Anionic polyacrylamide influence on the lead(II) ion accumulation in soil - the study on montmorillonite

Novel carbon-based composites enriched with Fe and Mn as effective and eco-friendly adsorbents of heavy metals in multicomponent solutions

With increasing demand for adsorbents highly effective in pollutant removal, carbon-based porous materials are becoming more and more popular. In this work, a new approach to the synthesis of such solids using an environmentally friendly, two-step preparation method is presented. A series of hybrid porous silica-containing carbon composites was synthesized, namely: metal free (C/SiO2), enriched with manganese (C/Mn/SiO2), as well as iron (C/Fe/SiO2). The effect of additives on the structure and morphology of the composites was evaluated using X-ray photoelectron spectroscopy (XPS), nitrogen adsorption/desorption and scanning electron microscope (SEM). The as-synthesized carbons were used as effective adsorbents for the simultaneous removal of heavy metals, including lead (Pb(II)) and zinc (Zn(II)) ions. In particular, it was determined that C/Mn/SiO2 sample demonstrated the highest adsorption capacity towards Pb(II) and Zn(II) ions. It was equal to 211.60 mg/g for Pb(II) and 74.95 mg/g for Zn(II). Zeta potential and surface charge density of the solids, with and without metals, were investigated to determine electrical double layer structure, whereas stability studies and aggregate size measurements were performed to estimate solid aggregation under selected conditions. It was established that solids with adsorbed metals formed suspensions with lower stability than those without ions. This, in turn, facilitates their separation from aqueous solutions.

Accumulation of toxic Pb(II) ions by the iron-containing minerals in the presence of ionic polyacrylamide soil conditioner

The aim of this research was to determine the adsorption-desorption, surface, electrokinetic, and stability properties of aqueous suspensions of iron-containing minerals in the presence of anionic polyacrylamide (AN PAM) and lead(II) ions. Three minerals found in the soil environment, akaganeite, goethite, and magnetite, were synthesized based on the precipitation method. The interaction mechanism of heavy metal ions with polymer flocculant, which are adsorbed on the soil mineral particles, was proposed. It was shown that the best affinity to the AN PAM or/and Pb(II), adsorbed both from single and mixed solution, shows akageneite (characterized by the highly developed specific surface area). Polymer-metal complexes formed in the mixed adsorbate systems are rather stable, evidence of which is reduced desorption and consequently limited bioavailability of toxic lead ions for organisms and plants in soil environment.

Ionic Polyacrylamides as Stability-Modifying Substances of Soil Mineral Suspensions Containing Heavy Metal Impurities

The accumulation of heavy metal in soils is a serious environmental problem. The aim of this paper was to compare the adsorption mechanism of ionic polyacrylamides (PAMs)—anionic and cationic with different contents of functional groups, on the surface of clay minerals—montmorillonite (type 2:1) and kaolinite (type 1:1), without and with the presence of heavy metal ions (Cr(VI) or Pb(II)). The dependence of solution pH, structure of mineral, type of PAM, ionic form of heavy metal, as well as order of adsorbates addition on the adsorption efficiency and stability of the clay mineral-polymer-heavy metal system was determined. In addition to adsorption and stability studies, electrokinetic and potentiometric titration measurements were performed. It was shown that the mixed PAM+heavy metal adsorption layers modify the surface properties of clay minerals significantly, which in many cases leads to the effective destabilization of the solid suspension and its separation from the liquid phase. Moreover, the most important factor, which influences the adsorbed amount of ionic polyacrylamide, turned out to be the internal structure of layered aluminosilicates and the presence of inter-package spaces capable of adsorbate molecules accumulating. For this reason the obtained adsorption capacity of montmorillonite is about 100 times higher in comparison to kaolinite.

Electroreduction of Bi(III) ions in the aspect of expanding the “cap-pair” effect: the role of the nanosized active complexes

The paper discusses the electroreduction of Bi(III) ions in the aspect of expanding the “cap-pair” effect.

The “cap-pair” rule is associated with the acceleration of the electrode’s processes by organic substances. The interpretation of the “cap-pair” effect mechanism was expanded to include the effect of supporting electrolyte concentration on the acceleration process and the type of electrochemical active as well as used protonated organic substances. It has also been shown that the phenomena occurring at the electrode/solution interface can influence a change in the dynamics of the electrode’s process according to the “cap-pair” rule.

Development of Pectin-Based Aerogels with Several Excellent Properties for the Adsorption of Pb2

Traditional aerogels lack specific functional groups for the adsorption of Pb2+, which results in a low adsorption capacity and limits the application scope. Novel porous pectin-based aerogels (PPEAs) were prepared by incorporating polyethylenimine (PEI) using ethylene glycol diglycidyl ether (EGDE) as a cross-linker for the removal of Pb2+ from water. The cross-linking mechanism, morphology, mechanical strength, thermal stability, adsorption properties, and mechanism of the aerogels were investigated. The aerogels possessed several desirable features, such as a large maximum Pb2+ adsorption capacity (373.7 mg/g, tested at pH 5.0), ultralight (as low as 63.4 mg/cm3), high mechanical strength (stress above 0.24 MPa at 50% strain), and easy recyclability. Meanwhile, the equilibrium adsorption data was well described by the Langmuir-Freundlich (Sips) model and the kinetic adsorption process was well fitted using the pseudo-second-order model. The donor groups, such as -NH2, and oxygen-containing functional groups were responsible for the Pb2+ adsorption, which was confirmed by the FTIR and XPS analysis. The excellent characteristics mean that PPEAs are highly effective adsorbents in the remediation of lead-containing wastewater.

An Overview on Composite Sorbents Based on Polyelectrolytes Used in Advanced Wastewater Treatment

Advanced wastewater treatment processes are required to implement wastewater reuse in agriculture or industry, the efficient removal of targeted priority and emerging organic & inorganic pollutants being compulsory (due to their eco-toxicological and human health effects, bio-accumulative, and degradation characteristics). Various processes such as membrane separations, adsorption, advanced oxidation, filtration, disinfection may be used in combination with one or more conventional treatment stages, but technical and environmental criteria are important to assess their application. Natural and synthetic polyelectrolytes combined with some inorganic materials or other organic or inorganic polymers create new materials (composites) that are currently used in sorption of toxic pollutants. The recent developments on the synthesis and characterization of composites based on polyelectrolytes, divided according to their macroscopic shape-beads, core-shell, gels, nanofibers, membranes-are discussed, and a correlation of their actual structure and properties with the adsorption mechanisms and removal efficiencies of various pollutants in aqueous media (priority and emerging pollutants or other model pollutants) are presented.

Comparison of lead(II) ions accumulation and bioavailability on the montmorillonite and kaolinite surfaces in the presence of polyacrylamide soil flocculant

Heavy metals, such as Pb(II), Cd(II), Hg(II), do not degrade like organic compounds and remain in soil for a long time. The presence of organic, mineral or polymeric substances (such as polyacrylamides) may contribute to the accumulation and immobilization of toxic metals in poorly absorbable form for living organisms. The main aim of the study was to compare the effectiveness of lead(II) ions immobilization on the layered aluminosilicate surfaces in the anionic polyacrylamide presence. The effectiveness of Pb(II) adsorption was tested depending on metal cation concentration, content of dissociable groups in added flocculant as well as internal structure of clay mineral. The desorption tests of heavy metal ions were performed by the use of water and EDTA (ethylenediaminetetraacetic acid). By means of measurements of suspension stability and aggregate size formed in the studied systems, the flocculating ability of anionic polyacrylamide was checked. The electrokinetic parameters of mineral particles, i.e. surface charge density and electrokinetic potential, without and with individual adsorbates were also determined. It has been shown that the Pb cations adsorbed amount and the effectiveness of their immobilization strongly depends on the polyacrylamide presence in the system and the internal structure of aluminosilicate.

Simultaneous Removal of Pb2+ and Zn2+ Heavy Metals Using Fly Ash Na-X Zeolite and Its Carbon Na-X(C) Composite

Pure zeolite (Na-X) and a zeolite–carbon composite (Na-X(C)) were investigated as adsorbents of heavy metals—Pb²⁺ and Zn²⁺ from an aqueous solution. These materials were synthesized from fly ash—a waste from conventional hard coal combustion. Both solids were characterized using XRD, SEM-EDS, nitrogen adsorption/desorption, particle size and elemental composition analyses. The adsorption study was performed at pH 5 in the systems containing one or two adsorbates simultaneously. The obtained results showed that the pure zeolite was characterized by a more developed surface area (728 m²/g) than its carbon composite (272 m²/g), and the mean pore diameters were equal to 1.73 and 2.56 nm, respectively. The pure Na-X zeolite showed better adsorption properties towards heavy metals than its Na-X(C) composite, and Zn²⁺ adsorbed amounts were significantly higher than the Pb²⁺ ones (the highest experimental adsorption levels were: for Zn²⁺—656 and 600 mg/g, and for Pb²⁺—575 and 314 mg/g, on the Na-X and Na-X(C) surfaces, respectively). The zinc ions are exchanged with the cations inside the zeolite materials structure more effectively than lead ions with a considerably larger size. In the mixed systems, the competition between both heavy metals for access to the active sites on the adsorbent surface leads to the noticeable reduction in their adsorbed amounts. Moreover, the hydrochloric acid was a better desorbing agent for both heavy metals, especially Pb²⁺ one (desorption reached 78%), than sodium base (maximal desorption 25%).

Hydroxyapatite with magnetic core: Synthesis methods, properties, adsorption and medical applications

This review presents the actual state of knowledge and recent research results on the magnetic composite synthesized from iron oxide (γ-Fe₂O₃ or Fe₃O₄) and hydroxyapatite. It can be obtained applying some methods, i.e. chemical precipitation, hydrothermal, sol-gel, and biomimetic or combined techniques which exhibit characteristic properties affecting the form of the prepared product. More specific details are discussed in this paper. A comparison of the discussed synthesis methods is presented. On the basis of selected publications, a comparison of the results of the analysis by XRD, FTIR, SEM and EDX methods for hydroxyapatite with a magnetic core was also presented. Moreover, the characteristics large adsorption capacity and specific area allow employing nanocomposites as adsorbents particularly in removal of toxic metal ions. Nowadays this issue is extremely vital due to large amounts of pollutants in the environment and greater ecological awareness of people. Moreover, magnetic hydroxyapatite can be also applied as a catalyst in various syntheses or oxidation reactions as well as in medicine in magnetic resonance imaging, hyperthermia treatment, drug delivery and release, bone regeneration or cell therapy.