Dyes are used by industries like plastics, textile, paper, pharmaceuticals, food and cosmetics industries. The discharge of synthetic dyes into the environment has become a significant environmental concern due to their potential toxicity and negative impact on aquatic life (Bhatia, 2021; Murugan, 2010). The textile industry is a major contributor to dye pollution, as it generates large amounts of wastewater containing various dyes and other chemicals (Sinha, 2020). Conventional methods for the removal of dyes, such as chemical oxidation, adsorption, ion exchange, electro-dialysis, reverse osmosis, electroplating, solvent extraction, ultra-filtration and coagulation, are often expensive and generate toxic byproducts (Nwabanne, 2021). Therefore, alternative and eco-friendly methods are needed for the removal of dyes from wastewater.
Biosorption, which involves the use of natural or modified biomaterials to remove contaminants from wastewater, has emerged as a promising alternative for the removal of dyes (Vasanthakumaret, 2021). One of the advantages of biosorption is that it does not generate secondary pollutants and can be used in conjunction with other methods to achieve efficient treatment of wastewater (Oladipupo, 2019). Studies have shown that plants have the ability to remove heavy metals and dyes from industrial effluents with better performance at lower cost (Malik, 2017).
While these biosorbents exhibit effective dye adsorption capabilities, the prolonged growth period of such plants and the resource-intensive steps accompanied by substantial chemical reagents and energy inputs for biosorbent preparation have hindered their widespread use in dye treatment (Ramachandra, 2006). Consequently, the demand for biomaterials that grow rapidly, require fewer steps, and involve eco-friendly biosorbent preparation has become imperative.
Elephant grass (Pennisetum purpureum) emerges as a fast-growing biomaterial with substantial potential. It has demonstrated effective biosorption properties for various pollutants, including heavy metals and dyes (Pandiangan, 2020). In this research, modified elephant grass was employed for biosorption purposes, targeting two commonly used dyes—Methyl Red and Thymol Blue—as well as their mixture. The modification process entailed treating elephant grass with an alkaline solution to enhance its surface area and thereby amplify its biosorption capacity (Siddiqui, 2017). Additionally, Elephant Grass presents itself as a cost-effective source of cellulose.
Notably, it boasts a high biomass production rate of approximately 87 t/ha/year and can be harvested five to six times annually. Equally significant, Elephant Grass contains a substantial cellulose content, ranging from 35–50% (Tongpoothorn, 2019). This unique composition positions Elephant Grass as an ideal alternative and a potentially sustainable source of precursors for the production of biosorbents.The use of modified elephant grass as a biosorbent for the removal of dyes from wastewater has been previously reported in the literature. For instance, Ghosh (2016) investigated the potential of untreated and acid-treated elephant grass for the removal of methylene blue dye from aqueous solutions. They reported that the acid-treated elephant grass exhibited higher biosorption capacity than the untreated grass. Similarly, Wang (2018) explored the use of alkali-modified elephant grass for the removal of anionic dyes, and they found that the modified grass had higher biosorption capacity and better stability than the untreated grass. In another study, Zhu (2020) used surface-modified elephant grass for the removal of Cr(VI) from aqueous solutions. They reported that the surface modification of the grass significantly enhanced its biosorption capacity for Cr(VI). Hence, the biosorbents used was also treated with Potassium Persulphate (K2S2O8) to modify the surface of the biosorbent so as to increase the adsorption capacity. (Sneha, 2021)
These studies highlight the potential of elephant grass as a biosorbent for the removal of various pollutants, including heavy metals and dyes. However, to the best of our knowledge, there are limited studies that have investigated the use of modified elephant grass for the removal of methyl red, thymol blue, and their mixture. Therefore, this study aims to fill this gap by investigating the biosorption properties of modified elephant grass for the removal of these dyes.
The objective of this study is to investigate the effectiveness of modified elephant grass for the biosorption of methyl red, thymol blue, and their mixture from aqueous solutions. The biosorption capacity of the modified elephant grass will be evaluated as a function of various parameters, such as pH, contact time, initial dye concentration, and temperature. Adsorption isotherms, kinetics and thermodynamic parameters were also evaluated and reported. The results of this study will provide insights into the potential use of modified elephant grass as a low-cost and eco-friendly biosorbent for the removal of dyes from wastewater.