Improving the energetic efficiency of direct-contact membrane distillation in mining effluent by using the waste-heat-and-water process as the cooling fluid

摘要

The water footprint of the gold mining sector can be drastically diminished by adopting technologies that promote water reuse. In this context, membrane distillation (MD) is a promising alternative as it can produce a high-quality permeate while utilizing the effluent-waste heat, thus diminishing operational costs, as seen in previous studies. However, other issues regarding MD in this application are yet to be addressed such as the effect of feed pretreatment, pH adjustment, membrane stability, and cleaning, and the possibility of using the process water as a cooling solution. This study is thus aimed at addressing these questions. The obtained results showed that the adoption of ultrafiltration as a pretreatment without pH adjustment provided the best results for scale mitigation, while maintaining a rejection of over 99% for the main solutes. In addition, the use of the process water did not result in any changes in the process and was thus demonstrated as a feasible alternative. Furthermore, after 210 days, the chemical stability study showed small morphological changes in the membrane surface that did not affect its selectivity. Finally, the absence of mechanical pressure in the process resulted in the formation of a loosely adhered fouling layer that was easily removed via physical cleaning. (C) 2020 Published by Elsevier Ltd.