Abstract: The present work is focussed on treating dye-laden polluted water by using a mustard straw-based activated carbon prepared using ZnCl2 and H3PO4 activation methods. The activation conditions based on the parameters reported in the literature are taken as follows: 700 °C activation temperature, impregnation ratio 2.0, and heating time 2 h. The textural and surface properties of mustard stalk activated carbon (MSAC) were studied by using SEM, nitrogen adsorption, and FT-IR, whereas its adsorption capacity was obtained using the methylene blue (MB) adsorption method. Activation of ZnCl2 and H3PO4 resulted in a BET surface area of 402 and 496 m2/g, respectively. The average pore diameter of the MSAC was found to be 2.13 and 2.59 nm for ZnCl2 and H3PO4 activation respectively. The Langmuir and Freundlich models were applied to evaluate the equilibrium parameters of MB adsorption. The monolayer adsorption capacity of MSAC by ZnCl2 and H3PO4 for MB removal from the Langmuir model were 122.25 and 213.21 mg/g respectively. Activation with H3PO4 was found to be more effective in modifying the structure of the mustard straw when compared with ZnCl2 and also it resulted in a higher adsorption capacity of MB. The present work highlights that the MSAC produced using H3PO4 activation is a low-cost bio-based adsorbent using abundant agricultural by-product namely mustard straw, and this adsorbent can be used in numerous industrially important applications.
