Designing a dual-functional ultrathin ZIF-L@GO adsorbent for simultaneous removal of phosphate and tetracycline hydrochloride: Adsorption capacity and mechanism

Inorganic phosphate and organic antibiotics, usually co-existing in wastewater, were difficult to simultaneously remove by common mono-functional adsorbents. In this work, by in-situ coating zeolitic imidazolate frameworks (ZIF-L) on graphene oxide (GO), a dual-functional ultrathin ZIF-L@GO-25 adsorbent was successfully prepared for efficient and simultaneous removal of phosphate and representative tetracycline hydrochloride (TC) from wastewater. ZIF-L@GO-25 exhibited maximum adsorption capacity for phosphate and TC respectively reached 116.3 +/- 2.1 mg g(-1) and 338.6 +/- 6.7 mg g(-1), benefiting abundant Zn-defect sites and dimethylimidazole rings exposed on its surface. Moreover, thanks to the specific innersphere complexation of Zn-defect/phosphate and pi-pi interaction between dimethylimidazole rings/TC molecules, > 95% removal efficiencies were achieved when the concentration of five competitive matters (Cl-, NO3-, SO42-, CO32- and humic acid) were 10 times that of phosphate/TC. Even with the binary pollutants co-existing system, only similar to 3% removal decreases occurred on both phosphate and TC. Thus, this work proposed a novel preparation method of developing ZIF-based composite adsorbents for the deep treatment of actual phosphate/antibiotics-polluted wastewater.