Adsorption Behaviors and Mechanisms of Cu2+, Zn2+ and Pb2+ by Magnetically Modified Lignite

In order to solve the problems of high content of Cu2+, Zn2+ and Pb2+ in acid mine wastewater (AMD), and limited adsorption capacity of lignite, the lignite was used as raw material to prepare magnetically modified lignite (MML), and adsorption performance of lignite and MML on Cu2+, Zn2+ and Pb2+ was investigated by static beaker experiment and dynamic continuous column experiment. At the same time, the adsorption mechanism was revealed by means of scanning electron microscopy (SEM), X-ray diffractometer (XRD) and Fourier transform infrared spectrometer (FTIR). The results showed that the adsorption processes of lignite and MML on heavy metal ions were more consistent with the Langmuir model, obeying the quasi first-order model and quasi second-order model, respectively. In addition, the intraparticle diffusion model indicated that the adsorption processes were jointly controlled by multiple adsorption stages. The dynamic continuous column experiments showed that the average removal rates of Cu2+, Zn2+ and Pb2+ were 78.00%, 76.97% and 78.65% for lignite and 82.83%, 81.57% and 83.50% for MML, respectively. Compared with lignite, the adsorption effect of MML was better. From SEM, XRD and FTIR tests, it can be seen that the magnetic modification process successfully loads Fe3O4 onto the surface of lignite, making the surface morphology rougher, and the adsorption process of MML on Cu2+, Zn2+ and Pb2+ is related to the O-H stretching vibration of carboxylic acid ions and Fe-O stretching vibration of Fe3O4 particles.

Prediction of 2D ferromagnetism and monovalent europium ions in the EuBr/graphene heterojunctions

Europium, one of the rare earth elements, exhibits +2 and +3 valence states and has been widely used for magnetic modification of materials. Based on density functional theory calculations, we...

First-Principles Electronic-Structure Study of Graphene Decorated with 4d-Transition Atoms

Adsorption configurations, electronic structures and net spins of graphene adsorbing 4d transition atoms are calculated by first-principles calculations to explore the magnetic modification of decorating metal atoms on graphene. Y, Zr and Nb atoms can be adsorbed on graphene sheet via ionic bonds with an evident charge transfer, while Mo, Tc, Ru and Rh atoms form covalent-like bonding with graphene carbon atoms due to orbital hybridization, as indicated by Mulliken atomic charges and electron density differences. The 4d-transition atoms can be adsorbed on a carbon-ring center and atomic-bridge with a high binding energy as the typical chemisorption, which leads to specific modifications in electronic-band character and magnetic properties by introducing electron-states near Fermi-level. By adsorbing 4d-transition atoms, the electronic structure of graphene will alter from a semi-metal to a metal character, and engender net spin magnetism from the spin-polarization in 5s and 4d orbitals of adsorption atoms. This paper provides a significant theoretical basis for further experimental explorations of the atom-decorated graphene in nanoelectronics.

Magnetically modified corn cob as a new low-cost biosorbent for removal of Cu (II) and Zn (II) from wastewater

Wastewater containing heavy metals can potentially harm the human and living organisms and also damage the environment and ecosystem. Wastewater containing total copper (Cu) and zinc (Zn) over the normal threshold will result in Wilson's disease and digestive health, respectively. One of the most widely used methods to remove heavy metals from wastewater is adsorption. One type of adsorbent that has gained interest among researchers was biomass-based adsorbent or biosorbent. In this work, magnetic modification was used to increase the adsorption capacity of the biosorbent. Therefore, the aim of this study was to determine the effect of magnetic modification of corncobs as biosorbent on the adsorption of Cu(II) and Zn(II) heavy metals from an aqueous solution. Magnetic modification with FeCl3.7H2O on corncobs has successfully increased the adsorption capability of Zn(II) and Cu(II) from aqueous solution. The optimum modification ratios for the adsorption of Zn(II) and Cu(II) were 1:2 and 2:1. The adsorption of these both heavy metals took place at temperature of 50°C with the adsorbent doses of 1 g and 1.5 g for Cu(II) and Zn(II), respectively. The highest adsorption percentages for the adsorption of Zn(II) and Cu(II) were 89.3% and 89.2%, respectively. Whereas, the maximum adsorption capacities of Cu(II) and Zn(II) were 75.76 mg/g and 63.93 mg/g, respectively. The adsorption mechanism of Zn(II) and Cu(II) has followed the Freundlich isothermal adsorption model.