RESUMO
Recently, novel composite materials are rapidly being explored for water treatment applications. However, their physicochemical behavior and mechanistic investigations are still a mystery. Therefore, our key prospect is to develop a highly stable mixed-matrix adsorbent system using polyacrylonitrile (PAN) support impregnated with amine-functionalized graphitic carbon nitride/magnetite (gCN-NH2/Fe3O4) composite nanofibers (PAN/gCN-NH2/Fe3O4: PCNFe) by simple electrospinning techniques. Various instrumental techniques were used to explore the structural, physicochemical, and mechanical behavior of the synthesized nanofiber. The developed PCNFe with a specific surface area of 39.0 m2/g was found to be non-aggregated and to have outstanding water dispersibility, abundant surface functionality, greater hydrophilicity, superior magnetic property, and higher thermal & mechanical characteristics making it favorable for rapid As removal. Based on the experimental findings from the batch study, 97.0 and 99.0 % of arsenite (As(III)) and arsenate (As(V)), respectively, could be adsorbed by utilizing0.02 g of adsorbent dosage within 60 min of contact time at pH 7 and 4, with an initial concentration of 10 mg/L. Adsorption of As(III) and As(V) followed the pseudo-second-order kinetic and Langmuir isotherm models with an sorption capacities of 32.26 and 33.22 mg/g, respectively, at ambient temperature. The adsorption was endothermic and spontaneous, in accordance with the thermodynamic study. Furthermore, the addition of co-anions in a competitive environment did not affect As adsorption except for PO43-. Moreover, PCNFe preserves its adsorption efficiency above 80 % after five regeneration cycles. The combined results of FTIR and XPS after adsorption further support the adsorption mechanism. Also, the composite nanostructures retain their morphological and structural integrity after the adsorption process. The facile synthesis protocol, high As adsorption capacity, and enhanced mechanical integrity of PCNFe foreshadow its huge prospects for real wastewater treatment.
RESUMO
In the present work, S doped graphitic carbon nitride (Sg-C3N4) 2D nanosheets were synthesized by performing a thermal polymerization reaction of thiourea at 500 °C. After that the surface of Sg-C3N4 was functionalized with Bi2O3/Ag composite nanoparticles via a chemical precipitation method followed by heat treatment at 330 °C. The prepared Sg-C3N4/Bi2O3/Ag ternary nanocomposites were used as a visible light active photocatalyst for catalytic degradation of rhodamine B (RhB) dye and tetracycline hydrochloride, under natural solar light. The prepared ternary nanocomposites were characterized by using UV-Vis DRS, FT-IR, FESEM, EDX, TEM, XRD, photoluminescence (PL), electrochemical impedance spectroscopy and XPS analytical techniques. The XRD, UV-Vis DRS and FT-IR studies clearly revealed the formation of ternary phases in the composites. From the TEM and EDX studies it was clearly observed that spherical Ag nanoparticles (5-10 nm) and irregular Bi2O3 particles (60-120 nm) were decorated on the surface of 2D S doped g-C3N4 nanosheets. XPS studies also confirmed the formation of the ternary nanocomposite system. The results from the photocatalytic degradation of RhB dye revealed that 95% of the RhB dye was decolorized within 90 min of contact time by Sg-C3N4/Bi2O3/Ag ternary nanocomposites under natural solar light. Among the different prepared photocatalysts, Sg-C3N4/Bi2O3/Ag (15%) was found to be the most efficient photocatalyst towards the decolourization of RhB dye. This result is ascribed to the optimum loading of Ag, formation of a hetero-junction between the ternary phases, more light harvesting capacity and the lowest recombination rate of charge carriers. Apart from the coloured RhB dye, the photocatalytic degradation of the non-coloured tetracycline hydrochloride (TCH) compound was also studied to understand the photosensitization effect on the degradation process. Again scavenger studies were also performed in order to understand the mechanism of photodegradation. It was observed that along with the electron and hole pairs generated by light photons, hydroxide radicals play an important role in the degradation mechanism. The reusability study indicates that the photocatalysts prepared were highly stable at room temperature and can be recycled and reused for up to four successful cycles without a major loss in their performance.
