Experimental study on mercury ions removal from aqueous solution by MnO2/CNTs nanocomposite adsorbent

Experimental study on mercury ions removal from aqueous solution by MnO2/CNTs nanocomposite adsorbent

MnO2-coated carbon nanotubes (MnO2/CNT) were prepared, characterized and used to remove Hg(II)from aqueous solution. Characterization of the prepared hybrid adsorbent was carried out usingtransmission electron microscopy (TEM), N2 adsorption–desorption, X-ray diffraction (XRD) and thermalgravimetric analysis (TGA). The synthesized MnO2/CNT sorbent possessed specific area of 110.38(m2 g 1), mesopore size (2.70 nm) and total pore volume of 0.522 (cm3 g 1). XRD diffraction analysisrevealed the birnessite-type MnO2 is produced through the hydrothermal synthesis and was coated onCNTs surface. A series of batch adsorption experiments were conducted to study the effect oftemperature, pH, initial concentration, the presence of other heavy metals and contact time on Hg(II)uptake by the adsorbent. Optimum conditions obtained were 50 8C, pH 5–7 and contact time of 80 min. Hg adsorption on MnO2/CNT was a fast process and the kinetics followed a pseudo-second-order rateequation. The adsorption isotherms were analyzed using Langmuir and Freundlich models, and theFreundlich equation best describes the interaction between mercury species and MnO2/CNT. Thermodynamic parameters of DH8, DS8 and DG8 were calculated and it was found that the Hg(II)species adsorption on the MnO2/CNT is endothermic and spontaneous. From the D–R isotherm, the meanfree energy was calculated as 7.07 kJ mol 1 indicating that the sorption of Hg(II) was taken place byphysico-chemical mechanism.

MnO2-coated carbon nanotubes (MnO2/CNT) were prepared, characterized and used to remove Hg(II)from aqueous solution. Characterization of the prepared hybrid adsorbent was carried out usingtransmission electron microscopy (TEM), N2 adsorption–desorption, X-ray diffraction (XRD) and thermalgravimetric analysis (TGA). The synthesized MnO2/CNT sorbent possessed specific area of 110.38(m2 g 1), mesopore size (2.70 nm) and total pore volume of 0.522 (cm3 g 1). XRD diffraction analysisrevealed the birnessite-type MnO2 is produced through the hydrothermal synthesis and was coated onCNTs surface. A series of batch adsorption experiments were conducted to study the effect oftemperature, pH, initial concentration, the presence of other heavy metals and contact time on Hg(II)uptake by the adsorbent. Optimum conditions obtained were 50 8C, pH 5–7 and contact time of 80 min. Hg adsorption on MnO2/CNT was a fast process and the kinetics followed a pseudo-second-order rateequation. The adsorption isotherms were analyzed using Langmuir and Freundlich models, and theFreundlich equation best describes the interaction between mercury species and MnO2/CNT. Thermodynamic parameters of DH8, DS8 and DG8 were calculated and it was found that the Hg(II)species adsorption on the MnO2/CNT is endothermic and spontaneous. From the D–R isotherm, the meanfree energy was calculated as 7.07 kJ mol 1 indicating that the sorption of Hg(II) was taken place byphysico-chemical mechanism.