Issue 3 [November]( Special Issue: Development and Evaluation of Sorbent Materials for Environmental Applications ) The mechanism of retention of vanadium oxo-species at the “titanium oxide / aqueous solution" interfaceTella E., Panagiotou G.D., Petsi T., Bourikas K., Kordulis C., and Lycourghiotis A., Pages:231-238 DOI: https://doi.org/10.30955/gnj.000736Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe mechanism of retention of vanadium oxo-species at the “titanium oxide/aqueous solution” interface was investigated over a wide pH range (4-9) and V(V) solution concentration (10-5-2×10-2 M) by combining equilibrium deposition experiments, potentiometric titrations, microelectrophoresis and “proton–ion” titration curves. It was inferred that the adsorbed V(V) oxo-species are retained inside the compact layer of the interface through hydrogen/coordinative bonds forming very probably innersphere complexes with the titania surface groups. Study of the Cu(II) removal from aqueous solutions by adsorption on titaniaGeorgaka A. and Spanos N., Pages:239-247 DOI: https://doi.org/10.30955/gnj.000717Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe removal of heavy metals from wastewaters is a matter of paramount importance due to the fact that their high toxicity causes major environmental pollution problems. One of the most efficient, applicable and low cost methods for the removal of toxic metals from aqueous solutions is that of their adsorption on an inorganic adsorbent. In order to achieve high efficiency, it is important to understand the influence of the solution parameters on the extent of the adsorption, as well as the kinetics of the adsorption. In the present work, the adsorption of Cu(II) species onto TiO2 surface was studied. It was found that the adsorption is a rapid process and it is not affected by the value of ionic strength. In addition, it was found that by increasing the pH, the adsorbed amount of Cu2+ ions and the value of the adsorption constant increase, whereas the value of the lateral interaction energy decreases. Heavy-metal uptake by a high cation-exchange-capacity montmorillonite: the role of permanent charge sitesStathi P., Papadas I.T. , Tselepidou A. and Deligiannakis Y., Pages:248-255 DOI: https://doi.org/10.30955/gnj.000722Paper Topic: General Issue: Issue 3Get Full Paper AbstractA High Cation Exchange Capacity (HCM) montmorillonite clay has been prepared by acetate treatment of Zenith clay. The HCM has been evaluated for metal-uptake from aqueous solutions. The present data show that the cation exchange sites can play a significant role in the adsorption of metals in smectite clays. A theoretical analysis scheme has been developed which shows that permanent-charge sites can become dominant in metal-uptake by clays. In addition, it was shown that the permanent charge can influence the ionic-strength sensitivity of the Point of Zero Charge of the clay. Removal of ammonia by clinoptiloliteZabochnicka-Swiatek M. and Malinska K., Pages:256-261 DOI: https://doi.org/10.30955/gnj.000724Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe important advantage of zeolite applied to water treatment is its high porosity when comparing to other minerals. The porosity results in good hydrodynamic properties (the increase in the pressure loss on the zeolite filters is 1.5-2.0 times smaller than in the case of sand filters) and adsorption roperties, and in turn high capacity which allows for adsorption of contaminants (a clinoptilolite filter allows for removal of phytoplankton and bacteria). The increase in the application of artificial fertilizers and gradual contamination of water resulted from discharging industrial wastewater into the environment led to the contamination of the environment by nitric compounds. Wastewater contains about 15-50 mg dm-3 of nitric compounds (based on nitrogen) – ammonia salts constitute about 55-60% whereas organic forms of proteins, pesticides and aminoacids about 40-50%. Natural clinoptilolite could be applied to remove ammonium ions from water and wastewater. The ammonium ion uptake behaviour of clinoptilolite is connected to the processes of ion exchange. The main aim of this investigation is to evaluate the adsorption capacity of clinoptilolite towards ammonium ions. According to the obtained results the adsorption capacity of clinoptilolite for the removal of ammonium ions demonstrates its potential application in the treatment of water, wastewater and sanitary landfill leachate contaminated with ammonia. The highest adsorption capacity of clinoptilolite towards ammonium ions of 3.79 mg g-1 was found for the initial concentration of 300 mg L-1. The highest removal level reached by clinoptilolite for ammonium was of 99.74% for the initial concentration of ammonia of 50 mg L-1. The effect of exposure time on maximum uptake of ammonia was found to be insignificant. Poly(sodium acrylate) hydrogels as potential pH-sensitive sorbents for the removal of model organic and inorganic pollutants from waterBekiari V. and Lianos P., Pages:262-269 DOI: https://doi.org/10.30955/gnj.000720Paper Topic: General Issue: Issue 3Get Full Paper AbstractAnionic poly(sodium acrylate), PANa, hydrogels bearing negatively charged –COO- groups were used as sorbents for the removal of colored organic or inorganic model pollutants, namely Crystal Violet and Cu2+, from water. It was found that PANa hydrogels adsorb stronger Cu2+ions than Crystal Violet, as a consequence of the formation of coordination complexes between the hydrogel and the metal ions, while just electrostatic interactions are the major driving forces for Crystal Violet. Furthermore, the influence of pH, i.e. the neutralization degree i of the hydrogel, on its adsorption efficiency was investigated. It is shown that the adsorption of Cu2+ ions follows stoichiometry, namely one metal ion per two carboxylate anions. On the contrary, the adsorption of Crystal Violet is much lower than the charged stoichiometry. Study of polyacrylic acid adsorption on the interface of hydroxyapatite – electrolyte solutionsHafez I.T., Paraskeva C.A., Klepetsanis P.G. and Koutsoukos P.G., , Pages:270-278 DOI: https://doi.org/10.30955/gnj.000718Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe adsorption of polyacrylic acid (PAA) on hydroxyapatite (HAP) from HAP saturated solutions was studied in this work as a function of PAA concentration, temperature, pH and ionic strength. In all experiments, the adsorption was studied under conditions of negatively charged adsorbent and adsorbate, respectively. These conditions ensured that adsorption was not electrostatically favored. The solution composition was found to influence significantly the maximum of the adsorbed amount. In fact, the adsorption of PAA, was found to increase with ionic strength, due to the decrease of double layer thickness of HAP particles. The effect of temperature and ionic strength on the kinetics of adsorption are also reported. Adsorption isotherms obtained at 30oC were found to be Langmuirtype, while at higher temperatures they were of the Brunauer-Emmett-Teller (BET) type. The absorbed amount of PAA was found to decrease with temperature, while it increased with ionic strength. For pH values lower than 6.5, the adsorption increased while for pH between 6.5 and 9 the adsorbed amount remained almost constant. Adsorption of atrazine in packed beds Kovaios I.D., . Paraskeva C.A, and Koutsoukos P.G, Pages:279-287 DOI: https://doi.org/10.30955/gnj.000719Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe adsorption of the herbicide atrazine in packed beds filled with solids modelling soil components, (silica and humic acid), was studied at conditions simulating the adsorption of atrazine in cultivated soils. The choice of only two constituents of soil in the experimental study was based on the assumption that these two compounds contribute significantly to the adsorption of herbicides in soil relative to others, like alumina, calcium carbonate, etc. Packed beds were filled with inorganic material (silica gel grains) and solid organic compounds (humic acid). Adsorption data were fitted to the Freundlich isotherm. The presence of humic acid, even in small quantities, increases considerably the amount of adsorbed atrazine. Increasing humic acid content in the packed beds, the amount of adsorbed atrazine increased. Reversibility tests showed that the adsorption of atrazine was reversible. Two steps for adsorption and desorption were observed. The first fast step is attributed to the physical adsorption on the free adsorption sites of the substrates washed by the solution, while the second slow step is attributed to the diffusion of the molecules of atrazine within the structure of the silica and of the humic acid. Study of the hydrodynamics of atrazine containing solutions flow in the packed beds filled with silica and humic acid showed that the morphology of insoluble humic acid upon hydration changed its shape resulting in its transport through the bed and clogging of the narrow pores of the medium. As a result the packed bed permeability was reduced by 99%. Effect of growth conditions on biosorption of cadmium and copper by yeast cellsAnagnostopoulos V.A., Symeopoulos B.D. and Soupioni M.J., Pages:288-295 DOI: https://doi.org/10.30955/gnj.000725Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe dependence of Cd(II) and Cu(II) uptake by yeast cells on the age and temperature of cell culture was studied. Saccharomyces cerevisiae, Kluyveromyces marxianus and Debaromyces Hansenii were chosen as typical yeasts, while Cd(II) and Cu(II) as typical metal pollutants. Our results revealed that higher metal uptake was obtained by cells grown at the optimum temperature (30 oC) of cell culture. It was also found that the exponential phase cells resulted in a higher metal uptake than the stationary ones. A first interpretation of relevant bibliographic data concerning the effect of growth phase on metal uptake is proposed, assuming that limited qualitative changes in the cell wall structure take place as the cells pass from exponential to stationary phase, in addition to quantitative modifications, which have been reported in the literature. According to our interpretation the relative abundance among quantitative and qualitative alterations of cell wall, determines if stationary or exponential cells attain the higher metal binding capacity. An indication supporting our approach may be the fact that our hypothesis implies a decrease of pKa values of cell wall carboxyl groups with the age of cells, which is consistent with data reported by other authors. Removal of refractory organic sulfur compounds in fossil fuels using MOF sorbentsBlanco-Brieva G., Campos-Martin J.M., Al-Zahrani S.M. and Fierro J.L.G., Pages:296-304 DOI: https://doi.org/10.30955/gnj.000721Paper Topic: General Issue: Issue 3Get Full Paper AbstractThe stringent new regulations to lower sulfur content in fossil fuels require new economic and efficient methods for desulfurization of recalcitrant organic sulfur. Hydrodesulfurization of such compounds is very costly and requires high operating temperature and pressure. Adsorption is a non-invasive approach that can specifically remove sulfur from refractory hydrocarbons under mild conditions and it can be potentially used in industrial desulfurization. Intensive research has been conducted in materials development to increase their desulfurization activity; however, even the highest activity obtained is still insufficient to fulfil the industrial requirements. To improve the adsorption capacity and sorbent regeneration, more work is needed in areas such as increasing specific desulfurization activity, hydrocarbon phase tolerance, sulfur removal at higher temperature, and development of new porous substrates for desulfurization of a broader range of sulfur compounds. This work comprehensively describes the adsorption of organo-sulfur compounds present in liquid fuels on metal-organic framework (MOF) compounds. It has been demonstrated that the extent of dibenzothiophene (DBT) adsorption at temperatures close to ambient (304 K) is much higher on MOF systems than on the benchmarked Y-type zeolite and activated carbons. In addition, the DBT adsorption capacity depends strongly on the MOF type as illustrated by the much higher extent of adsorption observed on the Cu-(C300) and Al-containing (A100) MOF systems than on the Fe-containing (F300) MOF counterpart. Activated carbon amendment to remediate contaminated sediments and soils: a reviewHilber I. and Bucheli T.D., Pages:305-317 DOI: https://doi.org/10.30955/gnj.000723Paper Topic: General Issue: Issue 3Get Full Paper AbstractActivated carbon (AC) amendment for reduction of contaminant exposure in polluted soils and sediments has recently emerged as a promising remediation technique. Here, we provide a short overview of the state-of-the-art in activated carbon (AC) amendment to such sites. Most studies not only in sediments but also in soils were carried out in the laboratory and only a few in the field. Consequently, practical experience at the field scale is largely lacking, and feasible engineering approaches for AC amendment still need to be developed, especially for soils. The effectiveness of the AC treatment was evaluated by comparison of pollutant concentration reduction in the various endpoints with those in the unamended control matrix. Endpoints in use comprise pollutant concentrations in benthic organisms, depletive and non-depletive methods to quantify pollutant exposures, as well as various toxicity endpoints of plants. Half of the studies in soils and 68% of the studies in sediments showed reduced pollutant availabilities of >50% after AC amendment. Observed low reductions (<50%) might be due to low exposure time, insufficient equilibrium time for coke breeze, biochar, and granulated AC, overload of AC material, different uptake pathways of benthic organisms, and pollutant reductions outside the dynamic range of toxicity endpoints. Further research is needed to establish ideal AC amendment conditions to sediments and soils, leading to significantly reduced pollutant bioavailability. Pages1 2 next › last »