[show abstract][hide abstract] ABSTRACT: The adsorptive characteristics of Ni(II) from aqueous media on histosol modified by simple chemical treatments was investigated. The chemical treatments have been achieved by mixing histosol with aqueous solution of common chemical reagents (HNO 3 , NaCl and NaOH, respectively), without the addition of supplementary additives. The influence of initial Ni(II) concentration and equilibrium contact time was studied in a series of batch experiments, in comparison with untreated histosol. An increase of adsorption capacity of histosol in case of treatments with NaCl and NaOH (15.58 % and 24.19 %, respectively) was obtained, and this is mainly attributed to the increase of functional groups availability from adsorbent surface. In addition a significant decrease of equilibrium contact time in case of modified histosol was also found. The experimental data were analyzed using two isotherm models (Langmuir and Freundlich) and three kinetics models (pseudo-first order, pseudo-second order and intra-particle diffusion model). The Langmuir model provides best correlation of equilibrium experimental data, and the pseudo-second order describes well the adsorption kinetics of Ni(II) on untreated and modified histosol. The histosol modified by considered simple chemical treatments has potential for serving as Ni(II) adsorbent, and the cost of these treatments is very low.
Studia Universitatis Babeș-Bolyai. Chemia 12/2013; 4:121-136. · 0.09 Impact Factor
[show abstract][hide abstract] ABSTRACT: Sorption of Pb(II) was studied by using a biosorbent mixture of algae waste biomass and Purolite A-100 resin in a packed-bed column. Mixing these two components was done to prevent the clogging of the column and to ensure adequate flow rates. Increasing of solution flow rate and initial Pb(II) concentration make that the breakthrough and saturation points to be attained earlier. The experimental breakthrough curves were modeled using Bohart-Adams, Thomas and Yoon-Nelson models, and the parameters for all these models were calculated. A regeneration efficiency of 98% was achieved using 0.1molL(-1) HCl and not significant changes in lead uptake capacity after three biosorption/desorption cycles were noted. The biosorbent mixture was able to remove Pb(II) from synthetic wastewater at pH 5.0 and flow rate of 3.5mLmin(-1), and the obtained effluent has better quality characteristics. The biosorbent mixture it is suitable for a continuous system for large-scale applications.
[show abstract][hide abstract] ABSTRACT: A simple, sensitive and selective spectrophoto-metric method is proposed for rapid and direct determina-tion of nitrate in small volumes of natural surface waters (maximum 2.0 ml), and optimal experimental conditions, along with other analytical parameters, have been evalu-ated. The method is based on the reaction between nitrate and chromotropic acid, in concentrated sulfuric acid media (95 %), when a yellow colored product is obtained. The visible spectra of this reaction product, recorded against a blank solution, show a maximum at 412 nm, and the absorbance remains stable for at least 24 h. The method allows the nitrate determination over the range 0.50 – 11.00 mg l -1 , with a molar absorptivity of 3.837 × 10 4 l mol -1 cm -1 and a detection limit of 0.12 ppm. The interfer-ences caused by several common ions (K + , NH 4 + , Na + , Ca 2 + , Mg 2 + , Al 3 + , Cl -, NO 2 -, HCO 3 -, CO 3 2-, H 2 PO 4 -, HPO 4 2-) which are present in most natural surface waters were determined. The validation of the spectrophotometric method was done by comparing the nitrate content obtained by the proposed method with those obtained by using the stand-ard method with sulphosalicylic acid, for all studied types of waters (drinking water, tap water, river water and sea water). The results show that the proposed method can be successfully used for direct determination of nitrate in small volumes of natural surface waters (maximum 2.0 ml). The main advantage of this method is that the colored reaction product appears immediately after mixing the reagents; other intermediary steps are not necessary.
Reviews in analytical chemistry 09/2012; 31(3-4):3-4. · 0.44 Impact Factor
[show abstract][hide abstract] ABSTRACT: Chromium and cadmium are heavy metals that occur naturally in the environment and especially in soils. Their toxic effect is
more pronounced at high concentrations and it depends on the oxidation states. While Cr (III) is considered an essential trace
element for the metabolism of living organisms, Cr (VI) has a higher mobility and is easily soluble in soils and can be leached into
surface water or groundwater, and taken up by plants. That leads to a toxic and carcinogenic effect to humans via inhalation for
long exposures. The concentrations and the form of heavy metals in soils and the behavior of their free ions in soils solution are
influenced by soil pH, organic matter (OM) content, cation exchange capacity (CEC), and clay mineralogy. This work presents
the toxicity effect of two common heavy metals that can be found in soil (chromium and cadmium) on two microbial strains,
which are also isolated from soil: Azotobacter sp. and Pichia sp. Batch tests where made using different concentrations of the
selected heavy metals and culture medium: for Azotobacter sp. strain was used a Sabouraud medium and for Pichia sp. strain a
YEPD medium (Yeast Extract, Pepton, Dextrose). The dry weights of the microbial culture were used to determine the microbial
growing, calculated in percent inhibition of dry weight versus concentrations of metal ions.
[show abstract][hide abstract] ABSTRACT: The biosorption of Pb(II), Cd(II), and Co(II), respectively, from aqueous solution on green algae waste biomass was investigated. The green algae waste biomass was obtained from marine green algae after extraction of oil, and was used as low-cost biosorbent. Batch shaking experiments were performed to examine the effects of initial solution pH, contact time and temperature. The equilibrium biosorption data were analyzed using two isotherm models (Langmuir and Freundlich) and two kinetics models (pseudo-first order and pseudo-second order). The results indicate that Langmuir model provide best correlation of experimental data, and the pseudo-second order kinetic equation could best describe the biosorption kinetics of considered heavy metals.
[show abstract][hide abstract] ABSTRACT: The adsorptive performances of alkaline treated peat have been investigated for the removal of Pb(II), Co(II), and Ni(II) ions from aqueous solutions. The influence of initial metal ions concentration and equilibrium contact time was studied in a series of batch experiments, in comparison with natural peat. An increasing of adsorption capacity of alkaline treated peat was obtained for all studied heavy metals (23.07% - Pb(II), 23.53% - Co(II), and 26.19% - Ni(II)). The Langmuir isotherm model was the best model for the mathematical description of studied heavy metals adsorption on alkaline treated peat. A significant decrease of equilibrium contact time in case of alkaline treated peat was also found. The kinetics of Pb(II), Co(II), and Ni(II) uptake by alkaline treated peat followed the pseudo-second order mechanism. The FT-IR spectrometry analysis showed that carboxylic (-COO) and hydroxyl (-OH) groups play an important role in the heavy metals binding process. The heavy metal could by easily eluted from the loaded adsorbent with 0.1 mol/L HCl and the adsorbent may be reused in several adsorption/desorption cycles. The alkaline treated peat has better adsorption characteristics for the removal of heavy metals from aqueous solutions, and the cost of this treatment is very low.
Separation Science and Technology - SEPAR SCI TECHNOL. 01/2011; 46(6):1023-1033.
[show abstract][hide abstract] ABSTRACT: Experimental results obtained for gold(III) extraction in aqueous polyethylene glycol (PEG)-based two-phase system using chloride ions as extracting agents are presented in this study. The experiments were performed by batch technique, using an aqueous two-phase system prepared by mixing equal volumes of 40% (w/w) PEG(1500) aqueous solution and 40% (w/w) (NH4)2SO4 aqueous solution, both in absence and in presence of chloride ions extractants. The influence of several experimental parameters, such as initial gold(III) concentration, salt stock solution pH and chloride ions extractant concentration on gold(III) extraction efficiency was investigated. The experimental results have shown that gold(III) is quantitatively extracted (>98%) into PEG-rich phase in acid media (pH⩽3.0) and at chloride ions concentration higher than 0.08molL−1. From the distribution coefficients determined as a function of chloride ions concentration into PEG-rich phase, the extracted species were identified. The comparison of the extraction behaviours of gold(III) and other metal ions (Cu(II), Co(II), Ni(II), Zn(II), Fe(III) and Pb(II)) was also examined. The validation of this method was done by recovery of gold from electrical wastes. The results present in this study show that the aqueous polyethylene glycol-based two-phase extraction system has potential for practical application in the extraction and separation of gold from chloride media.
Separation and Purification Technology - SEP PURIF TECHNOL. 01/2011; 80(3):620-625.
[show abstract][hide abstract] ABSTRACT: Chromium (Cr) is one of the most common metal contaminants in soil because of its use in ore refining, production of steel and alloys, metal plating, tanneries, wood preservation, and pigmentation. In soil environment, the most stable oxidation states of chromium are Cr (III) and Cr (VI). While Cr (III) is considered an essential trace element for the functioning of living organisms, Cr (VI) is toxic and carcinogenic to humans via inhalation for long exposures, since it is easily soluble and mobile in soils and can be leached into surface water or groundwater, and taken up by plants. The efficacy of remediation processes are highly dependent on chromium sorption and desorption kinetics and on the influence of competing solute anions. Models to predict the transport of Cr(VI) in soils must therefore incorporate these effects. The objective of the study was to speciate and to evaluate various soil Cr species in relation to soil properties. Adsorption and reduction of added Cr(VI) were characterized in soils with contrasting pH, organic matter contents, and chemical and mineralogical properties. Batch experiments are used to determine equilibrium sorption parameters for chromium by soil and to study sorption kinetics that are relevant to soil contamination sites. The distribution of metal contaminant in soils can be strongly localized by transport limitations and redox gradients within soil aggregates. The soils adsorption and reduction capacities were eventually overwhelmed, however, and permitted the passage of Cr(VI) into the underlying ground water.
[show abstract][hide abstract] ABSTRACT: In this study, the removal of nickel(II) ions from aqueous solutions using peat moss sampled from Poiana Stampei (Romania) under different experimental conditions (different initial concentrations of metal ion and contact time) was investigated, in batch experiments. The kinetics of adsorption process was followed based on the amount of nickel(II) ions retained at various time intervals, and the experimental results were analyzed using three kinetic models: pseudo-first order, pseudo-second order and intra-particle diffusion models. The rate constants of adsorption process for all these kinetic models were calculated. Good correlation coefficients were obtained for the pseudo-second order kinetic model, showing that nickel(II) uptake process followed the pseudo-second order rate expression. Adsorption isotherms were expressed by Langmuir and Freundlich adsorption models. The Langmuir model fit the experimental data with high correlation coefficient and better than Freundlich model and the maximum adsorption capacity was obtained as 32.89 mg/g, at 65 C. The effect of temperature on nickel(II) adsorption process was also investigated and various thermodynamic parameters (G, H and S) have been calculated.
[show abstract][hide abstract] ABSTRACT: The experimental studies have been performed on soil samples from Copou-Iasi, Bacau and Bârlad (România) glass houses. We have specially follow the aspects concerning to the distribution of occurrence forms, composition and structure of mineral and organic components, and the genetic correlations between these in conditions of soils from glass houses, respectively. The results regarding the distribution tendencies on profile and the correlations between mineral and organic components of studied soils have been correlated with the results of microscopic, spectral (IR and Raman) and X-ray diffraction studies, and with the results of thermodynamic modelling of mineral equilibriums and dynamics of pedogenesis processes, in conditions of soils from glass houses. The utilization of intensive cultivation technologies of vegetables in glass houses determined the degradation of morphological, physical and chemical characteristics of soils, by fast evolution of salted processes (salinization and / or sodization), compaction, carbonatation, eluviation-illuviation, frangipane formation, stagnogleization, gleization, etc. Under these conditions, at depth of 30-40 cm is formed a compact and impenetrable horizon with frangipane characteristics, expresses more or less. The aspects about the formation of frangipane horizon in soils from glasshouses are not yet sufficiently know. Whatever of the formation processes, the frangipane horizons determined a sever segregation in pedo-geochemical evolution of soils from glasshouses, with very important consequences on the agrochemical quality of these soils. The soils from glass houses are characterized by a very large variability of mineralogy and chemistry, which are traduced by intense modifications of superior horizons, in many cases there are conditions for the apparition of new pedogenetic horizons through new-pedogenesis processes. Under these conditions the definition of some general characteristics of soils from glasshouses is very difficult. Practically, each type of soil from this category has distinct pedological and chemical-mineralogical characteristics, mostly determined by the nature of parental material and by the exploitation technologies. Concerning to the pedogeochemistry of soils from glasshouses have not yet been written summary studies, most existing papers from literature are in fact, case studies of particular situations. The deficit of information from this field, together with the ambiguity of pedogenetical characters of diagnostic, makes difficult the unitary characterization of soils from glasshouses. Characteristic for the soils from glass houses are the intense modifications of soil profile, the large variability of mineralogy and chemistry, and the salinization processes of superior horizons. From chemical point of view, the soils from glass houses is characterized by high values of bases saturation, accessible phosphorus and ration between humic and fulvic acids. From mineralogical point of view, the soils from glass houses studied is characterized by a high heterogeneity degree, both as contents, and as occurrence and distribution forms of mineral and organic components in profile. Predominant quantitatively are clay minerals and as variety, the crystalline forms are most abundant. As regard the clay minerals type, the kaolin and illites have dominant weights in comparison with smectites and the other mineral components. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07).
[show abstract][hide abstract] ABSTRACT: Our studies have focused the apparition and manifestation conditions of pedogeochemical segregation phenomena in case of soils from Copou - Iasi, Bacau and Bârlad (Romania) glass house, and the effects of this on the pedogeochemical and agrochemical characteristics of soils from glass houses cultivated with vegetables. The utilization of intensive cultivation technologies of vegetables in glass houses determined the degradation of morphological, physical and chemical characteristics of soils, by rapid evolution of salted processes (salinization and / or sodization), compaction, carbonatation, eluviation-illuviation, frangipane formation, stagnogleization, gleization etc. Under these conditions, at depth of 30-40 cm is formed a compact and impenetrable horizon - Ahok(x) horizon. In function of exploitation conditions and by the chemical-mineralogical characteristics of soils from glasshouses, the Ahok horizons can have frangipane properties, expressed more or less. These horizons determined a geochemical segregation of soils from glass houses: (i) superior horizons, above Ahok(x) horizon evolve in weak oxidative conditions, weak alkaline pH, higher salinity, humidity and temperature; (ii) inferior horizons, below Ahok(x) horizon evolve in weak reducing conditions weak acid pH, lower salinity, humidity and temperature. Concomitant with the development of Ahok(x) horizons, the rapid degradation of the properties of soils from glasshouses is observed. The aspects about the formation of frangipane horizon in soils from glasshouses are not yet sufficiently know. Whatever of the formation processes, the frangipane horizons determined a sever segregation in pedogeochemical evolution of soils from glass houses, with very important consequences on the agrochemical quality of these soils. The segregation effects are manifested in the differential dynamics of pedogeochemical processes from superior horizons (situated above the segregation horizon), in comparison with the inferior horizons (situated below the segregation horizon), and in global evolution of degradation processes of soils from glasshouses. The results obtained by as have shown that together by mobile forms of Si, Al and Fe, at the formation of segregation horizons (frangipane), an important role has the phosphorus (organic. in special) and the organic-mineral complexes, respectively. The experimental results indicate a strong accumulation tendency, at the level of pedogeochemical segregation horizons - Ahok(x) horizons, of fin grain-size fractions and of amorphous forms of mineral components. Also, was observed that in the composition of soil aggregates from frangipane horizon, and important weight have the smectites, amorphous iron oxides and oxy-hydroxides, amorphous silica and organic matter. The particularity of pedogeochemical segregation horizon (frangipane) from Copou-Iasi glass house is given by the relatively high contents of: (i) phosphorus - organic, in special, as inositol-phosphoric esters; (ii) fulvic acids; (iii) organic-mineral complexes - with special composition and structure, and (iv) poly-metha-phosphate associated with aluminosilicated gel - from chemical point of view has the characteristics of a pseudo-solid solution by (SiO2)x(Al2O3)y(PO4)z type, where x / z = (10-16) / 1, and y / z = (3-5) / 1); this appear as nodular depositions ( = 3-5 mm) covered with thin iron-carbonated crust. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51-045/07).
[show abstract][hide abstract] ABSTRACT: In soils from glass houses, the speciation and inter-phases distribution
processes of heavy metals have a particular dynamic, different in
comparison with those from non-protected soils. The predominant
distribution forms of heavy metals in such soils types are: complexes
with low mass organic molecules, organic-mineral complexes, complexes
with inorganic ligands (hydroxide-complexes, carbonate-complexes,
sulphate-complexes, etc.) and basic salts. All of these have high
stabilities in conditions of soils from glass houses, and in
consequence, the separation and determination of speciation forms (which
is directly connected with biodisponibility of heavy metals) by usual
methods id very difficult and has a high uncertain degree. In this
study is presented an original method for the selective separation and
differentiation of speciation forms of heavy metals from glass houses
soils, which is based by the combination of solid-liquid sequential
extraction (SPE) with the extraction in aqueous polymer-inorganic salt
two-phase systems (ABS). The soil samples used for this study have been
sampled from three different locations (glass houses from Iasi, Barlad
and Bacau - Romania) where the vegetables cultivation have been
performed by three different technologies. In this way was estimated the
applicability and the analytical limits of method proposed by as, in
function of the chemical-mineralogical and physical-chemical
characteristics of soils. As heavy metals have been studied cadmium,
lead and chromium, all being known for their high toxicity. The
procedure used for the selective separation and differentiation of
speciation forms of heavy metals from glass houses soils has two main
steps: (i) non-destructive separation of chemical-mineralogical
associations and aggregates from soils samples - for this the separation
method with heavy liquids (bromophorme) and isodynamic magnetic method
have been used; (ii) sequential extraction of heavy metals from soil
fractions separated in the first step, by using combined SPE-ABS
procedure. For the preparation of combined extraction systems was used
polyethylene glycol (with different molecular mass: 2000, 4000 and
8000). As phase-forming inorganic salts and as selective extracting
agents we have used different usual inorganic reagents. The type and
concentration of phase-forming salts have been selected in function of,
both nature of extracted heavy metals and chemical-mineralogical
characteristics of soil samples. The experimental parameters
investigated in this study are: molecular mass of polyethylene glycol
and the concentration of polymeric solutions, nature and concentration
of phase-forming salts, nature and concentration of extracting agents,
pH in extraction system phase, type of extracted heavy metals, type of
speciation forms of heavy metals and their concentrations. All these
factors can influence significantly the efficiency and the selectivity
of separation process. The experimental results have indicate that the
combined SPE-ABS extraction systems have better separation efficiency,
in comparison with traditional SPE systems and ca realized a accurate
discrimination between speciation forms of heavy metals from soils.
Under these conditions, the estimation of inter-phases distribution and
biodisponibility of heavy metals has a high precision. On the other
hand, when the combined SPE-ABS systems are used, the concomitant
extraction of the elements from the same geochemical association with
studied heavy metals (inevitable phenomena in case of separation by SPE
procedures) is significant diminished. This increases the separation
selectivity and facilitated the more accurate determination of
speciation forms concentration. By adequate selection of extraction
conditions can be realized the selective separation of organic-mineral
complexes, which will permit to perform detailed studies about the
structure and chemical composition of these. Acknowledgments The
authors would like to acknowledge the financial support from Romanian
Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07 and
project PNCDI 2 - D5 no. 52-141 / 2008).
[show abstract][hide abstract] ABSTRACT: The chromium (VI) sorption to the natural soils samples was investigated by batch and column tests. Soil samples were previously analyzed and characterized. The influence of physico-chemical key parameters such as the initial concentration of chromium in solution, soil quantity, pH and the temperature of the solution has been considered in batch tests. The adsorption data are tested for a number of kinetic and isotherm equations. In order to understand the adsorption mechanism, the kinetic parameters of adsorption of chromium (VI) onto the natural soils were determined. An evaluation of thermodynamic parameters on Cr (VI) adsorption onto soil was made. The value of activation energy (Ea) suggests that the rise of the solution temperature favors sorption of chromium (VI) onto the soil, and the sorption process might be by chemical adsorption. The results are used further to determine chromium bioavailability and the need for soil remediation, based on risk assessment, since Cr (VI) is a powerful epithelial irritant, and a confirmed human carcinogen. Heavy metals are natural compounds in soil and they can not be destroyed. As essential elements, some heavy metals (cooper, selenium, zinc) are vital for human metabolism, but in high concentration they have a toxic effect . Presence of chromium in soils is a result of both natural processes and human activities. Its toxicity depends on oxidation states, Cr(III) with a reduced mobility and low toxic potential (similarly with Al and Fe) and Cr(VI) very mobile and with a higher toxic potential, even at very low concentrations . Breathing high levels of Cr(VI) can cause irritation to the nose, such as runny nose, nosebleeds, and ulcer and holes in the nasal septum. Ingesting large amount of Cr(VI) can cause stomach upsets and ulcers, convulsions, kidney and liver damage and even death [3,4]. Among the methods used to remove heavy metals from the environment, sorption and biosorption are studied in literature intensively in last decades [2,3].
[show abstract][hide abstract] ABSTRACT: Heavy metals produced and released by anthropogenic activities generate serious environmental problems. Ions of toxic metals can bind to the mineral surface in a number of ways, including absorption, adsorption, precipitation, ion exchange. The paper shows that the fate and migration of heavy metals in soils strongly depend on the physical properties and chemical and mineralogical composition of such environments. Cadmium is one of the most toxic metals with carcinogenic and teratogenic impacts. Leaching of cadmium through soil profiles has implications for both its accumulation in subsoil or contamination of groundwater. The main objective of the research entails the study of the transport of cadmium in soil matrix. Samples with specific amounts of carbonates, organic matter, chemical composition and various grain sizes were chosen. Solutions with different concentrations of CdSO 4 were prepared for the simulation of a contamination by Cd(II). The sorption of cadmium on all the soil particles and the equilibrium and kinetic parameters characterizing the process of adsorption in the soil matrix were estimated by the conventional batch techniques. Experimental sorption data from batch tests were evaluated by certain isotherms, which provided main sorption characteristics of soil samples for Cd. The results showed that concentrations of total dissolved cadmium and activity of its free ions in soil solution are influenced, sorbent characteristics, that is particle dimensions in this case.
[show abstract][hide abstract] ABSTRACT: RESUMEN La tartrazina, un colorante azoico aniónico, también co-nocido como Acid Yellow 23, Amarillo FD&C 5, CI 19140 o E102 (a Europa ABSTRACT Acid Yellow 23, an anionic azo dye, also known as Tartra-zine, FD&C Yellow 5, CI 19140 or E102 (in Europe) is widely used in medicine or cosmetics, foodstuff and textile indus-tries. In pharmaceuticals, Acid Yellow 23 is incorporated as additive in medicines, antacids, vitamin supplements, whereas in cosmetic industries, it is utilized in hair dyes, soaps, lotions, shampoos, bath gels, skin-care creams,: firstname.lastname@example.org deodorants, lipsticks and many others. Due to its very wide use for different purposes, Acid Yellow 23 may be commonly found in municipal wastewaters or wastewaters originating from textile, food, drugs and cosmetic industry. In this context, it may also result in negative impact on the environment through discharge of improperly treated wastewaters in receiving waters. In this work, the capacity of a Romanian soil to retain Acid Yellow 23 from aqueous solution by sorption has been investigated. The Freundlich, Langmuir and linear isotherm models were applied to de-scribe the process and the parameters of these equations were calculated. The sorption kinetics was investigated by applying five kinetic models aiming at establishing the model that best fits the sorption of the azo dyes onto the particles of investigated soil. RESUM La tartrazina, un colorant azoic aniònic, també conegut com Acid Yellow 23, Groc FD&C 5, CI 19140 o E102 (a Europa) és amplament utilitzat en medicina i cosmètica, així com a les indústries alimentària i tèxtil. En els produc-tes farmacèutics, la tartrazina s'incorpora com a additiu a medicines, antiàcids i suplements vitamínics, mentre que en cosmètica s'empra en tints capil·lars, sabons, locions, xampús, gels de bany, cremes per a la pell, desodorants, barres de llavis i moltes altres aplicacions. Donat que s'empra amplament amb diferents propòsits, la tartrazina es pot trobar sovint a les aigües residuals municipals i a les aigües residuals provinents de la indústria tèxtil, ali-mentària, farmacèutica i cosmètica. En aquest context, pot resultar també en un impacte negatiu sobre el medi ambient per abocament d'aigües residuals inadequada-AfinidAd LXVi,544, Noviembre-Diciembre 2009 466 ment tractades. En aquest treball, s'investiga la capacitat d'un sòl de Romania per retenir la tartrazina en solució aquosa mitjançant sorció. S'apliquen els models de Freun-dlich, Langmuir i de la isoterma lineal per descriure el pro-cés, i es calculen els paràmetres d'aquestes equacions. S'investiga la cinètica de la sorció aplicant cinc models cinètics per tal d'establir el model que millor s'ajusta al procés de sorció dels colorants azoics per les partícules del sòl investigat.
[show abstract][hide abstract] ABSTRACT: This study was undertaken to evaluate the adsorption potential of Romanian peat moss for the removal of mercury(II) from aqueous solutions. The batch system experiments carried out showed that this natural material was effective in removing mercury(II). The analysis of FT-IR spectra indicated that the mechanism involved in the adsorption can be mainly attributed to the binding of mercury(II) with the carboxylic groups of Romanian peat moss. Adsorption equilibrium approached within 60 min. The adsorption data fitted well the Langmuir isotherm model. The maximum adsorption capacity (qmax) was 98.94 mg g(-1). Pseudo-second-order kinetic model was applicable to the adsorption data. The thermodynamic parameters indicate that the adsorption process was spontaneous as the Gibbs free energy values were found to be negative (between -17.58 and -27.25 kJ mol(-1)) at the temperature range of 6-54 degrees C.
Journal of Environmental Science and Health Part A 07/2009; 44(7):700-6. · 1.25 Impact Factor
[show abstract][hide abstract] ABSTRACT: The pedological, mineralogical and geochemical studies performed by as on soils (s.s hortic antrosols) from Iasi (Copou glass house), Barlad and Bacau glass houses have show that, in most of cases, the profile of hortic antrosols have the following compositions: Aho-AC-C or Ck, and Aho-B/C or Ck, respectively. In function of parental material nature and specific exploitation technologies, can appear the diagnostic horizons of association (hiposalic-sc, hiponatric-ac etc.) and / or of transition (A/B, A/C, C/A, A+C, ABk etc.). Specific for soils from glass houses are intense modifications of soil profile, large variability of mineralogy and chemistry, salinization processes (by progressive accumulation of soluble salts) at superior horizons level and formation, at 50 cm depth, of a compact and impermeable horizon (frangipane horizon). From chemical point of view, the hortic antrosols are generally characterized by high values of saturation in bases, of accessible phosphorus and of ratio between humic and fulvic acids (organic matter is dominant in intense humified fraction). Regarding the formation conditions, the mineralogy and geochemistry of frangipane horizons, in this moment, in literature are not too many data. In case of studied soils, the frangipane horizons appear in specific forms, where their structure, morphology and chemistry varied in large limits. In hortic antrosols where are formed, the frangipane horizons determined a sever pedogeochemical segregation. Thus, the horizons situated above to the frangipane horizon evolutes in weak oxidant conditions, weak acid-neutral pH (5.87 - 6.95), high salinity and humidity, intense biological activity; while the horizons situated below to the frangipane horizon evolutes in weak reduction conditions, neutral - weak alkaline pH (7.61 - 8.04), reduced salinity and humidity, weak biological activity. This determined an important differentiation of micro-elements and organic compounds dynamic, evidenced by the reduction of the accessibility of these for cultivated vegetables, and have important consequences on the productivity and on the quality of obtained products. Under these conditions, in the same time with the formation of frangipane horizons, the fast degradation of physical-mechanical and chemical properties of antrosols occurs. The conditions for the frangipane horizons formation are not yet elucidated. Ours experimental results indicate that the formation of frangipane horizons in soils from glass houses is first determined by the intensive technologies used for vegetables cultivation, by the application of a supra-dimensional irrigation system, the maintaining of high and relatively constants humidity state and temperatures (in comparison with un-protected soils). The nature of parental material has also, an important influence on the physical-chemical and mineralogical properties of frangipane horizons and these control the formation and spatial extension rates of these horizons. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07).
[show abstract][hide abstract] ABSTRACT: The studies regarding the dynamic of microelements in hortic anthrosols (soils from glasshouses and solariums) are important both from scientific point of view and in special, for the implementation of durable ecological technologies of amelioration, conservation and superior capitalization of soil resources from protected areas (glasshouses and solariums). In case of hortic anthrosols, the application of intensive technologies for plants cultivation determined brusque and intense perturbations of equilibriums between microelements and mineral and organic components of anthrosols, which is reflected by a fast degradation of morphological and physic-chemical properties. But, in case of hortic anthrosols, the exploitation conditions determined a particular evolution of microelements, and of distributions and interactions way with soil components, respectively. The conditioning and the amelioration of hortic antrosols with ecologic polymeric materials is one of the method approved in this moment and according with the opinion of most of specialists, represent one of method with large applications in modern agriculture. The utilization of polymeric materials to the conditioning of soils have been studied over 50 years, their effects on morphological, physical and chemical properties of soils being know, in special for agricultural and polluted soils. Ours studied have been performed using soil profiles drawing from Copou-glass house, Iasi (Romania). Has been followed the modification of distribution for speciation forms of some micro-elements (Zn, Cu, Ni, Mn, Cr, P), between hortic antrosol horizons, and between chemical-mineralogical components of this, with the progressive salinization of superior horizons, in 2007-2008 period. For the experimental study have been used three types of water-soluble polymers, with different hydrophobicities: polyethylene glycol (molecular mass 2000, 4000 and 8000), vinyl acetate - ammonia maleate salt copolymer (AM-VA) and methylacrylate - ammonia maleate salt copolymer (AM-MMA). The separation, differentiation and determination of micro-elements speciation forms was done by combined solid-liquid sequential extraction (SPE) and extraction in aqueous polymer-inorganic salt two-phase systems (ABS) procedure, presented in some of ours previous studies. After extraction, the total contents of the micro-elements and fractions from these differential bonded by mineral and organic components of hortic antrosol have been determined by atomic absorption spectrometry. The specific interaction mechanisms of micro-elements with organic-mineral components of soils have been estimated on the basis of Raman and FT-IR spectra, recorded for fractions obtained after each extraction step. These data were correlated with those obtained by chemical analysis and UV-VIS spectrometry, and were used for to establish the type and weight of micro-elements speciation forms in studied antrosol. The conditioning with polymeric materials determined a limitation of formation and extension rate of frangipane horizon, and of salinity in superior horizons respectively, which are mainly responsible by the geochemical segregation and degradation of soils from glass houses. Under these conditions, increase the weight of mobile speciation forms of micro-elements and will be facilitated their accessibility for cultivated vegetables. Acknowledgments The authors would like to acknowledge the financial support from Romanian Ministry of Education and Research (Project PNCDI 2-D5 no. 51045/07).