Equilibrium and kinetic studies of Cd(II) ion adsorption from aqueous solution by activated red mud

Abstract

Red mud is an undesirable by-product of bauxite in Bayer process has been used as a low-cost adsorbent for the removal of Cd(II) from aqueous solution by batch mode of experiment. The red mud was activated by acid dilution followed by ammonia precipitation for better adsorption of Cd(II). To achieve optimum condition for adsorption, different variable parameters were studied. X-ray diffraction, SEM and EDX were used to characterize the adsorbent before and after cadmium adsorption. The maximum adsorption capacities of Cd(II) on activated red mud (ARM) were found to be 12.046 and 12.548 mg g −1 at temperature 293 and 303 K, respectively. Adsorption data of Cd(II) are best fitted to linearly transformed Langmuir isotherm with R 2 > 0.99. The pseudo-second-order model describes the kinetics of Cd(II) adsorption successfully to predict the rate constant of adsorption. Thermodynamic parameters reveal the endothermic, spontaneous and feasible nature of adsorption of Cd(II) onto ARM. The mass transfer study led to compute the external mass transfer coefficient (k f ) by the equation of McKay et al. and Weber-Mathews at temperature 293 and 303 K. The desorption efficiency of Cd(II) ions from ARM was 91.29% using 0.2-mol L −1 HCl.

Synthesis of triethylene tetramine–modified water‐insoluble corn flour caged in magnetic chitosan resin and its adsorption application for removal of patulin from apple juice

“…In this study, the calculated E values for patulin adsorption at different temperature were higher than 8 kJ/mol, reconfirming that the adsorption of patulin on TETA‐WICF/MCR was mainly chemisorptions process. Meanwhile, the Temkin constant ( b T ), that describes the heat of patulin adsorption, showed a slight increase with the increase of temperature, indicating the adsorption was an endothermic process (Sahu et al., 2016).…”

“…To explore the adsorption mechanism and potential rate‐controlling steps, the kinetic data of patulin onto TETA‐WICF/MCR were simulated with pseudo‐first‐order and pseudo‐second‐order kinetic models (Miyah, Lahrichi, Idrissi, Khalil, & Zerroup, 2018; Sahu, Mandan, Yadav, Dash, & Patel, 2016)…”

“…The adsorption isotherm is very important for defining adsorption behavior of a solid–liquid system. In this study, the isothermal adsorption data were fitted using four models, Langmuir, Freundlich, Dubinin–Radushkevich (D‐R), and Temkin (Roy, & Mondal, 2017; Sahu et al., 2016).…”

Equilibrium, kinetic and thermodynamic studies on the adsorption of atrazine in soils of the water fluctuation zone in the Three-Gorges Reservoir

“…To clarify the overall adsorption process of atrazine in the two soils, Langmuir and Freundlich sorption models have been used. The Langmuir isotherm model [45] assumes that the energy adsorbed on the surface of the adsorbent is uniform, the adsorbent does not migrate in the surface plane and there is no interaction between the adsorbed molecules [46,47], the equation for which is described as follows in Eq. (2): where q e is the amount of atrazine adsorbed by soil (mg kg −1 ); q m is the maximum amount of atrazine adsorbed (mg kg −1 ); K L (L mg −1 ) is a constant related to the adsorption energy; and C e is the equilibrium concentration of atrazine (mg L −1 ).…”

Synthesis of MnO2 Hollow Nanospheres through Selective Etching Method as an Effective Absorbent to Remove Methyl Orange from Aqueous Solution

“…The Lagergren-firstorder equation, pseudo-second-order equation, and intraparticle diffusion model were used to investigate the adsorption kinetics of the MO molecule on MHNSs, and the correlation coefficient value (R 2 ) was used to select the bestfit model [35,36]. Figures 8-10 present the analysis results of MHNSs acted on the MO solution with different dynamic models.…”