presence of oxygen, iron compounds (II) are unstable and oxidized to form compounds
of iron with a degree of oxidation +3. Iron compounds (II), as a rule, can be found in
underground waters. Their content usually does not exceed 1 mg/dm
3
, but can reach
several tens of mg/dm
3
. The basic forms of iron (II) are iron bicarbonate (II) and iron
sulfate (II).
Figure 1. Schemes of the existence of various forms of iron ions in water
It is known that the sorption properties of plant materials depends on the presence
of a small number of active (accessible) functional groups, porosity of the structure and
content of mineral substances, also on the type of raw material, conditions of
cultivation, etc. Vegetal wastes of food industry, such as apricot seed shells and walnut
shells were used as raw material. The primary task of the research work was to study
the chemical composition of the raw materials and estimate the volume of adsorption
pores. For this purpose, chopped raw material with a particle size of 0.5-1.0 mm was
used. The results of the study are shown in Table 1.
Obtained results indicate that both materials are similar in content of mineral
components, resins, fats and waxes and have the same volume of adsorption pores.
However, some differences in content of cellulose and lignin can be observed. And it
can be a decisive factor in ensuring the efficiency of sorption.
Investigation of the influence of the concentration of the Fe
3+
ions in initial water
on the sorption capacity of the sorbent suggests that with increasing content of cations,
the sorption capacity increases. According to the results of studies on the absorption
properties of plant wastes in relation to Fe
3+
ions, it was established that the maximum
sorption capacity of the apricot seed shells and walnut shells for Fe
3+
is 44 and 34 mg/g,
respectively, at the concentration of studied pollutant 50 mg/dm
3
. The residual
concentration of iron ions at the same time for the apricot seed shells and walnut shells
are 16 mg/dm
3
and 21 mg/dm
3
, respectively. Higher sorption ability of apricot seed
Total iron
Iron Fe
2+
Iron Fe
3+
In a complex form
Free
Free
Suspended
substances
FeS, FeCO
3
,
Fe(OH)
2
Soluble or finely dispersed forms
Mineral
compounds,
silicates,
phosphates
and others
Organic
compounds
with humic
acids
Suspended
substances
Fe(OH)
3
and
other
sediments
Soluble
substances
FeS, FeCO
3
,
Fe(OH)
2
Suspended forms
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