Jackfruit leaf as an adsorbent of malachite green: recovery and reuse of the dye
Dry leaf powder of jackfruit (Actocarpus heterophyllus) was utilized for the removal of an industrial dye malachite green from the aqueous solution by the batch adsorption method. The parameters which effect on adsorption such as adsorption dose, contact time between adsorbent and the dye in solution, and pH of the solution were studied and standardized. The scanning electron microscope (SEM) photography of the jackfruit leaf powder (JLP) indicated that it had a large number of pores, spaces and empty sites. The SEM photography of used JLP shows that the dye is confidently attached on the JLP. Fourier-transform infrared spectroscopy analysis of the adsorbent confirmed the presence of different functional groups like –OH, –NH and C=O on its surface, which can be correlated with the fine adherence of the dye on the surface of the adsorbent. Moreover, the shifting of the functional group on the surface of adsorbed adsorbents indicates the affinity of the dye towards the adsorbent. The Freundlich isotherm model with the correlation coefficient (r2) value of 0.9880 is considered as a suitable absorption model for adsorption of dye. The pH of the aqueous solution was reduced from pH 7 to pH 5. This helped the recovery of the 80% of the attached dye. The present work concludes that jackfruit leaf powder can be used as an efficient adsorbent to remove malachite green from aqueous medium and the adsorbed dye can also be recovered for reuse from the surface of the adsorbent.
KeywordsMalachite green Batch adsorption Jackfruit Recovery of dye
Industrial discharge water contains a large variety of inorganic and organic compounds. Their quality and quantity depends on the type of industry where it is produced. The presence of compounds is the reflection of raw materials being used for production and the chemicals utilized for processing of finished products of that industry . The industrial effluents if added to the natural water bodies either untreated or inadequately treated cause water pollution. Some industries like textile, plastic, leather, pulp and paper and tannery have been consumed a massive amount of different dyes for their production, and therefore, these industries generate huge amount of coloured effluent . When these effluents approach to the natural water bodies, they affect aquatic life, soil micro-flora and fauna of that vicinity and also cause toxicological and aesthetical problems. It is estimated that production of one kilogram of the finished product in textile industry generates on an average of the 150 L wastewater . Synthetic dyes are frequently used in industries due to low cost and more efficient as compared with natural dyes [16, 25]. Certain synthetic dyes are either non-biodegradable or stay for a longer period in the environment cause pollution. Thus, it is highly necessary to remove the dyes present in industrial effluents to beat water pollution. Physical methods like adsorption, electro-coagulation, ultra-filtration, ion exchange, etc., have been adopted for the removal of dyes from industrial waste water, but it is observed that each process has their own pitfalls . Activated carbon can be used as an adsorbent for the removal of dyes from aquatic solution, but limitation is high production cost . Many reports are available today on the use of plant parts as low-cost adsorbents for the removal of the dye from aqueous medium [12, 14, 28], but leaf powder is found to be quite suitable due to their availability and reproducibility. Plant leaf as an adsorbent for the removal of the basic dye has been reported by some workers [5, 7, 22], but reports on recovery of the dye after use are scanty.
2 Materials and methods
2.1 Preparation of the adsorbent
Jackfruit plant growing nearby GIET University was used for the preparation of the adsorbent. The plant was authenticated at the Floristic Laboratory, Botany Department, Berhampur University, Berhampur. The matured and healthy leaves were collected and then washed thoroughly in running tap water. They were dried in an oven at 80 °C for 48 h. The dried leaves were powdered by a domestic mixer and sieved in a 1-mm pore to get homogenous powder. The leaf powder was again washed thoroughly with distilled water to remove pigments and tannins present within it. The jackfruit leaf powder (JLP) is stored in an airtight container which is used as adsorbent for future use.
2.2 Preparation of the dye solution
Malachite green (MG) AR grade was obtained from HI Media Pvt. Ltd., Mumbai. One gram malachite green is added to 1 L double distilled water to prepare the stock solution. Later on, different working solutions were prepared from stock solution with distilled water.
2.3 Designing of the experiment
To recovery of the attached dye on the surface of the adsorbent, the pH of the solution was altered from pH 7 to pH 5 with 1 NH2SO4 and the amount of dye detached from the adsorbents was recorded carefully following the same procedure as mentioned earlier.
2.4 The characterization of the adsorbent
As adsorption is a surface phenomenon, the ultra-morphological structure of the adsorbents and the presence of any group on the surface of the adsorbent were analysed. The jackfruit leaf powder was observed under the scanning electron microscope (SEM) at different magnifications, and the photograph was taken. Similarly, to identify the existence of functional groups on the surface, the adsorbent was experiential with Fourier transmission infrared spectroscopy (FTIR) in a spectrum range from 400 to 4000 wavelength cm−1.
3 Results and discussion
3.1 Adsorbent dose standardization
3.2 Standardization of contact time
3.3 Standardization of pH
3.4 Surface characterization of the adsorbent
The adsorbent was prepared from leaves of jackfruit. The leaves were dried and made into powdered. The powder was sieved to maintain the homogenous size of ≤ 1 mm. Then, it was washed with distilled water for several times to remove the pigments and metabolites present in it. Now they are constituted of plant hard tissue only. The dried hard plant tissues are good adsorbents . The prepared adsorbent has more surface area due to smaller in size. Therefore, both the composition and size of the adsorbent together facilitate the adsorption of the dye.
3.5 Adsorption isotherm
To design an appropriate adsorption system, it is quite necessary to set up a proposed existing adsorption isotherm model with the experimental value. The adsorption values have been analysed with three popular isotherm models such as the Langmuir model, the Freundlich model and the BET model. The correlation coefficient (r2) value of the model was determined from the plotted graph, and the value close to one is considered as the most fitting model for designing of the adsorption system.
3.6 The Langmuir isotherm model
3.7 The Freundlich isotherm model
3.8 The BET isotherm model
Out of the studied three isotherm models with respect to adsorption of malachite green on the adsorbent, the maximum correlation coefficient value (r2 = 0.9880) is found at the Freundlich isotherm model. Therefore, Freundlich isotherm model is the best suitable model for adsorption of malachite green on the jackfruit leaf powder.
Earlier investigators reported that plant parts can be exploited for the removal of malachite green from the aqueous solution. Teak leaf powder , rice husk activated carbon , marine algae Caulerpa racemosa var, cylindracea  and wood apple shell  can be used for the removal of malachite green from the solution of 95, 94.91, 95.02 and 98.87%, respectively.
The dye used in the investigation is malachite green. It is popularly known as benzaldehyde green or aniline green. The dye is commonly used in silk, textile and leather industry for colouring the products. The structure and nature of malachite green are described earlier. Chemically, it is an acidic nature, but due to the presence of chromophores, it serves as the basic dye . The structure of the compound indicates that it has both the tertiary amino group and quaternary N+ group. These groups may have affinity towards the functional groups present in the adsorbent. The FTIR analysis of the adsorbent revealed that the prepared adsorbent is an organic compound constituents functional groups like –C=O, –CHO, –NH2, etc. Thus, the dye had firmly attached to the surface of the adsorbent.
The maximum removal efficiency of the adsorbent was found to be 97.8%. To recovery of the adsorbed dye from the surface of the JLP, the aqueous medium was slowly turned to an acidic environment (pH 5) using 1 NH2SO4. It was observed that about 80% of the attached dye was detached from the adsorbent.
Jackfruit tree is a medium-sized tree famous for its delicious fruit. The leaf of the plant is thick and oval shaped. The JLP was tested as an adsorbent to remove a basic dye, malachite green, from the aqueous solution. Malachite green is used in different industries for colouring the product. The JLP has maximum 97.8% removal efficiency of malachite green. The parameters that effect on adsorption such as adsorbent dose, contact time and pH of the aqueous solution for maximum adsorption were standardized. The adsorption dose was 0.4 g/L for maximum removal of the dye. Similarly, the contact time and pH of the solution were identified as 150 min and pH 8, respectively. The Freundlich isotherm model with correlation coefficient (r2) value 0.9880 was found suitable to design an adsorption model. Therefore, the present investigation can be concluded that JLP can suitably be used for the removal of malachite green from the aqueous solution. Moreover, due to low cost and easily available naturally at garden and forest, the technique is cost-effective as compared to the other removal processes.
The authors are highly thankful to management of GIET University, Gunupur, for providing laboratory facilities to carry out the investigation.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no competing interests.
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