1,4,5Lecturer, Department of Basic Sciences, Babcock University, Nigeria, 2Lecturer, Department of Chemical Sciences, Mountain Top University, Nigeria, 3Professor, Department of Industrial Chemistry, Federal University Of Technology, Owerri, Nigeria
Received: 20 Jan 2020 Revised and Accepted: 18 May 2020
Objective: One of the objectives of this work includes to expand the field of application of natural biomass for the treatment of dye effluents from industrial wastes. In addition, it is aimed at elucidating the dependency or otherwise of flow rate and bed height on adsorption using the fixed bed technique method of adsorption.
Methods: The biomass was characterized by scanning electron microscopy (SEM) in order to examine the morphology of the biomass. The screened biomass samples were characterized at 1000 x magnification, and 500 x magnification respectively for their surface morphologies. This was done using a scanning electron microscope (FEI–inspect/OXFORD INSTRUMENTS–X–MAX), which was equipped with an energy dispersive x-ray (EDAX) spectrophotometer employed for the elemental composition analyses. It was equally characterized with Fourier Transformed Infrared Spectroscopy (FTIR) before and after adsorption to ascertain the functional growth responsible for the adsorption. This was done using a Fourier Transformed Infrared (FTIR) Spectrophotometer (Perkin-Elmer, England) in the wavelength range of 350-4000 nm.
Results: Results for the biomass morphology obtained through the Scanning Electron Microscopy (SEM) showed the presence of some tiny pores. These pores represent sites where dye molecules could be trapped in the course of the adsorption. The result from the Fourier Transformed Infrared Spectroscopy (FTIR) after adsorption show that C-H, C ≡ H, and C ≡ C functional growth were responsible for the adsorption. For the methylene blue dye, at the flow rate of 20m3/s, the amount of dye adsorbed was 8.40 mg/g, 11.30 mg/g at 30m3/s and 13.64 mg/g at 40m3/s. For Bismarck brown Y dye, at the same range of flow rate, the amount of dye adsorbed ranged from 4.71 mg/g to 9.78 mg/g. indigo was the least adsorbed at the same range of flow rate. The values obtained ranged from 2.80 mg/g to 8.00 mg/g. In addition, at the bed height of 4.0–6.0x10-2(m), the amount of dye adsorbed ranged from 5.15 mg/g–24.62 mg/g for methylene blue dye. Within the same range of bed height, the amount of dye adsorbed ranged from 8.20 mg/g–15.00 mg/g for Bismarck brown Y dye, and 5.66 mg/g–14.86 mg/g for indigo dye.
Conclusion: From the results obtained, it is clearly seen that methylene blue dye was the most adsorbed, while the indigo dye was the least adsorbed within the same flow rate and bed height ranges. In addition, the three classes of dyes used in these investigations, which represent Cationic, Anionic and Neutral dyes, can adsorb on to Cedrus libani (Elizabeth Leaf) at various degrees. Also, the amount of dye adsorbed is dependent on the flow rate and bed height within the range of experimental consideration.
In each of the analyses, three different experiments were performed, and the mean values reported with their standard deviations.
Keywords: Bio-sorption, Cedrus libani, Sem, Adsorbent, Fixed bed
© 2020 The Authors. Published by Innovare Academic Sciences Pvt Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
DOI: http://dx.doi.org/10.22159/ijcr.2020v4i3.115. Journal homepage: https://ijcr.info/index.php/journal
Bio sorption can be defined as the abstraction of organic and inorganic species, including metals, dyes and odor-causing substances using live or dead biomass or their derivatives. This process can be achieved either through the batch or fixed bed technique. The batch process of adsorption occurs as a result of agitation between the biomass and the dye solution, such agitation is normally provided by a shaker or magnetic stirrer. On the other hand, the fixed-bed adsorption process are ubiquitous throughout the chemical process industries  Separation in a fixed bed is virtually in all practical cases, an unsteady state rate controlled process. Adsorption only occurs in a particular region of the bed known as the mass transfer zone (MTZ), which moves the bed.
This is practically achieved by allowing the dye solution to pass through the column containing the biomass from the down of the column to the top by the use of a peristaltic pump. The removal of dyes from solutions has been attempted in the past, using such techniques as advanced oxidation process (AOP), nanofiltration (NF) and reverse osmosis membrane [2, 3].
In recent times, the use of the bio-sorption technique for the removal of dye contaminants from solution has been found to be superior to other techniques based on the simplicity of design and operation . Activated charcoal is widely employed as an adsorbent. However, the use of activated charcoal is restricted due to the high cost. This has resulted in attempts by various workers to prepare low-cost alternative adsorbents .
Adsorption techniques are effective and attractive for the removal of non-biodegradable pollutant (including dyes) from wastewaters . Many low cost adsorbent and waste materials from industries and agriculture have been proposed by several researchers . These materials do not require any expensive additional pre-treatment step and could be used as an adsorbent for the removal of dyes from solutions.
An investigation was carried out on the kinetics and thermodynamic studies of adsorption of malachite green onto unmodified and EDTA modified groundnut husk, using the batch technique .
This work is carried out with the view of expanding the field of application of natural biomass for the treatment of dye wastewaters, and also to determine the adsorption capacity of Cedrus libani (Elizabeth leaf) on Methylene blue, Bismarck brown Y, and Indigo dyes respectively. Since such an in-depth comparisms has not been done on this biomass, the results obtained from the work will add to the expansion of knowledge in this area.
MATERIALS AND METHODS
The Methylene blue dye, Bismarck brown y dye, and Indigo dye used in these investigations were obtained from qualikem laboratory, Owerri, Nigeria. Other materials obtained here include analytical grade sodium hydroxide pellets, concentrated hydrochloric acid, distilled water etc.
The Cedrus libani (Elizabeth leaf) used in this work was obtained from Ikorodu area of Lagos, Nigeria which is located within the following coordinates 6.6194 ° N, and 3.5105 ° E. The sample was identified at the department of crop science at the Federal University of technology, Owerri, Nigeria with the voucher specimen number of FUT/CR/002/15. The biomass was washed severally with distilled water to remove any dirt from it. The washed biomass was air-dried for 10 d until a constant weight was obtained. The biomass was grinded with a new sonic domestic blender to avoid any form of contamination. It was screened using 600-800 micron-sized sieves and were stored in airtight containers ready for adsorption measurement.
The methods and techniques employed in these determinations are the standard methods which have been used by other researchers [8-10].
Characterization of the bio-sorbent
The surface structure and morphology of the Cedrus libani (Elizabeth leaf) was characterized at 1000 X magnification, 500 X magnification, and 250 X magnification, respectively for their surface morphology. This was done using scanning electron microscopy (SEM) (FEI-Inspect oxford instrument x-max), which was equipped with an energy dispersive x-ray (EDAX) spectrometer employed for elemental composition analysis.
The biomass sample was further characterized for their fundamental functional groups before and after the adsorption experiment using a Fourier Transformed Infrared (FTIR) spectrophotometer (Perkin Elmer, England) in the wavelength range of 350-400 nm using KBr powder and fluka library for data interpretation.
The fixed bed set up
The fixed bed was set up by packing wire gauze, glass wool, glass beads, glass wool, biomass, and glass wool in that order in a graduated condenser. Then a dye solution of a known concentration and pH pressurized from down to top where a known amount of bio-sorbent is placed with a peristaltic pump (CHEM-TECH Model X030-XB-AAAA365, China). Subsequently, a sample was collected for U. V analysis in a UV spectrophotometer (CAMSPEC M 106 Model. England) by monitoring the absorbance changes at a wavelength of maximum absorbance already determined for Methylene blue dye (600 nm), Bismarck brown y dye (320 nm), and Indigo dye (350 nm) respectively.
The variables investigated here include the effect of bed height and flow rate.
Effect of flow rate on adsorption
Experiments were carried out at different flow rate of 20 m3/s, 30 m3/s and 40 m3/s while keeping constant a bed height of 1×10-2 m, 40 mg biomass dose, 90 mg/l dye solution and a pH of 4 for Methylene blue dye, and a pH of 2 for Bismarck brown y, and Indigo dyes earlier determined as their best pH of maximum adsorption. The dye solution was subjected to pass through the column already prepared using the peristaltic pump. The samples collected were subjected to U. V analysis for absorbance measurements. Subsequently, the absorbance values were converted to concentration by the use of Beer Lamberts law. Similar experiments were carried out in triplicates and the mean values and standard deviations reported.
Effect of bed height on adsorption
Experiments were carried out at different bed heights of 4×10-2m, 5×10-2m and 6×10-2 m while keeping constant a flow rate of 10 m3/s, 90 mg/l dye solution, pH of 4 for Methylene blue dye, and a pH of 2 for both Bismarck brown y, and Indigo dyes earlier determined as their best pH of maximum adsorption. The dye solution was subjected to pass through the column already prepared using the peristaltic pump. The samples collected were subjected to U. V analysis for absorbance measurements. Subsequently, the absorbance values were converted to concentration by the use of Beer Lambert’s law. Similar experiments were carried out in triplicates and the mean values and standard deviations reported.
NOTE: The amount of dye adsorbed per gram biomass (qe) was calculated using the expression below.
Where V= Volume of the sample in dm3
Co= Initial dye concentration in mg/l
Ce= Equilibrium dye concentration in mg/l
M= Mass of the biomass in g
Fig. 1: Fixed bed technique apparatus
RESULTS AND DISCUSSION
Fig. 2: SEM morphology of Cedrus libani (Elizabeth leaf) (X500)
Fig. 3: SEM morphology of Cedrus libani (Elizabeth leaf) (X1000)
The SEM micrographs of Cedrus libani (Elizabeth leaf) revealed the presence of unevenly dispersed cavities on the surface of the biomass. These cavities provide sites where the molecules of the dyes could be trapped in the course of adsorption. The SEM micrographs of 500 X and 1000 X magnifications are shown in fig. 2, and 3 respectively.
Fig. 4: FTIR Spectrum of Cedrus libani (Elizabeth leaf) before adsorption
The FTIR spectrum of Cedrus libani (Elizabeth leaf) shown in fig. 4 reveals the presence of five major functional groups. The functional groups include O-H or N-H at 3420 nm, C-H at 2925.71 nm, CN, CC at 2363.57 nm, CO, CC at 1645 nm. As could be seen, the Cedrus libani (Elizabeth leaf) spectra (scanned between 350-400 nm) revealed broad peaks around 3420 nm, which lie well between 3200-3600 nm. This corresponds to the presence of OH functional groups on the surface of the biomass . Other prominent peaks were observed around 1645 nm and 1430 nm and are due to carbonyl (CO) stretching from aldehydes or ketones as reported by . The peaks observed around 1031 nm was attributed to the CO stretch due to primary alcohol. The combination of these functional groups arising from the OH and CO suggest the occurrence of a carboxylic functional group.
Fig. 5: FTIR spectrum of Cedrus libani (Elizabeth leaf) before adsorption
Fig. 6: FTIR Spectrum of Cedrus libani (Elizabeth leaf) with methylene blue dye after adsorption
Fig. 7: FTIR spectrum of Cedrus libani (Elizabeth leaf) before adsorption
Fig. 8: FTIR spectrum of Cedrus libani (Elizabeth leaf) with bismarck brown y dye after adsorption
Fig. 9: FTIR spectrum of Cedrus libani (Elizabeth leaf) before adsorption
Fig. 10: FTIR spectrum of Cedrus libani (Elizabeth leaf) with Indigo dye after adsorption
After the adsorption process, as shown in fig. 6, 8, and 10, there were depressions of the original peaks as shown in fig. 5, 7 and 9, respectively. From the depressions observed, we can determine the functional groups that were actually responsible for the adsorption reaction. The displacements occurred at 2931.00 nm and 3265.71 nm, indicating that the following functional groups C-H, CN and CC were responsible for the adsorption process. Furthermore, the functional groups did not disappear totally after the adsorption process. This indicates that the interaction of the dye molecules with Cedrus libani (Elizabeth leaf) was indeed a physical process.
Table 1: Effect of flow rate on the fixed bed adsorption of methylene blue dye, bismarck brown y dye and indigo dye on to Cedrus libani
|Flow rate (m3/s)||20||30||40|
|Methylene blue dye qe (mg/g)||8.40±0.01||11.30±0.01||13.64±0.02|
|Bismarck brown Y dye qe (mg/g)||4.71±0.01||8.80±0.01||9.78±0.01|
|Indigo dye qe (mg/g)||2.80±0.02||6.46±0.02||8.00±0.01|
Three experiments were carried out in each case, and the values shown in the above table represent the mean values and their standard deviations.
As could be seen from table 1, an increase in the flow rate caused a corresponding increase in the qe values for the biomass within the range of experimental consideration. A similar effect was reported by other researchers .
This could be attributed to the increase in the force of interaction between the dye solution and the biomass surface area. Methylene blue dye was the most adsorbed, while indigo dye was the least adsorbed.
Table 2: Effect of bed height on the fixed bed adsorption of methylene blue dye, bismarck brown y dye and indigo dye on to Cedrus libani
|Bed height (10-2m)||4||5||6|
|Methylene blue dye qe (mg/g)||5.15±0.02||20.35±0.01||24.62±0.01|
|Bismarck brown Y dye qe (mg/g)||8.20±0.02||11.00±0.01||15.00±0.01|
|Indigo dye qe (mg/g)||5.66±0.02||12.91±0.02||14.86±0.01|
Three experiments were carried out in each case, and values shown in the above table represent the mean values with their standard deviations.
Table 2 shows the effect of bed height on to the quantity of each dye adsorbed on to the adsorbent. The qe values for the biomass increased with an increase in bed height within the range of experimental considerations. The result indicates that longer the bed height, the higher the qe values. A similar situation has been reported in similar investigations . This could be due to the longer time of interactions between the biomass and the dye solutions. Methylene blue dye was adsorbed more while the indigo dye was the least in these considerations.
The findings of this research vividly show that the two variables-flow rate and bed height can affect the adsorption properties of Methylene blue dye, Bismarck brown y dye, and Indigo dye, respectively on to Cedrus libani (Elizabeth leaf) biomass. Increase in flow rate, and bed height gave rise to a corresponding increase in the qe value of the adsorbent.
I appreciate the entire staff of the state key laboratory for corrosion and protection (SKLCP) at the institute of metal research under the Chinese Academy of science, Shenyang, China. Here, I performed several advanced instrumental characterizations such as scanning electron microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR).
All the authors have contributed equally.
The reviewers’ comments are okay and have been taken into account in this revised version of the manuscript.
CONFLICT OF INTERESTS
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