Porous Al2O3-CNT Nanocomposite Membrane Produced by Spark Plasma Sintering with Tailored Microstructure and Properties for Water Treatment

Optimization of isotropic MoS2/PES membranes for efficient treatment of industrial oily wastewater

Elimination of tiny oil droplets nearly miscible with wastewater can be realized using membrane technology through ultrafiltration. The novelty of this work was to blend different phases of molybdenum disulfide (MoS2) in isotropic polyethersulfone (PES). We prepared isotropic PES membranes by optimizing nonsolvent vapour-induced phase separation (VIPS). Membranes were blended with MoS2 nanosheets of different phases to promote separation performance and antifouling resistance. FE-SEM revealed the flower-like surface morphology of MoS2 nanosheets. HR-TEM of MoS2 revealed 2H domains in the monolayer, flakes of a few layers and a d-spacing of 0.22 nm. Raman spectroscopy could be used to distinguish mixed-phase MoS2 from single-phase MoS2. Isotropic PES membranes modified with 70% 1T/2H MoS2 had a significantly high permeance to pure water (6911 kg m-2 h bar). The same membrane possessed a high efficiency of oil rejection of 98.78%, 97.85%, 99.83% for emulsions of industrial crude oil at 100, 1000 and 10 000 mg L-1, respectively. Removal of oil droplets from wastewater was dominated by a mechanism based on size exclusion. Isotropic PES modified with 2H MoS2 possessed superior oleophilicity, which resulted in low rejection of crude oil. Modified membranes showed excellent fouling resistance for three successive filtration cycles, as evidenced by enhanced antifouling parameters. Our study reveals how the phase composition of MoS2 nanosheets can significantly affect the performance of isotropic PES membranes during the ultrafiltration of oily wastewater.

Spark Plasma Sintering of SiAlON Ceramics Synthesized via Various Cations Charge Stabilizers and Their Effect on Thermal and Mechanical Characteristics

Oxygen-rich SiAlON ceramics doped with various nanosized metal oxide (MO) stabilizers were synthesized with a view to examine their effect on thermal and mechanical characteristics. The nanosized starting powder precursors comprising Si3N4, AlN, Al2O3, and SiO2 along with oxides of Ba, Y, Mg, La, Nd, Eu, Dy, Er, and Yb as the MO charge stabilizer were employed in developing different SiAlON samples. Ultrasonic probe sonication was utilized to develop a homogenous mixture of initial powder precursors followed by spark plasma sintering (SPS) of the samples at the low temperature of 1500 °C coupled with 30 min of isothermal treatment. Sample compositions (according to general formula of alpha SiAlON: Mm/vv+Si12−(m+n)Alm+nOnN16−n) selected in the present study are represented by m value of 1.1 and n value of 1.6. The synthesized samples were evaluated for their physical behavior, microstructural and crystal structure evolution, and thermal and mechanical characteristics. More specifically, the sintered ceramics were examined by X-ray diffraction and electron microscopy to comprehend and relate the structural characteristics with the densification, thermal conductivity, hardness, and fracture toughness. The high reactivity of the nanopowders and the localized heating provided by SPS resulted in densified ceramics with relative densities in the range of 92–96%. Vickers hardness values were found to be in the range of 12.4–17.0 GPa and were seen to be profoundly influenced by the grain size of the alpha SiAlON (primary) phase. The fracture toughness of the samples was measured to be in the range of 4.1–6.2 MPa·m1/2. SiAlON samples synthesized using Er and Yb charge stabilizers were found to have the highest fracture toughness of 5.7 and 6.2 MPa·m1/2, primarily due to the relatively higher content of the elongated beta phase. While there was no obvious relationship between the thermal conductivity and the alpha SiAlON metal charge stabilizers, the values were seen to be influenced by the grain size of alpha phase where Dy-SiAlON had the lowest thermal conductivity of 5.79 W/m⋅K and Er-SiAlON showed the highest value of thermal conductivity (6.91 W/m⋅K). It was concluded that scientifically selected metal oxide charge stabilizers are beneficial in developing SiAlON ceramics with properties tailored according to specific applications.