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The thermal behaviour of hay-based activated carbons modified with adsorption nanolayers of ionic polymers were investigated. The anionic and cationic forms of polyacrylamides (PAM) with different contents of ionizable groups were applied. Using spectrophotometry, potentiometric titration, microelectrophoresis, DCS (Differential Centrifugal Sedimentation) and thermal analysis methods, the adsorption and electrokinetic, properties, as well as thermal stability of studied activated biocarbons—PAM systems were established. It was shown that PAM adsorbed amounts on the activated biocarbon surfaces were considerably higher for cationic polyacrylamides than for anionic ones. The conducted TG-DSC-FTIR/MS analysis in helium showed a significant influence of the synthesis conditions on the content of oxygen surface groups of activated biocarbons obtained in conventional or microwave muffle furnace. The measurements carried out in the oxidizing atmosphere for the polymer-modified samples showed similarity to the original materials and were characterized by three main stages of decomposition: dehydration, decomposition of surface functional groups and, at high temperatures—combustion process. The main decomposition products were CO2 and H2O. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The sorption properties of Na-A-type synthetic zeolite, obtained from fly ash with regard to the phosphate(V) ions, were determined. The Na-A zeolite was prepared using hydrothermal conversion of fly ash with aqueous sodium hydroxide. The effects of solution pH and zeolite surface modification by ionic polyacrylamide (PAM) were examined. Both anionic and cationic forms of PAM were applied. The adsorption and electrokinetic data were obtained by means of spectrophotometric measurements, potentiometric titrations and zeta potential determination. It was shown that the presence of ionic polyacrylamide adsorption layers modifies the surface properties of the solid. The resulting composite material (zeolite/polymer) can be applied for effective removal of phosphate(V) ions from the liquid medium. Its regeneration possibilities are also considerable. Additionally, the use of fly ash for zeolite preparation leads to management of hazardous waste material. [ABSTRACT FROM AUTHOR]

The bioavailability of toxic heavy metals for organisms depends mainly on the soil physicochemical properties, i.e. type and granulometric composition, pH value, redox potential, individual fractions content and microorganisms presence. The addition of artificial fertilizers rich in humic substances or polyacrylamide soil flocculants may also affect the content of easily absorbed heavy metal forms. Due to their chelating properties, the added substances can bind metal ions in the form of complexes characterized by low mobility in soil environment. As a consequence, the immobilization process takes place, which is a desirable phenomenon for organism health. The aim of the study was to determine the structure of electrical double layer formed on the kaolinite surface in the mixed system of cationic polyacrylamide and lead(II) cations. The influence of cationic PAM presence on the Pb(II) ions sorption on the kaolinite surface as well as heavy metal ion addition on the polymer adsorbed amount on the same clay mineral were studied. The adsorption and electrokinetic properties of studied kaolinite/CT PAM/Pb(II) systems were determined based on the spectrophotometric study, zeta potential measurements as well as potentiometric titration. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Cr 2 O 3 suspension stability in ionic PAMs presence was determined using turbidimetry. • Mixed adsorption layers of AN PAM + CT PAM are formed at interface. • Mixture of adsorbates causes increase in removal efficiency of Cr 2 O 3. • Dual-polymer flocculation occurs in suspensions containing both form of ionic PAM. • AN PAM + CT PAM complexes adsorption affects electrokinetic properties of particles. Abstract 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 Cr 2 O 3 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. [ABSTRACT FROM AUTHOR]

The effects of the type of functional groups of ionic polyacrylamide (PAM) and solution pH on the adsorption, electrokinetic and stability properties of aqueous nanozirconia suspension were examined. The spectrophotometry, potentiometric titration, doppler laser electrophoresis and turbidimetry were applied for this purpose. It was demonstrated that adsorption of anionic PAM (containing carboxyl groups) decreases with the pH rise, whereas in the case of cationic PAM (with quaternary amine groups) it increases. The greatest impact of ZrO 2 suspension stability is found for cationic PAM at pH 6, at which electrosteric stabilization mechanism is dominant. [ABSTRACT FROM AUTHOR]

The influence of metal oxide type on the adsorption affinity of anionic polyacrylamide for the solid surface was studied. There were selected three metal oxides: chromium(III) oxide, zirconium(IV) oxide and aluminium(III) oxide. The adsorption behaviour of high-molecular weight polymer containing 30% of carboxyl groups was determined based on the results of spectrophotometric, electrokinetic and turbidimetric measurements. The anionic polymer exhibits the greatest adsorption on the surface of chromium(III) oxide whereas PAM affinity for the aluminium(III) oxide is the lowest. The polymer presence has a pronounced impact on the electrokinetic properties of examined suspensions manifesting in changes in pHpzc and pHiep values of PAM-containing systems compared to those without polyacrylamide. The anionic PAM addition at pH 6 has the greatest effect on the stability of metal oxide aqueous suspensions. [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 stability mechanism and thermal properties of the system alumina-anionic polyacrylamide (PAM) was studied. The polymer's adsorption properties in dependence on the following parameters solution pH (in the range 3-9), temperature (in the range 15-35 °C), and carboxyl groups' content in the PAM chains (in the range 5-30 %) were examined. The turbidimetry method was applied for determination of the suspension stability of alumina in the presence of PAM. The obtained results indicate that the polymer addition improves significantly AlO suspension stability at pH 6 and 9 (in the whole examined temperature range). PAM containing a larger number of carboxyl groups stabilizes solid particles more effectively (due to greater contribution of electrosteric interactions). Moreover, the polymer adsorption on the alumina surface causes changes in the thermal stability of the examined systems. In dependence on temperature, the higher the content of carboxyl groups in the PAM molecules, the greater the total mass loss. This is due to increased adsorption of polyacrylamide whose chains contain numerous -COOH groups. [ABSTRACT FROM AUTHOR]

The adsorption mechanism of anionic polyacrylamide (PAM) on the nanozirconia surface was examined. The effects of solution pH, carboxyl groups content in macromolecules and anionic surfactant (sodium dodecyl sulfate—SDS) addition were determined. The more probable structure of polymer adsorption layer was characterized based on the data obtained from spectrophotometry, viscosimetry and potentiometric titration methods. The adsorbed amount of polymer, size of macromolecules in the solution and surface charge density of ZrO 2 particles in the absence and presence of PAM were assessed, respectively. Analysis of these results indicated that the increase of solution pH and content of carboxyl groups in the polymeric chains lead to more expanded conformations of adsorbing macromolecules. As a result, the adsorption of anionic polyacrylamide decreased. The SDS presence caused the significant increase of PAM adsorbed amount at pH 3, whereas at pH 6 and 9 the surfactant addition resulted in reduction of polymer adsorption level. [ABSTRACT FROM AUTHOR]

The influence of temperature on the adsorption mechanism of anionic polyacrylamide (PAM) on the alumina surface was studied in the temperature range 15–35 °C. The structure of polymer adsorption layer was determined from spectrophotometric, surface charge and zeta potential measurements. These methods enable determination of the following parameters: adsorbed amount of polymer, surface charge density and zeta potential of Al 2 O 3 particles in the absence and presence of PAM. The influence of carboxyl groups content in the polyacrylamide macromolecules (varying from 5 to 50%) was also examined. The obtained results indicate that temperature influences the adsorption behaviour of anionic polyacrylamide on the Al 2 O 3 surface. Slight increase of PAM adsorbed amounts with the temperature rise was obtained for the polymer samples characterized by the higher anionic group content (20, 30 and 50%). In the case of PAM with 5% content of these groups significantly larger adsorption was observed at 25 °C. The PAM presence causes also changes in electrokinetic properties (zeta potential and surface charge density values, as well as pH pzc and pH iep positions) of the examined system in the temperature range 15–35 °C. [ABSTRACT FROM AUTHOR]

The effects of solution pH and the content of cationic groups in polyacrylamide (PAM) macromolecules on the stability mechanism of aqueous alumina suspension were investigated. The following experimental techniques were applied: spectrophotometry, potentiometric titration, microelectrophoresis, viscosimetry and turbidimetry. They enable determination of polymer adsorbed amount, surface charge density and zeta potential of solid particles in the presence and absence of PAM, as well as thickness of polymer adsorption layer, size of macromolecules in the solution and stability of the Al 2 O 3 –polymer systems, respectively. The obtained results indicate that adsorption of PAM increases with the increasing pH, whereas the thickness of polymeric adsorption layer decreases. Additionally, the greater the number of cationic groups in the PAM chains is, the higher adsorption was found. The polymer presence influences on the alumina suspension stability. At pH 3 and 6 the slight deterioration of stability conditions of solid particle covered with polyacrylamide was observed. At pH 9 the systems containing polymer are unstable, similarly to the suspension without PAM, but the mechanism of their destabilization is different. [ABSTRACT FROM AUTHOR]

The influence of solution pH on the adsorption mechanism of polyacrylamide (PAM) on the alumina surface and stability of its suspension in the presence of polymer were investigated. The structure of polymer adsorption layer was determined from the spectrophotometric, viscosity, surface charge and zeta potential measurements which enable determination of adsorbed amount of polymer, thickness of the polymer adsorption layer, surface charge density and zeta potential of Al 2 O 3 particles in the absence and presence of PAM. The measurements of stability of alumina suspension without and with adsorbed polyacrylamide were also carried out using two methods: spectrophotometry and turbidimetry. The obtained results indicate that solution pH influences the structure of PAM adsorption layer (decrease of adsorbed amounts of polymer and increase of its adsorption layer thickness with the increasing pH). These conformational changes of polyacrylamide molecules with the rising pH have an impact on stability of the alumina suspension. The most pronounced effect of polymer on the stabilization properties of investigated systems is observed for PAM addition at pH 6 resulting in a great destabilization of the alumina particles by bridging flocculation. [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]

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]