The effect of high-molecular compounds nature on the electroflotation removal of the metal compounds from electrolyte solutions

Abstract

• Removal of heavy metal ions (Fe (III), Ni (II), Cu (II), Pb (II) and Zn (II)) as part of the multi-component system from electrolyte solutions by means of electroflotation and filtration with presence of the high-molecular compounds (HMC) of different nature. • Effect of solution pH, metal and electrolyte concentration on the dispersed properties and electrokinetic potential of the dispersed low-soluble metal compounds and efficiency of their electroflotation removal. • Effect of HMC (flocculants and surfactants) with the anionic, cationic, non-ionic and amphoteric nature upon the dispersed properties, electrokinetic potential and efficiency of electroflotation and electroflotation with subsequent filtration removal of the low-soluble metal compounds particles in electrolyte solutions. • The efficiency of electroflotation removal of heavy metals from concentrated electrolyte solutions with the anionic HMS runs to 98–99% for all components. The process of removal of heavy metal ions as part of the multi-component system from electrolyte solutions by means of electroflotation and filtration with presence of the high-molecular compounds (HMC) of different nature has been studied. Studies were performed in solutions with ions of iron (III), nickel (II), copper (II), lead (II) and zinc(II), as well as NaCl and Na 2 SO 4 (pH 9.5–10.5). It has been shown that addition of the sulphate and sodium chloride mixture in 50 g/L concentration to solutions containing metal ions with total 0.1 g/L concentration reduced the absolute value of dispersed phase ζ-potential from −2.5 mV to −6 mV. The dispersed phase size is getting smaller, two particle types appear in the solution − 54 µm (72% of the total particle quantity) and 5.0 µm (28%). Rise of the total metal ion concentration up to 0.2 g/L results in reduction of the dispersed phase size: 1.5 µm (63%) and 46 µm (37%) particles prevail, the ζ-potential is reduced slightly (-7.1 mV). In this case, the rate of removal of the studied metals by mean of electroflotation is not more than 32–46%. Addition of the anionic HMS (flocculants and surfactants) to the solutions with the total concentration of metal ions of 0.2 g/L and salts of 50 g/L results in rise of dispersed phase ζ-potential and tends its value to the isoelectric point (±0 mV). When the cationic surfactants are added, the particle surface is recharged, the ζ-potential acquires the + values (5.3–7.8 mV). It has been concluded, that the rate of electroflotation removal of heavy metals from concentrated electrolyte solutions with the anionic HMS runs to 98–99% for all components. Subsequent solution filtration with the anionic flocculant allows for reduction of the residual concentration to the following values: 0.5∙10 -4 g/L for Fe (III), Cu (II) and Pb (II) ions and. 0.1∙10 -4 g/L for for Ni (II), 0.14∙10 -3 g/L for Zn (II). Addition of the cationic, non-ionic and amphoteric surfactants does not result in increase of electroflotation process efficiency.