Developing boron nitride-pyromellitic dianhydride composite for removal of aromatic pollutants from wastewater via adsorption and photodegradation

A series of boron nitride-pyromellitic dianhydride composites have been successfully synthesized by calcinating the mixtures of boron nitride (BN) and pyromellitic dianhydride (PA) at 350 °C, in which the composite (BNPA2) has the largest adsorption quantity (65.1 mg/g) for rhodamine B (RhB) and the best photo-removal efficiency for RhB under visible light irradiation. ¹H NMR characterizations for BN, PA and BNPA2 suggest that this composite is formed via the reaction between the OH groups in BN and PA. BNPA2 can also adsorb neutral red (NR), methyl orange (MO), tetracycline (TC) and atrazine (AT). NR and MO can be photo-removed by BNPA2 under visible light irradiation. Colorless TC and AT can also be degraded by BNPA2 under visible light irradiation, suggesting that BNPA2 is visible light responsible photocatalyst. BNPA2 has the highest photo-removal efficiency for the cationic RhB and NR, followed by the anionic MO. This is from that BNPA2 has negative surface. When anionic MO mixes with cationic RhB (or NR) together, BNPA2 prefers to remove cationic RhB (or NR) from the mixture solution under visible light irradiation and the removal efficiency of anionic MO by BNPA2 is also increased. Thus, electrostatic interactions between dyes and BNPA2 as well as between dyes play significant role in the removal process. •O^2- makes a main contribution for this photo-removal of these aromatic pollutants (dyes, TC and AT) by BNPA2 under visible light irradiation. Furthermore, the removal performance of BNPA2 for RhB, TC and AT can be effectively regenerated by visible light irradiation.

Carboxylate cross-linked cyclodextrin: A nanoporous scaffold for enhancement of rosuvastatin oral bioavailability

Cyclodextrins play an important role in supramolecular chemistry acting as building blocks than can be cross-linked by various linker molecules forming nano-porous structures called nanosponges (NS). NS have the ability to enhance the stability, solubility and bioavailability of various actives. This work aimed at elaborating rosuvastatin (ROS) loaded NS to improve its oral bioavailability. Carboxylate-linked NS were synthesized by reacting β-CD with pyromellitic dianhydride (PDA) at different molar ratios under specific conditions. ROS-loaded NS were prepared by lyophilisation technique and characterized for particle size, zeta potential, entrapment efficiency and drug release. Occurrence of cross-linking and ROS incorporation within the NS were assessed by DSC, FT-IR and SEM micrographs. NS prepared at a molar ratio of 1:6 of β-CD: PDA demonstrated the highest entrapment efficiency (88.76%), an optimum particle size of 275nm, a narrow size distribution (PDI of 0.392), and zeta potential of -61.9 indicating good colloidal stability. In vivo oral pharmacokinetics study in male Sprague Dawley rats showed that ROS-NS provided an outstanding enhancement in oral bioavailability compared to drug suspension and marketed tablets besides their physicochemical stability for 3month. Accordingly, ROS-NS represent a superior alternative to the conventional marketed formulation for effective ROS delivery.