Selective separation of elements from complex solution matrix with molecular recognition plus macrocycles attached to a solid-phase: A review

Solid-phase extraction (SPE) approach was introduced approximately five decades ago, and until then development of SPE materials is seamlessly continued. Lately, the SPE-based research is increasingly focused in developing more explicit materials to achieve meticulous separation of elements from complex solution matrices with high concentrations of interfering ions. One group of SPE materials includes those with macrocyclic ligands immobilized on a solid-phase, which are capable of selective separation and pre-concentration of elements, and such selectivity in metal retention is generally termed as molecular recognition. In the process, the designed \u27host\u27 material possesses a high degree of recognition to specific elements or groups of elements called \u27guest\u27, and the recognition capability remains effective at the very low concentrations of the \u27guest\u27 species or when those present in complex matrices. The routes to the development of element-selective SPEs, the operating principles, applications and limitations are discussed in this review. © 2013 Elsevier B.V

Chemical-induced washing remediation of metal-contaminated soils (Book Chapter)

The immobilization or removal of toxic components using aqueous extractants, with or without additives, is one of the commonly practiced techniques for the treatment of metal-contaminated soils. However, rather than the use of water alone, the solution with chemical-additives is preferred due to the less time requirement and better separation effectiveness. There is a long-favored list of additives that have been used for the chemical-induced washing remediation of soils, which include acids, bases, chelants, surfactants, and so forth. The objective of this chapter is to provide a brief overview of the chemical-assisted soil washing approaches. © Springer Japan 2016. All rights are reserved.[Book Chapter

Decontamination of spent iron-oxide coated sand from filters used in arsenic removal

Sand filters devised with iron-rich adsorbents are extensively promoted and deployed in the arsenic-prone south and south-east Asian countries (e.g., Bangladesh). The approach offers superior performance in removing arsenic while the spent sludge from the sand filters is an issue of concern due to the possibility of toxic releases after being discarded. In this work, a new technique is proposed for the treatment of spent iron-oxide coated sand (IOCS) from filters used in arsenic removal. Chelant-washing of the arsenic-loaded IOCS is combined with the solid phase extraction treatment to accomplish the objective. The unique point of the proposed process is the cost-effective scheme, which includes the option of recycling of the washing solvent beside the decontamination of the spent arsenic-rich sludge. © 2013 Elsevier Ltd

Selective separation of arsenic species from aqueous solutions with immobilized macrocyclic material containing solid phase extraction columns

金沢大学理工研究域物質化学系A combination of solid phase extraction (SPE) columns was used for selective separation of water-soluble arsenic species: arsenite, arsenate, monomethylarsonic acid (MMA) and dimethylarsinic acid (DMA). The SPE columns, namely AnaLig TE-01 (TE-01), AnaLig AN-01 Si (AN-01) and AnaLig As-01 PA (As-01), contain immobilized macrocyclic material as the sorbent and commonly known as molecular recognition technology (MRT) gel. The retention, extraction and recovery behavior of the MRT gel SPE columns were studied at pH 4-10. Fortified deionized water spiked with 100μM of arsenic species were treated at the flow rate of 0.2mLmin-1. HNO3 (1.0 and 6.0M) was used as eluent to recover the retained arsenic species from TE-01 and AN-01 SPE columns. Arsenic species retained in the As-01 column were eluted with HNO3 (0.1M) followed by NaOH (2.0M). Likely interference from the various coexisting ions (Na+, K+, Ca2+, Mg2+, Cl-, NO3-, CH3COO-, PO43-, SO42-, ClO4-) (10mM) were negligible. Quantitative separation of As(III), As(V), MMA and DMA was achieved based on the differences in extraction and recovery behavior of the MRT gel SPE columns with pH for different arsenic species. Complexation between arsenic species and MRT gel is the core phenomenon of the proposed technique as the complexation of MRT gels is expected to be stronger than the resin-based separation processes. MRT gel SPE columns are advantageous as compared with other reported SPE columns in terms of its performance with As(III). Effortless regeneration and unaltered separation performance of the sorbent materials for more than 100 loading and elution cycles are other sturdy characteristics to consider the MRT gel SPE columns for sensitive and selective arsenic species separation. © 2010 Elsevier Ltd

Remediation of toxic metal contaminated soil by washing with biodegradable aminopolycarboxylate chelants

Ex situ soil washing with synthetic extractants such as, aminopolycarboxylate chelants (APCs) is a viable treatment alternative for metal-contaminated site remediation. EDTA and its homologs are widely used among the APCs in the ex situ soil washing processes. These APCs are merely biodegradable and highly persistent in the aquatic environments leading to the post-use toxic effects. Therefore, an increasing interest is focused on the development and use of the eco-friendly APCs having better biodegradability and less environmental toxicity. The paper deals with the results from the lab-scale washing treatments of a real sample of metal-contaminated soil for the removal of the ecotoxic metal ions (Cd, Cu, Ni, Pb, and Zn) using five biodegradable APCs, namely [S,S]-ethylenediaminedisuccinic acid, imminodisuccinic acid, methylglycinediacetic acid, DL-2-(2-carboxymethyl) nitrilotriacetic acid (GLDA), and 3-hydroxy-2,2\u27-iminodisuccinic acid. The performance of those biodegradable APCs was evaluated for their interaction with the soil mineral constituents in terms of the solution pH and metal-chelant stability constants, and compared with that of EDTA. Speciation calculations were performed to identify the optimal conditions for the washing process in terms of the metal-chelant interactions as well as to understand the selectivity in the separation ability of the biodegradable chelants towards the metal ions. A linear relationship between the metal extraction capacity of the individual chelants towards each of the metal ions from the soil matrix and metal-chelant conditional stability constants for a solution pH greater than 6 was observed. Additional considerations were derived from the behavior of the major potentially interfering cations (Al, Ca, Fe, Mg, and Mn), and it was hypothesized that use of an excess of chelant may minimize the possible competition effects during the single-step washing treatments. Sequential extraction procedure was used to determine the metal distribution in the soil before and after the extractive decontamination using biodegradable APCs, and the capability of the APCs in removing the metal ions even from the theoretically immobilized fraction of the contaminated soil was observed. GLDA appeared to possess the greatest potential to decontaminate the soil through ex situ washing treatment compared to the other biodegradable chelants used in the study. © 2012 Elsevier Ltd

Effect of Extraction Variables on the Biodegradable Chelant-Assisted Removal of Toxic Metals from Artificially Contaminated European Reference Soils

Development of aminopolycarboxylate chelants (APCs) having enhanced biodegradability is gaining increasing focus to replace the EDTA and its homologs with those used widely for the ex situ treatment of contaminated soils and are potential eco-threats. The paper reports the chelant-assisted extraction of the toxic metals (Cd, Cu, Pb, and Zn) from the metal-spiked European reference soils (Eurosoil 1 and Eurosoil 4) using biodegradable APCs, namely EDDS, GLDA, and HIDS. The effects of chelant-to-metal molar ratio, solution pH, and metal/chelant stability constants were evaluated, and compared with that of EDTA. The selectivity aptitude of the biodegradable chelants towards the toxic metals was assumed from the speciation calculations, and a proportionate correlation was observed at neutral pH. Pre- and post-extractive solid phase distributions of the target metals were defined using the sequential extraction procedure and dissolution of metals from the theoretically immobilized fraction was witnessed. The effect of competing species (Al, Ca, Fe, Mg, and Mn) concentrations was proven to be minimized with an excess of chelant in solution. The highlight of the outcomes is the superior decontamination ability of GLDA, a biodegradable APC, at minimum chelant concentration in solution and applicability at a wide range of pH environments. © 2012 Springer Science+Business Media Dordrecht

Formation and stability of binary complexes of divalent ecotoxic ions (Ni, Cu, Zn, Cd, Pb) with biodegradable aminopolycarboxylate chelants (dl-2-(2-carboxymethyl)nitrilotriacetic acid, GLDA, and 3-hydroxy-2,2′- iminodisuccinic acid, HIDS) in aqueous solutions

The protonation and complex formation equilibria of two biodegradable aminopolycarboxylate chelants {dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2′-iminodisuccinic acid (HIDS)} with Ni 2+, Cu2+, Zn2+, Cd2+ and Pb 2+ ions were investigated using the potentiometric method at a constant ionic strength of I = 0.10 mol·dm-3 (KCl) in aqueous solutions at 25 ± 0.1 C. The stability constants of the proton-chelant and metal-chelant species for each metal ion were determined, and the concentration distributions of various complex species in solution were evaluated for each ion. The stability constants (log10 K ML) of the complexes containing Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ ions followed the identical order of log10 K CuL > log10 K NiL > log10 K PbL > log10 K ZnL > log10 K CdL for either GLDA (13.03 > 12.74 > 11.60 > 11.52 > 10.31) or HIDS (12.63 > 11.30 > 10.21 > 9.76 > 7.58). In each case, the constants obtained for metal-GLDA complexes were larger than the corresponding constants for metal-HIDS complexes. The conditional stability constants (log10 $$K-{\text{ML}}^{\u27}$$) of the metal-chelant complexes containing GLDA and HIDS were calculated in terms of pH, and compared with the stability constants for EDTA and other biodegradable chelants. © 2012 Springer Science+Business Media New York

Selective Separation of Tri- and Pentavalent Arsenic in Aqueous Matrix with a Macrocycle-Immobilized Solid-Phase Extraction System

A simple flow-based method was developed for the selective separation of arsenic species (+3 and +5) using a macrocycle-immobilized solid phase extraction (SPE) system, commonly known as molecular recognition technology (MRT) gel. Arsenic species in solution or in the eluent were subsequently quantified with graphite furnace atomic absorption spectrometry. The separation behaviors of As(III) and As(V) on MRT-SPE were investigated. It was found that As(V) can be selectively collected on the SPE system within the range of pH 4 to 9, while As(III) was passed through the MRT-SPE. The retention capacity of the MRT-SPE material for As(V) was found to be 0.25 ± 0.04 mmol g-1. The detection limit of the method for As(V) was 0.06 μg L-1, and the relative standard deviation was 2.9 % (n = 10, C = 1 μmol L-1). Interference from the matrix ions was studied. In order to validate the developed method, certified reference materials of effluent wastewater and groundwater samples were analyzed, and the determined values were in good agreement with the certified values. The proposed method was successfully applied to the speciation analysis of tri- and pentavalent arsenic in natural water samples showing satisfactory recoveries (≥ 98.7 %). © 2013 Springer Science+Business Media Dordrecht

Stability constants of Fe(III) and Cr(III) complexes with dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2\u27- iminodisuccinic acid (HIDS) in aqueous solution

The complex formation equilibria of Cr3+ and Fe3+ ions in aqueous solution with two biodegradable aminopolycarboxylate chelants (dl-2-(2-carboxymethyl)nitrilotriacetic acid (GLDA) and 3-hydroxy-2,2\u27- iminodisuccinic acid (HIDS)) were investigated. The potentiometric data obtained at the constant ionic strengths (I) of (0.1 and 1.0) mol·dm-3 KCl and at (25 ± 0.1) °C was processed with the aid of the computer program HYPERQUAD 2008. The formation constants of the proton-chelant and metal-chelant (log KML) species (M = Fe3+ or Cr 3+; L = GLDA or HIDS) were determined, and the concentration distributions of complex species in solution were evaluated for both metal ions. In various pH conditions, the interaction between the chelants (L = GLDA or HIDS) and the metal ions (M = Fe3+ or Cr3+) leads to the formation of different complexes formulated as MH2L+, MHL, ML-, M(OH)L2-, and M(OH)2L3-. The log KML values at I = 0.1 mol·dm-3 KCl (T = (25 ± 0.1) °C) were 15.27 (log KFe-GLDA), 14.96 (log K Fe-HIDS), 13.77 (log KCr-GLDA), 12.67 (log K Cr-HIDS), and at I = 1.0 mol·dm-3 KCl (T = (25 ± 0.1) °C) were 14.79 (log KFe-GLDA), 14.34 (log K Fe-HIDS), 12.90 (log KCr-GLDA), 12.09 (log K Cr-HIDS). The conditional stability constants (log K\u27ML) of the ML complexes were calculated in terms of pH in the range of 2 to 12 and compared with the same for EDTA and other biodegradable chelants (NTA and EDDS). © 2012 American Chemical Society