Adsorption of Reactive Dyes from Aqueous Solution Using Activated Carbon Prepared from Plantain Leaf Sheath Waste

Sangavi, G. et al., Adsorption of Reactive Dyes from Aqueous Solution…, Chem. Biochem. Eng. Q., 34 (3) 169–180 (2020) Adsorption of Reactive Dyes from Aqueous Solution Using Activated Carbon Prepared from Plantain Leaf Sheath Waste 169 This work is licensed under a Creative Commons Attribution 4.0 International License https://doi.org/10.15255/CABEQ.2020.1826 Sangavi, G., Argho Bakshi, Mathangi, G., and Nandhini Devi, G.* Department of Biotechnology, Anna University, Chennai, India Original scientific paper Received: May 20, 2020 Accepted: October 8, 2020 All parts of the plantain are widely used in India for various purposes. But plantain leaf sheath always ends up as waste material which accumulates as a biowaste. The present study focuses on the preparation of activated carbon using phosphoric acid as activating agent, and its efficacy as an adsorbent for the removal of reactive dyes, Reactive Green 19, and Reactive Red 141. Batch adsorption studies have been conducted and optimum adsorption conditions were determined as a function of contact time, initial dye concentration, adsorbent dosage, and pH. The experimental data were analyzed using Langmuir, Freundlich and Temkin isotherm models. The pseudo-first and second-order, intraparticle diffusion, and Elovich models were used to analyze the kinetic parameters of the adsorption system. Under the optimum conditions (initial dye concentration = 200 mg L–1, adsorbent dose = 1 g, pH = 2, contact time = 220 min for reactive green 19 and 180 min for reactive red 141), maximum percentage removal for reactive green 19 and reactive red 141 were obtained as 65.9 % and 72.7 %, respectively. The results demonstrate that activated carbon produced from chemical activation of the plantain waste has the potential of adsorbing reactive dyes from industrial effluents. Keywords: plantain waste, activated carbon, reactive green 19, reactive red 141, isotherm and k inetic models Introduction Textile industry dyes have a synthetic origin and complex chemical structure. Basic dyes, acid dyes, reactive dyes, direct dyes, azo dyes, mordant dyes, vat dyes, disperse dyes, and sulphur dyes1 are the different types of dyes used. During the dyeing process, the competition between the colouring reaction and the hydrolysis of the reactive group results in a loss of unfixed dye of approximately 20 to 25 %, which leads to the production of coloured effluents2. Water pollution from the dyeing industry is a matter of great concern, since a large quantity of effluents are discharged directly into the water bodies. The dye effluent is highly toxic in nature3. Major problems associated with colour effluent include lowering light penetration, photosynthesis, and damage to the aesthetic nature of the water surface4–6. Moreover, their degradation products may be mutagenic and carcinogenic7,8. Many dyes may cause allergic dermatitis, skin irritation, dysfunction of kidney, liver, brain, reproductive, and central nervous system9. Corresponding author: * Reactive dyes are formed by the combination of azo-based chromophores with different types of reactive groups, like vinyl sulphone, chlorotriazine, etc. Reactive dyes are commonly used in textile industries because of their favourable characteristics of bright colour, water-fastness, and simple application techniques with low energy consumption10. The current techniques used for the removal of dyes include adsorption, filtration, Fenton’s oxidation method, ozonization, solvent-extraction method, coagulation/flocculation, ion exchange, and bioremediation11–13. Among them, adsorption is effective and cheap when compared with other methods. Activated carbon, a broad-spectrum adsorbent, is capable of removing a wide range of pollutants from water. Activated carbon is a porous material that behaves as a powerful adsorbent because of its high surface area, adequate pore size distribution, and variable characteristics of surface chemistry, low ash content, and relatively high mechanical strength14. One of the major drawbacks is the reusability of activated carbon. Around 10–15 % of activated carbon is lost during the regeneration process, which in turn increases the overall cost of the treatment process. Therefore, preparation of activated carbon from cheaper materials, such as agricultural wastes, has gained great attention15. 170 Sangavi, G. et al., Adsorption of Reactive Dyes from Aqueous Solution…, Chem. Biochem. Eng. Q., 34 (3) 169–180 (2020) Agricultural waste is considered a rich source for activated carbon production. The use of agricultural waste as activated carbon precursors depicts a renewable and relatively less expensive route16. Preparation of activated carbon from agricultural waste materials, like wheat, corn-straw, sugarcane bagasse, cotton refuse, oat hull, almond shells, apricot-stones, corn cob, corn hull, cotton stalks, rice hull, rice husk and rice straw has been reported previously17. The mechanism of adsorption using activated carbon is represented in Fig. 1. Plantain is one of the world’s oldest fruit crops of the family Musaceae, cultivated widely in the tropical and subtropical regions of the world18,19. The world’s leading plantain producers are India, China, Uganda, Ecuador, Philippines, and Nigeria20. According to Indian Horticulture Database, plantain is cultivated over an area of 884 (‘000 Ha) and production was reported to be 30808 (‘000 MT) for the year 2017–18. The huge quantities of biomass generated by plantain farming go as waste due to non-availability of suitable technology for its com- F i g . 1 – Adsorption mechanism 171 Sangavi, G. et al., Adsorption of Reactive Dyes from Aqueous Solution…, Chem. Biochem. Eng. Q., 34 (3) 169–180 (2020) mercial utilization21. Though plantain leaf sheath is used for fibre production, a large quantity of it is dumped or burnt, hence causing environmental pollution. Only a few studies have been reported in the literature for the adsorption of reactive dyes (Table 3). In this research study, activated carbon was prepared from plantain leaf sheath waste using phosphoric acid activation. The prepared activated carbon was characterized by SEM and FTIR. Adsorption isotherm and kinetics have been studied for the dyes- Reactive red 141 and Reactive green 19. Materials and methods Materials Adsorbent Plantain leaf sheath waste used for the preparation of adsorbent was collected from a local market in Chennai, Tamilnadu. Adsorbate Reactive Green 19 and Reactive Red 141 dyes are used as adsorbates in this study. The dyes were procured from the commercial textile industry at Tamilnadu. The details of the reactive dyes are presented in Table 1. Preparation of the adsorbent The collected agro-waste was washed thoroughly with distilled water and oven-dried at 40 °C to obtain constant weight. The samples were ground and stored in polyethylene bags. Activated carbon was prepared according to the method in the literature22 with slight (...truncated)