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

Evaluation of the Effect of Polyethylenimine on Boron Adsorption by Soil Minerals

The removal of hazardous ions from water is crucial for safeguarding both the environment and human health. Soil minerals, integral components of soil, play a vital role as adsorbents for various contaminants, including heavy metal ions, organic dyes, and detergents. This study investigates the interaction between boron ions and soil minerals (gibbsite, kaolinite, and montmorillonite) in the presence of polyethylenimine (PEI). The minerals underwent characterization based on specific surface area, particle size distribution, zeta potential, and the presence of functional groups. The influence of PEI addition on the stability of the soil mineral suspension was evaluated by turbidimetry. Mineral-boron and mineral-boron-PEI interactions were explored under varying conditions, including pH, initial boron concentration, and mineral quantity, with all adsorption experiments conducted over 24 hours. Using the Langmuir isotherm, the maximum adsorption capacity of the studied minerals was determined for boron both without and in the presence of PEI. For gibbsite, kaolinite and montmorillonite, it was 30.63, 24.55 and 26.62 mg g-1, respectively, while in the presence of PEI, it increased to 33.11, 26.61 and 45.47 mg g-1, respectively. The addition of PEI enhanced boron adsorption from aqueous solutions, increasing the removal efficiency from 65 % to about 80 %.

Study of thermal decomposition of hay-based activated biocarbons modified with nanolayers of ionic polyacrylamide

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.

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.

Adsorption, viscosity and thermal behaviour of nanosized proteins with different internal stability immobilised on the surface of mesoporous activated biocarbon obtained from the horsetail herb precursor

The thermal analysis methods were used for the description of the adsorption behaviour of selected proteins differing in internal stability (ovalbumin (OVA) and lysozyme (LSZ)). These proteins were immobilised on the surface of activated biocarbon obtained from the horsetail herb precursor. The values of the hydrodynamic radius of both biopolymer macromolecules in the solution were determined by the use of the viscosimetry method. This parameter is important for the specification of the possibility of proteins nano-molecules to penetrate the nano-pores of the adsorbent which leads to the increase of biopolymers adsorption. Such behaviour is observed at the pH value which is very close to the pI value of specific biopolymer (the greatest adsorption of proteins on the activated carbon surface occurs- at pH 5 for OVA being 323 mg/g, as well as at pH 11 for LSZ which is 464 mg/g). Under such conditions, the proteins macromolecules assume conformations characterized by the lowest values of hydrodynamic radius, i.e. 2.76 nm for OVA and 1.07 nm for LSZ. The data obtained from the analysis of gaseous products of thermal decomposition of the samples indicated the types of biocarbon surface groups as well as the enabled specification of the protein macromolecules adsorption mechanism.