Modified materials based on layered minerals as ameliorants for the remediation of podzol in the industrial barren

Layered silicates, such as serpentine and vermiculite, have properties that make it possible to use materials based on them as components of environmental technologies. The possibility of soil remediation in industrially contaminated area, formed due to the long-term exposure to emissions from copper-nickel production (Monchegorsk, Murmansk region), was studied. Two materials were used as ameliorants in our study: expanded vermiculite and granular serpentine sorbent, a waste after using the purification technology of highly concentrated solutions from metals. These materials have a high sorption activity to several metals, a high specific surface area, the ability to retain moisture, and are available in quantities sufficient to work on the remediation of large areas. A study of the physicochemical properties of industrially polluted soil and ameliorants, direct phytotoxicity testing of podzol and its mixtures with expanded vermiculite and the serpentine sorbent (test plants - common oat Avna satva L. and red clover Trifolium pratnse L.) were carried out. The study results showed that the proposed materials were effective additives for increasing the pH of acidic soil, sorption and precipitation of Al and potentially toxic metals - Cu, Ni, Pb, Fe, and improving the soil hydrophysical and agrochemical characteristics. A positive response of test plants to the introduction of ameliorants into industrially contaminated soil was noted.

Estimation of the biosorption potential of certain representatives of the genus Bacillus in interaction with lead cation in vitro

The article presents data on the physicochemical and metabolically dependent mechanisms of detoxification by microorganisms of heavy metals that enter the environment during anthropogenic pollution. The taxonomic and physiological-biochemical diversity of microorganisms capable of neutralizing toxicants has been demonstrated. In the experimental part of the study, the combination of the methods used made it possible to fully assess the degree of toxicity and the effect of lead cations on the growth of bacteria of the genus Bacillus in a model experiment. Thus, the use of atomic absorption spectrophotometry and atomic force microscopy gave an idea of the level of biosorption of a given xenobiotic element from a substrate with localization of inactive forms of lead. The data obtained indicate the presence of an inhibitory effect of Pb (NO3) 2 and Pb (CH3COO) 2 in concentrations from 1 mM to 0.063 mM about the test organisms under study. The presence of cations with a nutrient substrate gives a false-positive idea of the degree of influence of lead on the growth of the studied microorganisms, since an increase in optical density in test samples is due to high sorption characteristics and, as a consequence, is characterized by an increase in relative optical density. An assessment of the detoxification mechanisms, which is expressed by active bioaccumulation of lead on the surface elements of the microbial cell up to 65% at the point of entering the stationary growth phase, indicates the promising use of representatives of this group of microorganisms as microbial bioremediation and correctors of excess content of this element in the body or ecosystem as a whole.

Sorption and Textural Properties of Activated Carbon Derived from Charred Beech Wood

The aim of this study was to prepare activated carbon materials with different porous structures. For this purpose, the biomass precursor, beech wood, was carbonized in an inert atmosphere, and the obtained charcoal was physically activated using carbon dioxide at 1273 K. Different porous structures were obtained by controlling the time of the activation process. Prepared materials were characterized in terms of textural (N2 sorption at 77 K), structural (XRD), and sorption properties (CO2, C2H4, C4H10). The shortest activation time resulted in a mostly microporous structure, which provided a high sorption of CO2. Increasing the activation time led to an increasing of the pores’ diameters. Therefore, the highest ethene uptake was obtained for the material with an intermediate activation time, while the highest butane uptake was obtained for the material with the highest activation time.

Novel and highly efficient functionalized bentonite for elimination of Cu2+ and Cd2+ from aqueous wastes

The aim of this study was to synthesize novel and highly efficient functionalized material (BNMPTS) for selective elimination of Cu²⁺ and Cd²⁺ from aqueous waste. The detailed insights of solid/solution interactions were investigated by X-Ray photoelectron spectroscopic analyses. The grafting of silane caused for significant decrease in specific surface area of bentonite from 41.14 to 4.65 m²/g. The functionalized material possessed significantly high sorption capacity (12.59 mg/g for Cu²⁺ and 13.19 mg/g for Cd²⁺) and selectivity for these cations. The material showed very high elimination efficiency at a wide range of pH ~2.0 to 7.0 for Cu²⁺, ~3.0 to 10.0 for Cd²⁺ and concentration (1.0 to 25.0 mg/L) for Cu²⁺ and Cd²⁺. A rapid uptake of these two cations achieved an apparent equilibrium within 60 minutes of contact. The increased level of background electrolyte concentrations (0.0001 to 0.1 mol/L) did not affect the elimination efficiency of these two cations by BNMPTS. Moreover, the common coexisting ions did not inhibit the removal of these toxic ions. Furthermore, high breakthrough volumes i.e., 1.4 and 3.69 L for Cu²⁺, 2.6 and 6.64 L for Cd²⁺ was obtained using 0.25 and 0.50 g of BNMPTS respectively in a fixed-bed column operations.

High Sorption and Selective Extraction of Actinides from Aqueous Solutions

The selective elimination of long-lived radioactive actinides from complicated solutions is crucial for pollution management of the environment. Knowledge about the species, structures and interaction mechanism of actinides at solid–water interfaces is helpful to understand and to evaluate physicochemical behavior in the natural environment. In this review, we summarize recent works about the sorption and interaction mechanism of actinides (using U, Np, Pu, Cm and Am as representative actinides) on natural clay minerals and man-made nanomaterials. The species and microstructures of actinides on solid particles were investigated by advanced spectroscopy techniques and computational theoretical calculations. The reduction and solidification of actinides on solid particles is the most effective way to immobilize actinides in the natural environment. The contents of this review may be helpful in evaluating the migration of actinides in near-field nuclear waste repositories and the mobilization properties of radionuclides in the environment.

Graphene Oxide-Chitosan Aerogels: Synthesis, Characterization, and Use as Adsorbent Material for Water Contaminants

Porous aerogels, formed by subjecting precursor hydrogels using a freeze-drying process, are certainly one of the most studied and synthetized soft materials, thanks to their important features such as elasticity, swelling behavior, softness, and micro and nanosized pores, which guarantee their applicability in various fields. Typically, these systems are synthetized working with natural or synthetic polymers, but in the last years great interest has been given to proper formulated aerogels able to combine polymeric structures with other moieties such as graphene or graphene oxide. This working strategy can be pivotal in many cases to tune important properties of the final system such as toughness, porosity, elasticity, electrical conductivity, or responsive behavior. In this work we propose the synthesis of chitosan graphene oxide aerogels obtained through self-assembly of graphene oxide sheets and chitosan chains. These three-dimensional systems were chemically characterized with IR and XRD technique and their inner structure was investigated through the scanning electron microscopy (SEM). Moreover, we mechanically characterized the material through dynamic mechanical analysis, showing the stability of these systems. Finally, the adsorption ability of these soft materials has been demonstrated using model molecules to simulate water contaminants showing the efficacy of those graphene-based systems even for the removal of anionic dyes. Complete removal of contaminants was obtained at low concentration of dyes in solution (100 mg/L), while with a higher amount of pollutant in the solution (350 mg/L) high sorption capacity (q > 200 mg/g) was observed.

Modified Starch Highly Porous Materials

A technique for starch modification by graft polymerization of acrylamide has been developed. The obtained copolymer is soluble in a wide range of pH 2 - 12. The modification of starch made it possible to freely combine it with aqueous acid solutions of chitosan, in order to achieve a synergistic effect of their properties. A porous material based on modified starch and its mixtures with chitosan, which has high sorption characteristics, has been developed. The resulting material is promising as a sorbent of heavy metal ions and packing materials for transportation and storage.

Eco-Friendly Ferrimagnetic-Humic Acid Nanocomposites as Superior Magnetic Adsorbents

Recyclable, cheap, eco-friendly, and efficient adsorbent materials are very important for the removal of pollution. In this work, we report the design and implementation of ferrimagnetic-humic acid nanocomposites as superior magnetic adsorbent for heavy metals. Ferrimagnetic and ferrimagnetic-humic acid nanocomposite particles with different morphologies were prepared using the coprecipitation method and hydrothermal synthesis method, respectively. The results show that the morphology of the nanoparticles prepared by the coprecipitation method is more uniform and the size is smaller than that by the hydrothermal synthesis method. Adsorption experiments show that the ferrimagnetic-humic acid nanoparticles prepared by the coprecipitation method has high sorption capacity for cadmium, and the maximum adsorption capacity is about 763 μg/g. At the same time, magnetic technology can be used to realize the recycling of ferrimagnetic-humic acid adsorbents.

Synthesis of Silver-Impregnated Magnetite Mesoporous Silica Composites for Removing Iodide in Aqueous Solution

Mag@silica-Ag composite has a high sorption ability for I− in aqueous solution due to its high surface area and strong affinity for the studied anion. The material adsorbed I− rapidly during the initial contact time (in 45 min, η = 80%) and reached adsorption equilibrium after 2 h. Moreover, mag@silica-Ag proved to selectively remove I− from a mixture of Cl−, NO3− and I−. The adsorption behavior fitted the Langmuir isotherm perfectly and the pseudo-second-order kinetic model. Based on the Langmuir isotherm, the maximum adsorption capacity of mag@silica-Ag was 0.82 mmol/g, which is significantly higher than previously developed adsorbents. This study introduces a practical application of a high-capacity adsorbent in removing radioactive I− from wastewaters.

Zeolite Lightweight Repair Renders: Effect of Binder Type on Properties and Salt Crystallization Resistance

Rendering mortars with lightweight zeolite aggregates were designed and tested. The effect of the type of binder used was also researched. For the hardened mortars, macrostructural parameters, mechanical characteristics, hygric and thermal properties were assessed. Specific attention was paid to the analysis of the salt crystallization resistance of the developed rendering mortars. Quartz sand was fully replaced in the composition of mortars with zeolite gave materials with low density, high porosity, sufficient mechanical strength, high water vapor permeability and high water absorption coefficient, which are technical parameters required for repair rendering mortars as prescribed in the WTA directive 2-9-04/D and EN 998-1. Moreover, the zeolite enhanced mortars exhibit good thermal insulation performance and high sorption capacity. The examined rendering mortars were found to be well durable against salt crystallization, which supports their applicability in salt-laden masonry. Based on the compatibility of the repair materials with those originally used, the lime and natural hydraulic lime zeolite mortars can be used as rendering mortars for the repair of historical and heritage buildings. The cement-lime zeolite render is applicable for repair purposes only in the case of the renewal of masonry in which Portland cement-based materials were originally used.