Abstract
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.
Highlights
Water pollution caused by metal ions has become a pressing global environmental issue, creating a serious threat to humans and aquatic organisms in view of their high toxicity, biological accumulation and persistency in nature (Vorosmarty et al 2010; Bakker 2012)
The characteristic peaks at the binding energy of 399.2 eV were attributed to the N 1s of ethylenediaminetetraacetic acid (EDTA) that appeared after modification (Figure 2(a) and 2(c)) (Zhao et al 2017)
Because the element nitrogen comes from EDTA, according to the mole ratio of element nitrogen and EDTA (M 1⁄4 292.2), the content of EDTA can be calculated to be 28.8% in UIO-67-EDTA
Summary
Water pollution caused by metal ions has become a pressing global environmental issue, creating a serious threat to humans and aquatic organisms in view of their high toxicity, biological accumulation and persistency in nature (Vorosmarty et al 2010; Bakker 2012). It is of great importance to search a simple and effective way for removal of heavy metal ions from waste water. Among the traditional techniques for metal ion removal, adsorption is regarded as one of the most promising methods due to its simplicity and efficiency (Li et al 2014). The complex functional groups can effectively boost adsorption capacity, most adsorbents still suffer from the disadvantage of specificity in heavy metal capture. There is a need to develop a multifunctional adsorbent containing high-density binding sites with strong binding affinity to diverse metal ions
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