Removal of Co(II) from aqueous solution by using hydroxyapatite

Adsorption characteristics of Pb(II), Cd(II) and Cu(II) on carbon nanotube-hydroxyapatite

Based on batch experiments, we investigate the adsorption characteristics of Pb(II), Cd(II) and Cu(II) on multi-walled carbon nanotube-hydroxyapatite (MWCNT-HAP) composites in detail and explore the effects of the solid-to-liquid ratio, pH, the ionic strength, reaction time and temperature on adsorption. The results show that the adsorption on MWCNT-HAP follows Pb(II)>Cu(II)>Cd(II). With an increasing solid-to-liquid ratio, the adsorption quantity of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP decreases, whereas the removal efficiency increases. The optimal pH for adsorption is 4.0∼6.0. The effect of the ionic strength on the adsorption of Cd(II) is pronounced, whereas that on the adsorption of Pb(II) and Cu(II) is small. In the single-component system and ternary-component system, the adsorption processes for Pb(II), Cd(II) and Cu(II) on MWCNT-HAP have fast kinetics, and the pseudo-second-order kinetics model can well describe the adsorption kinetics of the three heavy metals. The adsorption of Pb(II), Cd(II) and Cu(II) on MWCNT-HAP is spontaneous and endothermic, and the Langmuir model can well simulate the isothermal adsorption of Pb(II) and Cu(II), whereas the Langmuir and Freundlich models can be used to describe the isothermal adsorption of Cd(II).

Sorption behavior of Co-radionuclides from radioactive waste solution on graphene enhanced by immobilized sugarcane and carboxy methyl cellulose

Novel graphene-sugarcane bagasse-carboxy methyl cellulose (GSCCMC) nanocomposite have been synthesized via freeze-drying technique after preparation of graphene from natural graphite by modified Hummer method and evaluated as adsorbent for sorption of 60Co(II)-radionuclides from radioactive waste solution and real wastewater samples using a series of batch adsorption experiments and compared with graphene. The synthesized (GSCCMC) nanocomposite was characterized using Fourier transformer infrared (FT-IR), Transmission electron microscope (TEM), Thermal analysis, Elemental analysis, Specific Surface area (SBET) and X-ray diffraction (XRD), which confirmed the successful formation of graphene-sugarcane bagasse-carboxy methyl cellulose (GSCCMC) nanocomposite. Different parameters affecting the removal process including pH, contact time and metal ion concentration were investigated. Isotherm and kinetic models were studied. Adsorption kinetics described well by pseudo-second-order. The Langmuir model provides a better fitting than the Freundlich and Temkin models and the maximum adsorption capacity from Langmuir model were found to be 0.4186 and 0.2424 mol/g for (GSCCMC) nanocomposite and graphene (G), respectively. From Dubinin–Radushkevich (D–R) isotherm model, the sorption energy (E)-values of graphene (G) and (GSCCMC) are 10.16 and 10.564 kJ/mol, respectively and this mean the adsorption of 60Co(II)-radionuclides can be explained by chemisorption process, which is characteristic of ion exchange. Desorption of 60Co(II)-radionuclides from loaded (GSCCMC) nanocomposite was studied using different eluents (0.1 M HCl, 0.1 M NaOH and H2O). The data illustrated that 0.1 M HCl solution showed maximum desorption percent (D%) than other eluents. The economic viability of the adsorption process for the removal of 60Co(II) from wastewater samples was studied. The result indicated that the cost for preparation of (GSCCMC) nanocomposite is lower than for (GSCCMC) nanocomposite that prepared from purchase the graphene powder. Therefore, the synthesized (GSCCMC) nanocomposite was used as regenerated material for sorption of 60Co(II)-radionuclides from aqueous solutions and can be used for many times as a cost-effective and environmental friendly material in wastewater treatment.

Mesoporous hydroxylapatite/activated carbon bead-on-string nanofibers and their sorption towards Co(ii)

We fabricated mesoporous hydroxylapatite/activated carbon bead-on-string nanofibers from electrospun nanofibers by a hydrothermal method and evaluated their sorption towards Co(ii)viasorption kinetics and isotherms.