Competitive adsorption studies for removal of phenolic pollutants using Cassia fistula-derived activated carbon

Abstract Industrial effluent is a complex aqueous matrix comprising hazardous substances like phenols and toxic organics, often mixed with nutrients, suspended solids and multiple pollutants. Its constituents vary with industry, making it a significant environmental challenge requiring targeted treatment solutions. So, in the present research, competitive adsorption of phenol and 2,4-Dichlorophenol (2,4-DCP) onto Cassia fistula -derived activated carbon (CFPAC) was investigated. In case of phenol adsorption, the modified Langmuir isotherm was found to appropriately align with experimental data and achieving R 2 greater than 0.95 and least Marquardt's percent standard deviation (MPSD), although certain overestimation was observed in the predicted values. Similarly, in case of 2,4-DCP, the experimental values closely aligned with both modified Langmuir and modified Redlich–Peterson isotherm as reflected by higher R 2 ; however, the estimated values were underestimated. For both pollutants, the adsorption ratio (Rq i ) was less than one. Further, the P-factor (P fi ) was exceeding 1 along with positive ΔIE i implies an antagonistic type of interaction between phenol and 2,4-DCP. The binary desorption of pollutant was effective across for four adsorption–desorption cycles demonstrating the consistent performance of CFPAC. Graphical Abstract