Katarzyna Szewczuk-Karpisz

Removal possibilities of colloidal chromium (III) oxide from water using polyacrylic acid

The lack of water is the most serious threat to humanity that leads to more efficient water and sewage treatment. Currently, many scientists are looking for new coagulants, flocculants and physicochemical methods allowing for sufficient removal of pollutants from water. The presence of various types of pigments, including chromium (III) oxide, poses the major problem. Even small amounts of these substances inhibit life processes in water. In this paper, the stability of Cr2O3 suspension in the absence and the presence of polyacrylic acid (PAA) was determined. To explain the changes in the system stability, the adsorption and electrokinetic measurements were performed. The chromium (III) oxide suspension not containing PAA is the most stable at pH = 3. Under these conditions, each positively charged solid particle is surrounded by a negatively charged diffusion layer which protects from particle collision and aggregates formation (electrostatic stabilization). In turn, the Cr2O3 suspension containing the PAA is most unstable also at pH = 3. In this case, the polymer causes destabilization of the colloidal suspension, which results from charge neutralization of solid particles by adsorbed PAA.

Adsorption and thermal properties of the bovine serum albumin-silicon dioxide system

The adsorption, electrokinetic, thermal and stability properties of the silicon dioxide (silica, SiO2)/bovine serum albumin (BSA) system were determined. All measurements were carried out as a function of solution pH value. The highest amount of BSA absorbed on the silica surface was observed at pH 4.6 [the value close to the BSA isoelectric point (pI)], which is primarily related to the packed albumin conformation and the lack of adsorbent–adsorbate electrostatic repulsion. At pH 4.6, largest mass decrease was also noticed (thermogravimetric measurements). At pH 3, 7.6 and 9, the adsorption levels were much lower. This phenomenon is associated with the electrostatic repulsion between the BSA macromolecules and the silica particles as well as the expanded BSA structure. During biopolymer adsorption, the whole solid surface is coated with the albumin macromolecules. Then, the properties of the silica particles become similar to those of the BSA macromolecules. In the presence of albumin, the silica pHiep point is identical to the BSA pI value. It should also be noted that the albumin adsorption affects the SiO2 suspension stability. The greatest change was observed at pH 3. Under these conditions, the BSA addition causes electrosteric system stabilization.

Adsorption Properties of the Albumin–Chromium(III) Oxide System – Effect of Solution Ph and Ionic Strength

The phenomenon of protein adsorption on solid surfaces is important in many scientific areas. It is a common process, but very complicated. In this paper, both the mechanism of BSA, HSA, and OVA adsorption on chromium(III) oxide and the structure of formed adsorption layers were determined. The adsorption process was examined as a function of solution pH and ionic strengths. Regardless of the protein type the highest adsorption level was observed when the pH value of the solution was close to the protein isoelectric point. Under these conditions the macromolecules have a compact and folded conformation that allows for the packing of a larger amount on the unit Cr2O3 surface. The minimum adsorption rate, regardless of the protein type, was observed at pH = 3. It can be related to the expanded conformation of macromolecules and the electrostatic repulsion between the positively charged Cr2O3 surface and the positively charged polymer segments. The obtained results may be very helpful in the development of removal procedure of specific substances from the sewages and wastewaters. Furthermore, this information can be used to improve the separation processes carried out in food industry.

Adsorption and Stability Properties of Aqueous Suspension of Chromium (III) Oxide in the Presence of Synthetic and Natural Polymers: Possibilities of Solid Removal

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.

Comparison of Stability Properties of Nanozirconia Aqueous Suspension in the Presence of Selected Biopolymers

The effects of biopolymer type and solution pH on the adsorption mechanism on the nanozirconia surface were examined. Three natural polymers, bovine serum albumin (BSA), lysozyme (LSZ) and bacterial polysaccharide (EPS), were applied. The adsorption, surface charge, zeta potential and stability measurements were carried out in the pH range 3–10. The largest adsorption was found for EPS at pH 3 and the lowest for BSA at pH 3. Both EPS and BSA (of low internal stability) binding with the solid surface proceeds due to both electrostatic forces and hydrogen bridges formation. LSZ at pH 3 does not adsorb on the zirconia surface (electrostatic repulsion prevents binding of high internal stability protein). Lysozyme has the greatest influence on the zirconia suspension stability at pH 9 (deterioration of system stability as a result of solid surface charge neutralization by adsorbed LSZ). The BSA adsorption causes an insignificant increase of the ZrO2 suspension stability, which is connected with electrosteric forces appearance. The exopolysaccharide presence results in slight decrease of the solid system stability (polymer bridges formation at pH 6 and 9).