Preparation of recyclable materials for removing heavy metal ions in aqueous solution and wastewater applications

BACKGROUND Two functionalized nano-adsorbents were prepared by modifying carbon nanotubes and graphene oxide with active carboxyl groups, and used to remove Pb(II) heavy metal ions in aqueous solutions. The adsorbent combines the advantages of the active groups that can easily capture heavy metal ions and the high specific surface area of nanomaterials, has high adsorption capacity and affinity and is easily separated from the sample solution by centrifugation. RESULTS Both scanning and transmission electron microscopy images show that the walls of the carbon tubes are oxidized and the ports at both ends are also opened, and the graphene oxide surface has more folds, producing more active groups such as carboxyl and hydroxyl groups, which provide suitable active sites for the attachment of heavy metals. X-ray photoelectron spectroscopy shows that characteristic peak of lead appears in the energy spectrum after adsorption. Raman and infrared spectra show that the surface defects of the two materials have increased. The adsorption capacity calculated using the Langmuir equation was 118.82 and 178.23 mg g(-1) at pH = 5, and equilibrium adsorption capacity was reached at 120 min. The adsorption capacity of the materials for Pb2+ reaches the equilibrium concentration value when the concentration is 50 mg L-1. Wastewater experiments were carried out to prove that the materials can meet the relevant national standards for lead ions in actual wastewater. CONCLUSIONS The adsorption results for the two materials demonstrated that the materials prepared in the optimum conditions exhibited strong adsorption ability and high stability and with promise for practical applications. (c) 2021 Society of Chemical Industry