The general principles of Cu(II) binding to algal waste from agar extraction, composite material and algae
Gelidium, and different modelling approaches, are discussed. FTIR analyses provided a ...detailed description of the possible binding groups present in the biosorbents, as carboxylic groups (
d-glucuronic and pyruvic acids), hydroxyl groups (cellulose, agar and floridean starch) and sulfonate groups (sulphated galactans). Potentiometric acid–base titrations showed a heterogeneous distribution of two major binding groups, carboxyl and hydroxyl, following the quasi-Gaussian affinity constant distribution suggested by Sips, which permitted to estimate the maximum amount of acid functional groups (0.36, 0.25 and 0.1
mmol
g
−1) and proton binding parameters (
p
K
′
H
=
5.0
,
5.3
and
4
.4
;
m
H
=
0.43, 0.37, 0.33), respectively for algae
Gelidium, algal waste and composite material. A non-ideal, semi-empirical, thermodynamically consistent (NICCA) isotherm fitted better the experimental ion binding data for different pH values and copper concentrations, considering only the acid functional groups, than the discrete model. Values of
p
K
′
M
(3.2; 3.6 and 3.3),
n
M (0.98, 0.91, 1.0) and
p (0.67, 0.53 and 0.43) were obtained, respectively for algae
Gelidium, algal waste and composite material. NICCA model reflects the complex macromolecular systems that take part in biosorption considering the heterogeneity of the biosorbent, the competition between protons and metals ions to the binding sites and the stoichiometry for different ions.
This study presents the application of multivariate statistical tools for the evaluation of spatial variations and the interpretation of water quality data obtained in a monitoring program of Lis ...river basin surface water, Portugal. Twenty-seven physicochemical and microbiological parameters were determined in six water sampling campaigns at 16 monitoring sites during the period from September 2003 to November 2006. Correlation analysis, principal component analysis, and cluster analysis were performed to evaluate the main water pollution sources and to characterize the spatial distribution of water pollution profiles in river basin. The results achieved with the statistical methodologies led to distinguish natural and anthropogenic pollution sources. Additionally, monitoring sites with similar water pollution profile were identified, indicating that some monitoring locations can be changed to improve the spatial characterization of water quality in the river basin. CBO, CQO, P, and N were identified as significant variables affecting spatial variations, namely in the Lis river middle reach. Besides the identification of main pollution sources, the applied statistical tools were able to identify spatial patterns of water pollution in Lis river basin, which further helps in the reassessment of the number and location of monitoring sites.
Tissue-equivalent gases (TEGs), often made of a hydrocarbon, nitrogen, and carbon dioxide, have been employed in microdosimetry for decades. However, data on the first Townsend ionization coefficient ...(α) in such mixtures are scarce, regardless of the chosen hydrocarbon. In this context, measurements of α in a methane-based tissue-equivalent gas (CH4 – 64.4%, CO2 – 32.4%, and N2 – 3.2%) were performed in a uniform field configuration for density-normalized electric fields (E/N) up to 290Td. The setup adopted in our previous works was improved for operating at low pressures. The modifications introduced in the apparatus and the experimental technique were validated by comparing our results of the first Townsend ionization coefficient in nitrogen, carbon dioxide, and methane with those from the literature and Magboltz simulations. The behavior of α in the methane-based TEG was consistent with that observed for pure methane. All the experimental results are included in tabular form in the Supplementary material.
Water quality in Lis river, Portugal Vieira, Judite; Fonseca, André; Vilar, Vítor J. P. ...
Environmental monitoring and assessment,
12/2012, Letnik:
184, Številka:
12
Journal Article
Recenzirano
In the past 30 years, the Lis river basin has been subjected to constant ecological disasters mainly due to piggery untreated wastewater discharges. The aim of this study was to evaluate the effect ...of existing domestic, agricultural, and industrial activities on the water quality, and to propose a watershed plan to protect and manage surface water resources within the Lis river basin. For this purpose, 16 monitoring stations have been strategically selected along the Lis river stretch and its main tributaries to evaluate the water quality in six different sampling periods (2003–2006). All samples were characterized in terms of organic material, nutrients, chlorophyll, and pathogenic bacteria. Generally, the Lis river presents poor water quality, according to environmental quality standards for surface water, principally in terms of dissolved oxygen, biochemical oxygen demand, total nitrogen, and fecal coliform, which can be associated mainly with the contamination source from pig-breeding farms.
Dead algal biomass is a natural material that serves as a basis for developing a new family of sorbent materials potentially suitable for many industrial applications. In this work an algal ...industrial waste from agar extraction process, algae
Gelidium and a composite material obtained by immobilization of the algal waste with polyacrylonitrile (PAN) were physical characterized and used as biosorbents for dyes removal using methylene blue as model. The apparent and real densities and the porosity of biosorbents particles were determined by mercury porosimetry and helium picnometry. The methylene blue adsorption in the liquid phase was the method chosen to calculate the specific surface area of biosorbent particles as it seems to reproduce better the surface area accessible to metal ions in the biosorption process than the N
2 adsorption–desorption dry method. The porous texture of the biosorbents particles was also studied. Equilibrium isotherms are well described by the Langmuir equation, giving maximum uptake capacities of 171, 104 and 74
mg
g
−1, respectively for algae, algal waste and composite material.
Kinetic experiments at different initial methylene blue concentrations were performed to evaluate the equilibrium time and the importance of the driving force to overcome mass transfer resistances. The pseudo-first-order and pseudo-second-order kinetic models adequately describe the kinetic data. The biosorbents used in this work proved to be promising materials for removing methylene blue from aqueous solutions.
Water quality modelling of Lis River, Portugal Vieira, Judite; Fonseca, André; Vilar, Vítor J. P. ...
Environmental science and pollution research international,
2013/1, Letnik:
20, Številka:
1
Journal Article
Recenzirano
The aim of the study was to predict the impact of flow conditions, discharges and tributaries on the water quality of Lis River using QUAL2Kw model. Calibration of the model was performed, based on ...data obtained in field surveys carried out in July 2004 and November 2006. Generally the model fitted quite well the experimental data. The results indicated a decrease of water quality in the downstream area of Lis River, after the confluence of Lena, Milagres and Amor tributaries, as a result of discharges of wastewaters containing degradable organics, nutrients and pathogenic organisms from cattle-raising wastewaters, domestic effluents and agricultural runoff. The water quality criteria were exceeded in these areas for dissolved oxygen, biochemical oxygen demand, total nitrogen and faecal coliforms. Water quality modelling in different scenarios showed that the impact of tributaries on the quality of Lis River water was quite negligible and mainly depends on discharges, which are responsible by an increase of almost 45, 13 and 44 % of ultimate carbonaceous biochemical oxygen demand (CBOD
u
), ammonium nitrogen and faecal coliforms, for winter simulation, and 23, 33 and 36 % for summer simulation, respectively, when compared to the real case scenario.
Continuous metal ions biosorption from Pb/Cu and Pb/Cd solutions onto seaweed
Gelidium sesquipedale and a composite material prepared from an industrial algal waste was performed in a packed bed ...column. A binary Langmuir equation describes well the equilibrium data and indicates a good adsorption capacity. In the sorption process, Cd and Cu break through the column faster than Pb due to its lower affinity for the biosorbent. An overshoot in the outlet Cd concentration was observed and explained by competitive adsorption between Pb and Cd, whereby the higher Pb affinity for the biosorbent displaces bound Cd ions. A small overshoot happens for Cu adsorption in the presence of Pb ions. Desorption using 0.1
M HNO
3 as eluant, was 100% effective. A mass transfer model for the adsorption and desorption processes, considering an external and intraparticle film resistance, adequately simulates the column performance. A binary Langmuir equation was used to describe equilibrium for the saturation process and a mass action law for the desorption process. Elution process is defined as an ion exchange mechanism, between protons and metal ions.
Repeatability studies on fruit species are of great importance to identify the minimum number of measurements necessary to accurately select superior genotypes. This study aimed to identify the most ...efficient method to estimate the repeatability coefficient (r) and predict the minimum number of measurements needed for a more accurate evaluation of Brazil nut tree (Bertholletia excelsa) genotypes based on fruit yield. For this, we assessed the number of fruits and dry mass of seeds of 75 Brazil nut genotypes, from native forest, located in the municipality of Itaúba, MT, for 5 years. To better estimate r, four procedures were used: analysis of variance (ANOVA), principal component analysis based on the correlation matrix (CPCOR), principal component analysis based on the phenotypic variance and covariance matrix (CPCOV), and structural analysis based on the correlation matrix (mean r - AECOR). There was a significant effect of genotypes and measurements, which reveals the need to study the minimum number of measurements for selecting superior Brazil nut genotypes for a production increase. Estimates of r by ANOVA were lower than those observed with the principal component methodology and close to AECOR. The CPCOV methodology provided the highest estimate of r, which resulted in a lower number of measurements needed to identify superior Brazil nut genotypes for the number of fruits and dry mass of seeds. Based on this methodology, three measurements are necessary to predict the true value of the Brazil nut genotypes with a minimum accuracy of 85%.
We discuss the possibility of a quantum phase transition in ultra-cold spin-polarized Fermi gases which exhibit a p-wave Feshbach resonance. We show that when fermionic atoms form a condensate that ...can be externally tuned between the BCS and BEC limits, the zero temperature compressibility and the spin susceptibility of the fermionic gas are non-analytic functions of the two-body bound state energy. This non-analyticity is due to a massive rearrangement of the momentum distribution in the ground state of the system. Furthermore, we show that the low temperature superfluid density is also non-analytic and exhibits a dramatic change in behavior when the critical value of the bound state energy is crossed.
Copper desorption from Gelidium algal biomass Vilar, Vítor J.P.; Botelho, Cidália M.S.; Boaventura, Rui A.R.
Water research (Oxford),
04/2007, Letnik:
41, Številka:
7
Journal Article
Recenzirano
Desorption of divalent copper from marine algae
Gelidium sesquipedale, an algal waste (from agar extraction industry) and a composite material (the algal waste immobilized in polyacrylonitrile) was ...studied in a batch system. Copper ions were first adsorbed until saturation and then desorbed by HNO
3 and Na
2EDTA solutions.
Elution efficiency using HNO
3 increases as pH decreases. At pH=1, for a solid to liquid ratio
S/
L=4
g
l
−1, elution efficiency was 97%, 95% and 88%, the stoichiometric coefficient for the ionic exchange, 0.70±0.02, 0.73±0.05 and 0.76±0.06 and the selectivity coefficient, 0.93±0.07, 1.0±0.3 and 1.1±0.3, respectively, for algae
Gelidium, algal waste and composite material.
Complexation of copper ions by EDTA occurs in a molar proportion of 1:1 and the elution efficiency increases with EDTA concentration. For concentrations of 1.4, 0.88 and 0.57
mmol
l
−1, the elution efficiency for
S/
L=4
g
l
−1, was 91%, 86% and 78%, respectively, for algae
Gelidium, algal waste and composite material.
The
S/
L ratio, in the range 1–20
g
l
−1, has little influence on copper recovery by using 0.1
M HNO
3.
Desorption kinetics was very fast for all biosorbents. Kinetic data using HNO
3 as eluant were well described by the mass transfer model, considering the average metal concentration in the solid phase and the equilibrium relationship given by the mass action law. The homogeneous diffusion coefficient varied between 1.0×10
−7
cm
2
s
−1 for algae
Gelidium and 3.0×10
−7
cm
2
s
−1 for the composite material.
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