Preparation of multi-walled carbon nanotubes (MWCNT) and graphene oxide (GO) incorporated Cr-TA@SSZ composite metal-organic frameworks and their use as adsorbents for adsorptive removal of TPA, BA, and p-tol from wastewaters

Abstract

In the present work, multi-walled carbon nanotubes (CNT) and graphene oxide (GO) were incorporated with the MIL-101(Cr)/Sulfasalazine (Cr-TA@SSZ) composite. The composite MOFs have been synthesized by adding oxidized multi-walled carbon nanotube and GO with different ratios GO: CNT from (0:1, 10:5, 10:7, and 1:0) in situ during the synthesis of Cr-TA@SSZ by a hydrothermal approach. The resulting samples were characterized by X-ray diffraction (XRD), ASAP, Transmission electron microscopy (TEM), scanning electron microscopy (SEM), and thermal gravimetric analysis (TGA) analysis. The synthesized composite adsorbents were used for the adsorption of terephthalic acid (TPA), para-toluic acid (p-tol), and benzoic acid (BA). The results were compared with other adsorbents such as: GO, CNT, AC, Cu-BTC, Fe-BTC, MIL-101 (Cr), and MIL. -53(Al) and ZIF-8. Adsorption experiments indicated that the amount of TPA adsorption by Cr-TA@SSZ/CNT is higher than other composites but lower than some mother MOFs. The most important reasons include the larger molecule size, having two carboxyl groups, which leads to better interaction with micropores, and non-polarity of TPA. Adsorption experiments of BA and p-tol also demonstrated that Cr-TA@SSZ/CNT composite has the highest adsorption rate. Due to the improvement of the capillarity mechanism by increasing the diameter of pores, on the other hand, the polarity of BA and p-tol molecules, these two molecules were better adsorbed in Cr-TA@SSZ/CNT composite, which has both functional groups and larger pores. Furthermore, adsorption experiments using industrial wastewater from a TPA production plant showed that the highest purification efficiency belongs to Cr-TA@SSZ/CNT and Cr-TA@SSZ. Cr-TA@SSZ/CNT and Cr-TA@SSZ removed 41.6% and 40% COD from the concentrated phase (equivalent to 13670 and 13000 ppm) and removed 79.8% and 77.3% COD from the diluted phase (equal to 4390 and 4250 ppm) wastewater.