Removal of multiple metal ions from wastewater by a multifunctional metal-organic-framework based trap.

The design and preparation of multifunctional adsorbent for practical wastewater treatment is still an enormous challenge. To remove multiple metal ions from wastewater, we developed a broad-spectrum metal ions trap named UIO-67-EDTA by incorporation of ethylenediaminetetraacetic acid into robust UIO-67. The adsorption experiments for 15 kinds of heavy metal ions including hard acid (Mn, Ba, Al, Cr, Fe), borderline acid (Co, Ni, Cu, Zn, Pb, Sn, Bi), soft acid (Ag, Cd, Hg), and two kinds of dissolved minerals (Mg, Ca) show that the trap is very effective both in batch adsorption processes and breakthrough processes. At a pH value of 4.0, the removal efficiency for all metal ions was over 98% within 10 min, and the maximum static adsorption capacity for the representative metal ions Cr, Hgand Pb was up to 416.67, 256.41, and 312.15 mg g, respectively. The adsorption kinetics fitted well with the pseudo-second-order model, indicating that the chemical adsorption was the rate-determining step in the adsorption process. Meanwhile, the material showed high stability and recyclability, the removal efficiency for the three representative metals was still maintained over 93% after five consecutive adsorption cycles.