Effect of Rhamnolipids and Lipopolysaccharides on the Bioleaching of Arsenic-Bearing Waste

The adsorption of biosurfactants and polysaccharides changes the surface properties of solid particles, which is important for controlling the release of arsenic compounds from the solid phase and preventing undesirable bioleaching. Microbial leaching and scorodite adhesion experiments, including pure and modified mineral material, were conducted in a glass column with a mineral bed (0.8–1.2 mm particle size) to test how rhamnolipids (Rh) and lipopolysaccharides (LPS) affect surface properties of mineral waste from Złoty Stok (Poland) and secondary bio-extraction products (scorodite). Adsorption tests were conducted for both solid materials. The adsorption of Rh and LPS on the solids was shown to modify its surface charge, affecting bioleaching. The highest bio-extraction efficiency was achieved for arsenic waste with adsorbed rhamnolipids, while the lowest, for the LPS-modified mineral. Under acidic circumstances (pH~2.5), the strongly negative zeta potential of arsenic-bearing waste in the presence of Rh creates conditions for bacteria adhesion, leading to the intensification of metal extraction. The presence of a biopolymer on the As waste surface decreases leaching efficiency and favours the scorodite’s adhesion.

On the effect of salvarsan on blood clotting. Trost (Arch. f. Derm. u. Syph., 1922, Bd. 139)

In order to find out the effect of organic arsenic compounds in the form of salvarsan and its derivatives on blood clotting the author set a series of in vitro and in vivo experiments by the methods of Brkеrʹa and Schultz'a. These experiments convinced the author that organic arsenic compounds such as salvarsan already in minimal amounts cause in vitro clotting retardation.

210 cases of relapsing fever baked by neosal-varsan

The issue of treating relapsing fever with organic arsenic compounds is 15-17 years old.

Development of iron-containing sorption materials for water purification from arsenic compounds

The paper is devoted to the development of a method for obtaining and using iron-containing sorption materials for the effective removal of arsenic compounds of different oxidation states from an aqueous medium. It is known that arsenic compounds have a harmful effect on biota due to high toxicity. The paper theoretically and experimentally substantiates the choice of iron-containing materials as the main sorbent material for arsenic compounds removal from the aqueous medium. A series of iron-containing adsorbents, including powder, activated carbon-based granular and suspension sorbents, was synthesized by different methods (heterogeneous and homogeneous precipitation). Experimental studies have confirmed that the adsorption of arsenate ions on iron-containing sorption materials corresponds to the pseudo-second order of the reaction (R2=0.999), which is inherent in adsorption processes. It was determined that oxyhydroxide sorption materials obtained by the homogeneous precipitation demonstrate higher sorption activity (up to 70 mg/g for As(III) and over 70 mg/g for As(V)). It was found that activated carbon-based iron-containing sorption materials showed approximately 2 times lower efficiency than powder iron(III) oxide, iron(III) oxyhydroxide and amorphous iron(III) hydroxide. It was shown that the use of microfiltration membranes is promising for the removal of spent suspension iron-containing sorption materials. Experimental studies have confirmed that the use of the combination “fine-particle iron(III) oxyhydroxide/membrane” allows removing arsenic compounds from contaminated water to the sanitary requirements level (less than 10 μg As/l) and separating effectively the spent fine-particle sorbent from water