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The main purpose of the investigations was to explore the protein adsorption on porous materials, as well as to identify the mechanisms of protein attachment without and with other common environmental contaminants, such as drugs, polymers or surfactants. This study applied the Na-X zeolite for the adsorption of bovine serum albumin (BSA) from solutions with various pH values. Electrophoretic mobility measurements and potentiometric titrations were conducted in systems containing both protein and/or PAA (poly(acrylic acid) polymer/DCF (diclofenac) drug/SDS (sodium dodecyl sulfate) surfactant to investigate the protein binding mechanisms in the complex adsorbate systems. In addition, aggregate size and stability measurements were performed in the investigated systems. Based on the research results, it was possible to conclude that the protein adsorbed most preferably on the zeolite surface at a pH value close to its isoelectric point (pI) (102.15 mg/g), and protein adsorption was the lowest in the solutions with strongly alkaline (29.61 mg/g) or acidic (77.45 mg/g) pH values. Thus, the examined zeolitic material can be considered an effective adsorbent for protein removal from an aqueous solution. [ABSTRACT FROM AUTHOR]

The main aim of this study was the determination of temperature influence on adsorption mechanisms of anionic poly(acrylic acid) (PAA) and cationic polyethylenimine (PEI) on the surface of activated carbons (AC) obtained via chemical activation of nettle (NE) and sage (SA) herbs. All measurements were performed at pH 3 at three temperature values, i.e., 15, 25 and 35 °C. The adsorption/desorption of these polymers from single and mixed solution of adsorbates was also investigated. The viscosity studies were additionally performed to obtain hydrodynamic radius values characterizing polymeric macromolecules conformation in the solution. These data are very important for the explanation of changes of linear dimensions of polymer chains with the rise of temperature caused by the modification of polymer–solvent interactions. Moreover, the XPS studies for the systems showing the highest adsorbed amounts in the specific temperature conditions were carried out. These were the systems containing PEI, PAA and NE–AC activated carbon at 25 °C. In such a case, the maximum adsorption capacity towards PAA macromolecules from a single solution of adsorbate reaches the value of 198.12 mg/g. Additionally, the thermodynamic parameters including the free energies of adsorption, as well as changes in free enthalpy and entropy were calculated. [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]

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]

Wastewaters containing organic and inorganic contaminants such as dyes, heavy metal ions, salts, and surfactants are considered to be a serious environmental problem in human society. Adsorption is the most popular technique for wastewater treatment. In this paper, a new mesoporous silica-alumina oxide (97% SiO 2 , 3% Al 2 O 3 ) synthesized by pyrogenic method was proposed as a sorbent for acid (C.I. Acid Orange 7), reactive (C.I. Reactive Black 5) and direct (C.I. Direct Blue 71) dyes as well as for heavy metal (Co(II), Cu(II), Ni(II), Zn(II)) ions removal from the aqueous solutions and wastewaters. The batch method was employed. The parameters such as phases contact time (1–360 min), initial metal and dyes concentrations (10, 20, 30 mg/L), effect of hydrochloric acid concentration (0.1–6.0 M), anionic surfactant (0.1–1.0 g/L) and salt (5–20 g NaCl/L) as well as wastewater decolorization were studied. The kinetic and equilibrium studies were also performed. An equilibrium time of 1 min and >240 min was required for the adsorption of heavy metal ions and dyes onto mixed oxide, respectively. The experimental data were better fitted to the Freundlich equation than to the Langmuir one. The potentiometric titrations indicated that dyes and heavy metal ions adsorption influence the structure of electrical double layer at the mixed oxide - liquid interface which was evidenced by changes in the solid surface charge density. The results showed that the mixed oxide could be an effective adsorbent especially for heavy metal ions removal from aqueous and industrial wastewaters. [ABSTRACT FROM AUTHOR]

In this paper adsorptive removal of hazardous dye C.I. Reactive Black 5 from aqueous solutions was investigated using the mixed silica-alumina oxides including of 4% SiO2 and 96% Al2O3 as well as 97% SiO2 and 3% Al2O3. The kinetic studies revealed that with the increasing initial dye concentration from 10 to 30 mg/l and contact time from 1 to 240 min, the sorption capacities (qt) increased and the equilibrium was observed after 240 min. Sorption of C.I. Reactive Black 5 on 4% SiO2 and 96% Al2O3 and 97% SiO2 and 3% Al2O3 takes place through the pseudo-second-order mechanism rather than the pseudo-first-order one. The experimental data were fitted using the Langmuir and Freundlich isotherm models. The effect of the auxiliaries such as anionic surfactant (sodium dodecyl sulphate) and sodium chloride on C.I. Reactive Black 5 removal was investigated in the 10 mg/l C.I. Reactive Black 5-0.1-1 g/l sodium dodecyl sulphate or 5-20 g/l NaCl systems. The potentiometric titrations indicated that the presence of C.I. Reactive Black 5 changed the surface charge density of silica-alumina mixed oxides, especially in the case of 4% SiO2 and 96% Al2O3 system. [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 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]

Untreated or partially purified effluents from the textile, paper, plastic, leather, food and cosmetic industries containing dyes and pigments are a serious environmental problem. Therefore, in this paper, adsorptive removal of acid (C.I. Acid Orange 7, AO7), reactive (C.I. Reactive Black 5, RB5) and direct (C.I. Direct Blue 71, DB71) dyes from aqueous solutions and wastewater was investigated using mixed silica–alumina oxide consisting of 4% SiO 2 and 96% Al 2 O 3 (SA96). Kinetic studies revealed that with the increasing initial dye concentration from 10 to 30 mg/L and contact time from 1 to 240 min, the sorption capacities ( q t ) increased, and the equilibrium of adsorption for AO7 and RB5 was observed after 180 min and 240 min for DB71. Sorption of the dyes on SA96 takes place through the pseudo second-order mechanism rather than the pseudo first one or intraparticle diffusion. The experimental data fitted better the Langmuir isotherm model than the Freundlich one. The monolayer sorption capacities ( Q 0 ) were found to be 41.4 mg/g, 47.1 mg/g and 49.2 mg/g for AO7, RB5 and DB71, respectively. The effect of the auxiliaries such as anionic surfactant (SDS) and sodium chloride on removal of DB71 was investigated in the 10 mg/L DB71 containing 0.1–1 g/L SDS or 5–20 g/L NaCl systems. It was observed that DB71 sorption was reduced with the increasing amount of SDS in the system while NaCl does not influence on the dye uptake by SA96. The adsorption of dyes causes increase of the solid surface charge density (σ 0 ) and shift of pH pzc point toward higher pH values. This is a result of formation of a greater number of positive surface sites due to the interactions with the anionic adsorbate. The greatest effects were obtained for the system containing DB71. The addition of NaCl to the SA96–DB 71 system results in noticeable lowering of σ 0 in the pH range 4.4–8.3. In the presence of anionic surfactant, the considerable increase of σ 0 was obtained. [ABSTRACT FROM AUTHOR]

The effects of type and content of polymer functional groups on the adsorption mechanism on the chromium (III) oxide surface were studied. Both synthetic [poly(acrylic acid) (PAA), anionic polyacrylamide (PAM), poly(aspartic acid) (ASP), block co-polymer of ASP with poly(ethylene glycol) (ASP-b-PEG)] and natural [bovine serum albumin, ovalbumin, human serum albumin, bacterial polysaccharide (exopolysaccharide EPS)] polymers were applied. For this purpose, adsorption, surface charge, zeta potential and stability measurements were carried out. The largest adsorption was found for the ASP-b-PEG (synthetic polymer) and EPS (natural polymer). The most effective destabilizers for Cr2O3 removal from the aqueous suspension were PAA 240,000 and ASP 6800. [ABSTRACT FROM AUTHOR]

In this study, we compared the adsorption of methionine, cysteine and cystine at the mercury/chlorate (VII) interface. Changes in the surface tension with the potential of the zero charge γz and relative surface excess Γ'of methionine, cysteine and cystine as a function of their concentration indicate that the adsorption of the studied amino acids increases in the order of methionine >cystine> cysteine. For all the systems examined, linear dependences ln[x(1-Θ)/Θ f(Θ)] (Frumkin isotherm) and ln (Γ'/c) = f (Γ') (virial isotherm) were obtained. Changes in the adsorption parameters as a function of the supporting electrolyte concentration indicate the competitive adsorption of amino acids and ClO4- ions and electrostatic interactions between the water dipoles and adsorbates in the double layer. [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]

Highlights: [•] Adsorption mechanisms of two polyamino acids on the surface of Cr2O3 was proposed. [•] The Gran's method was used to estimate the polyamino acids dissociation constants. [•] In the presence of polyamino acids the change in surface charge density was observed. [•] The shift of pHpzc value depend on the type of the functional groups in polymer chain. [ABSTRACT FROM AUTHOR]

Chromium(III) oxide is an amphoteric, dark green solid. This most stable dye is widely used in construction and ceramic industries as well as in painting. In this study, the attempt is made to determine flocculating properties of exopolysaccharide (EPS) synthesized by the bacteria Sinorhizobium meliloti 1021, which would increase the efficiency of chromium(III) oxide removal from sewages and wastewaters. The conditions under which EPS is the most effective destabilizing component of chromium(III) oxide suspension have been determined too. In order to characterize the structure of electric double layer formed at the solid/supporting electrolyte (EPS) solution interface, electrokinetic potential measurements and potentiometric titration were performed. The EPS amount adsorbed on the chromium(III) oxide surface as a solution pH function was also measured. Moreover, the stability of CrO suspension in the absence and presence of S. meliloti 1021 EPS was estimated. The pooled analysis of all obtained results showed that EPS causes chromium(III) oxide suspension destabilization in the whole examined pH range. The largest change in the system stability before and after the polymer addition was observed at pH 9. It is probable that under these conditions bridging flocculation occurs in the examined system. [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]