Ultrafiltration treatment of wastewater contained heavy metals complexed with palygorskite

Palygorskite was applied in complexation-ultrafiltration treatment of heavy metals in wastewater under different pH and ionic strength. The results indicated that the rejection of heavy metals increased significantly with pH value, and decreased slightly with an increase of ionic strength of Na⁺ and Cl^–. A certain concentration of NaCl significantly reduced the rejection rate of Cu²⁺. The rejection of Cu²⁺, Zn²⁺ and Cd²⁺ could reach over 86.8%, 93.6% and 93.7% at pH of 7 and 0.1 mol/L NaCl. The rejection of heavy metals was severely affected by low molecular weight competing complexing agents and the effect of sodium tartrate was greater than triethanolamine. In the presence of sodium tartrate, the rejection of Cu²⁺, Zn²⁺ and Cd²⁺ could arrive over 81.4%, 57.6% and 60.5% at pH of 7 in 20 min. Palygorskite was offered a potential complexing agent for the removal of heavy metals in wastewater at the complexation-ultrafiltration process.