Enhanced adsorption performance of Reactive Red 120 azo dye from aqueous solution using quaternary amine modified orange peel powder

Orange peel powder was chemically modified to enhance quaternary amine type content on the surface of adsorbent which was named as quaternary amine modified orange peel powder (QAMOPP). The effecting parameters on adsorption of Reactive Red (RR) 120 such as pH (2.0-9.0), contact time (0-300 min), adsorbent dosage (0.01-0.07 g/30 mL), initial RR120 concentration (100-1000 mg/L) and temperature (298-338 K) were studied. The QAMOPP was extensively characterized for its surface chemical bonding, morphological structure, and specific surface area, total pore volume and average pore diameter by employing FTIR, SEM and BET analysis. The experimental adsorption kinetic data followed the pseudo-second-order kinetic model equation with a regression coefficient of >0.9941 for all studied temperatures. The activation energy (E-a) is calculated to be 12.1 kJ/mol by using the Arrhenius equation. Adsorption isotherms of RR120 on QAMOPP were correlated with two- and three-parameter non-linearized isotherm equations viz. Langmuir, Freundlich, Dubinin-Radushkevich (D-R), Temkin, Sips, Toth, Khan and Redlich-Peterson (R-P). It was observed that the Langmuir (R-2 = 0.9996) and Khan (R-2 = 0.9991) were the best fit isotherm models to predict RR120 adsorption onto QAMOPP. pH study revealed that the adsorption capacity decreased with an increase in pH of the solution. Optimum adsorption of RR120 onto QAMOPP was observed at pH 2.0 (344.8 mg/g). The adsorption performance of QAMOPP increased with contact time until 110 min, when it became nearly constant. The negative values (-1.9114 to -5.9208 kJ/mol) of Delta G degrees, the positive values (0.102 kJ/mol K and 28.4 kJ/mol) of Delta S degrees and Delta H degrees parameters indicate that the adsorption of RR120 onto QAMOPP was spontaneous, feasible and endothermic, respectively. Desorption experimental studies showed optimum RR120 recovery (92%) when 0.1 M NaOH was used as an eluent. Hence to remove RR120 from aqueous media QAMOPP can be considered as a powerful alternative adsorbent material. (C) 2019 Elsevier B.V. All rights reserved.