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 (Mn²⁺, Ba²⁺, Al³⁺, Cr³⁺, Fe³⁺), borderline acid (Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Pb²⁺, Sn²⁺, Bi²⁺), soft acid (Ag⁺, Cd²⁺, Hg²⁺), and two kinds of dissolved minerals (Mg²⁺, Ca²⁺) 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 Cr³⁺, Hg²⁺and Pb²⁺ was up to 416.67, 256.41, and 312.15 mg g^-1, 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.