Kinetics, isotherm, and thermodynamic studies of the adsorption of reactive red 195 A dye from water by modified Switchgrass Biochar adsorbent

• Switchgrass Biochar was modified using cationic surfactant to prepare a novel adsorbent for dye removal.
• The pseudo-second order kinetic model exhibited the best fit with the experimental results.
• The Langmuir isotherm is the most appropriate model for this study.
• The adsorption of RR-195A dye from different water samples was always more than 90%.

A method is described for efficient decolorization of reactive red 195 A dye (RR-195A) from aqueous and wastewater samples using modified Switchgrass Biochar (SB) by tetradecyltrimethyl ammonium bromide (TTAB) as a cationic surfactant for the formation of a novel SB-TTAB adsorbent. The different controlling experimental conditions such as solution pH, initial dye concentration, contact time, adsorbent mass, interfering ions and temperature have been investigated and optimized. Adsorption equilibrium using Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) isotherm models have been also studied and the best fit was related to the Langmuir adsorption isotherm. Adsorption kinetics have been tested and illustrated using pseudo first-order, pseudo-second-order, intraparticle diffusion and Elovich models. The collected results confirmed that the pseudo-second order kinetic model exhibited the best fit with the experimental data. Thermodynamic parameters were calculated and the results referred to an exothermic nature and spontaneity of the adsorption process. Improved decolorization of reactive red 195 A dye from textile industrial wastewater and other water samples were successfully established. Excellent recovery values of RR-195A dye by SB-TTAB adsorbent were determined in the ranges of 96.61–98.76%, 97.79–99.26%, 94.24–100.0% and 90.98–92.96% (±1.0–4.0%) from tap water, raw water, wastewater and sea water, respectively.

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