Surface modification of mixed sorbents with sulfide ions for purification of galvanic wash water of copper plating process
Proceedings of the NTUU “Igor Sikorsky KPI”. Series: Chemical engineering, ecology and resource saving(2020)
摘要
Galvanic wastes are the main source of heavy metals entering the environment and irrational use of water as a technical resource. In order to rationally use purified water in closed production cycles and reuse removed/regenerated metals, it is important to study and implement local systems of rinsing water in electrochemical production. The complex water purification of copper plating of galvanic and sulphide-alkaline wastewater of petrochemical productions with the use of regenerated mixed sorbent (AC + K) depending on the order of modification of the sorption surface and pH of the initial medium has been investigated: method A, modification of copper (II), pH = 1.5-2.5; method B, sulfide-hydrosulfide modification of copper (II), pH = 12.6-13.2, as well as the concentration of the original sulfide-alkaline solution. A method of topochemical purification of galvanic copper flushing waters from copper (II) ions is proposed. It was found that the primary sorption of sorbents/ions Cu2+, S2-, HS- has a selective character, is determined by morphology, heterogeneity and the presence of active centers on the surface of the studied sorbents and therefore has a different investigated adsorption sequence. The obtained data indicate a slight adsorption of Cu2+ on the matrix surface, which is explained by both the nature of the adsorbate and the morphology of the adsorbent (AC + K) after its acid-base activation. It is obvious that the mixed microporous sorbents (AC + K) studied by us show cation exchange properties. Mainly carboxyl groups carry out sorption/binding of Cu2+ ions. It was found that the maximum sorption of copper (II) ions on the matrix surface, which has a small number of acidic carboxyl groups, takes place in a strongly acidic medium at pH = 1.5-2.5. Preliminary modification of the surface of sorbents (AC + K) with more active sulfide and hydrosulfide ions leads to a significant increase in its selective adsorption relative to copper (II) ions. Modification of the surface of mixed sorbents (AC + K) with sulfur-containing ions (S2-, HS-) allowed increasing the degree of extraction of copper (II) cations from the washing galvanic waters of the copper-plating process by 51.9%. Adsorption of sorbents by method A or method B begins with the formation of a sorption complex between the sorbate (Cu2+, S2-, HS-) and the primary activated center of the sorbent (AC + K). Taking into account the possible catalytic influence of the surface of activated carbon on the passage of topochemical transformations, the change of the valence-coordination node CuO2S2(H2O)2 will take place with the formation of the intermediate [CuS2]. It was found that topochemical reactions of formation of copper (II) CuSx polysulfides (x=2,3) take place on the surface of activated carbon, followed by their disproportionation to copper (II) sulfide and elemental sulfur. IR spectral and X-ray phase studies have established the possibility of undergoing topochemical transformations.The obtained results allow to recommend modification of carbon sorption materials with sulfur-containing ions (S2-, HS-) for more complete sorption extraction of Cr3+, Fe2+, Fe3+, Pb2+, Cd2+, Cu2+, Ni2+, Co2+, Zn2+ ions or their binary mixtures. It has been envisaged to use mixed sorbents (AC + K) with sulfur and copper (II) sulfide sorbed on their surface as components of special purpose greases.
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关键词
galvanic wash water,copper plating process,sulfide ions,mixed sorbents,surface modification
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