Decontamination of solutions containing Cu(II) and ligands tartrate, glycine and quadrol using metallic iron

Decontamination of solutions containing Cu(II) complexes with tartrate, glycine and quadrol (N,N,N'N'-tetrakis(2-hydroxypropyl)ethylenediamine) using metallic iron depends on pH and proceeds best in mildly acidic solutions. Cu(II) is completely removed from all solutions containing the ligands investigated. The degree of ligand removal from solutions considerably differs. Tartrate is relatively rapidly and completely removed from solutions. A complete removal of glycine is prolonged. The removal of quadrol from solutions using metallic iron is negligible. Electrochemical investigations showed that tartrate and glycine have inhibitory influence on anodic dissolution of iron at pH 2 and enhance it at pH 4. Quadrol does not exhibit any significant influence on iron dissolution. Chemical analysis and FT-IR investigations have shown that the content of organic compounds is the greatest in the precipitate formed in solutions containing tartrate, while it is considerably lower in glycine containing solutions. The precipitate formed in quadrol-containing solutions during the treatment with metallic iron contains only negligible amount of organics.

Decontamination of solutions containing EDTA using metallic iron

EDTA removal from solutions using metallic iron was carried out at different values of pH, iron load and concentrations at free access of air and in closed vessels. The EDTA destruction was investigated using chemical and capillary electrophoresis analysis. Fe corrosion was studied voltammetrically and the composition of the precipitate formed was investigated using FT-IR spectroscopy and chemical analysis. The EDTA decomposition is remarkably enhanced by the addition of Cu(II) to the EDTA solutions and access of air. The precipitation of the derivatives of insoluble Fe with EDTA or its decomposition products proceeds along with the destruction of EDTA. In closed systems the main EDTA removal reaction is precipitation with iron ions.

Copper(II)-EDTA sorption onto chitosan and its regeneration applying electrolysis

Cu(II)-EDTA (ethylendiaminetetraacetate) complexes are widely used in the manufacture of printed circuit boards. In order to avoid the outlet into the environment the sorption of complexes onto chitosan is proposed. The uptake of both Cu(II) and EDTA proceeds in weakly acidic (pH 3-5) and strongly alkaline (pH > 12) solutions. In acidic solutions EDTA sorption prevails. FT-IR investigations have shown that in acidic solutions the amide bonds between -COOH groups of EDTA and -NH2 groups of chitosan were formed. In alkaline solutions the single EDTA sorption does not proceed. In this media the sorption is enhanced by Cu(II) ions. The possible sorption mechanisms are discussed. The uptake of both Cu(II) and EDTA by chitosan depends on the ratio between them in solutions. EDTA sorption in acidic solutions increases with increase in its concentration while that of Cu(II) decreases. In alkaline solutions the sorption of both Cu(II) and EDTA increases with increase in Cu(II) concentration. The use of electrolysis enables to regenerate chitosan and to reuse it. During electrolysis copper is deposited onto the cathode and EDTA is oxidized onto the anode. The current efficiency depends on the current intensity, the load of chitosan and the pH of the background electrolyte. Electrolysis under the most favorable conditions ensures the 10-cycles regeneration without considerable changes in the sorption properties of chitosan. FT-IR spectra of the initial and regenerated chitosans are similar.

Recovery of EDTA from complex solution using Cu(II) as precipitant and Cu(II) subsequent removal by electrolysis

Ethylendiaminetetraacetate (EDTA) is a chelating agent widely used in industry and agriculture. Resistant to chemical and biological degradation EDTA represents a serious ecological problem. In order to avoid the outlet into the environment a new method of EDTA recycling has been proposed. The method involves substituting of the metal ions in EDTA complexes by Cu(II) and formation of an insoluble Cu2EDTA.4H2O compound at the excess of Cu(II) ions in weakly acidic solutions. Cu(II) ions substitute such metal ions as Ni(II), Zn(II), Co(II), Cd(II), Ca(II) and Mg(II). After treatment of the precipitate with water only, acidic or alkaline solutions the copper from the suspension formed can be removed by electrolysis. The highest current efficiency under galvanostatic conditions is in alkaline solutions, however, the highest yield of EDTA recovery is in acidic solutions. FT-IR investigations and chemical analysis of the precipitate formed have shown that in acidic and in alkaline solutions, H4EDTA and Na2H2EDTA.2H2O were formed, respectively. Electrolysis in acidic solutions gives the best results, i.e. the formed H4EDTA contains the highest amount of EDTA (95%) and the lowest amount of copper (0.01%).

Microbiological degradation of a spent offset-printing developer

To decontaminate spent offset-printing developer Polychrome 4003, several microorganisms were separated from the soil that has been used for developer dumping for 3 years. Two organism cultures were isolated and identified to genus Geomyces pannorum and Bacteria spp. These organisms, as well as commercial Septic Gobbler (SG) bacteria, were used to decontaminate the developer. Reduction of both the chemical oxygen demand (COD) and the amount of total identified organic compounds reached 30% after 40 day treatment of waste suspension by G. pannorum and Bacteria spp. A substantially higher degree of COD reduction by approximately 80% and the total amount of identified organic compounds by approximately 90% was achieved when SG bacteria have been applied for the same period. According to a rapid electrophysiological test with macrophytic algae Nitellopsis obtusa, the toxicity of spent offset-printing developer Polychrome 4003 was classified as extremely toxic (>100 toxic units, T.U.), and it remained at the same level after treatment with G. pannorum and Bacteria spp. More effective biodegradation with SG bacteria diminished toxicity substantially.

Recycling of Ni(II)-citrate complexes using precipitation in alkaline solutions

When the excess of Ni(II) ions as compared to citrate concentration is used both Ni(II) ions and citrate can be precipitated in alkaline solutions. The ratio between Ni(II) and citrate in the precipitate and completeness of citrate precipitation depends on the ratio between the Ni(II) and citrate concentrations in the initial solution and its pH. The data of chemical analysis, potentiometric titration, FT-IR as well as visible spectrophotometric investigations suggest that Ni(II) in the insoluble compound is bound with three -COO- groups and -OH group of the citrate. The insoluble compound also contains SO4(2-) and hydroxides. The treatment of this precipitate with H2SO4 enables to recover a soluble Ni(II)-citrate complex, which can be reused in practice, and to remove the excess of Ni(II) in the form of insoluble Ni(OH)2.