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The sorption of copper(II) ions in a wide range of pH by two Russian carbon sorbents BAU-A and MIU-S was studied. Sorbents varied in structure, surface area, pH of the point of zero charge (pH ZPC ), and graphitization degree. The sorption studies were conducted in batch mode. The removal of copper(II) ions from a solution at pH 4, 5, 6, and 6.7 is described by the classical adsorption isotherms of Freundlich, Langmuir, and Dubinin-Radushkevich. With an increase in pH from 4 to 6.7, the sorption capacity of sorbents increases, from 0.910 to 7.163 mg/g for BAU-A, and from 0.265 to 3.307 mg/g for MIU-S. The relationship between the degree of crystallinity and the sorption properties of sorbents has been established.

Removal of heavy metal ions, in particular, divalent nickel ions from natural and wastewater, is of great importance for the environment. Nickel (II) ions are very toxic and provoke many diseases. The purpose of this work was to study the possibility of removing toxic nickel (II) ions from polluted water using an iron (III) chloride (FeCl3) coagulant. It is shown that the removal of nickel ions from aqueous solution by iron (III) hydroxide precipitate formed during the coagulation process at pH 7 and 8 is described with satisfactory accuracy by the classical adsorption isotherms of Freundlich, Langmuir, and Dubinin-Radushkevich. The studies performed with the use of X-ray powder diffraction and thermal analyses, IR, Raman, and Mössbauer spectroscopy have shown that the uptake of nickel ions by iron (III) hydroxide precipitate is due to simple physical adsorption and is not accompanied by the formation of mixed iron and nickel compounds. No alloying of the formed iron (III) hydroxide precipitate with nickel ions takes place either. The formed iron (III) hydroxide precipitate is a two-line ferrihydrite having the gross formula Fe 2 O 3  × 3H 2 O. Its sorption capacity for nickel ions is almost an order of magnitude higher than that of some mineral and carbon sorbents, and at pH 7 and 8, it is 60.5 and 141.9 mg/g, respectively. PRACTITIONER POINTS: Coagulant FeCl 3 cleans contaminated solutions from Ni(II) ions. Iron (III) hydroxide precipitated at pH 7 and 8 is a two-line ferrihydrite Fe 2 O 3  × 3H 2 O. Removing of Ni(II) ions is described by classical adsorption isotherms. The most complete removal of Ni(II) ions occurs at pH = 8., (© 2022 Water Environment Federation.)