Properties of metal complexes obtained by the disposal of galvanic sludge by complexons

Disposal of galvanic sludge has priority in terms of protecting the environment from pollution by heavy metals. The processes of the selective action of pyrocatechol complexons and disodium salt of ethylenediaminetetraacetic acid (EDTA-Na) in relation to metal ions contained in a galvanic sludge have been studied. The complexon structure affects the extraction degree of heavy metal ions from galvanic sludge: pyrocatechol and EDTA-Na are selective for copper, nickel, chromium, and zinc. The extraction degree of metal ions increases with acidification of the medium with sulfuric acid. Acidification also contributes to the maximum separation of the precipitate from the complexonate solution. The structures of complexonates are different: chelate complexes with a coordinated metal ion in cycles, and protonated complexes. The structure of copper complexonates formed by pyrocatechol and EDTA-Na was confirmed by EPR spectroscopy. When a suspension of galvanic sludge is treated by pyrocatechol, in the EPR spectra the paramagnetic copper(ΙΙ) complexes are noted with the following parameters: aCu = 7.8 mT; g = 2.045. Almost simultaneously, another signal has been detected in the EPR spectra of the pyrocatecholate complex, which belongs to a copper complex with a lower splitting constant on copper nuclei (aCu = 7.1 mT) and with a significant shift of the g factor to the low field region, g = 2.078. In the extraction processes of metal ions from their galvanic sludge by the EDTA-Na complexon, a superposition of EPR signals has been recorded. The EPR spectrum consists of 5 broadened HFS components: аCu(1) ≈ 6.6; aCu(2) ≈ 5.4 mT. The values equal: g1 = 2.078, g2 = 2.043. Structures of metal complexonates with the copper ion are proposed. Metal complexonates contain copper, nickel, chromium, and zinc. Calcium, iron, and traces of lead have been found as impurities, which do not affect the use of complexonates in agriculture. Optimized parameters of the utilization processes of galvanic sludge using pyrocatechol and EDTA-Na complexons. The technological scheme of disposal has been developed. Experimental samples of metal complexonates for agricultural use have been devised. When catechol is used, the concentrations of metal ions in the resulting solution are (mg/L): copper 8.0; nickel 5.0; chromium 3.2; zinc 2.0. In the case of EDTA-Na they are (mg/L): copper 7.8; nickel 4.8; chromium 3.4; zinc 2.2.