Recovery of water and sulfides from liming wastewaters

Abstract

The desalination and treatment of tannery unhairing wastewater by electrodialysis (ED) is investigated in this research in order to separate, concentrate, recover and reuse low molecular weight charged species (S2−, HS−, OH−, Cl−, Ca2+, Na+ and amino acids), and to separate proteins and recycle treated water. Therefore, a novel electrodialysis membrane configuration was proposed. This was based on a double anti–fouling membrane. The ED anion exchange membrane (AEM), which is very sensitive to organic fouling, was protected by an ultra filtration membrane impermeable to the negatively charged proteins that could not reach the AEM surface. The experimental results were quite promising, and in spite of only one desalination compartment ED cell; the demineralization efficiency was 56 ± 1.25% (5.5–2.4 mS/cm), with a sensitive removal of sulphide, calcium and chloride. The organic matter (protein, peptides…) was isolated in the dilute compartment. The most important result was the total absence of membrane fouling.The experimental results remarkably proved the initial hypothesis, and suggested promising solutions for industrial pollution, where the membrane processes have never been successful.