Impact of polyacrylamide with different contents of carboxyl groups on the chromium (III) oxide adsorption properties in aqueous solution

Accumulation of toxic Pb(II) ions by the iron-containing minerals in the presence of ionic polyacrylamide soil conditioner

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.

Management of hazardous fly-ash energy waste in the adsorptive removal of diclofenac by the use of synthetic zeolitic materials

Zeolite-carbon composites (Na-P1(C), Na-X(C)) and pure zeolites (Na-P1, Na-X) were synthesized from hazardous high-carbon fly ash waste (HC FA) via hydrothermal reaction with sodium hydroxide (NaOH). These solids were applied in the removal of diclofenac (DCF) from aqueous solution, with and without poly(acrylic acid) (PAA). The experiments included adsorption-desorption measurements, as well as electrokinetic and stability analyses. The obtained results showed that HC FA and Na-P1(C) had the greatest adsorption capacity towards DCF, i.e., 26.51 and 21.19 mg/g, respectively. PAA caused considerable decrease in the DCF adsorption due to the competition of both adsorbates of anionic character for active sites. For example, the adsorbed amount of DCF on Na-P1 without PAA was 14.11 mg/g, whereas the one measured with PAA was 5.08 mg/g. Most of prepared solids were effectively regenerated by the use of NaOH. Desorption degree reached even 73.65% in the single systems (with one adsorbate) and 97.24% in the mixed ones (with two adsorbates). Zeolitic materials formed suspensions of rather low stability, which underwent further deterioration in the organic molecules presence. All the results obtained in this study indicated that HC FA can be successfully managed in the removal of organic substances.

Dual lignin-derived polymeric systems for hazardous ion removals

The functionalization of lignin derivatives for ion removals is a promising method to expedite their use in treating industrial wastewater. In this work, kraft lignin (KL) was polymerized with [2-(methacryloyloxy)ethyl]trimethylammonium methyl sulfate (METAM) or acrylic acid (AA) in an acidic aqueous suspension system to produce cationic and anionic water-soluble lignin polymers with high molecular weights. Then, the interaction of soluble ions and KL-METAM and KL-AA was investigated using a Quartz crystal microbalance (QCM) and a vertical scan analyzer (VSA). The QCM, X-ray photoelectron spectroscopy (XPS) and contact angle measurement results showed that the adsorption efficiency of KL-AA was better than KL-METAM for ions due to the stronger electrostatic interaction, cationic π-interaction, and chelation between ions and KL-AA. Based on adsorption, sedimentation, and aggregate size analyses, the dual polymer systems of KL-AA/KL-METAM were more effective than KL-METAM/KL-AA in removing ions. Among Zn²⁺, Cu²⁺, and K⁺; Zn²⁺ interacted more effectively with polymers in all scenarios because it has higher reactivity for interacting with other elements. As the efficiency of ion removals was more remarkable than past reported findings, the system of KL-AA/KL-METAM may be a promising alternative for the removal of dissolved ions from solutions.

Comparison of lead(II) ions accumulation and bioavailability on the montmorillonite and kaolinite surfaces in the presence of polyacrylamide soil flocculant

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.

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.

Study on Adsorption and Aggregation in the Mixed System of Polyacrylamide, Cu(II) Ions and Innovative Carbon-Silica Composite

The paper presents an original study on adsorption and aggregation phenomena in a mixed system consisting of a macromolecular compound, heavy metal ions and an innovative adsorbent. The authors used ionic polyacrylamides (PAM), Cu(II) ions and carbon–silica composite (C-SiO₂) in the experiments. Such a system has not yet been described in the literature and therefore, the article is of significant novelty and great importance. The composite was prepared by mixing phenol–formaldehyde resin with silica and pyrolysis at 800 °C. The adsorbed amounts of Cu(II) ions and PAM were determined spectrophotometrically. C-SiO₂ was characterized using potentiometric titration, microelecrophoresis and Fourier Transform Infrared Spectroscopy (FTIR) analysis. In turn, the C-SiO₂ aggregation was established turbidimetrically as well as using a particle size analyzer. The obtained results indicated that both Cu(II) ions and ionic polyacrylamide were adsorbed on the composite surface at pH 6. The highest noted adsorbed amounts were 9.8 mg/g for Cu(II) and 35.72 mg/g for CT PAM-25%. Cu(II) ions increased the anionic PAM adsorbed and reduced the cationic PAM one. The adsorption of anionic PAM (50 ppm) stimulated the solid aggregation significantly. What is more, Cu(II) ions enhanced this process. The size of particles/aggregates formed without additives equaled 0.44 μm, whereas in the mixed Cu(II)/AN PAM system, they were even at 1.04 μm.

Investigation of adsorption mechanism of phosphate(V) ions on the nanostructured Na-A zeolite surface modified with ionic polyacrylamide with regard to their removal from aqueous solution

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.

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.

Recovery of cutting fluids and silicon carbide from slurry waste

The wafer slicing process generates large amounts of slurry waste. The recovery of cutting oil and abrasives from slurry waste can reduce both the cost and environmental damage. A process combining magnetic precipitation and flocculation was developed for the recovery of cutting oil. A magnetic precipitation tank was employed for storage of the slurry and acceleration of the settlement of suspended particles. The larger particles further aggregate upon adding a non-aqueous flocculant comprising polyacrylamide (PAM) and ethylene glycol (EG). The recycled oil product is obtained by centrifugation and bag filtration. The physical properties and wafer dicing tests indicate that the recycled oil is qualified. Wafer manufacturers can thus reduce costs by using this process to produce recycled oil. A magnetic reactor with alkaline aqueous successfully recycled the SiC powder from the slurry waste by converting all the silicon species into sodium silica for further use. The results demonstrate that the magnetic reactor is able to remove most metal species and that the alkaline aqueous medium can recover all the Si substances in a sodium silicate solution, also called water glass.

The mechanism of anionic polyacrylamide adsorption on the montmorillonite surface in the presence of Cr(VI) ions

The anionic polyacrylamide AN PAM (with various contents of carboxyl groups) adsorption mechanism on the montmorillonite surface was examined. The effect of hazardous chromium(VI) ions addition was studied. The anionic polyacrylamide is a popular soil flocculant, commonly used to prevent erosion of arable soils. On the other hand, polymeric macromolecules can increase the accumulation of various toxic substances, such as heavy metal ions (among others Cr(VI) ions) in soil minerals. For this purpose the adsorption properties of soil mineral - montmorillonite in relation to mixed system containing AN PAM and Cr(VI) ions was investigated. The impact of solution pH, order of individual adsorbates addition, chromium(VI) ions concentration and anionic groups content in the polymeric macromolecules were determined. The montmorillonite was characterized using the low-temperature nitrogen adsorption/desorption method, XRF, FTIR and SEM techniques. In turn, the adsorption and electrokinetic properties of examined montmorillonite - AN PAM - Cr(VI) systems were examined by means of spectrophotometry, potentiometric titration and microelectrophoresis methods.

Adsorption of Uranyl Ions at the Nano-hydroxyapatite and Its Modification

Nano-hydroxyapatite and its modification, hydroxyapatite with the excess of phosphorus (P-HAP) and hydroxyapatite with the carbon ions built into the structure (C-HAP), were prepared by the wet method. They were studied by means of XRD, accelerated surface area and porosimetry (ASAP), and SEM. The size of crystallites computed using the Scherrer method was nano-hydroxyapatite (HAP) = 20 nm; P-HAP-impossible to determine; C-HAP = 22 nm; nano-HAP/U(VI) = 13.7 nm; P-HAP/U(VI)-impossible to determine, C-HAP/U(VI) = 11 nm. There were determined basic parameters characterizing the double electrical layer at the nano-HAP/electrolyte and P-HAP/electrolyte, C-HAP/electrolyte inter faces: density of the surface charge and zeta potential. The adsorption properties of nano-HAP sorbent in relation to U(VI) ions were studied by the batch technique. The adsorption processes were rapid in the first 60 min and reached the equilibrium within approximately 120 min (for P-HAP) and 300 min (for C-HAP and nano-HAP). The adsorption process fitted well with the pseudo-second-order kinetics. The Freundlich, Langmuir-Freundlich, and Dubinin-Radushkevich models of isotherms were examined for their ability to the equilibrium sorption data. The maximum adsorption capabilities (q _m ) were 7.75 g/g for P-HAP, 1.77 g/g for C-HAP, and 0.8 g/g for HAP at 293 K.

Synthesis of nanocomposites from polyacrylamide and graphene oxide: Application as flocculants for water purification

Polyacrylamide/graphene (PAM/GO) based nanocomposites were synthesized and applied as flocculating agent for cleansing the solvent phase. In order to obtain the better dispersion of the graphene nanoplatelets in matrix the functionalization was carried out using acid and upon analytical characterization the successful fine dispersion of FGNp was found in the PAM matrix. The influence of GO concentrations on viscosity, charge demand, flocculating and dewatering with ambient micrometer-sized ground calcium carbonate (GCC) was well evaluated and elucidated. It was found that on increasing the GO content in the PAM/GO nanocomposites, the filtered weight of GCC suspensions also increases, and the filtrate turbidity decreased and it was also observed that on adding the GO both η and supernatant turbidity reduced: by growing GO concentrations, there was a fall in η and turbidity of cleaned water. The retention mechanism proceeds through a parallel method to microparticle retention system which is done via bridge/patch among pulp and filler.

Impact of anionic polyacrylamide on stability and surface properties of the Al2O3-polymer solution system at different temperatures

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 Al₂O₃ 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.

Adsorptive removal of As(III) ions from water using spent grain modified by polyacrylamide

In order to enhance the removal efficiency of As(III), a pre-oxidation process is generally applied first to convert As(III) to As(V), which may cause unwanted new contaminants. To overcome this problem, efforts were made to develop an effective way to remove As(III) directly without an oxidation step. The effect of polyacrylamide polymers (PAMs) such as anionic PAM, cationic PAM and nonionic PAM, on As(III) ion adsorption by spent grain (SG) was investigated. The physico-chemical properties of the three PAM-polymerized SGs (APSG (anionic PAM-polymerized modified spent grain), CPSG (cationic PAM-polymerized spent grain) and NPSG (nonionic PAM-polymerized spent grain)) were analyzed using Fourier transform infrared (FT-IR), scanning electron microscope (SEM) and zeta potential. Batch experimental data showed that the sequence of preferential adsorption for As(III) was APSG>CPSG>NPSG. Active functional groups such as amino group (NH2), carbonyl group (CO), C-N bond of the amide group (CONH2), and hydroxyl group (O-H) were responsible for As(III) adsorption. Many tubular structures occurring on the surface of APSG possibly increase the specific surface areas and favor the adsorption of As(III) ions. A fixed-bed study was carried out by using APSG as an adsorbent for As(III) from water. Three factors such as bed height, initial concentration and flow rate were studied, and breakthrough curves of As(III) were obtained. The Adams-Bohart model was used to analyze the experimental data and the model parameters were evaluated.