New complexing sorbents have been manufactured via chemical surface-modification of highly dispersed boehmite (γ-AlO(OH)) by phosphonic complexones (PCs), namely, by nitrilotri(methylenephosphonic) acid (NTP), 1-hydroxyethane-1,1'-diphosphonic acid (HEDP), N -hydroxyethylimino- N , N -di(methylenephosphonic) acid (HEIDP), and imino- N , N -diacetic- N -methylenephosphonic acid (IDAMP). The manufactured PC–boehmite materials have been characterized by XRD, BET, SEM, TEM, and IR spectroscopy. Modified boehmites, in which the modifier anchor is one of the phosphonic functions of the complexone, exhibit the properties of a complexing support for double-charged metal ions. The kinetic characteristics and sorption capacities of PC–boehmites have been determined. The complexing selectivity on the modified surface are arranged in the following decreasing order: Pb(II) > Cu(II) > Zn(II) ≈ Ni(II) ≈ Co(II) ≈ Cd(II) > Ca(II). The stability of the sorbed state of metal ions changes along the series of surface-anchored complexones in the following order: IDAMP > NTP > HEDP > HEIDP. The trends elucidated point to a close correlation between complexa formation involving phosphonic complexones in solution and on the boehmite surface.

We report the results of our studies of the protolytic and coordination equilibria of formation of mono- and polynuclear heteroligand complexonates containing cobalt(II) and nickel(II) salts and EDTA, as well as monoamine complexons, such as iminodiacetic acid and hydroxyethyliminodiacetic acid. The experimental data obtained by absorption spectrophotometry were processed using the mathematical models that allowed us to assess the probability of existence of a broad range of complex species in the solution and to select the species sufficient for the experimental data to be reconstituted from them. The compositions of the polynuclear heteroligand cobalt(II) and nickel(II) complexonates were determined. The pH ranges of their existence were found; the equilibrium constants of the reactions and the stability constants of the resulting complexes were calculated. An assumption is made about their structure.

Effect of complexons of polyaminopolycarboxylic acid series (IDA, NTA, EDTA, and DTPA) and polyphosphonic acid series (HEDP, NTP, and EDTP) on Cu(II) cations sorption on goethite (α-FeOOH) from aqueous solutions has been studied. Obtained results have been considered in the context of complexation reactions in bulk solution and on sorbent surface. It has been found that all complexons (except for EDTA), depending on nature, produce on goethite surface (≡FeOH) triple complexes of type A (surface–metal–complexon) of composition ≡FeOCuLH i 1+i−n and ≡FeOCuL(OH) j 1−j−n or type B (surface–complexon–metal) of composition ≡FeLH i Cu3+i-n and ≡FeLCu(OH) j 3−j−n . pH-Ranges for complex existence and stability constants for the surface complexes have been determined. Factors affecting the character of complexon effect (immobilization/remobilization) on the sorbed metal have been analyzed.

Coordination equilibria in the Co(II)–Ni(II)–2-aminopropanoic acid (HAla)–EDTA system have been studied spectrophotometrically at different molar ratios of the reagents in a wide pH range. It has been found that, when metal ions are in excess with respect to EDTA at pH 5–9, polyheteronuclear complexonates [(CoAla)Edta(NiAla)] 2– , [(CoAla 2 )Edta(NiAla 2 )] 4– , [(NiAla 2 )Edta(CoAla 2 ) 2 ] 4– , [(CoAla 2 )Edta(NiAla 2 ) 2 ] 4– , and [(NiAla 2 ) 2 Edta(CoAla 2 ) 2 ] 4– form in a solution. The equilibrium constants of formation of these complexes and their overall stability constants have been calculated. Possible structures of the polynuclear complexonates are discussed.

The influence of some complexing agents of (poly)aminopolycarboxylic acids (diethylenetriaminopentaacetic acid (DTPA), ethylenediaminotetraacetic acid (EDTA), nitrilotriacetic acid (NTA), and iminodiacetic acid (IDA)) on the sorption of Cu 2+ by crystal and amorphous (hydr)oxides of Fe(III), Al(III), and Mn(IV) that are widespread mineral components of soils was studied. The obtained results are considered in terms of complex-formation in the solution and on the sorbent’s surface. The effect of the complexing agents on the metal sorption (mobilization/immobilization) is determined by (1) the stability, structure, and sorption capability of compexonates formed in the solution; (2) the acidity, and (3) the nature of the sorbent. The desorption effect on Cu 2+ cations was found to change in the following sequence of complexing agents: EDTA > DTPA ≫ NTA > IDA. The high-dentate complexing agents (EDTA, DTPA) had the greatest impact on ?u 2+ cations bound with crystalline (hydr)oxides of Fe, Al, and Mn. The low denticity of the complexing agents (IDA, NTA) and binding of ?u 2+ with amorphous sorbents leads to the weakening of desorption. The decrease in acidity promoted the mobilization of the metal under the influence of complexing agents; the increase in acidity caused its immobilization. The growth in the mobility of heavy metals bound with soil (hydr)oxides of Fe, Al, and Mn due to the complexing agents entering the surface and ground water is considered a factor of ecological risk.

Complexation in the Co(II)‒Ni(II)‒aminoethanoic acid (HGly)‒EDTA (H4Edta) system was studied at different molar ratios of components by absorption spectrophotometry. The mathematical modeling of A = f(pH) curves was used to establish that bi-, tri-, and tetranuclear heteroligand complexes like [(CoGly)Edta(NiGly)]2‒, [(CoGly2)Edta(NiGly2)]4‒, [(CoGly2)Edta(NiGly2)2]4‒, [(CoGly2)2Edta(NiGly2)]4‒, and [(CoGly2)2Edta(NiGly2)2]4‒, whose accumulation fraction attained 80‒100% at optimal pH values, were formed depending on the ratio of reagents and the acidity of a medium. The formation equilibrium and total stability constants of these complexes were calculated, and a hypothesis about their structure was made.

Complexation in systems containing vanadyl cations and organophosphonic acid complexone anions (POC, Pocj), such as 1-hydroxyethylidenediphosphonic acid (HEIDP, Heidp4−), nitrilotrimethylphosphonic acid (NTP, Ntp6−), and 2-phosphonobutane-1,2,4-tricarbocylic acid (PBTC, Pbtc5−), was studied by absorption spectroscopy and potentiometry. The molar and protonic compositions of the complexonates formed and the regions of their formation and existence were determined. The equilibrium constants of reactions and the stability constants of the complexonates were calculated. Experimental data were processed by the mathematical models that were able of evaluating the possibility of the existence of a wide spectrum of complex species in solution and to select the species sufficient to confirm experimental data.

The results of mathematical simulation of sorption equilibria with the participation of divalent cations of heavy metals (HMs), chelant (EDTA), and insoluble forms of humic acids (HAs) are discussed. It is shown that the formation of chelates of metals with EDTA in solutions results in the decreasing sorption of the metals by humic acids. We also analyzed the effect of the acidity of the medium and the HM: EDTA: HA ratio (in a wide range) on the desorption of metals. The desorbing effect of EDTA on the metals is the highest at pH 3–5 and increases with an increase in the concentration of EDTA and a decrease in the concentration of HAs. With respect to the remobilization of metals under the impact of EDTA, the metal cations can be arranged into the following sequence: Cu(II) > Ni(II) > Pb(II) ≫ Cd(II) > Co(II) > Zn(II). The obtained data have been used to analyze the remobilization / extraction of HMs from soils with a high content of humic substances.

Protolytic and coordination equilibria in ternary systems containing a nickel(II) salt, ethylenediaminetetraacetic acid, and monoamine complexones, such as iminodiacetic, hydroxyethyliminodiacetic, and nitrilotriacetic acids, were studied by absorption spectroscopy against the background of NaClO4 at I = 0.1 and T = (20 ± 2)°C. Experimental data were processed by mathematical models that were able of evaluating the possibility of existence of a wide spectrum of species in solution and to select the species sufficient for the experimental data to be reproduced from them. The compositions of polynuclear heteroligand complexonates were determined, the pH regions of their existence were established, and the equilibrium constants of reactions and the stability constants of the complexes were calculated.

Методами абсорбционной спектроскопии и потенциометрии изучено комплексообразование в системах, содержащих катионы ванадила и анионы фосфорорганических комплексонов (ФОК, Pocj): 1-гидроксиэтилидендифосфоной (ГЭИДФ, Geidp4), нитрилотриметилфосфоновой (НТФ, Ntp6) и 2-фосфонобутан-1,2,4-трикарбоновой (ФБТК, Pbtс5) кислот. Определен мольный и протонный состав образующихся комплексонатов, а также области их формирования и существования. Рассчитаны константы равновесия реакций и константы устойчивости найденных комплексонов. Обработка экспериментальных данных производилась с помощью математических моделей, позволяющих оценить возможность существования в растворе широкого спектра комплексных частиц и выделить из них те, учет которых достаточен для подтверждения экспериментальных данных.