Efficient Removal of Pb(II) and Cd(II) from Industrial Mine Water by a Hierarchical MoS2/SH-MWCNT Nanocomposite

Rashi Gusain; Neeraj Kumar; Elvis Fosso-Kankeu; Suprakas Sinha Ray

doi:10.1021/acsomega.9b01603

Efficient Removal of Pb(II) and Cd(II) from Industrial Mine Water by a Hierarchical MoS₂/SH-MWCNT Nanocomposite

ACS Omega. 2019 Aug 14;4(9):13922-13935. doi: 10.1021/acsomega.9b01603. eCollection 2019 Aug 27.

Authors

Rashi Gusain^{1

2}, Neeraj Kumar¹, Elvis Fosso-Kankeu³, Suprakas Sinha Ray^{1

2}

Affiliations

¹ DST-CSIR National Centre for Nanostructured Materials, Council for Scientific and Industrial Research, Pretoria 0001, South Africa.
² Department of Chemical Sciences, University of Johannesburg, Doornfontein, Johannesburg 2028, South Africa.
³ Water Pollution Monitoring and Remediation Initiatives Research Group, School of Chemical and Minerals Engineering, North West University, P. Bag X6001, Potchefstroom 2520, South Africa.

Abstract

In this study, we investigate the adsorption capability of molybdenum sulfide (MoS₂)/thiol-functionalized multiwalled carbon nanotube (SH-MWCNT) nanocomposite for rapid and efficient removal of heavy metals [Pb(II) and Cd(II)] from industrial mine water. The MoS₂/SH-MWCNT nanocomposite was synthesized by acid treatment and sulfurization of MWCNTs followed by a facile hydrothermal reaction technique using sodium molybdate and diethyldithiocarbamate as MoS₂ precursors. Morphological and chemical features of the nanocomposite material were studied using various characterization techniques. Furthermore, the effects of adsorbent (MoS₂/SH-MWCNT nanocomposite) concentration, contact time, initial concentration of heavy-metal ions, and reaction temperature were examined to determine the efficiency of the adsorption process in batch adsorption experiments. Kinetics and isotherm studies showed that the adsorption process followed pseudo-second-order and Freundlich adsorption isotherm models, respectively. Thermodynamic parameters calculated using van't Hoff plots show the spontaneity and endothermic nature of adsorption. MoS₂/SH-MWCNT nanocomposite demonstrates a high adsorption capacity for Pb(II) (90.0 mg g^-1) and Cd(II) (66.6 mg g^-1) following ion-exchange and electrostatic interactions. Metal-sulfur complex formation was identified as the key contributor for adsorption of heavy-metal ions followed by electrostatic interactions for multilayer adsorption. Transformation of adsorbent into PbMoO_4-x S _x and CdMoO_4-x S _x complex because of the adsorption process was confirmed by X-ray diffraction and scanning electron microscopy-energy-dispersive spectrometry. The spent adsorbent can further be used for photocatalytic and electrochemical applications; therefore, the generated secondary byproducts can also be employed for other purposes.