The basic characterization of a biosorbent includes evaluation of maximum sorption capacity qmax and affinity b parameter in the case of Langmuir equation. The mostly advantageous in the case of both bioremoval and biobinding would be for a sorbent to have simultaneously high sorption capacity and affinity. In Figure 8 there are shown sorbents with different characteristics.
Sorbent 1 possesses high affinity and high maximum binding capacity.
This is the best sorbent. Sorbent 2 possesses high maximum sorption capacity but low affinity.
Sorbent 3 — high sorption affinity but low maximum sorption capacity and sorbent 4 — low affinity and low maximum sorption capacity. The latter sorbent possesses the worse characteristics. In bioremoval processes of particular importance is affinity of a biosorbent. This is related with the potential applications of this process as polishing treatment in order to reduce the concentration of pollutants below the acceptable limits.
Potentials of biosorption and bioaccumulation processes for heavy metal removal
Similarities and Differences Between Biosorption and Bioaccumulation Isotherms for different types of sorbents. For this reason the mostly desired characteristic would be high affinity of sorbent to sorbate, which is low equilibrium concentration of pollutant reached even at low equilibrium sorption capacities. Therefore, it is recommended to use sorbent possessing characteristics such as material 1 and 3 Figure 8. If we are interested in other than bioremoval applications — biobinding e.
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In this case it is recommended to use either sorbent 1 or 2. Prior the analysis, the studied materials are digested with mineral acids, preferably in microwave oven in closed vessels. This generates times dilution. The analytical process should be controlled by the use of certified reference materials that have similar matrix as the analyzed material. It is recommended to perform semi-quantitative analysis of samples prior the quantitative analysis in order to evaluate the expected levels of analytes and to determine the main components. The knowledge of the levels of the main components is used in the preparation of calibration solutions.
The mostly advantageous is to add the main components into the calibration solution. Such an approach minimizes matrix effects and also in some extent, interferences.
Among these processes, two types of methods can be distinguished, which have common mechanisms, but the goals are different — bioremoval and biobinding. In the case of bioremoval, the goal is to achieve the highest possible removal of toxic metal ions via either biosorption or bioaccumulation processes. Figure 9. Biosorption and bioaccumulation understood as bioremoval and biobinding. This use of biosorption and bioaccumulation methods is recommended as the final, polishing step, before the final discharge of effluents. Biobinding processes that can be applied in environmental protection include biomonitoring.
In this case, the aim would be not to bind the highest amounts of metals but to assess the concentration and bioavailability of pollutant in the environment. Biobinding processes can also find another application — in the production of highly bioavailable mineral feed additives. In this case the goal would be to bind the highest quantities of metals via either biosorption or bioaccumulation. The content of toxic metals in tissues or in the biomass of each organism reflects the level of a given contaminant in the environment.
But, on the other hand, not every organism has the potential to be a good biomonitor or biondicator.
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First of all, biomonitoring should be ethically correct. Sampling of biomonitor tissues should not be invasive, nor should not pose destruction or deterioration of an organism, nor pain. Another issue is that the concentration factor of a pollutant in the studied material should be high enough to be possible to determine after digestion and dilution of a sample.
Criteria of good biomonitor fulfill particularly non-living tissues, such as human hair , animal fear or birds feather, as well as animal products, advantageously consumable, such as eggs and milk . Also, plant tissues are good biomonitors of soil pollution . The analysis of human hair provides the information on pollution of environment in which an organism lives, as well as contamination of food and drinks .
The level of soil pollution can be determined by the analysis of plant tissues . It was also found that it is possible, through the use of specially elaborated extraction procedures to determine content of bioavailable forms of metals and on this basis knowing so-called transfer factor to predict the composition of plants that are to be cultivated on a given soil . The property that is used in biomonitoring is that a mechanism that protects an organism from the excessive accumulation and toxic effects posed by a given contaminant is excretion outside an organism via Using Bioaccumulation in Biomonitoring of Environmental Pollution 33 different routes: urine and feces, sweat and also transfer to external non-living tissues, such as hair and nail or birds feather.
Elements enter living organism via different routes: are transferred from air, water, foods, drugs, through skin, respiratory tract and gastro-intestinal tract. Metals are transported by blood and deposited in organs . The elements are distributed in an organism by blood and deposited in organs and tissues . The elements that are present in hair can be divided into macroelements and trace elements.
The latter group consists of toxic trace elements and essential trace elements microelements that comprises of major essential trace elements Fe, Zn and Cu and minor essential trace elements Mn, Se, Cr, Co, Ni, Si, F, I . Table 4 presents the composition of hair from a population living in urban and industrialized area . Table 4. Human hair, for instance, fulfills these criteria. Although human hair can be theoretically considered as reliable and convenient biological indicator of environmental pollution, there have been some problems encountered in the elaboration of reference values for the concentration of metals in human hair, in particular some problems with the standardization of the method occurred.
It was found that the level of elements in hair is the function of age, sex, and hair color, as well as hair treatments, including hair coloring and undulation as well as other treatments that affect the structure of hair. Also sex, Using Bioaccumulation in Biomonitoring of Environmental Pollution 35 nutritional habits and smoking  influence the composition of hair.
In studying the composition of hair it is also necessary to consider inter-elementinteractions: antagonisms and synergisms . It is also significant to distinguish between internal originating from the body and external deposition.
Potentials of biosorption and bioaccumulation processes for heavy metal removal
There exist elaborated washing procedures i. Hair mineral analysis supplies information which could be used in environmental sciences as well as in medicine. Beside the potential of using hair as reliable and convenient biomonitor of environmental pollution, it was found that some problems with elaboration of reference values for elements concentration in human hair and interpretation problems were encountered. Elements in hair are incorporated into its keratin structure. Affinity for metals is due to the presence of cystine in keratin, follicular melanin, which binds cations to its carboxyl groups .
Melanin is the main pigment of hair. Blond hair contain lower concentration of melanin when compared with black hair. Therefore, blond hair contain less cations binding agent and typically tend to contain less cations. This is needed to take into consideration while interpreting results of hair mineral analyses.
Many studies proved that the composition of hair reflects elemental status of an organism. Hair mineral analysis, if correctly interpreted, could show a multiplicity of information — not only on environmental pollution, but also on food status of human and diseases. Beside that this technique is known for ca. Since the concentration of elements in hair is very low on the level of ppm, ppb or even ppt , over years the reference values changed along with the development of more sensitive and more advanced analytical techniques.
Probably because of this, in the literature many confusing information are found. Reference values reported in the literature for healthy people which were not exposed to environmental pollution, show contradictory information Table 4. In the past years, it was discovered that multielemental composition of human hair is strongly correlated with personal characteristics, such as age, sex, hair color, cosmetic treatments hair coloring, perm, shampoos , structure of hair and its growth rate, human race and even geographical location.
It was hypothesized that the content of trace elements in hair is the consequence of adaptation of the population to environmental factors climate, geographical and geochemical factors, eating habits . Available reference values did not take into consideration these characteristics, beside that recent literature information 36 Katarzyna Chojnacka showed that these parameters should be considered in interpretation of results of hair mineral analysis.
Only then it would be possible to state whether a given person was exposed to toxic metals, or suffers for deficiency of a microelement.
The results of hair mineral analysis should not be interpreted as the results of blood tests. In contrast with the results of blood analysis, the content of elements in hair is not related with homeostatic mechanisms. Differences in the concentration of elements from the reference values are frequently observed before the appearance of symptoms.
This is a very good tool in forecasting physiological disorders. The concentration of trace elements in hair is, as literature reports, times higher than in blood, times higher than in urine . Additionally the results of hair mineral analysis are the picture of chronic, not temporary exposure as in blood or urine of elemental status of an organism and reflect an average exposure of a given subject .
While analysis of the composition of hair gives a good description of status of toxic elements Hg, As, Pb, Cd , there are problems with interpretation of status of nutritional elements. Elevated concentration of nutritional elements in hair does not necessarily reflects its elevated concentration in the whole organism, but could mean higher excretion of this element to hair tissue and consequently lower concentration of this element in other tissues and organs, showing thus its poor absorption.
Literature review clearly shows that more epidemiological studies are needed to make hair analysis a useful tool in the assessment of environment exposure and health of human. Table 5 lists advantages and disadvantages of hair mineral analysis. Problems which arise in hair mineral analysis are mainly related with either analytical procedures different analytical techniques yield different results or with problems with interpretation of results.
Human hair is excretory, not functional tissue. During the growth of hair, elements become permanently incorporated into its structure. The process is irreversible and non-equilibrium. The elemental composition of hair is the record of history of elemental metabolism and exposure to toxic elements. The results of hair analysis could be the basis of diagnosis of physiological disorders related with malfunction of metabolism of nutritional and toxic elements. Hair is important in terms of mechanism of elimination of toxic elements from an organism . The growth rate of hair is ca.
The analyses of fragments which are 1 cm long enable to recall the history of exposure of a given person in the previous months. When a given person is not exposed anymore, after a period of time, the concentration in hair gradually approaches the normal value . Factors influencing response of a given person include age, sex, bodyweight, nutritional, genetic and immunological status.
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