Produção Nacional
Revisado por pares
Integration of two-stage nanofiltration with arsenic and calcium intermediate chemical precipitation for gold mining effluent treatment
2018; Taylor & Francis; Volume: 40; Issue: 13 Linguagem: Inglês
10.1080/09593330.2018.1432692
ISSN1479-487X
AutoresLaura Hamdan de Andrade, Wadson L. Pires, Luiza B. Grossi, Alice Aguiar, Míriam Cristina Santos Amaral,
Tópico(s)Environmental remediation with nanomaterials
ResumoThe aim of this study was to evaluate an innovative treatment route for gold-mining effluents rich in calcium, arsenic, and sulfate. This treatment route comprised two nanofiltration (NF) stages and a two-step intermediate precipitation. Arsenic and iron coprecipitation (first step) and calcium carbonate precipitation (second step) were assessed aiming to treat the first-stage NF concentrate and increase the permeate recovery rate in a second-stage NF. The pH, the molar ratio of Fe/As (first step), and the molar ratio of CO3/Ca (second step) were optimized by using rotational central composite design. Under optimal conditions, the arsenic removal was 99.8% (at pH = 7.0 and Fe/As = 4.0), and the calcium removal was 99.5% (at pH 11.5 and CO3/Ca = 3.5). The supernatant of Ca precipitation had very basic pH and had to be acidified before the second-stage NF. The pH 8.5 proved to be the best one regarding retention efficiency and flux. The flux decay of the second-stage NF was attributed to both osmotic pressure increase and reversible fouling resistance. It was concluded that the proposed treatment system is efficient for the treatment of gold-mining wastewater, ensuring higher production of treated effluent and an easy disposable of the final concentrate.
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