Efficacy of parthenium hysterophorus waste biomass compared with activated charcoal for the removal of CI Reactive Red 239 textile dye from wastewater

Abstract In the quest to find an eco‐friendly, cost‐effective and efficient alternative to expensive and non‐biodegradable activated charcoal (AC), in the current study the potential of a weed, parthenium hysterophorus (PH), has been explored as a bio‐adsorbent for purification of textile wastewater. Root, stem and leaves of PH weed have been used as bio‐adsorbents in raw and surface‐treated forms and compared with AC for removal of toxic textile dye CI Reactive Red 239 (Remazol Brilliant Red 3BS [RBR 3BS]) from wastewater. The surface treatment carried out using QAS (N‐Cetyl‐N,N,N–trimethylammonium bromide) in the current study is a novel way to enhance the dye adsorption capacity of raw adsorbents of PH. Characterisation tools like Fourier Transform–infrared spectroscopy, scanning electron microscopy, elemental analysis and potential of zero charge have been used to confirm the surface treatment. The impact of various process variables like pH, dosage of adsorbent, contact time, solution temperature and dye concentration have been studied. Isothermal, kinetic and thermodynamics modelling for adsorption data have been thoroughly investigated to ascertain the mechanism of adsorption. Statistical error functions like root mean square error, chi‐square test, sum of absolute error and normalized standard deviation (NSD) have been used to validate the adsorption data. Results revealed that novel surface treatment significantly improved the dye adsorption capacity of raw PH adsorbents (ca. 15‐16 times). Of all the weed bio‐adsorbents, surface‐treated PH stem showed the highest dye adsorption capacity (105 mg/g), which was 10‐folds greater than commercial grade AC (10.4 mg/g at 27°C). For both adsorbents, surface‐treated PH stem and AC, adsorption followed pseudo‐second order kinetics, and the Langmuir isotherm was the best fit with film diffusion as a rate‐controlling step. Thermodynamic parameters infer the spontaneous and exothermic nature of adsorption. Therefore, in the current study, surface‐treated PH stem bio‐adsorbent has been revealed as a superior alternative to AC for the removal of RBR 3BS dye from wastewater, opening a new gateway to the utilisation of waste weeds for the purpose of wastewater treatment.