Green complexation for heavy metals removal from wastewater by Keggin-polyoxometalates enhanced ultrafiltration

Abstract

The presence of heavy metals in wastewater has become a serious issue and a global concern for the environment and public health with rapid progress of modern textile industry. To minimize the health risks of heavy metals their complexation to a chelating agent constitute a promising process using membrane separation. We highlight for the first time the use of Keggin type-polyoxometalates (PW12) as complexing agent to eliminate heavy metals from synthetic textile wastewater. Indeed, filtration experiments were performed through the ultrafiltration organic regenerated cellulose membrane (3KDa). Effects of pressure (1–2.5 bar), PW12 concentration (10–50 mg·L−1), salt concentration (10−4–2 M) and pH value (2–12) on cadmium (Cd) and copper (Cu) removal were regularly explored. Experimental data showed that the addition of PW12 improves metal removal efficiency (up to 90%). The addition of NaCl salt significantly decreases the metals retention to 42%. The retention drop is probably due to the competition between Na+ and metals on complexation same negative sites of the PW12 and to the electric double-layer compressing. 24 full factorial design has been used to evaluate the most influencing parameters. The results obtained revealed that the maximum metal retention was 99% for both Cd and Cu. HIGHLIGHTS The PW12 is a new eco-friendly candidate used to improve membrane performance.; PW12-assisted ultrafiltration process can remove up to 99% of Cd and Cu metals.; Toxic metals were complexed with the anionic PW12 forming stable complex.; We attempt to study the effects of pressure, PW12 concentration, ionic strength, and pH value on heavy metals removal.; 24 full factorial design was used for optimization of removal parameters.;

Keywords

• complexation-ultrafiltration
• full factorial design
• heavy metals removal
• polyoxometalates
• waste water