Search results for "aqueous solution"
showing 10 items of 1610 documents
Optical mercury sensing using a benzothiazolium hemicyanine dye.
2006
[structure: see text] The selectivity and sensitivity of a benzothiazolium hemicyanine dye toward mercury(II) in aqueous solutions are described. Mercury ions coordinate to the dye forming a 1:1 complex. This interaction induces a color change in the dye at micromolar concentrations of mercury. Furthermore, the color change and quenching of the dye emission are selective for mercury when compared with other ions such as lead(II), cadmium(II), zinc(II), or iron(II).
Modelling Cd(II) removal from aqueous solutions by adsorption on a highly mineralized peat. Batch and fixed-bed column experiments
2006
This paper evaluates the potential use of a locally available organic soil amendment as a low-cost adsorbent. The removal of cadmium from aqueous solutions was studied by means of kinetic, batch and fixed-bed experiments. Batch experiments were conducted to evaluate the process kinetics and the removal equilibrium over a broad pH range. Pseudo-second-order kinetics and Freundlich equilibrium parameters were obtained. Six column experiments were carried out at different flow-rates and feed concentrations. Breakthrough curves showed higher metal retention than expected from the batch adsorption isotherms. Column modelling assuming rate-controlled pore diffusion was successfully performed. The…
Sorption properties of algae Spirogyra sp. and their use for determination of heavy metal ions concentrations in surface water.
2010
Abstract Kinetics of heavy-metal ions sorption by alga Spirogyra sp. was evaluated experimentally in the laboratory, using both the static and the dynamic approach. The metal ions – Mn2+, Cu2+, Zn2+ and Cd2+ – were sorbed from aqueous solutions of their salts. The static experiments showed that the sorption equilibria were attained in 30 min, with 90-95% of metal ions sorbed in first 10 min of each process. The sorption equilibria were approximated with the Langmuir isotherm model. The algae sorbed each heavy metal ions proportionally to the amount of this metal ions in solution. The experiments confirmed that after 30 min of exposition to contaminated water, the concentration of heavy meta…
Cadmium and Copper Removal by a Granular Activated Carbon in Laboratory Column Systems
2000
Single and competitive removal of Cd and Cu from aqueous solutions by using Darco 12–20 mesh granular activated carbon in column systems has been investigated. Seven experiments modifying the initial pH and the flow rate were performed. Results showed the efficiency of activated carbon as a sorbent for both metals. pH is shown to be the decisive parameter on metal removal in the column; metal removal increases when the influent pH value is raised. The influence of the flow rate for the experimental conditions is negligible. Batch adsorption and column data are compared. Column modeling assuming local equilibrium and rate-controlled pore diffusion was performed.
Cadmium and Zinc Adsorption onto Activated Carbon: Influence of Temperature, pH and Metal/Carbon Ratio
1996
The adsorption characteristics of cadmium and zinc onto a granular activated carbon were studied. Cadmium and zinc removals increased on raising pH and temperature, and decreased on raising the molar metal/carbon ratio. The adsorption processes were modelled using the surface complex formation (SCF) Triple Layer Model (TLM) with an overall bidentate species. A dependence of the SCF constant on pH, the molar metal/carbon ratio and temperature was observed, and a correlation for log K ads was determined. The SCF model successfully predicted cadmium and zinc removals.
Sorption of thallium(I) ions by peat.
2013
The increasing industrial use of thallium has raised the need for removal of this highly toxic element from wastewater. Thallium is more toxic than cadmium, copper, zinc, lead and mercury and as it is easily accumulated in humans, animals and plants, it poses a threat to both the environment and human health. Peat has been used as an effective, relatively cheap and easily available sorbent to treat waters containing heavy metals. In this study, peat was characterized and used as sorbent for the removal of Tl(I) ions from aqueous solution. The effect of initial Tl(I) concentration, pH, contact time, temperature and ionic strength was studied in batch mode. The maximum sorption capacity of pe…
Metal speciation in biological fluids — a review
1996
The literature on the speciation of metal ions in biological fluids is comprehensively reviewed. Critical examination on this subject reveals that major work has been done in blood and urine. Speciation in materials like milk has not yet been widely studied. On the other hand, only few references could be found on sweat, saliva, cell lysate, cerebrospinal, seminal, tear and bronchoalveolar fluids. The topics studied for these fluids were mainly the speciation of arsenic, mercury, aluminium and selenium. Work on the speciation of other elements like zinc, chromium, cadmium, lead, copper, iron etc. have also been carried out in such matrices. The present literature survey includes also a crit…
Molecular Self-Assembly Versus Surface Restructuring During Calcite Dissolution.
2016
Organic additives are known to alter the mineral-water interface in various ways. On the one hand, organic molecules can self assemble into ordered structures wetting the surface. On the other hand, their presence can affect the interfacial morphology, referred to as surface restructuring. Here, we investigate the impact, of a class of calcium-complexing azo dyes on the dissolution of calcite (10.4) using high-resolution atomic force microscopy operated in aqueous solution, with a focus on the two constitutional isomers Eriochrome Black T and Eriochrome Black A. A very pronounced surface restructuring is observed in the presence of the dye solution, irrespective of the specific dye used and…
Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy
2014
Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic - yet decisive - question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used…
A new simple approach to evaluate pedogenic clay transformation in a Vertic Calcisol
2006
The aim of this study is to characterize the pedogenic clay minerals by using simple approach: Mixing mineralogical and geochemical findings. The fine clay fractions (< 0.1 μm) of a Vertic Cambisol profile were studied by means of X-ray diffraction (XRD), infrared spectroscopy (FTIR) and cation exchange capacity (CEC). Qualitative and quantitative mineralogical compositions of the clay mixture were determined. Moreover, chemical equilibria and thermodynamic stabilities of minerals (calcite, gypsum, kaolinite, smectites and illites) were studied using results of ionic activities obtained from total concentration of various aqueous species in water extracts from soil-saturated pastes. XRD ana…