Methylene blue dye mitigation from contaminated water using <i>Brassica oleracea</i> waste leaf powder: A sustainable approach

Cabbage (Brassica oleracea) is a popular vegetable grown and consumed worldwide and is valued as a low-cost source of essential minerals. It is widely cultivated in different parts of the world, resulting in the vast production of waste. These cabbage-waste leaves exhibit good adsorption ability. A commonly used cationic dye is methylene blue (MB). Its presence in water causes various health problems. Therefore, the present study aims to remove MB from polluted water using Brassica oleracea-waste leaf powder. Its surface area is 13.945 m2/g with pore size less than 2 nm. Therefore, it has microporous nature with good adsorption ability. The optimum contact time and pH of the present investigation are 60 min and 10, respectively. 93.74% MB removal is achieved at pH 6.0, a contact time 60 min, temperature 30°C, MB concentration 50mg/L and cabbage-waste leaf powder 10g/L. The experimental data obey Langmuir, pseudo-second-order, Dubinin–Radushkevich (D.R.), Weber Morris and Temkins' kinetics/isotherms. The monolayer MB uptake is 18.87 mg/g. The D.R. isotherm's mean sorption energy (0.74kJ/mol) and Temkin isotherm's heat of sorption (3.62J/mol) indicate physisorption nature of the process. The material can be recycled and reused up to three cycles successfully using 0.1 M HCl.