Investigation of the colloidal Cr2O3 removal possibilities from aqueous solution using the ionic polyamino acid block copolymers

Physicochemical and Adsorption Properties of Nanoporous Activated Biocarbons from Thermochemical Treatment of Horsetail Herb

In this study, the adsorption characteristics of novel activated biocarbons prepared from horsetail herb (a popular and troublesome weed) by physical activation (using carbon dioxide) and chemical one (using phosphoric(V) acid) in the process of simultaneous proteins immobilization in multicomponent solutions were examined. The carbon materials were characterized in terms of their porous structure, acidic-basic properties, and surface morphology. The binding mechanisms of such proteins as bovine serum albumin (BSA) and lysozyme (LSZ), differing in internal stability, were determined alone and in their blends. This was done based on the comprehensive analysis of the results of adsorption/desorption, surface, electrokinetic and stability measurements. These experiments were carried out over a wide pH range of 3-11. They included the following issues: (1) determination of the protein adsorbed/desorbed amounts on/from a surface of activated biocarbons; (2) study of the kinetics of these processes; (3) examination of the macromolecules impact on the surface charge density and zeta potential of the carbon materials; and (4) determination of the suspension stability and size of aggregates formed in the examined systems. The analysis of the obtained results indicated the differences in the binding mechanism of both proteins that is of key importance for their simultaneous immobilization on activated biocarbons surface in the soil environment.

Adsorption Capacity of Carbon-Silica Composites Towards Diclofenac in Poly(acrylic acid) Containing Systems: A Crucial Study on Common Wastewater Contaminants

Diclofenac is one of the most popular over-the-counter non-steroidal anti-inflammatory drug and poly(acrylic acid) is a frequently used as thickener, filler or stabilizer. For these reasons, they are common organic contaminants in raw wastewater. The purpose of the presented studies was to compare the adsorption capacity of three carbon-silica composites - metal-free C/SiO2, iron-enriched C/Fe/SiO2 and manganese-enriched C/Mn/SiO2 towards diclofenac. The studies were carried out in single, and mixed systems in the presence of poly(acrylic acid) polymer. Adsorption, desorption and kinetics of the adsorption process were investigated. The concentration of diclofenac in the supernatants was determined using high-performance liquid chromatography. The solids were also characterized with an ASAP apparatus using low-temperature nitrogen desorption adsorption isotherms at liquid nitrogen temperature. In addition, potentiometric titrations and electrophoretic mobility measurements, as well as stability tests of the studied suspensions were carried out. The most efficient composite among investigated ones proved to be C/Fe/SiO2 removing diclofenac at the level of 46.68 mg/g for its initial concentration of 90 ppm. The results obtained clearly demonstrated that the carbon-silica composites are effective in separation of drugs from aqueous solutions and can be successfully used in the future for the removal of organic pollutants from water environment.

Study on electrical double layer nanostructure on zeolitic materials’ surface in the presence of impurities of different nature

The aim of the research was to compare the adsorption mechanisms of heavy metal ions (Pb(II) and Zn(II)), as well as organic substances [diclofenac molecules and pol(acrylic acid) macromolecules on the surfaces of Na-X and Na-P1 synthetic zeolites as well their Na-X© and Na-P1© carbon composites]. The single and mixed adsorbate systems were considered. The more probable structures of the formed adsorption layers were proposed based on the results of the solid surface charge density and zeta potential experiments. The great applicability of the analysis of the parameters characterizing the electrical double layer in determination of the binding mechanism of simple inorganic ions and more complex organic molecules on the surface of the examined solids from the one- and two-component solutions was proved. Moreover, the changes of the surface and electrokinetic factors after the addition of the organic molecules enable specification of drug molecule orientation as well as the polymeric chain conformation at the solid/liquid interface.

Understanding the Mechanism of Cs Accumulation on Stainless Steel Suspended in Nuclear High-Level Liquid Waste

In a nuclear facility, the surface of stainless steels (SS) was found to be contaminated during the processing of radioactive liquid waste. Their safe and secure disposal is highly challenging to the nuclear industry. If the fundamental property of steel corrosion could be evaluated, successful decontamination and effective decommissioning strategies could be planned. Although individual radionuclide contamination behavior on SS metal was studied, till date, SS contamination behavior under the exposure of high-level liquid waste (HLLW) was unexplored. In view of this, investigations were carried out to understand the nature of contamination in SS 304L alloy under the exposure of simulated HLLW (SHLLW). For understanding of radionuclide adsorption behavior on structural materials, scanning electron microscopy/energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy have been utilized for SS 304L. The solutions were analyzed using inductively coupled plasma optical emission spectroscopy to calculate the changes in the elemental composition of the solution and corrosion behavior of SS. The passivation of SS coupons was observed in the presence of HNO₃ due to enrichment of Cr at the surface. The deposition of Cs and Mo was noticed, while SS coupons were exposed to SHLLW. At 3 M HNO₃ and room temperature, the SS surface is mildly passivated by Cr enrichment by formation of a Cr oxide layer on the SS surface. However, the passive layer was not thick enough to attenuate the signal from the substrate below the passivated layer. Hence, Fe⁰ and Cr⁰ were also found along with Cr³⁺ and Fe³⁺ (in small quantity). When temperature was elevated to 70 °C, the SS surface was completely covered with the Cr oxide layer, and hence no Cr⁰ signal was observed. The small signal of Fe⁰ indicated that the signal from the substrate surface is present below the passive layer. During the passivation process, Cr diffused toward the passive layer, thereby producing a Cr-depleted layer below the passive layer (Cr⁰ signal was not seen). In the case of SHLLW at 70 °C, the surface was fully covered by Cr³⁺, Mo⁶⁺, and Cs⁺. Fe and Ni were not observed at all. This finding will help to design an effective corrosion inhibitor and suitable decontamination agent. In addition to that, this information was found to be useful in designing high-performance novel and modern age reactor materials with improved characteristics.

Activated Bio-Carbons Prepared from the Residue of Supercritical Extraction of Raw Plants and Their Application for Removal of Nitrogen Dioxide and Hydrogen Sulfide from the Gas Phase

The waste materials left after supercritical extraction of hop cones and marigold flowers were tested as precursors of activated bio-carbons. Adsorbents were produced by means of the physical (also called thermal) activation method using CO₂ as the gasifying agent. All the activated bio-carbons were tested for the removal of NO₂ and H₂S from the gas phase under dry and wet conditions. The effects of the type of precursor and the activation procedure on the porous structure development, the acid-base properties of the surface, as well as the sorption capacities of the materials produced were also checked. The final products were bio-carbons of medium developed surface area with a basic surface nature, characterized by their high effectiveness in removal of gas pollutants of acidic character, especially nitrogen dioxide (sorption capacities in the range from 12.5 to 102.6 mg/g). It was proved that the toxic gas removal efficiency depends considerably on the sorption conditions and the activation procedure. All materials showed greater effectiveness in gas removal when the process of adsorption was carried out in the presence of steam.

Aggregation and thermal properties of nanostructured montmorillonite covered with mixed adsorption layers of cationic polyacrylamide and hazardous lead(II) ions

The aim of the study was to investigate the influence of nanostructured montmorillonite surface modification by the cationic polyacrylamide and the lead(II) ions on the thermal and aggregation properties of solid particles covered with mixed adsorption layers. The effects of cationic groups content in the polymeric macromolecules, the order of individual adsorbates addition, and lead(II) ions concentration were determined. Using spectrophotometry, potentiometric titration, microelectrophoresis, turbidimetry, DCS (Differential Centrifugal Sedimentation) and thermal analysis methods, the adsorption, electrokinetic, aggregation properties, as well as the thermal stability of studied montmorillonite—CT PAM—Pb(II) systems were established. It was shown that applied polymeric substance (soil flocculant) causes accumulation of lead(II) ions, which are hazardous at very low concentrations. Nevertheless, the chemical nature of these interactions may limit the bioavailability of this heavy metal for plants.

Investigations of chromium(III) oxide removal from the aqueous suspension using the mixed flocculant composed of anionic and cationic polyacrylamides

The main purpose of experiments was determination of the adsorption mechanism of two forms of ionic polyacrylamide (PAM) on the surface of chromium(III) oxide dispersed in the aqueous medium. This was performed in relation to anionic polyacrylamide (AN PAM) and cationic one (CT PAM) in the simple systems (containing only one selected polymer) and in the mixed systems (containing both ionic forms of PAM). The turbidimetry was applied to determine the stability of examined suspensions. To explain the obtained changes in suspension stability after the polymer addition, polyacrylamide adsorbed amount, surface charge density and zeta potential of solid particles were determined. It was found that the solution pH, order of both adsorbates addition as well as the time interval between the AN and CT PAM addition have considerable influence on the structure of polymeric adsorption layer formed on the Cr₂O₃ surface. It was also proved that changes in the PAM adsorbed amount in the systems containing mixed adsorbates result from formation of AN PAM - CT PAM complexes. They are bounded at the interface in the formed multilayer. As a result, the dual-polymer flocculation occurs more effectively than the destabilization process in the suspensions containing only one type of adsorbate.

Removal of trivalent chromium from aqueous solution using aluminum oxide hydroxide

Water is second most essential for human being. Contamination of water makes it unsuitable for human consumption. Chromium ion is released to water bodies from various industries having high toxicity which affects the biota life in these waters. In this study aluminum oxide hydroxide was tested for its efficiency to remove trivalent chromium from aqueous solutions through batch mode experiments. Chromium concentrations in aqueous solutions and tannery waste water before and after adsorption experiments were determined using flame atomic absorption spectrometry. The effects of pH, contact time, initial concentration and adsorbent dosage on the adsorption of Cr(III) were studied. The study revealed that more than 99 % removal of Cr(III) was achieved over wide range of initial pH (3–10). The optimum conditions for the removal of Cr(III) were found to be at pH 4–6 with 40 g/L adsorbent dose at 60 min of contact time. The adsorption capacity was assessed using Langmuir and Freundlich isotherms. The equilibrium data at varying adsorbent dose obeyed the two isotherms. The adsorbent was found to be efficient for the removal of Cr(III) from tannery waste effluent.