Characteristics of Adsorption/Desorption Process on Dolomite Adsorbent in the Copper(II) Removal from Aqueous Solutions.

The removal of hazardous heavy metals that have been released into the environment due to industrial activities has become an important issue in recent years. The presented study concerned the removal of copper(II) ions from aqueous solutions using dolomites. Dolomite is a very attractive adsorbent due to its wide availability, low cost, good adsorption, and environmental compatibility. The paper describes the properties of D-I and D-II dolomites from two different open-cast mines in Poland. The properties of natural adsorbents were determined based on point of zero charges (PZC), elemental analysis of the adsorbent composition, FT-IR, XRD, and SEM spectra analysis. Depending on the initial concentration of the solution used, the adsorption efficiency of copper(II) ions was 58-80% for D-I and 80-97% for D-II. The adsorption mechanism in the case of D-II dolomite was mainly based on ion exchange, while chemisorption dominated the D-I dolomite surface. Considering the possibility of the regeneration and reuse of the adsorbent, dolomite D-II is a better material (the desorption efficiency of copper(II) ions was 58-80%). The adsorption behavior of dolomites has been described using six adsorption isotherms. The best fit was obtained for the Redlich-Peterson, Jovanovic, and Langmuir isotherms, indicating that monolayer adsorption occurred. The maximum adsorption capacity for copper(II) was 378 mg/g of D-I and 308 mg/g of D-II.

Significance of MnO2 Type and Solution Parameters in Manganese Removal from Water Solution.

A very low concentration of manganese (Mn) in water is a critical issue for municipal and industrial water supply systems. Mn removal technology is based on the use of manganese oxides (MnOx), especially manganese dioxide (MnO2) polymorphs, under different conditions of pH and ionic strength (water salinity). The statistical significance of the impact of polymorph type (akhtenskite ε-MnO2, birnessite δ-MnO2, cryptomelane α-MnO2 and pyrolusite ß-MnO2), pH (2-9) and ionic strength (1-50 mmol/L) of solution on the adsorption level of Mn was investigated. The analysis of variance and the non-parametric Kruskal-Wallis H test were applied. Before and after Mn adsorption, the tested polymorphs were characterized using X-ray diffraction, scanning electron microscope techniques and gas porosimetry analysis. Here we demonstrated the significant differences in adsorption level between MnO2 polymorphs' type and pH; however, the statistical analysis proves that the type of MnO2 has a four times stronger influence. There was no statistical significance for the ionic strength parameter. We showed that the high adsorption of Mn on the poorly crystalline polymorphs leads to the blockage of micropores in akhtenskite and, contrary, causes the development of the surface structure of birnessite. At the same time, no changes in the surfaces of cryptomelane and pyrolusite, the highly crystalline polymorphs, were found due to the very small loading by the adsorbate.

Characteristics of the Properties of Absodan Plus Sorbent and Its Ability to Remove Phosphates and Chromates from Aqueous Solutions.

The aim of the research was to characterize the parameters of the diatomite sorbent Absodan Plus as well as to assess its suitability for the adsorption of chromates and phosphates from acidic aqueous solutions simulating the conditions occurring in some types of industrial wastewater. The scope of the research includes XRD, SEM, BET, and PZC analyses, and 3D observation of commercial diatomite granules and batch tests to determine the constants of kinetics and the equilibrium of chromates and phosphates adsorption. Absodan Plus is a diatomite commercial material containing an amorphous phase (33%) and is also the crystalline phase of quartz, hematite, and grossite. The material is macro- and mesoporous and its specific surface area is about 30 m2/g. Its PZC is around pH = 5.5-6.0 and in an acidic environment is able to adsorb the anions. The saturation of the adsorbent surface with molecules of the adsorbed substance occurs after 2 h for chromates and 2.5 h for phosphates. The maximum adsorption capacity of Absodan Plus in terms of phosphorus and chromium amounts to 9.46 mg P/g and 39.1 mg Cr/g, respectively. As shown by XRD analysis, Absodan Plus contains an admixture of hematite, which can support the removal of chromium and phosphorus.

Characterisation and utilisation of solid waste from coal combustion to modelling of sorption equilibrium in a bi-component system metal-dye.

It was found that the chemical enhancement of fly ash from coal combustion by tetrabutylammonium bromide treatment yields an effective and economically feasible material for the treatment of chromium and basic dye Rhodamine B containing effluents. Characterisation of coal fly ash and treatment with tetrabutylammonium bromide were done by using a Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, confocal three-dimensional microscope, X-ray diffraction and laser particle sizer. The studies of equilibrium in a bi-component system by means of extended Langmuir, extended Langmuir-Freundlich and Jain-Snoeyink models were analysed. The estimation of parameters of sorption isotherms in a bi-component system metal-dye has shown that the best-of-fit calculated values of experimental data for both sorbates have been the Jain-Snoeyink model and the extended Langmuir model, but only in the case of a Rhodamine B. The maximum monolayer adsorption capacity of the fly ash-tetrabutylammonium bromide was found to be 863 mg g-1 and 670 mg g-1 for chromium and Rhodamine B, respectively.

Enhanced sorption capacity of a metal-dye system from water effluents by using activated industrial waste.

Activated coal fly ash (FA) treated with NaOH and hexadecyltrimethylammonium bromide (HDTMABr) was used as adsorbent for removal of cadmium(II) ions and rhodamine B (RB) from an aqueous solution. Characterization of fly ash and FA-HDTMABr were done using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and X-ray diffraction (XRD). The sorption equilibrium in the system was analysed using isotherm models, such as Freundlich, Langmuir, generalized Langmuir-Freundlich, Redlich-Peterson, Jovanovic, extended Jovanovic, Tóth, Frumkin-Fowler-Guggenheim, Fowler-Guggenheim-Jovanovic-Freundlich, Temkin, Dubinin-Radushkevich, Halsey, Brunauer, Emmett and Teller. The evaluation of the fit of the isotherms studied experimentally was carried out by means of the reduced chi-square test and the coefficient of determination. The maximum monolayer adsorption capacity of the FA-HDTMABr was found to be 744 mg·g-1 and 666 mg·g-1 for Cd(II) and RB, respectively. The PFO, PSO, Elovich mass transfer, liquid film diffusion and intra-particle diffusion models were analysed. Sorption kinetics data were well fitted by the PSO model. The Elovich and intra-particle model also revealed that there are two separate stages in the sorption process, namely, external diffusion and intra-particle diffusion.

Investigations of chemical fraction of Co and Ni in industrial fly ash and mobility of metals in environmental conditions.

The quantitative evaluation of chemical fraction of Co and Ni in the industrial fly ash by methods of five step sequential extraction was carried out in order to characterize metal mobility in environmental conditions. The research involved (i) water-soluble (pH=7), (ii) acid-soluble (pH=5), (iii) oxide, (iv) sulfide and (v) residue metal fractions. It was discovered, that the total extraction of the studied metals from fly ash to solutions take place in the following quantities Co - 35.5 and Ni - 153.0mgkg(-1). The investigations of chemical fractions proved that the subject metals occur mainly in fly ash as: oxide (Co - 7.0, Ni - 28.5mgkg(-1)) and residue (Co - 11.5, Ni - 42.5mgkg(-1)) as well as sulfide (Co - 8.5, Ni - 46.5mgkg(-1)). Low concentrations of metals for water-soluble fraction (Co - 0.7, Ni - 1.2mgkg(-1)) and acid-soluble fraction (Co - 4.5, Ni - 23.5mgkg(-1)) were observed. The fractions of Co and Ni leachable from the ash in environmental conditions contain: 24.0% (Co) and 23.3% (Ni) of metal total amount in the industrial fly ash. The obtained mobility parameter of Co and Ni can be applied to estimate the concentration increase of mobile and hardly mobile forms of these metals in soil polluted with the ash.

Investigations of sequential leaching behaviour of Cu and Zn from coal fly ash and their mobility in environmental conditions.

The quantitative evaluation of chemical fraction of Cu and Zn in the coal fly ash by methods of five-step sequential extraction was carried out in order to characterize metal mobility in environmental conditions. The research involved (i) water-soluble (pH 7), (ii) acid-soluble (pH 5), (iii) oxide, (iv) difficult reducible and (v) residual metal fractions. It was discovered, that the total extraction of the studied metals from coal fly ash to solutions take place in the following quantities Cu-39.0mgkg(-1) and Zn-89.0mgkg(-1). The investigations of chemical fractions proved that the subject metals occur mainly in coal fly ash as: oxide (Cu-12.0mgkg(-1), Zn-37.0mgkg(-1)) and residual (Cu-9.5mgkg(-1), Zn-27.0mgkg(-1)) as well as difficult reducible (Cu-16.5mgkg(-1), Zn-22.0mgkg(-1)). Low concentrations of metals for water-soluble fraction (Cu