Proportional modulation of zinc-based MOF/carbon nanotube hybrids for simultaneous removal of phosphate and emerging organic contaminants with high efficiency

Three multifunctional adsorbents of carbon-based metal-organic framework (MOF) derivatives have been successfully prepared by varying zeolitic imidazolate framework-8 (ZIF8) and multiwalled carbon nanotube (MWCNT) ratio. Thus-synthesized nanocomposites are adopted to simultaneously remove conventional phosphate and emerging organic contaminants (EOC). Among the three hybrids, ZIF8/CNT40 possessing Zn: -OH (CNT) similar to 1:2 harvests the largest contaminant removal efficiency. For the single system of phosphate, the maximum phosphate adsorption capacity of ZIF8/CNT40 reaches 188.5 mg g(-1), and maintaining removal percentage of 100% and >92% in wastewater containing phosphate of 0.98 mg L-1 and 5.93 mg L-1 at neutral condition, respectively. As for phosphate-EOC binary system, the presence of phosphate has no significantly adverse impact on EOC removal. Nevertheless, the removal efficiency of phosphate is impeded by the presence of EOC, and this adverse impact of acetaminophen (AAP) and/or triclosan (TCS) is highly likely to be more serious in the binary system of phosphate and TCS. Such negative influences tend to be relived for ZIF8/CNT40 harnessing better tolerance of structure. Furthermore, these experimental results have shown a good agreement with the theoretical calculation, suggesting ZIF8/CNT hybrids hold a significant prospect for phosphate and EOC sequestration in environmental wastewater with complex components to eliminate growing eutrophication and increasing concern of EOC.

Automated summary

Three multifunctional carbon-based metal-organic framework (MOF) adsorbents were successfully prepared by adjusting the ratio of zeolitic imidazolate framework-8 (ZIF8) and multiwalled carbon nanotubes (MWCNT). Among these, ZIF8/CNT40 showed the highest removal efficiency for both conventional phosphate and emerging organic contaminants (EOC). The maximum phosphate adsorption capacity of ZIF8/CNT40 was 188.5 mg g(-1), and it maintained high removal rates in wastewater with low and high phosphate concentrations. In the binary system of phosphate-EOC, the presence of phosphate did not significantly impact EOC removal, but the presence of EOC hindered phosphate removal efficiency. Furthermore, the negative impact of EOC, such as acetaminophen (AAP) and/or triclosan (TCS), was more pronounced in the presence of both phosphate and TCS, indicating the importance of material structure tolerance for effective contaminant removal.