New Sorbents Based On Modified Silica
NEW SORBENTS BASED ON MODIFIED SILICA
FOR TREATMENT OF NATURAL WATER AND SEWAGE
V. A. Kalibabchuk, T. D. Reva, V. N. Zaitsev
National Medical University and T. Shevchenko University Kyiv Ukraine
The accumulations of environmentally toxic elements in plants require the development of reliable methods for the determination of micro amounts of these elements on the base of other major impurities. The methods for the determination should be simples and reliable. Adsorption on the solid materials with chemically modified surface for the selective pre-concentration fits those requirements, which unite in themselves a good selectivity and high concentration factors with a simplicity and reliability of the analysis. According to the above-mentioned, we have studied the utilization of silica gel with chemically attached chelating groups for the pre-concentration of some toxic metals.
For the research next adsorbents was chosen:
Dien-SiO2
Edta-SiO2
PyCOOH-SiO2
ADFK-SiO2
Phen-SiO2
NHPSN-SiO2
Properties the interaction of listed above adsorbents with Ca2 +, Cd2 +, Hg2+, Zn2 +, Pb2 +, Fe2 + and Fe3+, Ni and Cu ions have been studied in water solutions of metal nitrates in variable acidic conditions in statistic and dynamic conditions.
The analysis of a curve completeness of extraction allows to make a conclusion that silica modified with EDTA, is suitable for separation Hg from the solution since complete adsorption of this metal is take place at рН = 3 and higher. At the same time, only 20 % of Cd and Са can be extracted on the adsorbent surface. PyCOOH-SiO2 allows selectively separate Pb, Zn and Cd. Pb can be completely extracted from solution at рН 3.5 and higher, whereas Zn has only 70 %, and Cd 40% adsorption. Dien-SiO2 allows to separate Pb, Zn, Hg, and Cd since at рН = 4 complete adsorption of Pb is only observe. Hg adsorbs of half, and adsorption of Cd is not observed, see figures.
b
a
Fig. Adsorption of metals ions on EDTA-SiO2 (a) and PyCOOH-SiO2 (b) from pH
Sorbent, modified with ADFK can be used for selective extraction Zn, Pb and Hg from a water solution. From рН = 4 ADFK-SiO2 completely adsorbs Zn and Hg and for 70% of Pb. Sorbent, modified by Phen is suitable for group extraction of all toxic metals studied. Their complete extraction is observed at рН higher then 2. NHPSN-SiO2 adsorbent has high selectivity to heavy ions. It allows adsorb most of the metals at рН > 2. At this conditions Zn adsorbs on 50 %, Pb on 80 %, and Hg - on 75%.
Performance of the adsorbents can be caricaturized by рН for 50%-s\’ extraction from solution. According to those values affinity of metals decreases in series:
PyCOOH-SiO2: Zn > Pb > Cd; EDTA-SiO2: Cd>Ca; NHPSN: Pb>Zn; Dien-SiO2: Pb > Hg > Cd; Phen-SiO2: complete adsorption; ADFK-SiO2: Zn > Pb > Hg > Ca
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