Development of Membranes Based on Alkali-Activated Phosphate Mine Tailings for Humic Acid and Copper Removal from Water

Recycling mine tailings present a good alternative to manage the waste generated from mining and mineral processing industries. The geopolymer technology provides a green solution to the utilization of mining tailings, avoiding its negative environmental impacts. In this study, we used phosphate mine tailings to produce a novel geopolymeric membrane useful for removing copper ions and humic acid from an aqueous solution. Hydrogen peroxide was used in different concentrations as a porogenic agent, and the membranes exhibited good compressive strength (11.15–43.67 MPa) and high BET surface area (321–384 m 2 g −1 ), depending on the amount of hydrogen peroxide used in the synthesis. The hydraulic permeability of the membranes increased from 4.12 × 10 −5 to 11.84 × 10 −5 m s −1 bar −1 when H 2 O 2 was added, but the rejection of copper and humic acid remained nearly the same. Copper ions are adsorbed on the membrane surface, while negligible adsorption was measured for humic acid. The geopolymeric membranes efficiently removed Cu 2+ from water through the combined action of adsorption and rejection by the geopolymer inorganic membrane. The performance of the porous membrane in the removal of copper or humic acid from water increased by factors of 7–19 in comparison to the non-porous membrane.