Advanced material and approach for metal ions removal from aqueous solutions

Modified chitosan: Insight on biomedical and industrial applications

Chitosan (CS), a by -product of chitin deacetylation can be useful in a broad range of purposes, to mention agriculture, pharmaceuticals, material science, food and nutrition, biotechnology and of recent, in gene therapy. Chitosan is a highly desired biomolecule due to the existence of many sensitive functional groups inside the molecule and also because of its net cationicity. The latter provides flexibility for creating a wide range of derivatives for particular end users across various industries. This overview aims to compile some of the most recent research on the bio-related applications that chitosan and its derivatives can be used for. However, chitosan's reactive functional groups are amendable to chemical reaction. Modifying the material to show enhanced solubility, a greater range of application options and pH-sensitive targeting and others have been a major focus of chitosan research. This review describes the modifications of chitosan that have been made to improve its water solubility, pH sensitivity, and capacity to target chitosan derivatives. Applying the by-products of chitosan as antibacterial, in targeting, extended release and as delivery systems is also covered. The by-products of chitosan will be important and potentially useful in developing new biomedical drugs in time to come.

Luminescent Alendronic Acid-Conjugated Micellar Nanostructures for Potential Application in the Bone-Targeted Delivery of Cholecalciferol

Vitamin D, an essential micronutrient crucial for skeletal integrity and various non-skeletal physiological functions, exhibits limited bioavailability and stability in vivo. This study is focused on the development of polyethylene glycol (PEG)-grafted phospholipid micellar nanostructures co-encapsulating vitamin D3 and conjugated with alendronic acid, aimed at active bone targeting. Furthermore, these nanostructures are rendered optically traceable in the UV-visible region of the electromagnetic spectrum via the simultaneous encapsulation of vitamin D3 with carbon dots, a newly emerging class of fluorescents, biocompatible nanoparticles characterized by their resistance to photobleaching and environmental friendliness, which hold promise for future in vitro bioimaging studies. A systematic investigation is conducted to optimize experimental parameters for the preparation of micellar nanostructures with an average hydrodynamic diameter below 200 nm, ensuring colloidal stability in physiological media while preserving the optical luminescent properties of the encapsulated carbon dots. Comprehensive chemical-physical characterization of these micellar nanostructures is performed employing optical and morphological techniques. Furthermore, their binding affinity for the principal inorganic constituent of bone tissue is assessed through a binding assay with hydroxyapatite nanoparticles, indicating significant potential for active bone-targeting. These formulated nanostructures hold promise for novel therapeutic interventions to address skeletal-related complications in cancer affected patients in the future.

Recovery of Phosphorus and Metals from the Ash of Sewage Sludge, Municipal Solid Waste, or Wood Biomass: A Review and Proposals for Further Use

This review provides an overview of methods to extract valuable resources from the ash fractions of sewage sludge, municipal solid waste, and wood biomass combustion. The resources addressed here include critical raw materials, such as phosphorus, base and precious metals, and rare earth elements for which it is increasingly important to tap into secondary sources in addition to the mining of primary raw materials. The extraction technologies prioritized in this review are based on recycled acids or excess renewable energy to achieve an optimum environmental profile for the extracted resources and provide benefits in the form of local industrial symbioses. The extraction methods cover all scarce and valuable chemical elements contained in the ashes above certain concentration limits. Another important part of this review is defining potential applications for the mineral residues remaining after extraction. Therefore, the aim of this review is to combine the knowledge of resource extraction technology from ashes with possible applications of mineral residues in construction and related sectors to fully close material cycle loops.

Fe3O4-chitosan nanocomposite as a magnetic biosorbent for removal of nickel and cobalt heavy metals from polluted water

Recently, natural polymers like chitosan have gained attention as promising adsorbents for water treatment. By combining chitosan with magnetic nanoparticles, their adsorption capabilities can be enhanced. In this study, chitosan-magnetite nanocomposite (CMNC) was synthesized via coprecipitation method to remove nickel and cobalt from aqueous solutions. The physicochemical properties of the synthesized CMNC were investigated by various techniques, including FESEM, TEM, XPS, FTIR, XRD, and VSM. The electron microscopy results confirmed the uniform dispersion of magnetite nanoparticles within CMNC nanocomposites, while VSM confirmed their significant magnetic properties. The adsorption experiments showed that at optimal conditions (pH = 6, contact time = 2 h, adsorbent dosage = 2 g/l), CMNC has high adsorption capacities of 30.03 mg/g for Ni2+ and 53.19 mg/g for Co2+. Furthermore, the adsorption data fitted best with the Langmuir isotherm, show that the active sites on CMNC are energetically homogenous. According to kinetic analysis, the experimental data were in good agreement with both pseudo-second-order and intra-particle diffusion models, which suggest that chemical sorption, along with mass transfer steps, influence the overall adsorption process. Finally, investigating the thermodynamic parameters (∆Gads, ∆Hads, ∆Sads) showed that the adsorption process on CMNC was endothermic and spontaneous, with stronger interactions observed between CMNC and Co2+ compared to Ni2+.

Sensitive ratiometric sensor for Al(III) detection in water samples using luminescence or eye-vision

A facile, quick, and sensitive ratiometric luminescence sensor is designed for detection aluminum ions in water samples using luminescence or eye-vision. This approach relies on the emission change of the europium(III) complex with 3-(2-naphthoyl)-1,1,1,-trifluoro acetone (3-NTA) after interaction with various concentration of aluminum ions. The addition of aluminum ions suppressed the Eu(III) emission at 615 nm under 333 nm excitation, while simultaneously enhancing the ligand emission at 480 nm. Optimum detection was obtained in methanol. The quantification of aluminum ions using ratiometric method was determined by plotting the luminescence ratio (F_480nm/F_615nm) versus aluminum ions concentration. The calibration plot was obtained within the range 0.1-100 µM with LOD = 0.27 µM. Additionally, the concentration of aluminum ions can be estimated semi-quantitatively by visually observing the luminescence colour change of the probe from red to light green and then to dark green after being excited by a UV lamp with 365 nm. As far as we are aware, this is the first luminescent lanthanide complex-based ratiometric probe for the detection of aluminum ions. The probe showed remarkable aluminum ions selectivity relative to that of other metal ions. The suggested sensor was used effectively to identify aluminum ions in water samples with good results.

Green-Emissive Copper Nanocluster with Aggregation-Enhanced Emission for Selective Detection of Al3

Selective detection of Al³⁺ is of great significance both for the benefit of human health and environmental safety considerations. In this work, a sensitive and selective fluorescence assay for Al³⁺ was proposed based on the green-emissive Cu nanoclusters (Cu NCs). Different from the commonly reported works, the green emissive Cu NCs showed dual emission bands at 450 and 510 nm, attributed to the reaction product between polyvinyl pyrrolidone and ascorbic acid and the Cu core, respectively. Al³⁺ could induce the aggregation of Cu NCs by forming covalent bonds, which results in the enhancement of photoluminescence intensity. This enhancement phenomenon is rather selective to Al³⁺ , which endows the detection in real samples. These results provide new insights for the fluorescence mechanisms of metal NCs, which also provided a functional luminescent material for various applications, such as chemical sensing, bioimaging and photoelectric devices.

Assessment of Selected Heavy Metals Concentration Level of Drinking Water in Gazer Town and Selected Kebele, South Ari District, Southern Ethiopia

Drinking water quality is fundamental to human physiology and health. The aim of this study was to assess the quality of drinking water in Gazer Town and selected kebele, in south Ari district, South Omo zone, Southern Ethiopia. A total of four drinking water samples were collected from densely populated urban areas of the Gazer Town and one rural Kebele. All the collected samples were analyzed for eight heavy metals, (Cd, Co, Cu, Cr, Fe, Mn, Pb, and Zn) using standard procedures. The results were compared with other national and international standards. Among the analyzed samples, drinking water samples collected from selected kebele (Aynalem kebele), show mean concentrations heavy metals in (μg/L), (Mn (973 ± 10), Cu (1068 ± 1.5), Cr (2785 ± 25), Fe (4302 ± 15), Cd (1218 ± 18), Pb (720 ± 12), Co (1478 ± 3), and Zn (1790 ± 5)), and the results revel except, Co and Zn metals, all show concentrations higher than the national and international standards (such as USEPA (2008), WHO (2011), and New Zealand) recommended values. Among the eight heavy metals analyzed from drinking waters in Gazer Town, Cd and Cr were below the method detection than that of all sampling area. However, the concentration of Mn, Pb, Co, Cu, Fe, and Zn were ranged from mean values of 9 μg/L, 17.6 μg/L, 7.6 μg/L, 12 μg/L, 765 μg/L, and 494 μg/L, respectively. Except Pb metals, the analyzed metals in waters were below the currently recommended guidelines for drinking. Therefore, the government should adopt some treatment technologies such as sedimentation and aeration to minimize the concentration of zinc for safe drinking the water to the community of Gazer Town.

Removal of hazardous ions from aqueous solutions: Current methods, with a focus on green ion flotation

Hazardous ions, like those of heavy metals, cause significant health and environmental problems when they are discharged into water resources naturally or through various industrial processes. Removing these ions from water is of significant importance in the provision of high-quality water for drinking and agricultural usage. This work discusses current techniques that are frequently used for the removal of heavy-metal ions from aqueous solutions by absorption, particularly the use of biodegradable surfactants in ion flotation. Certain new surfactants promise high efficiency in their use in the ion-flotation process and in their application in industrial-water treatment to remove heavy metals. As an example, this work demonstrates the high efficiency of surfactants based on an amino-acid (L-cysteine) in removing a range of heavy-metal ions in a simple, single-stage ion-flotation process. High foaming ability, the ability to operate in various temperatures and pHs, decomposing into natural products and high binding affinity for heavy-metal ions make the cysteine-based surfactants a highly suitable compound to replace current commercial surfactants in ion- and froth-flotation processes. Removal of particular ions can also be achieved in ion flotation; a suitable choice of parameters, such as pH and surfactant concentration, favours the surfactant binding to those ions. Further intensive work is required to develop an optimal process to recover valuable elements from waste solutions.

Real-Time On-Site Multielement Analysis of Environmental Waters with a Portable X-ray Fluorescence (pXRF) System

Strict regulations are in place to control the effluents of mining sites and other industries. Heavy metal contamination of aquatic systems caused by leakages is difficult to mitigate as it takes time to detect and localize the leak. Dynamic sampling would drastically reduce the time to locate leakages and allow faster actions to reduce the impact on the environment. The present study introduces a novel portable multielement water analysis system to simultaneously measure Mn, Ni, Cu, Zn, Pb, and U in water samples from natural sources within 15 min from the sampling. The metals are preconcentrated from a 10 mL water sample into a nanoporous filter based on bisphosphonate-modified thermally carbonized porous silicon. The metals can be conveniently analyzed from the filter with a portable XRF analyzer in field conditions. The system was empirically calibrated for a lake water matrix with neutral pH and low alkaline metal concentration. A strong correlation between the XRF intensities and the ICP-MS results was obtained in a concentration range from 50 to 10 000 μg/L. With a DPO-2000C XRF analyzer, the detection limits were 103, 86, 92, 35, 44, and 43 μg/L for Mn, Ni, Cu, Zn, Pb, and U, respectively. The corresponding values with X-MET8000 Expert Geo were 137, 46, 62, 38, 29, and 54. The system was successfully validated with simulated multielement lake water samples and piloted in field conditions. The system provides an efficient way to monitor metals in environmental waters in cases where quick on-site results are needed.

Rationally designed carboxymethylcellulose-based sorbents crosslinked by targeted ions for static and dynamic capture of heavy metals: Easy recovery and affinity mechanism

A separable spherical bio-adsorbent (CMC-Cr) was prepared for capturing heavy metal ions by simple coordination and cross-linking between targeted ions of Cr³⁺ and carboxymethyl cellulose (CMC). A simple alternation of the CMC incorporation allowed the interconnected networks within the microspheres of preformed solid CMC to be adjusted. The excellent network structure could achieve the maximum collision between the adsorbent and the heavy metal cations in the wastewater. Through investigations, CMC-Cr-2 beads were determined as the optimal adsorbent. The adsorption performance of novel materials was evaluated by examining their adsorption behavior on Pb(II) and Co(II) under both static and dynamic conditions. The results showed that the adsorption behavior of CMC-Cr-2 beads on both two heavy metal cations could be fully reflected by the Freundlich model. Under the theoretical conditions, the maximum adsorption capacities were 97.26 and 144.74 mg/g. The kinetic results for the adsorption of two heavy metal cations on CMC-Cr-2 beads were consistent with the Pseudo-second-order kinetic model. Moreover, the correlation coefficient of the Thomas model was significant in the dynamic adsorption performance tests. Five regeneration cycle studies were successfully carried out on CMC-Cr-2 beads to evaluate reusability and stability. The applicability of CMC-Cr-2 beads in authentic aqueous solutions (both the single and binary pollutant systems) was also studied, and the results indicated that CMC-Cr-2 beads had a high potential for practical implementation. Furthermore, by analyzing the surface interactions of two heavy metal cations with the CMC-Cr-2 beads based on FTIR and XPS characterization, a basic understanding of the interaction between bio-sorbents and pollutants in wastewater can be obtained.

Chitosan functionalized with heptadentate dinucleating ligand applied to removal of nickel, copper and zinc

The preconcentration of metal ions present at low concentration levels in aqueous systems and the selective removal of potentially toxic metals are important applications of adsorption processes. In this study, a heptadentate dinucleating ligand was anchored to chitosan for use in adsorption studies on Zn(II), Cu(II) and Ni(II) ions. The novel adsorbent was characterized by ¹³C NMR and FT-IR spectroscopy, TGA and BET surface area analysis. The degree of substitution of the ligand in chitosan, obtained from CHN analysis, was 0.73. The adsorption kinetics followed a pseudo-second-order model. The rate constants and the adsorption capacities for multicomponent systems decreased in the order Cu(II) >> Ni(II) ∼ Zn(II), indicating the preferential adsorption of Cu(II). For Cu(II) ions, the Langmuir model provided the best fitting to the experimental data, and the monolayer Cu(II) adsorption capacity was 0.404 mmol g^-1, while the linear isotherm described Zn(II) and Ni(II) ion adsorption.

Efficient recovery of palladium nanoparticles from industrial wastewater and their catalytic activity toward reduction of 4-nitrophenol

Discharge of heavy metals from various sources of industrial wastewater poses significant environmental and health concerns. Thus, efficient recovery of precious metals from wastewater employing sustainable, rapid, and cost-effective treatment methods is highly desirable. In this work, palladium nanoparticles (Pd NPs) were successfully recovered from industrial wastewater using a pulsed laser process in the absence of additives or reducing agents. Notably, the developed approach is faster and more environmentally friendly than other conventional recovery methods. The recovered Pd NPs were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), and inductively coupled plasma optical emission spectroscopy (ICP-OES). Various pulsed laser parameters (i.e., laser wavelength, power, and irradiation time) were optimized to obtain ideal conditions for the pulsed laser ablation process. Effective recovery of the Pd metal from industrial wastewater was achieved at a laser wavelength of 355 nm, power of 40 mJ/pulse, and irradiation time of 30 min. The Pd NPs exhibited excellent catalytic activity toward the reduction of 4-nitrophenol. Thus, the recovered materials showed remarkable potential for application in degradation of toxic aromatic nitro compounds in the environment.

Removal of nickel from aqueous solution using synthesized IL/ZnO NPs

In this paper, the removal of nickel from aqueous solution was studied using zinc oxide nanoparticles (ZnO NPs) and zinc oxide nanoparticles functionalized ionic liquid (IL/ZnO NPs) by batch adsorption and solid phase extraction (SPE) methods, respectively. The synthesized IL/ZnO NPs was characterized by FT-IR, SEM, XRD, XPS, and DLS techniques. The optimum conditions were experimentally determined by varying the parameters such as feed concentration, contact time, adsorbent dosage, pH, and temperature using both the adsorbents. From the optimum conditions, it was found that the feed concentration is 10 ppm, contact time is 120 min, adsorbent dosage is 0.2 g, pH is 6, and temperature is 60 °C with the maximum percentage removal of 81% for ZnO Nps, whereas, for IL/ZnO NPs, the feed concentration is 10 ppm, contact time is 90 min, adsorbent dosage is 0.1 g, pH is 6, and temperature is 60 °C with the maximum percentage removal of 92.5%. On comparison with the results, IL/ZnO NPs was an efficient adsorbent for the removal of nickel from aqueous solution as well as the effluents of electroplating and stainless steel industries. The percentage removal of nickel was analyzed by inductively coupled plasma-optical emission spectrometry (ICP-OES). The sorbents were regenerated and reused effectively.

Synthesis of Magnetite-Based Polymers as Mercury and Anion Sensors Using Single Electron Transfer-Living Radical Polymerization

In this work, hydrophilic polymers modified with iron oxide nanoparticles, such as iron oxide-poly(2-dimethylaminoethyl methacrylate) [P(DMAEMA)] magnetite-based and iron oxide-poly(acrylamide) [P(AAm)] magnetite-based polymers, were prepared via a single electron transfer-living radical polymerization approach. Bile acid and 2-bromo-2-methylpropionic acid were covalently attached onto the surface of Fe3O4 nanoparticles, and these immobilized magnetite nanoparticles were used as an initiator for the polymerization. The binding capabilities of different ions, such as Hg2+, CN-, Cl-, F-, and NO3 -, were tested using these polymeric sensors monitored by UV-vis spectroscopy. Magnetite-based P(DMAEMA) showed enhanced binding capability due to the presence of tertiary amine groups. In addition, it was possible to easily separate the bound ions from aqueous media using an external magnetic field.

Current advancement and future prospect of biosorbents for bioremediation

The increasing use of heavy metals, synthetic dyes and pesticides is a major environmental concern. Wastewaters containing heavy metals and dyes, extensively released from small and large scale industries enter excessively into food chains resulting in mutagenesis, carcinogenicity and serious health impairments in living systems. The arrays of technologies are implemented to date to remediate both inorganic and organic contaminants from wastewaters. Among which, adsorption is the most attractive method as it employs eco-friendly, sustainable and cost-effective biomaterials. Use of bioadsorbents is advantageous over the conventional adsorbents. Clay, chitin, peat, microbial biomass and agricultural wastes are commonly used bioadsorbants. These bioadsorbents are extensively used for elimination of dyes, heavy metals, adsorption of toxic industrial effluents, removal of fertilizers/pesticides, atmospheric pollutants and nuclear waste from the environment. The current review presents state of the art knowledge on various types of biosorbents, their uses, and mechanism of action. Various strategies to enhance the efficiency of bioadsorbents and physicochemical conditions to remediate dyes and heavy metals from waste streams are also incorporated in this review. Use of nano-bioadsorbents in industries to minimize the hazardous effect of solid and liquid waste has also been discussed.

Removal of heavy metal ions by capacitive deionization: Effect of surface modification on ions adsorption

Activated carbon cloth (ACC) coated with zinc oxide (ZnO) nanoparticles (NPs) have been used as electrodes in flow-by capacitive deionization (CDI) system. Aqueous solution of individual Pb²⁺ and Cd²⁺ ions and mixed Pb²⁺ and Cd²⁺ ions were used as test contaminant in CDI system to study the effect of surface modification upon ions removal efficiency. Due to the aggregated structure of ZnO NPs on ACC surface, the modified ACC electrodes develop the additional surface area as well as dielectric barrier therefore resulting in higher specific capacitance. In addition, coating with ZnO NPs effectively reduced physical adsorption whereby enhanced the ions adsorption rate and capacity during electrosorption process. Upon incorporating with ZnO NPs, the electrosorption efficiency was enhanced from 17% to 33% for Pb²⁺, from 21% to 29% for Cd²⁺ and from 21% to 35% for mixed Pb²⁺ and Cd²⁺ ions. The power consumption of individual ions and mixed ions removal process for ACC and ZnO NPs modified ACC were also discussed. Furthermore, used ACC electrodes surfaces were examined using photoelectron spectroscopy (XPS) and results were also conferred. The CDI ACC electrodes with ZnO NPs showed a promising and an effective way for heavy metal removal applications.

Heavy metal adsorption using structurally preorganized adsorbent

The adsorbent had two types of functional groups and six binding sites in one coordination unit. The presence of the amide group shows good anti-interference to alkali metals and alkali soil metals.

Stable surface functionalization of carbonized mesoporous silicon

A new method to produce functional surfaces on porous silicon allow long term use of the material in aqueous environments.

Effects of soil amendments on the growth response and phytoextraction capability of a willow variety (S. viminalis × S. schwerinii × S. dasyclados) grown in contaminated soils

This study was conducted to evaluate the effects of lime and bisphosphonates (BPs) such as N10O chelate amendment on the growth, physiological and biochemical parameters, and phytoextraction potential of the willow variety Klara (Salix viminalis × S. schwerinii × S. dasyclados) grown in soils heavily contaminated with copper (Cu), nickel (Ni) and zinc (Zn). The plants were irrigated with tap or processed water (mine wastewater). The results suggest that the combined effects of the contaminated soil and processed water inhibited growth parameters, gas exchange parameters and chlorophyll fluorescence (Fv/Fm) values. In contrast, malondialdehyde (MDA) content, organic acids, total phenolic and total flavonoid contents, and the accumulation of metals/metalloids in the plant tissues were increased compared to the control. When the soil was supplemented with lime and N10O; growth, physiological, biochemical parameters, and resistance capacity were significantly higher compared to unamended soil treatments, especially in the contaminated soil treatments. The combined lime‒ and N10O‒amended soil treatment produced higher growth rates, resistance capacity, photosynthesis rates and phytoextraction efficiency levels relative to either the lime‒amended or the N10O‒amended soil treatments. This study provides practical evidence of the efficient chelate‒assisted phytoextraction capability of Klara and highlights its potential as a viable and inexpensive novel approach for in situ remediation of Cu‒, Ni‒ and Zn‒contaminated soils and mine wastewaters.

Efficacy of engineered GO Amberlite XAD-16 picolylamine sorbent for the trace determination of Pb (II) and Cu (II) in fishes by solid phase extraction column coupled with inductively coupled plasma optical emission spectrometry

Graphene oxide (GO) was immobilized innovatively through azo spacer arm onto the surface of polymeric Amberlite XAD-16 resin in order to expose all oxygen functionalities freely available for metal ions coordination and further modification with picolylamine which governs selectivity. The GO Amberlite XAD-16 picolylamine enables the development of SPE column coupled with ICP-OES for preconcentration and determination of Pb (II) and Cu (II) in water and fish samples. Elution was performed by mild acid (2M HCl) no other carcinogenic organic solvent was used, prevents ligand leaching. Under optimized conditions, the preconcentration factors of 150 and detection limits 1.434 and 0.048 µg L⁻¹ for Pb (II) and Cu (II)  were obtained respectively.

Exploring various ligand classes for the efficient sequestration of stannous cations in the environment

Metal pollution, coming from both natural and anthropogenic sources, has become one of the most serious environmental problems. Various strategies have been tested with the aim of removing heavy metals from environment. In this contribution, containing a robust experimental work together with a critical literature analysis, the sequestering ability of a variety of ligands towards Sn²⁺ cation will be evaluated in the conditions of several natural fluids, i.e. sea water, fresh water, human blood plasma, urine and saliva. 13 structural and 11 thermodynamic descriptors will be selected for a total of thirty-eight molecules belonging to different classes (carboxylic acids, amines, amino acids, phosphonates, polyelectrolytes etc. …). For the filling of those missing data relative to the 11 thermodynamic descriptors, different strategies will be adopted, including simple correlations and Nipals algorithm. The evaluation of the sequestering ability of the ligands is assessed in terms of estimation of pL_0.5 (total concentration of ligand required to bind the 50% of metal in solution), an empirical parameter that takes into account all the side reactions in solutions and does not depend on the speciation scheme. Partial least square calculations were performed to model the pL_0.5 and to determine its correlation with the abovementioned descriptors. The possibility to design and build up new tailor-made molecules capable of effectively sequester Sn²⁺ in various conditions is crucial for practical applications in biosphere, hydrosphere and lithosphere.

A membrane electroflotation process for recovery of recyclable chromium(III) from tannery spent liquor effluent

A two-compartment membrane electroflotation reactor has been demonstrated for recovery of recyclable chromium(III) from tannery spent liquor effluent. Dimensionally stable RuO₂/TiO₂-Ti and Ti were used as anode and cathode, respectively. The spent liquor effluent was used as catholyte and 0.01 N H₂SO₄ used as anolyte which was separated by Nafion 117 membrane. About 98% of chromium(III) was recovered and the removal efficiency correlated with the presence of organics in the effluent. The advantage of two-compartment membrane electroflotation process is capable of removing chromium(III) without oxidising it into chromium(VI) in chloride containing tannery spent liquor effluent. The mechanism of chromium(III) removal has been discussed. The recovered Cr(OH)₃ was successfully demonstrated for tanning of cowhide.

Impacts of coagulation-flocculation treatment on the size distribution and bioavailability of trace metals (Cu, Pb, Ni, Zn) in municipal wastewater

This study investigated the impact of coagulation-flocculation treatment on metal form and bioavailability in municipal wastewater. Real humus effluent samples were separated into particulate, colloidal and truly dissolved fractions before and after treatment with either ferric chloride (FeCl₃) or the biopolymer Floculan. Results revealed that both reagents effectively (≥48%) eliminated Cu, Pb and Zn from the particulate fraction and removed Cu and Zn from the colloidal fraction in conjunction with colloidal organic carbon (COC). Although organics in the truly dissolved fraction were resistant to removal, Floculan reduced Cu in this fraction by 72% owing to the complexation of free Cu ions to phenol and amino groups along the polymeric chains, revealing an additional removal pathway. In fact, COC removed in the CF process by Floculan was replaced with truly dissolved compounds, input as a result of this reagents organic composition. Floculan, therefore, reduced the soluble concentration of Cu and Zn without changing the DOC concentration, thus reducing the bioavailability of these metals in treated effluent. FeCl₃ did not reduce the bioavailability of target metals, thus did not deliver any environmental benefit. This work provides important information for the selection and development of high performance coagulants to improve metal removal.

Wavelength selective separation of metal ions using electroactive ligands

Photo-induced electron transfer to an irreversibly electroactive ligand is introduced as a novel method for separating meta ions.

Surface decontamination in fuel manufacture plants by chelating solution of nanoparticles

A nanoparticles chelating solution was synthesized by copolymerization of acrylonitrile (AN) and methacrylic acid (MAA) by radiation induced polymerization technique using 17 kGy irradiation doses. A high copolymer yield was obtained by using 80/20% of AN/MAA and comonomer concentration of 50% (w/w) at a dose rate of 2.58 KGy/h. The resultant cyano group (–CN) of nano-poly(AN/MAA) was converted by chemical modification using hydroxylamine (NH2–OH) to an amidoxime group [–C(=NOH)NH2], which was then confirmed by Fourier transform infrared spectroscopy (FTIR). The physico-chemical properties of poly(AN/MAA) and amidoximated poly(AN/MAA) nanoparticles were studied by FTIR, transmission electron microscopy (TEM), dynamic light scattering (DLS) and thermal gravimetric analysis (TGA). The morphological analysis by TEM and DLS showed a spherical and uniform size of the amidoximated poly(AN/MAA) nanoparticles. TGA results indicated that the thermal stability of poly(AN/MAA) increased by the amidoximation process. The surface decontamination due to uranium was also investigated by the prepared chelating nanoparticles solution. A high purity germanium detector (HPGe) was used as a surface contamination detection tool. The results showed the presence of peaks at different energies, namely, 186.2 keV for Ra-226 (U-238) and 143.76 keV, 163.35 keV and 205.31 for U-235 before the decontamination process. The disappearance of these peaks after decontamination confirmed the applicability and efficiency of the nanoparticles solution in uranium surface decontamination.

Mopping up the Oil, Metal, and Fluoride Ions from Water

The recycle, cleaning, and reuse of water are highly important for environmental remediation. This issue is addressed by creating a fluorescent zwitterionic spirocyclic Meisenheimer complex with high chelating propensity for toxic metals using low-cost starting materials and a one-pot synthesis technique. The resulting material is able to detect fluoride up to 12.8 ppb level and remove 82% aqueous fluoride from 1000 mL of 100 ppm fluoride solution in a single contact. The material demonstrates rapid kinetics and is capable of dropping the toxic metal ion (Pb/Hg/Cd) concentration below 0.2 ppb within 10 min. A resin-free, precipitation-free, and reusable technique has been developed for the removal of toxic metal ions and fluoride from extremely polluted water. Moreover, utilizing its extreme hydrophobicity, polystyrene sponges have been coated with the Meisenheimer complex to mop up oil spill and organic solvents from a biphasic mixture.

On the Reaction of Carbonyl Diphosphonic Acid with Hydroxylamine and O-alkylhydroxylamines: Unexpected Degradation of P-C-P Bridge

Derivatives of methylenediphosphonic acid possess wide spectra of biological activities and are used in enzymology as research tools as well as in practical medicine. Carbonyl diphosphonic acid is a promising starting building block for synthesis of functionally substituted methylenediphosphonates. Investigation of the interaction of carbonyl diphosphonic acid with hydroxylamine clearly demonstrates that it is impossible to isolate oxime within the pH range 2–12, while only cyanophosphonic and phosphoric acids are the products of the fast proceeding Beckmann-like fragmentation. In the case of O-alkylhydroxylamines, corresponding alcohols are found in the reaction mixtures in addition to cyanophosphonic and phosphoric acids. Therefore, two residues of phosphonic acid being attached to a carbonyl group provide new properties to this carbonyl group, making its oximes very unstable. This principally differs carbonyl diphosphonic acid from structurally related phosphonoglyoxalic acid and other α-ketophosphonates.

Synthetic Procedures Leading towards Aminobisphosphonates

Growing interest in the biological activity of aminobisphosphonates has stimulated the development of methods for their synthesis. Although several general procedures were previously elaborated to reach this goal, aminobisphosphonate chemistry is still developing quite substantially. Thus, innovative modifications of the existing commonly used reactions, as well as development of new procedures, are presented in this review, concentrating on recent achievements. Additionally, selected examples of aminobisphosphonate derivatization illustrate their usefulness for obtaining new diagnostic and therapeutic agents.

Synthesis of medronic acid monoesters and their purification by high-performance countercurrent chromatography or by hydroxyapatite

We achieved the synthesis of important medronic acid monoalkyl esters via the dealkylation of mixed trimethyl monoalkyl esters of medronic acid. Two methods were developed for the purification of medronic acid monoesters: 1) small scale (10–20 mg) purification by using hydroxyapatite and 2) large scale (tested up to 140 mg) purification by high-performance countercurrent chromatography (HPCCC).