Pristine wild sugarcane (Saccharum spontaneum) as a biosorbent for removal of methylene blue from wastewater: isotherm, kinetics and regeneration studies

Abstract

Saccharum spontaneum, popularly known as Kashful (KF) is a seasonal perennial grass with thin culms, mostly an abundantly growing shrub during the autumn season in southern Asia. It is used as no-cost scavenger to convincingly arrest methylene blue, a recalcitrant dye from colored effluent. FTIR, FESEM-EDX, and BET surface area characterize the material well whereas the surface activity was evaluated from zero-point charge (pH_ZPC = 6.720). FTIR highlights the presence of polyphenolic and carboxylate moieties. The surface texture is rod-like with intermittent non-homogeneous pores with occasional fractures. The equilibrium reaches within 60 min with the maximum adsorption capacity of 20.917 mg/g. The fibrous powder of kashful stalk (KFS) follows pseudo-second-order (R² = 0.999 for linear and R² = 0.985 for non-linear) kinetics and both Langmuir and Freundlich isotherm model (for linear, Langmuir R²=0.995; for non-linear, R² = 0.994 for both Langmuir and Freundlich model). The uptake process was spontaneous (ΔG= −3.077 kJ/mol) and endothermic (ΔH = 17.815 kJ/mol). 1:1 methanol could regenerate the dye-loaded material in up to 55% and onward efficiency was conducive for three consecutive cycles. Industrial effluent analysis suggests a real-time removal of ∼55% in the first cycle. Saccharum spontaneum could be exercised to solve environmental problems related to colored water.

NOVELTY STATEMENT

Saccharum spontaneum, also known as wild sugarcane is an abundantly available long grass with relatively slender culms; usually 100–150 cm tall, grows in the autumn season (August-October) in the south-east part of Asia, and displays steady tillering. Being a non-preferred meal for local herbivores, the material lies abandoned as bio-waste. At the same time, the search for a newer and cleaner alternative for wastewater treatment is on the rise. In line with the waste-to-wealth protocol for a sustainable environment, we have demonstrated the facile uptake of a recalcitrant dye methylene blue (20.917 mg/g) using its stalks powder. The present method is free from any hazardous chemical activation, acid-base treatment, or pyrolysis. With the ability to treat industrial effluent, the material highlights an impactful application in a lab-to-land fashion.

Graphical Abstract

Keywords:

• Kashful
• methylene blue
• Saccharum spontaneum

Acknowledgements

SD, PPS, and MAQ thank the Central University of Jharkhand for fellowships.

Disclosure statement

The authors report there are no competing interests to declare.