Zinnat Ara Begum

Abstract: The first application of solid phase extraction (SPE) started approximately five decades ago, and until then development of SPE materials is continued, and it seems to be a never-ending story. Lately, research is focused in developing more explicit materials to achieve meticulous separation of ions from solutions containing complex matrices with high concentrations of interfering ions. One group of SPE materials includes those with macrocyclic ligands immobilized on a silica or polymer support; this type of SPE has been reportedly available for ion-selective separation and pre-concentration of ions, and the technique is commonly known as molecular recognition technology (MRT). In MRT, the designed ‘host’ materials possess a high degree of recognition to specific ions or groups of ions called ‘guest’, and the recognition capability remains effective at the very low concentrations of the ‘guest’ ion or when those present in complex matrices. In this book, application of different MRT-SPE materials for the selective separation of trace ecotoxic ions from the aqueous matrix are described, and the effects of the various chemical species or forms on MRT-based separations are discussed.

Abstract: 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 Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ ions was investigated using the potentiometric method at a constant ionic strength of I = 0.10 mol•dm–3 (KCl) in aqueous solutions at 25 ± 0.1C. 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 (logKML) of the complexes containing Ni2+, Cu2+, Zn2+, Cd2+ and Pb2+ ions followed an identical order of logKCuL>logKNiL>logKPbL>logKZnL>logKCdL when using GLDA (13.03>12.74>11.60>11.52>10.31) as when using HIDS (12.63>11.30>10.21>9.76>7.58). In each case, the constants obtained for metal-GLDA complexes were higher in magnitude than the corresponding constants for metal-HIDS complexes. The conditional stability constants (logK´ML) 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.

Abstract: 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, 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'-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.

Abstract: A simple flow-based method was developed for the simultaneous separation of some transition metal ions (Co, Ni, Cu, Zn, Cd) from aqueous systems which show ecotoxic effects when present at elevated concentrations. A silica-gel-bonded macrocycle system, commonly known as molecular recognition technology (MRT) gel, was used for solid phase extraction (SPE) of the target analytes. The collection behavior of the MRT-SPE system was studied in terms of pH. Fortified deionized water samples containing 250 µg L–1 of each of the elements were treated at the flow rate of 1 mL min–1. The collected analytes were then eluted by 3 M HNO3, and introduced for inductively coupled plasma optical emission spectrometry determination. The detection limits of the proposed technique were in the range of 0.004–0.099 µg L-1 for the studied metal ions. The validity of the proposed separation technique was checked with spiked ‘real’ water samples and satisfactory recoveries (96–102%) were observed. The non-destructive nature and highly selective ion-extraction capability of the SPE material are some focal points of the proposed method.

Abstract: Aminopolycarboxylate chelants (APCs) are extremely useful for a variety of industrial applications, including the treatment of toxic metal-contaminated solid waste materials. Because non-toxic matrix elements compete with toxic metals for the binding sites of APCs, an excess of chelant is commonly added to ensure the adequate sequestration of toxic metal contaminants during waste treatment operations. The major environmental impacts of APCs are related to their ability to solubilize toxic heavy metals. If APCs are not sufficiently eliminated from the effluent, the aqueous transport of metals can occur through the introduction of APCs into the natural environment, increasing the magnitude of associated toxicity. Although several techniques that focus primarily on the degradation of APCs at the pre-release step have been proposed, methods that recycle not only the processed water, but also provide the option to recover and reuse the metals, might be economically feasible, considering the high costs involved due to the chelants used in metal ion sequestration. In this paper, we propose a separation process for the recovery of metals from effluents that contain an excess of APCs. Additionally, the option of recycling the processed water using a solid phase extraction (SPE) system with an ion-selective immobilized macrocyclic material, commonly known as a molecular recognition technology (MRT) gel, is presented. Simulated effluents containing As(V), Cd(II), Cr(III), Pb(II) or Se(IV) in the presence of APCs at molar ratios of 1:50 in H2O were studied with a flow rate of 0.2 mL min-1. The ‘captured’ ions in the SPE system were quantitatively eluted with HNO3. The effects of solution pH, metal-chelant stability constants and matrix elements were assessed. Better separation performance for the metals was achieved with the MRT-SPE compared to other SPE materials. Our proposed technique offers the advantage of a non-destructive separation of both metal ions and chelants compared to conventional treatment options for such effluents.

Abstract: Separation of trace levels of lead from concentrated-matrix electroless nickel plating (ENP) waste solutions is required to meet the increasingly stringent environmental regulations. A solid phase extraction (SPE) system using a molecular recognition technology (MRT) gel was used for the selective separation of trace levels of lead (Pb) from the waste discharge of ENP operations, followed by subsequent analysis with inductively coupled plasma optical emission spectrometry (ICP-OES). Two SPE-MRTs, AnaLig® Pb-01 and AnaLig® Pb-02, packed in 3 mL polypropylene cartridges were used to treat the synthetic metal-waste solutions that were used to simulate the typical metal mixture in ENP bath waste. The fortified solutions contained 100–1000 µg L−1 of Pb in an HNO3 matrix with pre-added Ni, Cu and other interfering elements (1000 mg L−1). After the sample treatment, the SPE-MRT cartridges were washed with water and 0.1 M nitric acid, followed by elution with 0.03 M EDTA. The matrix elements (e.g., Ni, Cu) were completely removed at the washing step, while the ‘captured’ Pb was quantitatively eluted, as determined by ICP-OES measurements. The detection limit of the proposed method was 2.6 µg L−1. ‘Real’ samples from commercial ENP operations were used to assess the validity of this method, and almost quantitative Pb recovery was observed. The excellent Pb selectivity of the SPE-MRT system indicates the potential of the proposed technique for trace-level Pb separation from the Pb-containing high matrix aqueous waste discharge.

Abstract: The concern over ensuing fresh water scarcity has forced the developing countries to delve for alternative water resources. In this study we examined the potential of stagnant surface water bodies (SSWBs) as alternative fresh water resources in the densely populated Chittagong metropolitan area (CMPA) of Bangladesh – where there is an acute shortage of urban fresh water supply. Water samples, collected at one month intervals for a period of one year from 12 stations distributed over the whole metropolis. Samples were analyzed for pH, water temperature (WTemp), turbidity, electrical conductivity (EC), total dissolved solids, total solids, total hardness, dissolved oxygen (DO), chloride, orthophosphates, ammonia, total coliforms (TC) and trace metal (Cd, Cr, Cu, Pb, As and Fe) concentrations. Based on these parameters different types of water quality indices (WQIs) were deduced. WQIs showed most of CMPA-SSWBs as good or medium quality water bodies while none were categorized as bad. Moreover, it was observed that the minimal water quality index (WQIm), computed using five parameters: WTemp, pH, DO, EC and turbidity gave reliable estimate of water quality. The WQIm gave similar results in 72% of the cases compared with other WQIs which were based on larger set of parameters. Based on our finding, we suggest the wider use WQIm in developing countries for assessing health of SSWBs as it will minimize the analytical cost to overcome the budget constraints involved in this kind of evaluations. It was observed that except turbidity and TC content, all other quality parameters fluctuated within the limit of World Health Organization suggested standards for drinking water. From our findings we concluded that if the turbidity and TC content of water from SSWBs in CMPA are taken care of, they will become good candidates as alternative water resources all round the year.

Abstract: 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 100 µM of arsenic species were treated at the flow rate of 0.2 mL min–1. HNO3 (1.0 and 6.0 M) 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 (0.1 M) followed by NaOH (2.0 M). Likely interference from the various coexisting ions (Na+, K+, Ca2+, Mg2+, Cl–, NO3–, CH3COO–, PO43–, SO42–, ClO4–) (10 mM) 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.

Abstract: Moringa oleifera Lam. seed oil of the indigenous-cultivar of Bangladesh was extracted using n-hexane (H), light petroleum ether (b.p. 40–60C) (LPE) and chloroform/methanol (50:50, v/v) mixture (CM). The oil content ranged from 37.50% (H) to 40.20% (CM). The moisture, protein, ash and crude fiber contents of seed residues, and the density, refractive index, color, acidity, saponification value, iodine value, unsaponifiable matter content, oxidative state, sterols, tocopherols and fatty acid composition of the extracted oil were determined. The oil contained a high amount of oleic acid (C18:1) of up to 74.41% and a high ratio of monounsaturated to saturated fatty acids with moderate oxidative stability. The results of the present study were compared with those reported in literature for different regional habitats, and species variants.

Abstract: Electronic wastes have become the foremost stream of solid waste in almost all the countries of the world over a short span of last few years. The digital information and communication technology (ICT) revolution that the mankind is undergoing now has substantially contributed in creating this scenario. Popularly abbreviated as E-wastes, electronic waste comprises of all out-of-date discarded or otherwise unused electronics and peripherals thereof – the bulk being computers of many descriptions, consumer electronics and mobile phones. Necessarily, a huge amount of electronics is replaced by individuals and organizations each year but people are increasingly purchasing more electronics than they really need with the rapid introduction of cheaper, sleeker and alluring gadgets. The technology and trends are changing quite rapidly rendering usable electronics obsolete and make us to go for newer versions of the same thing thereby adding up to the volume of outmode electronics. Bulk of these ends up into landfills, for USA 80-85% of e-wastes goes to landfills as estimated by US-EPA. Volume of e-wastes is a big concern but the high content of heavy metals, e.g. lead, chromium, cadmium and mercury, etc., along with harmful organic compounds in the electronic products is a bigger concern for mankind. To some, the name ‘e-waste’ is ironic as it contains over 60% recyclables including iron, copper, aluminum, gold and other metals let alone the polymers from casings of disposed electronic products. The increasing flow of e-wastes naturally stimulated various solution responses, one of which is the boom in e-waste recycling business, in the form of formal industry in developed part of the world while manual and archaic disassembly of wastes in developing countries most of which are imported from developed countries for recycling. The non-recyclable parts of these wastes, including the toxicants, are finding their way into the environment which has led to the formulation of Basel Ban, an amendment to the Basel Convention to restrict trans-boundary movement of e-waste. However, the e-waste flux from developed to developing countries is on the rise due to win-win economics of informal recycling. Our knowledge about the chemistry of distribution, speciation, transport and environmental fate of these hazardous elements in and outside landfills are still sketchy though some researchers have initiated in-depth studies to assess and predict the eco-environmental consequences of the toxicants from disposed e-wastes. The incineration at the informal reprocessing sites contaminates the air and soils with polychlorinated and polybrominated dibenzo-p-dioxins and dibenzofurans, polycyclic aromatic hydrocarbons, etc. On the other hand, acid leaching processes contaminate the freshwater sources and sediments with heavy metal, which is exacerbated through the entry of these pollutants into the food cycle. Besides the contamination of the surroundings, the recycling process itself poses health risks to the workers due to the chemicals used in recycling and hazardous byproducts from the recycled wastes. Within the scope of this chapter, we will provide a brief overview, in light of the recent findings, of the toxic environmental releases from the e-waste disposal and recycling processes and their effects.

Abstract: Phytoremediation utilizes different plant species as a media of containment, destruction, or extraction of contaminants from different matrices including soil and water. Plants require essential metals i.e. Cu, Mn, Fe, Zn, Mo, etc. for growth and as such they are capable of accumulating these metals. Plants can also accumulate Cd, Cr, Pb, Co, Ag, Se, Hg, etc., which are apparently non-essential for their growth and survival. This metal-accumulating property of plants has made them very popular in recent days in the remediation of metal-contaminated soil. This approach of remediation has the benefit of cost savings compared to the conventional treatment options. Plants capable of concentrating metal pollutants at enhanced rate - the hyperaccumulators - are commonly used for metal-polluted soil remediation. But, the bioavailability of the metals limits the performance of hyperaccumulators since a large proportion of metals in contaminated soils exist in ‘non-labile’ state. There came the application of synthetic chelants to enhance the mobility and phytoavailability of metals to remediating plants. Various chelants are available which forms bioavailable and water-soluble stable metal complexes facilitating phytoextraction of these metals at enhanced rates by plants. While chelants are used because of their powerful metal solubilizing properties, it is the same characteristic which gives them the potential of becoming an eco-environmental threat. Environmental concerns are evoked due to the high persistency and poor photo-, chemo- and biodegradability of metal-chelant complexes. Different approaches have been proposed to combat the eco-environmental concerns raised by the use chelants in phytoremediation. Within the scope of this chapter, we will focus on the chelant assisted phytoremediation approaches for the removal of heavy metal contaminants from soil and eco-environmental consequences associated with it.

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