Modelovanje sorpcionih izotermi jona Ni(II) na otpadnim cementnim materijalima

Otpadni cementni materijali (beton i fasada) su bazirani na kvarcu i kalcitu. Prvenstveno zahvaljujući kalcitu i baznom karakteru, ove matrice su pokazale visok afinitet prema jonima nikla. Ispitivanje uticaja početne koncentracije jona Ni u rastvoru na sorbovanu količinu omogućava definisanje sorpcionih izotermi. U ovom radu su prikazani rezultati matematičkog modelovanja izotermi Langmuir-ovim i Freundlich-ovim modelom. Langmuir-ov model znatno bolje opisuje eksperimentalne podatke dobijene za sorpciju na betonu, dok je sorpcija otpadnom fasadom bolje opisana Freundlich-ovom izotermom

Functionalized biogenic hydroxyapatite with 5-aminosalicylic acid - Sorbent for efficient separation of Pb2+ and Cu2+ ions

The biogenic hydroxyapatite (BHAP), obtained by proper treatment of bovine bones, was functionalized with 5-aminosalicylic acid (5-ASA). The coordination of 5-ASA to the surface of BHAP leads to the charge transfer (CT) complex formation accompanied with absorption in visible spectral range. The sorption ability of surface-modified BHAP with 5-ASA (5-ASA/BHAP) for removal of Pb2+ and Cu2+ ions from single- and bi-component solutions was compared with unmodified BHAP. The thorough characterization of both sorbents, BHAP and 5-ASA/BHAP, was performed including X-ray diffraction analysis (XRD), transmission electron microscopy (TEM), nitrogen adsorption-desorption isotherms, as well as diffuse reflection spectroscopy. Sorption kinetics and equilibriums for both ions (Pb2+ and Cu2+) by as-prepared BHAP and 5-ASA/BHAP are quite different. Functionalized sorbent demonstrated faster sorption kinetic and higher maximum sorption capacity for Pb2+ ions from bi-component solutions. From equimolar Pb2+ and Cu2+ mixture with a total concentration of 10-2 mol/L, 66% of Pb2+ was recovered using BHAP, while 97% using 5-ASA/BHAP. These preliminary data indicate potential applicability of properly functionalized hydroxyapatite for selective removal of heavy metal ions from contaminated water.The peer-reviewed version: [http://cer.ihtm.bg.ac.rs/handle/123456789/3015

Microwave sintering of fine grained HAP and HAP/TCP bioceramics

The effect of microwave sintering conditions on the microstructure, phase composition and mechanical properties of materials based on hydroxyapatite (HAP) and tricalcium phosphate (TCP) was investigated. Fine grained monophase HAP and biphasic HAP/TCP biomaterials were processed starting from stoichiometric and calcium deficient nanosized HAP powders. The HAP samples microwave (MAT) sintered for 15 min at 900 degrees C, with average grain size of 130 nm, showed better densification, higher density and certainly higher hardness and fracture toughness than samples conventionally sintered for 2 h at the same temperature. By comparing MW sintered HAP and HAP/TCP samples, it was concluded that pure HAP ceramics have superior mechanical properties. For monophase MW sintered HAP samples, the decrease in the grain size from 1.59 mu m to 130 nm led to an increase in the fracture toughness from 0.85 MPa m(1/2) to 1.3 MPa m(1/2). (C) 2009 Elsevier Ltd and Techna Group S.r.l. All rights reserved

Amendment Type and Dose Effects onto Coexisting Copper, Lead, and Nickel Ions Distribution in Soil

The use of soil additives for toxic metals chemical stabilization aims to decrease in situ the pollutants' mobility and availability. In this study, the effectiveness of rinsed red mud (RBRM) and annealed animal bones (B400) was compared in terms of Cu, Pb and Ni stabilization in two contaminated soils with contrasting properties Dystric Cambisol (CM dy) and Rendzic Leptosol (LP rz). The mobility of metals in unamended soil samples (control) and samples amended with 1% and 5% of selected additives were compared using sequential extraction protocol. The relative content of metals in readily and potentially available fractions was higher in CM dy (62% Pb, 13% Cu, and 31% Ni in exchangeable fraction) than in LP rz ( lt 5% of Pb, Cu, Ni in exchangeable fraction). In CM dy, both additives have caused a decrease in metal mobility with an increase of their doses. The effect of 5% sorbent addition was most pronounced related to Pb immobilization, provoking decrease of exchangeable Pb content to lt 10%. Furthermore, B400 addition has redistributed investigated metals from the exchangeable to the residual phase more effectively than RBRM, and its effect on metal mobility decreased in the order Pb gt Cu gt Ni. Amending of LP rz soil had limited effects with no apparent decrease in exchangeable metal content. The effects of soil type variation, the type of additive and the additive dose onto metal mobility were compared according to ANOVA results. The content of readily and potentially available forms of metals was found to be (i) significantly correlated with all investigated variables for Pb, (ii) significantly correlated with soil type for Cu, and (iii) not in significant correlation with selected variables for Ni. Complex impacts of soil properties and treatment conditions on the mobility of co-contaminants emphasize the need for an individual approach to each case of contamination

The role of different minerals from red mud assemblage in Co(II) sorption mechanism

A range of industrial by-products are currently under the consideration as cost-effective alternatives to conventional sorbent materials for environmental clean-up and remediation applications. Bauxite residue (red mud) has demonstrated exceptionally high potential for the immobilization of cationic pollutants. Due to heterogeneity of such material, determination of the role of individual mineral phases in the overall sorption mechanism is a challenging task. To enlighten the mechanism of Co(II) sorption by mineral assemblage of the red mud, sequential extraction analysis of Co-loaded sample was combined with the microscopic and spectroscopic studies performed by Scanning Field Emission Electron Microscope (FE-SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS). Sorbed Co(II) ions were found associated with operationally defined Fe,Mn-oxide and carbonate/acid soluble fractions. Binding of Co(II) by the red mud was achieved primarily by means of chemisorption/surface precipitation on Fe- and Ti-oxides. In coexistence with these highly selective surfaces, gibbsite and silica appeared to be low affinity sites for Co(II). Incongruent dissolution of sodalite phase was detected, indicating that its function was not to ensure sorption centers, but to increase the solution pH creating favorable environment for Co(II) binding by Fe- and Ti-oxides. The results demonstrate high stability of sorbed Co(II) and synergistic action of mineral constituents as essentially important property for red mud implementation as a purifying and remediation agent