Enhanced removal of Ni(II) from aqueous solutions by effective acid functionalization of carbon nanotube based filters

Abstract

Multiwalled carbon nanotubes (MWNTs) have shown a promising efficiency as an adsorbent, owing to their large surface area and affinity for heavy metal ions. Nevertheless, the effective functionalization of the MWNT is essential to enhance the surface reactivity towards heavy metal removal. In order to elucidate this functionalization, acid treatment of mixture of HNO3/H2SO4 followed by H2SO4/H2O2 for etching process was conducted. The acid functionalized MWNTs (F-MWNTs) were characterized with SEM, EDS, BET surface area and FTIR. The obtained results confirm the formation of oxygen groups attached to the surfaces of treated nanotubes (e.g. carboxyl) which alter their physicochemical properties and enhance the surface reactivity. The removal of Ni(II) from aqueous solutions by using immaculate and functionalized MWNT-filters (F-MWNTs) was studied as a function of pH, initial concentration of Ni(II), MWNT mass and contact time. F-MWNT filters showed an enhancement of the removal efficiency of Ni(II) up to 99.8% for concentration 10 ppm with exceptionally high adsorption capacity that could reach 333.3 mg/g. The adsorption isotherm is well fitted by the Langmuir equation. The ion exchange mechanism between F-MWNTs and Ni(II) ions is suggested as well-situated mechanism. It was found that F-MWNT filters can be reused through many cycles of regeneration with high performance. Our investigation demonstrated that F-MWNT filters are effective and can be appreciably considered as resourceful and economical adsorbent for heavy metal removal from wastewater.