Evaluation of an extreme acid-resistant sulphonamide based nanofiltration membrane for the valorisation of copper acidic effluents

Abstract

The exhaustion of Cu reserves minable and processable with the available technology is forcing the hydrometallurgical copper industry to seek alternative sources. Following circular economy principles, researchers’ attention has focused on the recovery of valuable metals from the acidic waste streams generated. Nowadays, membrane technologies are being selected as the first alternative for the treatment and valorisation of such acidic waste streams. Among them, a new generation of high acidity resistance nanofiltration (NF) membranes offer the alternative for acid recovery while providing a metal-enriched stream. In this work, the extreme-acid resistant Duracid membrane was evaluated for the valorisation of different synthetic acidic waste streams from the hydrometallurgical Cu industry. These waters were characterised by a high acidity (pH 0.5–1.5) and the presence of Fe (11–14 g/L), Zn (0.7–1.4 g/L) and As (0.5–0.7 g/L), among others. Initially, the membrane was characterised by different techniques (SEM, FTIR-ATR, XPS). Experiments were performed under constant and varying permeate flux and feed water composition. Metals were effectively rejected (>90%), whereas H+ easily permeated through the membrane. The experimental results were adjusted to the Solution-Electro-Diffusion-Film (SEDF) model to determine the membrane permeances to species. Empirical mathematical equations were developed and validated to express the dependence of permeances on solution composition. Finally, the prediction capability of the SEDF model, together with the developed empirical equations for the permeances, was proposed as a tool for designing a NF unit to valorise acidic streams from the hydrometallurgical Cu industry. The model predicted gypsum scaling onto the membrane and therefore anticipated the need of applying antiscalants.