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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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Nettle and the sage herbs were used to obtain carbonaceous adsorbents. For the biochar preparation the precursors were dried and subjected to conventional pyrolysis. Activated carbons were obtained during precursor impregnation with phosphoric(V) acid and multistep pyrolysis. The textural parameters and acidic-basic properties of the obtained adsorbents were studied. The activated carbons prepared from the above herbs were characterized by the largely developed specific surface area. The obtained carbonaceous adsorbents were used for polymer removal from aqueous solution. Poly(acrylic acid) (PAA) and polyethylenimine (PEI) were chosen, due to their frequent presence in wastewater resulting from their extensive usage in many industrial fields. The influence of polymers on the electrokinetic properties of activated carbon were considered. PAA adsorption caused a decrease in the zeta potential and the surface charge density, whereas PEI increased these values. The activated carbons and biochars were used as polymer adsorbents from their single and binary solutions. Both polymers showed the greatest adsorption at pH 3. Poly (acrylic acid) had no significant effect on the polyethylenimine adsorbed amount, whereas PEI presence decreased the amount of PAA adsorption. Both polymers could be successfully desorbed from the activated carbons and biochar surfaces. The presented studies are innovatory and greatly required for the development of new environment protection procedures. [ABSTRACT FROM AUTHOR]

• As(V) and Cd(II) impact on PAA and PEI determination in water samples was studied. • Activated carbons from waste plant biomass were used as adsorbents of heavy metals. • The adsorptive removal of heavy metal ions in ionic polymers presence was examined. • The maximum adsorption capacities are 135.8 mg/g for Cd(II) and 109.6 mg/g for As(V). • Electrokinetic properties of biocarbons were affected in multicomponent systems. Activated biocarbons (AC) obtained in the process of simultaneous pyrolysis and activation of lemon balm (LB) and mint (MT) herbs with H 3 PO 4 were used to purify aqueous solutions of cadmium, arsenate, polyethylenimine (PEI) and poly(acrylic acid) (PAA). The metals show high toxicity in the whole range of their concentrations, whereas the polymers are cytotoxic at high concentrations. The efficiency of As(V) removal from an aqueous solution depends on the pH value, while the Cd(II) adsorption on the activated biocarbons surface is independent on this parameter. The maximum adsorbed amounts are 135.8 mg/g for Cd(II) and 109.6 mg/g for As(V), respectively. The removal of metals ions and polymers from binary systems is lower in comparison to the one-component solutions. This is a consequence of the formation of polymer-metal complexes, that tend to remain in the solution. Additionally, the surface charge density, zeta potential, the size of activated biocarbons aggregates in the aqueous suspensions and the influence of toxic metal ions on the determination of the concentration of polymers in water samples was investigated. The obtained results proved that the PEI concentration can be effectively determined in the presence of metal ions, whereas the procedure of PAA determination requires additional validation. [ABSTRACT FROM AUTHOR]

This paper deals with the adsorption of heavy metal ions on the surface of carbonaceous materials obtained via the chemical activation of biomass. Waste plum stones, pine sawdust and horsetail herb were used as the precursors of carbonaceous adsorbents. The effect of the precursor type and preparation procedure on the physicochemical properties of activated biocarbons and their sorption abilities towards Pb(II) and Cu(II) ions have been checked. The obtained micro-mesoporous activated biocarbons were characterized by determination of elemental composition and ash content, the number of surface functional groups and pH of water extracts as well as textural study based on low temperature nitrogen adsorption/desorption and scanning electron microscopy. Additionally, the electrokinetic studies including solid surface charge density and zeta potential determination were performed. Moreover, the adsorption data modelling (equilibrium and kinetics), XPS results analysis and comparison of parameters characterizing electrical double layer formed at the solid-liquid interface enabled the specification of the mechanism of heavy metals binding with the activated biocarbons surface. The maximum adsorption capacity towards copper and lead ions (177.5 and 178.1 mg/g, respectively) was found for plum stone-based activated biocarbon. For all carbonaceous materials, better fit to the experimental data was achieved with a Langmuir isotherm than a Freundlich one. In turn, a better fit of the kinetics data was obtained using the pseudo-second order model. [ABSTRACT FROM AUTHOR]

A series of new synthetic carbonaceous adsorbents has been prepared via physical and chemical activation of residue of alcoholic fermentation of corn starch. Two different variants of thermal treatment procedure - microwave and conventional heating have been applied for preparing of the activated biocarbons. All the samples under investigation were characterised by elementary analysis, surface area measurements as well as determination of the number of surface functional groups. The electrokinetic properties of examined materials were studied using potentiometric titration and electrophoresis methods, which enabled determination of the surface charge density and zeta potential of activated biocarbon particles. Moreover, sorption properties of the carbonaceous materials towards two organic dyes - methylene blue and malachite green were tested. The final products were activated biocarbons of medium developed surface area ranging from 21 to 879 m2/g, showing acidic character of the surface and various content of surface functional groups. More favourable textural parameters as well as sorption properties toward both organic dyes were revealed by chemically activated samples. The obtained results indicated also considerable effect of adsorbed dye molecules on the structure of electrical double layer formed at the solid/liquid interface. [ABSTRACT FROM AUTHOR]

Purpose: Heavy metal soluble forms pose a threat to plants, soil microflora, and microfauna. To limit their toxicity and mobility, various immobilizing additives are being developed. The main aim of the study was to determine the influence of soil flocculant (cationic polyacrylamide (CtPAM)) on the hexavalent chromium ion reduction and accumulation on the kaolinite surface. In this way, the efficiency of the selected polymer conditioner in the soil remediation was determined. Materials and methods: The adsorbed amounts of Cr(VI) and CtPAM on the kaolinite surface was determined spectrophotometrically (spectrophotometer UV/Vis) using specific indicators. The structure of electrical double layer formed on the kaolinite surface in the mixed system of cationic polyacrylamide and Cr(VI) ions was described based on the adsorptive measurements, zeta potential measurements, as well as potentiometric titration. The kaolinite aggregation in the presence of CtPAM and/or Cr(VI) ions was determined spectrophotometrically and proved using SEM microscopy. The reduction process of Cr(VI) to Cr(III) occurring in the adsorption layer was determined by diffuse reflectance spectroscopy (DRS). Results and discussion: The obtained results indicated that cationic polyacrylamide contributes to Cr(VI) reduction to Cr(III) form in the kaolinite suspension. This heavy metal ions are strongly adsorbed by the applied clay mineral, especially at pH 5 (then the Cr(VI)-adsorbed amount equals 5.42 mg/g). The CtPAM addition favors the Cr(VI) ion immobilization on the kaolinite surface. In the conditioner presence, the heavy metal-adsorbed amount is even at 7.34 mg/g. The adsorption of CtPAM and chromium(VI) ions induces changes in the kaolinite surface charge density and electrokinetic potential. What is more, both substances favors the kaolinite aggregation. Conclusions: Cationic polyacrylamide may be considered a substance reducing the toxicity of chromium(VI) ions in the natural environment and decreasing their availability for soil organisms. It can improve the soil structure (by stimulating aggregation) and reduce environment pollution with heavy metals simultaneously. [ABSTRACT FROM AUTHOR]

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/SiO 2), enriched with manganese (C/Mn/SiO 2), as well as iron (C/Fe/SiO 2). 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/SiO 2 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. [Display omitted] • New approach to the synthesis of eco-friendly and effective adsorbents was made. • Carbon-silica composites (C –SiO 2) with manganese (Mn) or iron (Fe) were obtained. • During incorporation of Mn or Fe, abundant hydroxyl groups were introduced. • C/Mn/SiO 2 adsorbed the highest amount of lead (211.60 mg/g) and zinc (74.95 mg/g). • Composites with adsorbed metals formed large aggregates with size up to 1056 nm. [ABSTRACT FROM AUTHOR]

This paper focused on the protein and polysaccharide adsorption mechanism on the surface of common soil mineral – silica (SiO 2), as well as the biopolymer adsorption effect on the solid aggregation. For the experiments, the proteins of various internal stability were selected, i.e. bovine serum albumin (BSA), ovalbumin (OVA) and lysozyme (LSZ). Moreover, the study involved exopolysaccharide (EPS) synthesized by soil bacteria Sinorhizobium meliloti. The adsorption layer structure on the silica surface and the solid aggregation tendency in the biopolymer presence were established and explained based on the turbidimetric, adsorption and zeta potential measurements. The measured biopolymer adsorbed amounts, biopolymer conformation on the SiO 2 surface and solid aggregation were strongly dependent on the pH conditions. The stimulating effect on SiO 2 aggregate formation was stated at pH 4.6 for BSA, OVA and LSZ, whereas at pH 7.6 – for LSZ and EPS. The strongest impact was noticed at pH 7.6 in the lysozyme presence (the TSI value increased by 40 units). The presented results can contribute to a better understanding of mineral-organic associations formation under selected soil conditions. Moreover, they may be helpful in developing innovative substances limiting destructive erosion effect. Unlabelled Image • Biopolymer adsorption on SiO 2 is strictly dependent on electrostatic interactions. • Biopolymers affect the silica zeta potential and aggregation significantly. • The strongest positive effect on silica aggregation was noted for lysozyme at pH 7.6. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the lysozyme (LSZ) adsorption impact on the silica suspension stability was established. In other words, the stabilization/destabilization mechanism of the SiO 2 /LSZ system was explained based on the adsorption, electrokinetic and stability measurement results. Lysozyme adsorbs on the silica surface in the whole pH range. This process contributes to the changes in silica surface charge and zeta potential values. The lysozyme addition influences the system stability too. At pH 7.6 and 9, a large decrease in the silica suspension stability was found. It is connected with the neutralization of solid negative charge by the positively charged macromolecules. As a result, large aggregates can be formed, which is highly desirable in the silica removal procedure. Graphical abstract Image Highlights • Lysozyme (LSZ) adsorption is possible in the pH range from 3 to 9. • LSZ adsorption changes the silica surface charge and zeta potential. • In the LSZ presence, a large drop in the system stability was noticed at pH 7.6 and 9. [ABSTRACT FROM AUTHOR]

Cr 2 O 3 dispersions are considered to be dangerous for aqueous ecosystems and for this reason it is necessary to develop methods allowing solid particles separation. Structure of the adsorption layer formed at the solid surface determines the colloidal suspension stability. Moreover, in the case of ionic polymers the solution pH considerably affects the chains arrangement. Hence, the influence of cationic poly( l -lysine) and its copolymers adsorption on the chromium(III) oxide (Cr 2 O 3 ) particles stability was investigated. Although the analyzed substances are characterized by the similar average molecular weight, they exhibit various macromolecular structures resulting from the different PEG and polyamino acid length ratios. The sample's stability was examined by the use of the turbidimetric method enabling the Turbiscan Stability Index (TSI) parameter calculation. As one can see, solid suspensions without the tested polymers are relatively unstable. At pH 4, introduction of the cationic macromolecules causes the increase in the sample stability. This can be explained by the electrostatic repulsion between the totally ionized polymeric chains adsorbed on the adjacent Cr 2 O 3 particles. At pH pzc , changes in the TSI values are related to the different polymer chain arrangements. [ABSTRACT FROM AUTHOR]

The adsorption mechanism of cationic polyacrylamide (PAM) on the mesoporous nanozirconia was studied. The effects of solution pH (in the range 3–10) and cationic groups content (20–80%) in the polymeric chains were examined. The influence of polymer adsorption on both the structure of electrical double layer and stability of aqueous ZrO 2 suspension was determined. It was shown that the porosity of zirconia (mean pore diameter 31 nm) has the greatest impact on the PAM adsorption level at pH 9, at which molecules can penetrate into the pores. As a result, the greatest amount of adsorbed polyacrylamide was obtained. The specific conformation of adsorbed macromolecules (containing positively charged cationic groups) is responsible for the observed decrease of the solid surface charge density and increase of the zeta potential of nanozirconia particles. Polyacrylamide has the greatest impact on the ZrO 2 suspension stability at pH 6 (significant improvement of the system stability due to electrosteric interactions). [ABSTRACT FROM AUTHOR]

The turbidimetry and static light scattering methods were applied to specify the stability conditions of aqueous nanozirconia suspension. The stability coefficients and mean sizes of formed aggregates (flocks) were determined. The effects of solution pH (in the range 3–10), presence of anionic polyacrylamide (PAM), carboxyl groups content in its macromolecules (5–50%), as well as anionic surfactant (sodium dodecyl sulfate - SDS) addition were examined. The obtained changes in the system stability after the polymer (and surfactant) addition were explained based on adsorption (PAM adsorbed amount) and electrokinetic data (zeta potential). Analysis of the obtained results indicated that the simultaneous presence of the polymer and surfactant at pH 6 has the greatest influence on the nanozirconia suspension stability. Under such conditions considerable improvement of the system stability takes place due to the electrosteric interactions between solid nanoparticles. [ABSTRACT FROM AUTHOR]

The solution pH impact on the adsorption process of the block copolymers on the colloidal silica surface was investigated. All polymeric chains consist of the poly(ethylene glycol) (PEG) fragment and the suitable ionic polyamino acid segment (poly- l -lysine or poly- l -aspartic acid). PEG is a biocompatible water-soluble polymer, which is widely used in the biopharmaceutical industry because of its excellent water solubility, chain mobility, and non-immunogenicity. When it comes to polyamino acid block, it is also highly biocompatible, non-toxic, and economic with versatile functional groups such as carboxyl or amino groups. The analyzed substances are characterized by different polymer chain structures but have similar average molecular weight. Adsorption amount was measured with a static method using a UV–vis spectrophotometer. Based on the values obtained from the electrokinetic measurements (the surface charge density and the zeta potential), the interactions between the block copolymer macromolecules and the solid surface were explained. As a result, it was possible to determine the mechanism of compounds binding at the silicon dioxide–aqueous solution interface. It is worth emphasizing that both studied macromolecular compounds and the adsorbent are broadly applied in many branches of industry as well as in medicine. [ABSTRACT FROM AUTHOR]

Disposal of the environmentally dangerous metal oxide suspensions from the waste water is an essential problem. The polymers adsorption can be one of the most effective and suitable methods. In the presented paper the ionic diblock copolymers impact on the Cr 2 O 3 suspensions was investigated. The copolymer adsorption layers structure was determined on the basis of the adsorption and electrokinetic (surface charge density and zeta potential) tests. The polymers adsorption amount was measured using the static method from aqueous solutions. Additionally, the application of the turbidimetric method enabled determination of the interactions between the system constituents. Analysis of this data allows the estimation of the most probable stabilization (or destabilization) mechanism of the Cr 2 O 3 suspensions in the presence of the studied macromolecular compounds. Hence, the Cr 2 O 3 suspensions are unstable in the presence of the anionic copolymer at pH 3 and the cationic one in the alkaline medium. [ABSTRACT FROM AUTHOR]

The influence of a kind of support electrolyte on the ionic polyamino acids adsorption at the chromium (III) oxide - polymer solution interface was investigated. The NaCl and CaCl2 were used as the background electrolytes. In order to determine the effect of the electrolyte, the same value of ionic strength of the test solutions were taken. It was proved that formation of intermolecular and intramolecular complexes in the presence of divalent calcium ions is responsible for essential changes in polymer adsorption. Related to the ionic character of polyamino acid two different adsorption behaviours can be observed. The increase of the ASP adsorption amount in the presence of calcium ions may be explained by formation of complexes between the dissociated carboxylic groups and Ca2+ ions. The opposite situation takes place in the case of polylysine - the application of CaCl2 results in the dramatic decrease in the polymer adsorption caused by blocking the active sites available for LYS macromolecules. In order to make a comprehensive analysis, the zeta potential and surface charge density measurements were performed taking into account the kind of the background electrolyte. The above-mentioned tests were carried out in the absence and presence of the polyamino acid at two different concentrations - 10 and 100 ppm respectively. [ABSTRACT FROM AUTHOR]

The worldwide production of colored products and intermediates is increasing year on year. The consequence of this is an increase in the number of liquid effluents containing toxic dyes entering the aquatic environment. Therefore, it is extremely important to dispose of them. One of the techniques for the elimination of environmentally harmful dyes is adsorption. The main purpose of this study was to explore the possibility of using a carbon and silica (C/SiO2)-based composite for the removal of the azo dye C.I. Basic Red 46 (BR46). The adsorption capacity of C/SiO2 was found to be temperature dependent and increased from 41.90 mg/g to 176.10 mg/g with a temperature rise from 293 K to 333 K in accordance with the endothermic process. The Langmuir isotherm model seems to be the better one for the description of experimental data rather than Freundlich or Dubinin–Radushkevich. The free energy (ΔGo) confirmed the spontaneous nature of BR46 adsorption by C/SiO2. Kinetic parameters revealed that BR46 uptake followed the pseudo-second-order equation; however, the external diffusion plays a significant role. Surfactants of cationic, anionic and non-ionic type influenced BR46 retention by C/SiO2. The electrokinetic results (solid surface charge density and zeta potential) indicated that the adsorption of cationic dye and surfactant influences the structure of the electrical double layer formed at the solid–liquid interface. [ABSTRACT FROM AUTHOR]

Abstract: The influence of temperature on the adsorption mechanism of polyacrylamide (PAM) on the silica surface was studied in the temperature range 15–35°C. The structure of polymer adsorption layer was determined from spectrophotometric, viscosity, surface charge and zeta potential measurements. These methods enable determination of the following parameters: adsorbed amount of polymer, macromolecules conformation in the solution and thickness of the polymer adsorption layer, surface charge density and zeta potential of SiO2 particles in the absence and presence of PAM. The measurements of stability of silica suspension without and with adsorbed polyacrylamide were also carried out. The obtained results indicate that temperature influences the conformation of PVA chains in the solution and the structure of polymer adsorption layer. The temperature rise causes polymer coils developing which results in: the decrease of polymer adsorption, the increase of linear dimensions of PAM chains in the solution, the creation of thicker adsorption layer of the polymer on the solid surface and the slight lowering of zeta potential of solid particles. Taking into account the conformational changes of polymer chains with the increasing temperature main reasons responsible for stability of the investigated system were given. [Copyright &y& Elsevier]

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. [Display omitted] • Polyacrylamide flocculant impact on Pb(II) adsorption on soil mineral surface was studied. • Effects of Pb(II) concentration, polymeric groups content and mineral type were examined. • Desorption degree of Pb(II) (bioavailability) using water and EDTA was determined. • Accumulation of heavy metal ions by polyacrylamide adsorption layers was confirmed. • Montmorillonite shows significantly higher tendency for Pb(II) immobilization than kaolinite. [ABSTRACT FROM AUTHOR]

In order to propose a novel, effective adsorbent of Cu(II) ions, hybrid carbon-mineral nanocomposites with metallic elements (Mn/Fe in the case of B-6, Mn – B-8) were examined. A combination of mechanochemical and pyrolytic methods was used to obtain these bimodal micro-mesopore systems. First, mechanochemical mixing of phenol-formaldehyde resin and inorganic compounds in a ball mill was carried out. Then, the pyrolysis of the mixture under inert atmosphere at 800 °C was performed. The obtained composites were characterized using nitrogen adsorption/desorption, Fourier transform infrared spectroscopy, electron microscopes as well as X-ray diffraction, X-ray fluorescence and X-ray photoelectron spectroscopy. Adsorption, electrokinetic and aggregation studies were also performed, in the absence and presence of poly(acrylic acid) (PAA) – a macromolecular compound commonly used in industry and agriculture, which may be present in wastewater together with copper(II) ions. Under examined conditions (at pH 5 and 6), Cu(II) adsorbed amount was higher on the B-8 surface than on the B-6 one. At pH 6 for the initial Cu(II) concentration 100 ppm, 51.74% of the ions was adsorbed on B-8% and 46.68% – on B-6. Heavy metal adsorption contributes to stronger aggregation of nanocomposite particles. Thus, the presented bimodal solids, especially that containing Mn (called B-8), can be considered as adsorbents in heavy metal removal from aqueous solutions. [Display omitted] • Innovative carbon-mineral nanocomposites with metallic elements were explored. • Bimodal solid with Mn had slightly higher adsorption capacity than that with Mn/Fe. • 51.74% of Cu(II) ions were adsorbed on the selected nanomaterial. • Poly(acrylic acid) enhanced the Cu(II) adsorption on the examined materials. • Cu(II) addition contributed to stronger aggregation of nanocomposite particles. [ABSTRACT FROM AUTHOR]

• Mesoporous engineered biochar obtained from horsetail herb was prepared. • Adsorption removal of proteins differing in internal stability was examined. • pH effect on electrokinetic and aggregation properties of biochar was determined. • The most favourable conditions for proteins removal were at their pI points. • The maximal LSZ and OVA adsorption capacities reach about 500 and 400 mg/g. The aim of the study is the determination of adsorption mechanism of two proteins characterized by different internal stability (ovalbumin – OVA, lysozyme – LSZ) on the surface of horsetail herb-based engineered biochar (AC) as well as aggregation degree of the selected solid in the presence of biopolymer in the wide pH range (3–11). The engineered biochar was characterized based on the results of nitrogen adsorption/desorption isotherm method, Boehm titration and elemental compound analysis. The adsorption/aggregation mechanisms were determined using spectrophotometric adsorbed amount measurements, zeta potential, potentiometric titration, turbidity measurements and CPS analyses. Mesoporous horsetail herb-based engineered biochar shows the highest adsorption capacity related to OVA and LSZ at protein isoelectric point (i.e. pH 5 for OVA, pH 11 for LSZ). The OVA and LSZ adsorbed amounts is 395.4 and 493.7 mg/g, respectively. Under the same conditions, the OVA and LSZ presence stimulates the AC particle aggregation. As a result, at selected pH values large protein amounts can easily be removed from the aqueous solution using eco-friendly carbonaceous adsorbent. [ABSTRACT FROM AUTHOR]

Nowadays, due to increasing environment pollution, the amount of heavy metals in soil becomes higher and higher. The introduced metals are usually toxic and harmful for plants and animals. Taking this fact into account, in this paper it was checked if common clay mineral – montmorillonite, modified by soil flocculant (cationic polyacrylamide, CT PAM) can immobilize chromium(VI) and lead(II) ions and thus decreases their bioavailability. The adsorbed amounts of polymer, ions and polymer/ions on the montmorillonite surface were measured spectrophotometrically. The electrical double layer structure formed around montmorillonite particles without and with heavy metal ions/polymer was also determined. The obtained results indicate that cationic polyacrylamide captures both lead and chromium ions and increases their adsorbed amount on the montmorillonite surface. Thus, the cationic flocculant usage may enhance the heavy metal immobilization. Unlabelled Image • Cationic polyacrylamide (CT PAM) captures heavy metal ions from the solution. • CT PAM increases the Cr(VI) and Pb(II) ion immobilization on montmorillonite. • In soil flocculant presence, heavy metal availability for organisms is reduced. [ABSTRACT FROM AUTHOR]

The main aim of the study was to investigate the electrical double layer (EDL) structure formed at the gibbsite/supporting electrolyte/anionic polyacrylamide (PAM) interface. It was carried out based on the results of the following measurements: the FTIR spectroscopy, the adsorption and zeta potential measurements as well as the potentiometric titration. The solid texture properties were also determined using the nitrogen adsorption/desorption isotherm method. The obtained results showed that the anionic polyacrylamide adsorbs on the gibbsite surface in the whole examined pH range. The adsorption amount strongly depends on the pH value, i.e. the higher pH is, the lower adsorption level is observed. The PAM adsorption changes both the surface charge density and the zeta potential of gibbsite. The data presented are greatly helpful in assessing PAM flocculating ability relative to the soil mineral. [ABSTRACT FROM AUTHOR]

• Aggregation of natural schwertmannite (SCH) with adsorption layers was examined. • SCH coating was performed using cadmium(Cd), copper(Cu), and polyacrylamide(PAM). • Both trace metals and polymer enhanced their adsorption on SCH. • Simultaneous presence of Cu/Cd and PAM accelerated SCH flocculation. This paper aimed at the aggregation mechanism of natural schwertmannite (SCH) particles covered with layers composed of two different substances, i.e., trace metals (cadmium (Cd), copper (Cu)) and commercial polyacrylamide tackifier (PAM). The mineral applied was taken from the Muskau Arch area (Poland) and characterized. Coating of SCH with Cu, Cd, and PAM was conducted in the systems containing one- or two substances. To estimate the mineral aggregation with and without specific adsorption layers, the stability study was carried out. The obtained results indicated that the accumulation of both trace metal ions and polymer was higher in the mixed adsorption layers. Then, the adsorption efficiency of Cd increased even by 25.10% (pH 5). The highest growth in the PAM adsorption was noted at pH 6, i.e., by 49.73% (in the presence of Cu) and 42.80% (Cd). The aggregation of the SCH particles covered with mixed adsorption layers was stronger than that without adsorbates. Under these conditions, the turbidity of the system was only 57.2 NTU (Nephelometric Turbidity Units), whilst after 60 min, 54.4 NTU. In the simultaneous presence of PAM and trace metal ions, the solid particles formed flocs of considerable size. The polymer formed specific bridges between them and thus facilitate their contact (flocculation). What is more, trace metal ions mediated connection of the particles coated with PAM. [ABSTRACT FROM AUTHOR]