Enhancing Wastewater Reuse in Phosphate Mining: Nanofiltration-Based Removal of Silica and Chloride Ions
Abstract
Rasha Amer Hajarat, Jafar S. Slehat, Bayan M. Badwan, Serena M. Ejelat, Sewar El-Hashem and Shatha A. Alzedaneen
High silica and chloride content make phosphate-mining wastewater hard to treat: both drive scaling, fouling, and corrosion in downstream equipment. Here, a ceramic nanofiltration (NF) membrane was tested against this problem, targeting silica (Si4+) and chloride (Cl1-) removal from synthetic SiCl4 solutions and from real effluent supplied by the Jordan Phosphate Mines Company (JPMC), with transmembrane pressure (TMP), ion concentration, and pH all varied to see how each affected rejection. The best performance came from the real JPMC effluent: 97.1% Si4+ rejection and 99.9% Cl1- rejection at 5 bar TMP. The two feedwaters behaved differently. In the synthetic solutions, electrostatic repulsion between the positively charged membrane surface and the cationic Si4+ dominated, so Si4+ rejection came out higher; in the real wastewater, a more complex ionic matrix shifted that balance toward Cl1-, pointing to a change in the underlying separation mechanism. Fouling rose with SiCl4 concentration, but a NaOH cleaning cycle reversed it fully and restored membrane permeability. Together, these results indicate that ceramic NF can treat phosphate-mining wastewater well enough to support water reuse, lower treatment costs, and reduce environmental discharge.