficient values (R12= 0.9273, R22=0.8242). It suggests that the pseudo-first-order
248
kinetics can explain the adsorption of chromium ion on biochar, as the graph of ln{(Qe-Qt)/Qe,} vs.
249
time t shows a good linear fit (R12= 0.9273) as illustrated in Fig. 6(a). Whereas pseudo-second-order
250
cannot describe a good linear fit (R22=0.8242) as interpreted in Fig. 6(b). The pseudo-first-order
251
equation suggested that the adsorption method follows first-order adsorption kinetic. The ratio of
252
adsorption is related to the number of unoccupied sites of biochar. The range of slope is a measure of
253
adsorption intensity between zero (0) and one (1) which indicates more heterogeneous character as its
254
value gets closer to zero.
255 256
3.6 Adsorption Isotherm analysis
257
Fig. 7(a) and 7(b) show that the obtained correlation coefficient values were R12=0.9159 and
258
R22=0.9784, respectively. These values indicate that Freundlich isotherm is more suitable than
259
Langmuir for chromium adsorption by Eichhornia crassipes biochar from tannery wastewater. The
260
value of 1/n from the Freundlich model was 3.15>1, which specifies the favourable adsorption
261
conditions for Eichhornia crassipes biochar and adsorption will physical process at multi-layer
262
adsorption on the heterogeneous surface.
263 264
3.7 Adsorbent selection
265
According to Barrett (Barrett, 1989), 25 plants of water hyacinth can cover 10,000 m2 of water surface
266
during the growing season with about two million which weighs almost like a fully loaded jumbo jet.
267
In enclosed or slow current water, colonies can amalgamate to form two-meter thick of continuous
268
mats of living and decaying organic material. The mats of water hyacinth fill reservoirs, spoiling
269
water resources, infest rivers, dam drainage channels. The mats indirectly deplete the water supply’s
270
dissolved oxygen, thereby asphyxiating fish and phytoplankton.
271
The huge growth rate of water hyacinth causes a problem for the water surface which ensures its
272
availability for biochar production. Moreover, the utilization of water hyacinth will reduce the
273
problems and ensure clean water body.
274 275
4. Conclusions
276
The full body of the wasteful aquatic weed, Eichhornia crassipes was utilized to produced biochar. In
277
a batch-wise laboratory experiment, chrome tanning wastewater was treated with hyacinth biochar to
278
remove chromium from chrome tanning wastewater through adsorption. The removal efficiency of 8
279
chromium found at an optimized condition was 99%. The reduction of chloride, BOD, and COD were
280
56%, 93.4% and 92.6%, respectively although other parameters were slightly increased. The
281
investigation directs that Eichornia crassipes biochar gives a promising result as an effective
282
adsorbent to remove chromium that will minimize pollution load from the tannery industry. The study
283
could be a better option to utilize Eichornia crassipes biochar for treatment of spent chrome liquor in
284
the house prior to discharge.
285 286
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by discharging of high-chromium-containing wastewater from the tanneries at Hazaribagh,
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20. Heraldy, E., Wireni, & Lestari, W. W. (2016). Biosorption of Cu(II) ions by cellulose of cabbage
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biosorbent
from
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agricultural
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21. Jafari, N. (2010). Ecological and socio-economic utilization of water hyacinth (Eichhornia
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49. http://dx.doi.org/10.4314/jasem.v14i2.57834
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22. Kelley, C., Mielke, R. E., Dimaquibo, D., Curtis, A. J., & DeWitt, J. G. (1999). Adsorption of
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Eu(III) onto Roots of Water Hyacinth. Environmental Science & Technology, 33(9), 1439-1443.
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https://doi.org/10.1021/es9807789
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23. Levis, A. G., Bianchi, V., Tamino, G., & Pegoraro, B. (1978). Cytotoxic Effects of Hexavalent
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and Trivalent Chromium on Mammalian Cells In Vitro. British Journal of Cancer, 37(3), 386-
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396. doi: 10.1038/bjc.1978.58
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24. Lubovich, K. (2009). Cooperation and competition: managing transboundary water resources in
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the Lake Victoria Region. FESS Working Paper No. 5. Foundation for Environmental Security
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and Sustainability, Falls Church, Virginia, 5, 1-28.
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25. Molokwane, P. E., Meli, C. K., & Chirwa, E. M. N. (2008). Chromium (VI) reduction in activated
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sludge bacteria exposed to high chromium loading. Water Science and Technology, 58(2), 399-
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405. doi:10.2166/wst.2008.669
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26. Prabu, K., Shankarlal, S., Natarajan, E. (2012). A Biosorption of Heavy Metal Ions from Aqueous
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Solutions Using Fish Scale (Catlacatla). World Journal of Fish and Marine Sciences, 4, 73-77.
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doi: 10.5829/idosi.wjfms.2012.04.01.56237
365
27. Saranya, N., Nakeeran, E., Giri Nandagopal, M. S., & Selvaraju, N. (2017). Optimization of
366
adsorption process parameters by response surface methodology for hexavalent chromium
367
removal from aqueous solutions using Annona reticulate Linn peel microparticles. Water Science
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and Technology, 75(9), 2094-2107. doi: 10.2166/wst.2017.092.
369 370
28. SLTC, Society of Leather Technologist and Chemists. (1996). Official Methods of Analysis. Northampton, UK.
371
29. Tang, W. Q., Zeng, R.-Y., Feng, Y.-L., Li, X.-M., & Zhen, W. (2013). Removal of Cr(VI) from
372
aqueous solution by nano-carbonate hydroxylapatite of different Ca/P molar ratios. Chemical
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Engineering Journal, 223, 340-346. https://doi.org/10.1016/j.cej.2013.02.094
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30. Van Driesche, R., Blossey, B., Hoddle, M., Lyon, S., & Reardon, R. (2002). Biological Control
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of Invasive Plants in the Eastern United States. USDA Forest Service Publication FHTET-2002-
376
04.
377
Accessed 24 October 2019.
https://www.fs.fed.us/foresthealth/technology/pdfs/BiocontrolsOfInvasivePlants02_04.pdf
11
Table Table I. Data comparison between raw sample and treated sample
Table I. Data comparison between raw sample and treated sample Parameters Raw sample This study MoEF (1997) Unit pH 3.6±0.3 8.3±0.1 6–9 TDS 44.3±0.6 48.9±0.2 2100 g/L EC 73.7±0.7 80.5±0.4 1.20 mS Salinity 44.9±0.5 50.0±0.6 – ppt Cr 3190.12±0.7 27.33±0.4 2.0 mg/L Chloride 19015±0.4 8366.6±0.2 600 mg/L BOD 3621±34 239±19.3 250 mg/L COD 5213±43 387±7.2 400 mg/L
20
Table II. Comparison with the previous study Table II. Comparison with the previous study Previous study Cr removal (%) Dahbi et al. 2002 90 Aravindhan et al. 2004 83 Elabbas et al. 2015 99 Elabbas et al. 2015 99 This study 99
21
Interaction time 30 min 6h 840 min 30 min 15 min
Figure Captions Fig. 1 Schematic diagram for the chromium removal treatment process Fig. 2 FT-IR spectrum of pure water hyacinth biochar and chromium loaded biochar Fig. 3 Batch wise chromium removal efficiency with different adsorbent dose: 1 g, 2 g, 3 g, 4 g, and 5 g; each batch 70 mL wastewater with 15 min interaction time Fig. 4 Batch wise chromium removal efficiency at different solution pH Fig. 5 Batch wise chromium removal efficiency on different interaction time: 5, 10, 15, 20, and 25 min; each batch 70 mL wastewater with 4 g charcoal Fig. 6 Pseudo-first-order (a) and pseudo-second- order (b) kinetics of adsorption Fig. 7 Linearized adsorption isotherms Langmuir (a) and Freundlich (b)
12
Figure 1
Wastewater collection Physicochemical analysis and filtration Filtrate mixed with prepared biochar Stirring and allowed for settling Filtration and physicochemical analysis
13
Figure 2
80
Transmittance (%)
75
70
65 Pure biochar Cr-loaded biochar
60 4000 3600 3200 2800 2400 2000 1600 1200 800 -1
Wavenumber (cm )
14
400
Figure 3
Chromium removal (%)
100
80
60
40
20
0 1
2
3
4
Adsorbent dose (g/70 mL wastewater)
15
5
Figure 4
Chromium removal (%)
100
80
60
40
20
0 5.9
6.2
6.5
6.8
7.1
7.4
Solution pH
16
7.7
8.0
8.3
Figure 5
Chromium removal (%)
100
98
96
94
92
90 5
10
15
20
Interaction time (min)
17
25
Figure 6
-4.8
1st Order
(a)
-5.6 y=-0.0534x-5.3314 ln{(Qe-Qt)/Qe}
2
R1 =0.9273 -6.4
-7.2
-8.0
-8.8 0
6
12
18
24
30
36
42
48
54
60
Contact time (min)
20
2nd Order
(b)
16
{Qt/(Qe-Qt)}
y=-0.2896x+16.3807 2
R2 =0.8242
12 8 4 0 0
10
20
30
40
Contact time (min)
18
50
60
Figure 7
10
Freunlich
(a)
8
y=1.9327x+2.6723 2
lnQe
R2 =0.9784 6
4
2 0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
lnCe
1.5
Langmuir
(b)
y=759.2664x-0.4211
1.2
2
R1 =0.9187
1/Qe
0.9 0.6 0.3 0.0 0.0004
0.0008
0.0012 1/Ce
19
0.0016
0.0020
0.0024
S2665-9727(20)30004-0
DOI:
https://doi.org/10.1016/j.indic.2020.100022
Reference:
INDIC 100022
To appear in:
Environmental and Sustainability Indicators
Received Date: 8 November 2019 Revised Date:
6 January 2020
Accepted Date: 15 January 2020
Please cite this article as: Hashem, M.A., Hasan, M., Momen, M.A., Payel, S., Nur-A-Tomal, M.S., Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater, Environmental and Sustainability Indicators, https://doi.org/10.1016/j.indic.2020.100022. This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. © 2020 The Author(s). Published by Elsevier Inc.
Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater Md. Abul Hashem*, Mehedi Hasan, Md. Abdul Momen, Sofia Payel, Md. Sharuk Nur-A-Tomal Department of Leather Engineering, Khulna University of Engineering & Technology (KUET), Khulna-9203, Bangladesh
Corresponding author
: Dr. Md. Abul Hashem Associate Professor Department of Leather engineering Khulna University of Engineering & Technology Khulna-9203, Bangladesh Tel.: +88 041 774344; Fax: +88 041 774403 E-mail address: [email protected], [email protected]
1
Water hyacinth biochar for trivalent chromium adsorption from tannery wastewater
1 2 3 4
Abstract
5
This investigation studied the utilization of water hyacinth (Eichhornia crassipes) as biochar for
6
adsorption of trivalent chromium ion. The prepared biochar has been characterized by Fourier
7
transforms infrared spectroscopy (FTIR) before and after the experiment. The trivalent chromium ion
8
adsorption efficacy on biochar was investigated considering parameters e.g., adsorbent dose,
9
interaction time, and relative pH. In the batch-wise treatment process, 70 mL chromium loaded
10
tannery wastewater was treated with prepared biochar as adsorbent, shaken for a fixed period, rested,
11
and the chromium, as well as pollution load, was measured. Chromium content in the untreated
12
wastewater and treated wastewater at optimized conditions was 3190.1 and 27.3 mg/L, respectively.
13
The chromium ion adsorption on biochar was 99%. The chloride, biochemical oxygen demand
14
(BOD), and chemical oxygen demand (COD) reduction were by 56%, 93.4%, and 92.6%,
15
respectively. The use of aquatic weed Eichhornia crassipes as biochar could be a novel economical
16
alternative to adsorb trivalent chromium ion from the tannery wastewater.
17 18
Keywords: Chromium; Biochar; Tannery; Biochemical Oxygen Demand; Chemical Oxygen Demand
19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36
1
37
1. Introduction
38
Conserving the environment has become a major critical issue in developing the industrial sector. The
39
abundant biomass available in the environment is being tried to utilize in producing the value-added
40
product or as remediation. The water hyacinth (Eichhornia crassipes) is a floating aquatic weed
41
abundantly available in the tropical and sub-tropical areas growing on the water surface. Recently,
42
hyacinth has been listed as one of the 100 most intrusive exotic species in the world (Jafari, 2010).
43
The water hyacinth germinates during the summer season and the hibernation time of the seeds are up
44
to 20 years (Lubovich, 2009). Studies show that hyacinth diffusion requires a 12-day time period to
45
reproduce the population with an 8% increase (APIRIS, 2005). In most tropical and sub-tropical
46
countries, the infestation of Eichhornia crassipes is a serious problem due to their rapid adaptability
47
(Van Driesche et al. 2002). This huge biomass obstructs the surface water flow, hydraulic turbine and
48
irrigation channel.
49
Chromium is discharged into the aquatic environment from anthropogenic sources like tannery
50
industries, metal finishing industries, electroplating, and so on. The contamination of water, soil or
51
sediment with chromium is a major significant concern for the environment because of the possibility
52
of entering into the food chain.
53
Tanning agent, basic chromium sulfate is used by 90% tanning industries (Arabindha et al. 2004)
54
where only 60% chromium penetrates the pickled pelt and the rest of the 40% chromium is discharged
55
with the wastewater (Fabiani et al. 1997). Hashem et al. (2015) showed that the amount of chromium
56
in the discharged chrome tanning wastewater ranged between 2656-5420 mg/L. The universal
57
oxidative states of chromium are trivalent and hexavalent. Levis et al. (1978) reported that within the
58
cell Cr(III) unites to nucleotide bases in DNA to provide genotoxic effects. A group of researchers (El-
59
Shahawi et al. 2008) showed the kinetic transformation of chromium from trivalent to hexavalent is
60
fast even in the presence of mild oxidants. Hexavalent chromium, Cr(VI) is extremely virulent and
61
may cause contact dermatitis on the skin and act as a trigger for many ailments (Bulut et al. 2009).
62
Several types of research have been tried to remove hexavalent chromium using Annona reticulate
63
Linn peel microparticles (Saranya et al. 2017), mixed-culture of bacteria (Molokwane et al. 2008),
64
metal oxide photocatalysts (Cheng et al. 2015) and some studies like eggshell and powdered marble
65
(Elabbas et al. 2016), charcoal of bone (Dahbi et al. 2002), nano carbonate-hydroxylapatite (Tang et
66
al. 2013), three-phase three-dimensional electrode reactor (Grace Pavithra et al. 2017), nano spherical
67
shell necklaces (Azzam et al. 2017) have been carried out as an attempt to remove Cr(III) from
68
aqueous solution. Most of these techniques are developed for homogenous tannery wastewater
69
treatment and rather complex procedures for industrial applications.
70
In many countries, chromium content in the spent chrome is strictly regulated e.g., the discharge level
71
of chromium is 2 mg/L for Bangladesh (ECR 1997). Therefore, chromium removal from various
72
industrial wastewater especially tannery wastewater is an important issue for environmental
73
protection. 2
74
Recently, the application of a biological substance to remove metal especially heavy metals from the
75
contaminated wastewater has become a popular emerging technique. In this technique, biomass
76
accumulates heavy metals from the wastewater through the physicochemical pathway (Hossain et al.
77
2012). Prabu et al. (2012) stated that the adsorption process has some benefits: i) a substantial amount
78
of energy saving, ii) short time process, iii) inexpensive, and iv) available widely. However, in the
79
adsorption process, some essential parameters have to be controlled.
80
The water hyacinth has been tried for biogas (Barua and Kalamdhad, 2019), biodiesel (Alagu et al.
81
2019), removal of Cr(III) (Kelley et al. 2000) and so on. But it has yet to try in tannery wastewater as
82
an adsorbent. Considering the availability of the hyacinth in Bangladesh, water hyacinth could be an
83
economical adsorbent to utilize in over 187 tanneries (EPB, 2014) in Bangladesh.
84
This investigation studied the effectiveness of Eichhornia crassipes biochar to remove pollution from
85
tannery wastewater, especially chromium, without any conditioning. Several parameters like
86
adsorbent load, interaction time, and relative pH were studied with the kinetics and thermodynamic
87
study of the process.
88 89
2. Materials and Methodology
90
2.1 Wastewater collection
91
Chromium-containing wastewater was collected from the SAF Leather Industries Ltd., Jessore,
92
Bangladesh. The wastewater was collected into a polyethylene container, pre-washed with diluted
93
nitric acid, and immediately transported to the laboratory for the experiment.
94 95
2.2 Adsorbent preparation
96
Green Eichhornia crassipes was collected from a nearby pond of the university campus, Khulna
97
University of Engineering & Technology, Khulna, Bangladesh. The root of the Eichhornia
98
crassipes was removed and the forepart was dried at the open air. Dried Eichhornia crassipes was
99
burnt at 475-500°C assuring an inert environment in a muffle furnace for 2 h. The burnt Eichhornia
100
crassipes was cooled in desiccator, ground, sieved with 80-mesh and stored for further experiment.
101 102
2.3 Reagents
103
The required reagents perchloric acid (HClO4) (Merck, India), concentrated nitric acid (HNO3)
104
(Merck KGaA, Germany), sulphuric acid (H2SO4) (Merck KGaA, Germany), glass beads (Loba
105
Chemie, India), ferrous-ammonium sulfate (Merck, India), N-phynylanthralinic acid (Merck, India)
106
were obtained from local scientific store, Khulna, Bangladesh.
107 108
2.4 FTIR study of adsorbent
109
The Fourier transform infrared spectroscopy (FTIR) study of pure adsorbent and chromium-loaded
110
adsorbent was carried out to find the relative functional group from the adsorption spectrum. The 3
111
Fourier transform infrared spectrometer (FTIR 1600, Perkin-Elmer) data spectrum was recorded
112
between 400 and 4000 cm–1 wavelength.
113 114
2.5 Laboratory analysis
115
The physicochemical analysis of wastewater was carried out regarding pH, electrical conductivity
116
(EC), chloride content, salinity, total dissolved solids (TDS), biochemical oxygen demand for 5 days
117
(BOD5), chemical oxygen demand (COD) and total suspended solids (TSS). The pH was determined
118
by using the calibrated pH meter (UPH-314, UNILAB, USA). The TS, TSS, and TDS of the initial
119
and treated wastewater were carried out following APHA-2540 D method. The EC and salinity of the
120
were measured with the conductivity meter (CT-676, BOECO, Germany). The BOD5 and COD values
121
were determined following the APHA standard method 5210 B and 5220 C (APHA 2012),
122
respectively. Chloride content was determined following the Mohr method. Triplicate measurement
123
was done for each analysis/measurement.
124 125
2.6 Chromium determination
126
The official analytical methods of the Society of Leather Technologist and Chemists (SLTC 1996)
127
was followed for chromium (Cr) determination. A 25 mL sample was taken in an Erlenmeyer flask
128
(250 mL) and mixed with HNO3 (15 mL) followed by HClO4/H2SO4 mixture (15 mL). Then, the
129
mixture was gently boiled until a pure orange-red colour; boiling was continued for one more minute.
130
After that, the flask was removed from the heating source and rapidly cooled by whirling in a cold
131
water bath. Subsequently, 75 mL distilled water was carefully added with a few glass beads (anti-
132
bumping granules) and boiled for 10 min to remove any presence of free chlorine. Slowly, 10 mL
133
30% H2SO4 was added and the mixture was cooled at 20°C. The solution was titrated with freshly
134
prepared 0.1N ferrous ammonium sulfate where N-phenyl anthranilic acid was used as an indicator.
135
The end colour was indicated by a colour change from the violet to green. Finally, the Cr was
136
calculated.
137 138
2.7 Treatment of spent chrome wastewater
139
The treatment of chromium wastewater by Eichhornia crassipes biochar was performed by following
140
the batch operation starting with the raw wastewater filtered through the filter paper (0.45 µm pore
141
size). Then, 70 mL permeate liquor was added with Eichhornia crassipes biochar; stirred for a fixed
142
period and allowed for settling. After settlement, the mixture was filtered through a filter paper (0.45
143
µm pore size) and chromium content measurement was performed following the official methods of
144
SLTC 1996. The schematic flow diagram is shown in Fig. 1.
145 146
2.7.1 Optimization process
4
147
The maximum removal efficiency was found from the optimization of the treatment process. The
148
batch-wise test was made on the chromium removal parameters: adsorbent load, relative pH, and
149
interaction time. The parameters were optimized examining chromium removal efficiency.
150 151
2.8 Kinetics analysis
152
Adsorption kinetics causes the adsorption process rate. Adsorption mechanism depends on the
153
physicochemical properties of adsorbent. Pseudo-first-order, as well as the pseudo-second-order
154
adsorption kinetics model was considered. Pseudo-first order model can be written as:
ln(Qe − Q t ) = lnQe − K1t...(i)
155 156
Equation (i) can be expressed by rearranging ln
157
Qe − Qt = − K 1 t...(ii) Qe
158
At equilibrium condition in the pseudo-first-order kinetics, Qe is the adsorbent quantity (mg/g) at time
159
t (min) with the equilibrium constant K1 (min-1).
160
The pseudo-second-order model was analyzed based on the following equation (iii): t
161
Qt
162
=
1 K 2Qe 2
+
t Qe
...(iii)
By rearranging the equation (iii) can be written Qt
163
Qe − Q t
= K 2Q e t...(iv)
164
In the equation (iv), K2 is the equilibrium constant for per mg adsorbent per min of time (t).
165
2.9 Isotherm analysis
166
The interaction of adsorbent with the adsorbate is termed as adsorption isotherm. It is a key parameter
167
to determine the adsorbent efficiency and enhancing adsorbent consumption. In this report, Langmuir
168
and Freundlich isotherm to analyze the adsorbent characteristics of Eichhornia crassipes biochar.
169
Langmuir model estimates the adsorption onto the solid surface uniformly. Also, it gives unitary layer
170
adsorption in the analogous sites and the homogenous structure of adsorbent (Gimbert et al. 2008).
171
Langmuir isotherm implies the following equation:
172
173
Qe =
Q m K LCe 1 + K LCe
By rearranging the equation (v) can be written: 5
...(v)
1
174
Qe
=
1 Ce
×
1 Qm K L
+
1 Qm
...(vi)
175
In the equation (vi), at an equilibrium condition adsorbed chromium content in the unit of mg/g is Qe
176
and Ce is the mg amount of chromium in per liter of solution. The maximum adsorption capacity of
177
biochar is symbolized by Qm (mg/g) and Langmuir constant, KL (L/g) which is associated with the
178
free energy of adsorption. Also, the data were investigated with the Freundlich isotherm model. The
179
logarithmic equation of Freundlich isotherm can be stated as: 1 n
Q e = K f Ce ...(vii)
180 181
Equation (vii) can be written as: lnQe = ln K f +
182
1 n
lnCe ...(viii)
183
In the equation (viii), Kf is the Freundlich adsorption constant, which shows the adsorption capacity of
184
Eichhornia crassipes biochar, and the relation between the adsorbate and adsorbent is represented by
185
constant n.
186 187
3. Results and Discussion
188
3.1 FTIR analysis
189
Fig. 2 represents the FTIR analysis of the pure and Cr loaded biochar dictating a fluctuation of the
190
peak intensity. The shift indicates the alteration of frequency in the functional groups of the biochar
191
due to the adsorption of chromium. A significant band shift in the region of 500 to 1500 cm-1 is due to
192
hydroxyl groups of phenols present on the adsorbent surface (Saranya et al. 2017). The wavelength
193
was shifted from around 1600 cm-1 to 1787 cm-1 due to the N-H bending vibration of amide groups.
194
The distinctive band of C–N was shifted at the peak maximum 1184 to 1205 cm-1 showing its
195
involvement in adsorption. The strong, sharp change in intensity from 3500-3700 cm-1 region
196
indicates the involvement of O-H stretching vibration. The disappearance of the peak at 1828 cm-1 is
197
due to the adsorption of Cr(III) by stretching of C=O functional group. The analysis indicates various
198
responsible functional groups e.g., O-H, C=O, N-H for the adsorption of chromium by Eichhornia
199
crassipes biochar.
200 201
3.2 Adsorbent dose and solution pH
202
Adsorbent dose and pH are the most critical factors that have a substantial effect on the chromium
203
eradication in the treatment procedure. The effect of adsorbent dose and solution pH fluctuation on
204
chromium removal efficiency are depicted in Fig. 3 and Fig. 4 respectively. In real chrome tanning
205
wastewater, initial chromium concentration was 3190.1 mg/L. The number of adsorbent dose (1 g to 5 6
206
g per 70 mL wastewater) and 15 min were kept constant for interaction time. Fig. 3 implies that with
207
increasing the adsorbent dose chromium adsorption efficiency was increased. The chromium removal
208
efficiency was 99% at an adsorbent dose of 4 g for 70 mL of wastewater. Subsequently, the chromium
209
adsorption capacity was somewhat increased with increasing the adsorbent dose.
210
Fig. 4 expresses the effect of solution pH on chromium removal efficiency. It can be seen that the
211
removal efficiency was increased with increasing the solution pH up to pH 7.7. There was a negligible
212
change in chromium removal efficiency up to pH 8.3. After that, the system was reached an
213
equilibrium condition. During adsorption of chromium on biochar, pH is accountable for the
214
promotion of the metal-binding site, especially chromium. Chonjacka (2005) showed that at higher
215
pH the hydrolysis adsorption occurs and chromium is precipitated as insoluble colloidal chromium
216
hydroxide. Supporting this remark, the experiment also showed that at higher pH, chromium removal
217
was more than it was at lower pH. Therefore, it was projected that at 4 g adsorbent dose for 70 mL
218
wastewater, maximum chromium was removed with the relative pH 8.2. It also explained that
219
Eichhornia crassipes biochar was an action of solution pH.
220 221
3.3 Interaction time
222
Interaction time is another essential parameter for chromium adsorption. Fig. 5 depicts the chromium
223
removal efficiency on interaction time. Batch wise treatment of chromium removal efficacy for 5, 10
224
and 15 min was 98.5%, 99.8%, and 99.8%, respectively and at 20 and 25 min, the removal efficiency
225
was unchanged. The metal adsorption achieved with long time duration and higher chance to form
226
metal hydroxide especially, chromium hydroxide. Fig. 5 implies that chromium adsorption capacity
227
was enhanced with the increasing contact time. It appears that after a period of time e.g., 10 min,
228
chromium adsorption reached a steady-state (99.8%). Afterwards, the chromium adsorption capacity
229
was removal efficiency was constant. Hence, it was assumed that the maximal chromium adsorption
230
occurred at 10 min.
231 232
3.4 Treatment process efficiency
233
The results of the investigation at optimized conditions represent in Table 1. After all stages of
234
treatments, the obtained physicochemical parameters pH, TDS, EC, salinity, chromium, BOD, COD,
235
and chloride were 8.3, 48.9 g/L, 80.5 mS, 50.0 ppt, 27.33 mg/L, 239 mg/L, 387 mg/L, and 8366.6
236
mg/L, respectively. The maximum chrome removal efficiency was 99.14%. The pH seemed within
237
the discharge level after treatment although other parameters e.g. TDS, EC, and salinity were
238
somewhat bigger. The chloride, BOD, and COD reduction were 56%, 93.4%, and 92.6%,
239
respectively.
240
The comparison with the previous studies is depicted in Table 2. In this present study, comparatively
241
less interaction time was required than previous studies to obtain maximum chromium removal
7
242
efficiency. The Eichhornia crassipes biochar is a better choice for pollution removal from tannery
243
wastewater.
244 245
3.5 Adsorption kinetics analysis
246
Fig. 6 represents the pseudo-first-order and pseudo-second-order adsorption kinetics with their
247
correlation coefficient values (R12= 0.9273, R22=0.8242). It suggests that the pseudo-first-order
248
kinetics can explain the adsorption of chromium ion on biochar, as the graph of ln{(Qe-Qt)/Qe,} vs.
249
time t shows a good linear fit (R12= 0.9273) as illustrated in Fig. 6(a). Whereas pseudo-second-order
250
cannot describe a good linear fit (R22=0.8242) as interpreted in Fig. 6(b). The pseudo-first-order
251
equation suggested that the adsorption method follows first-order adsorption kinetic. The ratio of
252
adsorption is related to the number of unoccupied sites of biochar. The range of slope is a measure of
253
adsorption intensity between zero (0) and one (1) which indicates more heterogeneous character as its
254
value gets closer to zero.
255 256
3.6 Adsorption Isotherm analysis
257
Fig. 7(a) and 7(b) show that the obtained correlation coefficient values were R12=0.9159 and
258
R22=0.9784, respectively. These values indicate that Freundlich isotherm is more suitable than
259
Langmuir for chromium adsorption by Eichhornia crassipes biochar from tannery wastewater. The
260
value of 1/n from the Freundlich model was 3.15>1, which specifies the favourable adsorption
261
conditions for Eichhornia crassipes biochar and adsorption will physical process at multi-layer
262
adsorption on the heterogeneous surface.
263 264
3.7 Adsorbent selection
265
According to Barrett (Barrett, 1989), 25 plants of water hyacinth can cover 10,000 m2 of water surface
266
during the growing season with about two million which weighs almost like a fully loaded jumbo jet.
267
In enclosed or slow current water, colonies can amalgamate to form two-meter thick of continuous
268
mats of living and decaying organic material. The mats of water hyacinth fill reservoirs, spoiling
269
water resources, infest rivers, dam drainage channels. The mats indirectly deplete the water supply’s
270
dissolved oxygen, thereby asphyxiating fish and phytoplankton.
271
The huge growth rate of water hyacinth causes a problem for the water surface which ensures its
272
availability for biochar production. Moreover, the utilization of water hyacinth will reduce the
273
problems and ensure clean water body.
274 275
4. Conclusions
276
The full body of the wasteful aquatic weed, Eichhornia crassipes was utilized to produced biochar. In
277
a batch-wise laboratory experiment, chrome tanning wastewater was treated with hyacinth biochar to
278
remove chromium from chrome tanning wastewater through adsorption. The removal efficiency of 8
279
chromium found at an optimized condition was 99%. The reduction of chloride, BOD, and COD were
280
56%, 93.4% and 92.6%, respectively although other parameters were slightly increased. The
281
investigation directs that Eichornia crassipes biochar gives a promising result as an effective
282
adsorbent to remove chromium that will minimize pollution load from the tannery industry. The study
283
could be a better option to utilize Eichornia crassipes biochar for treatment of spent chrome liquor in
284
the house prior to discharge.
285 286
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287
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11
Table Table I. Data comparison between raw sample and treated sample
Table I. Data comparison between raw sample and treated sample Parameters Raw sample This study MoEF (1997) Unit pH 3.6±0.3 8.3±0.1 6–9 TDS 44.3±0.6 48.9±0.2 2100 g/L EC 73.7±0.7 80.5±0.4 1.20 mS Salinity 44.9±0.5 50.0±0.6 – ppt Cr 3190.12±0.7 27.33±0.4 2.0 mg/L Chloride 19015±0.4 8366.6±0.2 600 mg/L BOD 3621±34 239±19.3 250 mg/L COD 5213±43 387±7.2 400 mg/L
20
Table II. Comparison with the previous study Table II. Comparison with the previous study Previous study Cr removal (%) Dahbi et al. 2002 90 Aravindhan et al. 2004 83 Elabbas et al. 2015 99 Elabbas et al. 2015 99 This study 99
21
Interaction time 30 min 6h 840 min 30 min 15 min
Figure Captions Fig. 1 Schematic diagram for the chromium removal treatment process Fig. 2 FT-IR spectrum of pure water hyacinth biochar and chromium loaded biochar Fig. 3 Batch wise chromium removal efficiency with different adsorbent dose: 1 g, 2 g, 3 g, 4 g, and 5 g; each batch 70 mL wastewater with 15 min interaction time Fig. 4 Batch wise chromium removal efficiency at different solution pH Fig. 5 Batch wise chromium removal efficiency on different interaction time: 5, 10, 15, 20, and 25 min; each batch 70 mL wastewater with 4 g charcoal Fig. 6 Pseudo-first-order (a) and pseudo-second- order (b) kinetics of adsorption Fig. 7 Linearized adsorption isotherms Langmuir (a) and Freundlich (b)
12
Figure 1
Wastewater collection Physicochemical analysis and filtration Filtrate mixed with prepared biochar Stirring and allowed for settling Filtration and physicochemical analysis
13
Figure 2
80
Transmittance (%)
75
70
65 Pure biochar Cr-loaded biochar
60 4000 3600 3200 2800 2400 2000 1600 1200 800 -1
Wavenumber (cm )
14
400
Figure 3
Chromium removal (%)
100
80
60
40
20
0 1
2
3
4
Adsorbent dose (g/70 mL wastewater)
15
5
Figure 4
Chromium removal (%)
100
80
60
40
20
0 5.9
6.2
6.5
6.8
7.1
7.4
Solution pH
16
7.7
8.0
8.3
Figure 5
Chromium removal (%)
100
98
96
94
92
90 5
10
15
20
Interaction time (min)
17
25
Figure 6
-4.8
1st Order
(a)
-5.6 y=-0.0534x-5.3314 ln{(Qe-Qt)/Qe}
2
R1 =0.9273 -6.4
-7.2
-8.0
-8.8 0
6
12
18
24
30
36
42
48
54
60
Contact time (min)
20
2nd Order
(b)
16
{Qt/(Qe-Qt)}
y=-0.2896x+16.3807 2
R2 =0.8242
12 8 4 0 0
10
20
30
40
Contact time (min)
18
50
60
Figure 7
10
Freunlich
(a)
8
y=1.9327x+2.6723 2
lnQe
R2 =0.9784 6
4
2 0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
lnCe
1.5
Langmuir
(b)
y=759.2664x-0.4211
1.2
2
R1 =0.9187
1/Qe
0.9 0.6 0.3 0.0 0.0004
0.0008
0.0012 1/Ce
19
0.0016
0.0020
0.0024