Waste printed circuit boards (WPCB) residues were mechanically processed to concentrate their metal content aiming to reduce costs of the subsequent recovery of copper, tin, and lead. A fully dry route was proposed to avoid the generation of liquid effluents that would require additional treatment. Firstly, 10.7% of the residue was segregated by magnetic separation; the remaining nonmagnetic fraction was comminuted and sieved. Ceramic and polymer materials (1/3 of the total weight) concentrated in the finer and the coarser size fractions, while metallic materials (2/3 of the total weight) concentrated in the intermediate size fraction (90.7, 94.5, and 95.6% of the total copper, tin, and lead contained in the milled WPCB, respectively). The fractions between 0.3-1.20 mm were submitted to gravity separation using a zig-zag air classifier; enrichment of copper (from 43±11% to 68±5%), tin (from 10±3% to 17±1%), and lead (from 4±1% to 6.4±0.5%) were obtained.

Magnetic nanoparticles can improve the efficiency of phase separation time in multi-stage operations when a magnetic field is present. As such operations involve contact with aqueous and/or organic solutions, hydrophilic magnetic nanoparticles synthesized through the co-precipitation method were functionalized with oleic acid to attain hydrophobic magnetic nanoparticles. Both nanoparticles were characterized morphologically, chemically and magnetically. The results revealed that the particles (size ≈ 10 nm) consisted of an iron oxide mixture of magnetite and maghemite. The functionalization with oleic acid was effective in converting them into hydrophobic nanoparticles. Both particles were ferro/ferrimagnetic and the presence of oleic acid did not interfere significantly in the saturation magnetization value. The chemical stability of both nanoparticles were also evaluated, as an attempt of simulating broad industrial conditions to which the nanoparticles may be subjected; the hydrophilic nanoparticles were resistant at pH ≥ 4, while the hydrophobic nanoparticles were stable at pH ≥ 3.

A aplicação da técnica de extração por solventes para a recuperação de metais e da água a partir de resíduos e efluentes industriais é apresentada nesse trabalho. Os seguintes estudos de caso foram analisados: (1) separação seletiva e concentração de Zn contido em efluentes gerados na indústria de zinco, (2) separação de Zn e Fe presentes em efluentes da indústria de galvanização a quente e (3) recuperação de Co e Ni a partir de baterias de celular descarregadas. Dados obtidos em escala de laboratório e em escala-piloto foram empregados para demonstrar a potencialidade da técnica no tratamento de efluentes, visando à reutilização, tanto dos metais, quanto da água, que seriam inutilizados, resultando em economia de energia com redução de impactos ambientais, além da minimização dos custos relacionados ao transporte de materiais perigosos e manutenção de aterros.

The use of solvent extraction to recover metals and water from industrial residues is highlighted in this work. The method was applied (1) to selectively concentrate Zn from effluents generated by the zinc industry, (2) to separate Zn and Fe from spent pickling effluents produced by the hot-dip galvanizing industry, and (3) to recover Co and Ni from spent batteries. Batch and pilot scale data was used to point out solvent extraction as a feasible method to reuse both metals and water thus resulting in energy savings with reducing environmental impacts, minimizing costs required to transport hazardous materials to waste sites, to replace the discharged wastewater and to produce the raw material that would be previously discharged as wastes.

Os métodos de precipitação química, cristalização e extração líquido-líquido foram aplicados visando propor alternativas para o tratamento de efluentes líquidos gerados pela indústria de galvanoplastia. Efluentes de diversas empresas do setor, localizadas no estado de Minas Gerais (Brasil), foram coletados e caracterizados. O efluente estudado, proveniente de empresa de galvanização de zinco a quente, continha cerca de 90 g/L de ferro total, 35 g/L de zinco e menores quantidades de Al, Ni e Cu, em meio ácido clorídrico (pH = 0,6). A separação seletiva entre ferro e zinco não se mostrou eficiente por precipitação, sendo a técnica adequada somente no tratamento do efluente, ao contrário da cristalização e extração líquido-líquido utilizando-se TBP como agente extratante. A integração destas técnicas ainda requer estudos mais detalhados visando à otimização de custos e das condições operacionais.

Separation methods such as chemical precipitation, crystallization and liquid-liquid extraction have been investigated aiming to treat effluents generated by the galvanic industry. Effluent samples generated by several companies located in the state of Minas Gerais (Brazil) were collected and chemically characterized. For this work, a typical zinc hot-dip galvanizing effluent containing about 90 g/L of total iron, 35 g/L of zinc and minor amounts of Al, Ni, Cu, in HCl medium (pH = 0.6) was treated. A selective separation between metals zinc and iron was not achieved by chemical precipitation, which was found adequate to threat water only. On contrary, zinc and iron was separated very efficiently by crystallization and liquid-liquid extraction using TBP as extractant agent. The integration of these methods to recover zinc and iron from effluent still requires more detailed studies.