The Adsorption of Cd(II) on Manganese Oxide Investigated by Batch and Modeling Techniques

Abstract

Manganese (Mn) oxide is a ubiquitous metal oxide in sub-environments. The adsorption of Cd(II) on Mn oxide as function of adsorption time, pH, ionic strength, temperature, and initial Cd(II) concentration was investigated by batch techniques. The adsorption kinetics showed that the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by pseudo-second-order kinetic model with high correlation coefficients (R2 > 0.999). The adsorption of Cd(II) on Mn oxide significantly decreased with increasing ionic strength at pH < 5.0, whereas Cd(II) adsorption was independent of ionic strength at pH > 6.0, which indicated that outer-sphere and inner-sphere surface complexation dominated the adsorption of Cd(II) on Mn oxide at pH < 5.0 and pH > 6.0, respectively. The maximum adsorption capacity of Mn oxide for Cd(II) calculated from Langmuir model was 104.17 mg/g at pH 6.0 and 298 K. The thermodynamic parameters showed that the adsorption of Cd(II) on Mn oxide was an endothermic and spontaneous process. According to the results of surface complexation modeling, the adsorption of Cd(II) on Mn oxide can be satisfactorily simulated by ion exchange sites (X2Cd) at low pH and inner-sphere surface complexation sites (SOCd+ and (SO)2CdOH− species) at high pH conditions. The finding presented herein plays an important role in understanding the fate and transport of heavy metals at the water–mineral interface.

The investigation into the adsorption removal of ammonium by natural and modified zeolites: kinetics, isotherms, and thermodynamics

“…The intraparticle diffusion rate constant k 3 was calculated from the slope of the line obtained by plotting q t and t 0.5 . The correlation coefficient for the pseudo-second-order model is the highest among the four kinetic models, revealing that the pseudo-second-order model best describes the adsorption kinetics of ammonium onto M-Zeo, and that chemisorption dominates in the adsorption process (Huang et al, 2017;Liao et al, 2012). This conclusion matched the fitting results from the D-R isotherm.…”

RETRACTED: Enhanced Adsorption of Zn(II) onto Graphene Oxides Investigated Using Batch and Modeling Techniques

“…The adsorption of Zn(II) on GO is simulated using the diffuse layer model (DLM) of surface complexation modeling with the help of the FITEQL v 4.0 code [ 28 , 30 ]. The values of the protonation and deprotonation constants (logK + and logK − ) are described using Equations (2) and (3), respectively: where SOH is represented as the amphoteric surface groups on GO.…”

One-pot mechanochemical ball milling synthesis of the MnOx nanostructures as efficient catalysts for CO2 hydrogenation reactions

“…14,15 The manganese-based compounds are crucial components in supercapacitors, electrochemical cells for rechargeable batteries, the degradation of organic dyes, removal of the heavy metals from the polluted water, water oxidation and soot combustion. [16][17][18][19][20][21][22] Typically, catalytic activity for CO 2 reduction and hydrogenation can be improved by a tiny amount of doping or tuning by promoting noble metals such as platinum. 23 Nonnoble metal-doped catalysts such as copper 24 also exist for CO 2 hydrogenation, but they are barely mentioned in the literature.…”