Pressure and osmotically driven membrane processes: A review of the benefits and production of nano-enhanced membranes for desalination

This review focuses on current research attempts to develop nano-enhanced polymeric desalination membranes. The novel contribution made by this work as compared to many recent reviews on membrane enhancement is that a critical review is made of the effect that the morphological, optical and magnetic properties of the applied nanomaterials have on the efficiency of desalination membranes. The focus on nanomaterials in this review is on both applying new chemical compositions at various concentrations, and also on altering the nanomaterials' morphology and other properties to reach the optimal membrane efficiency for desalination applications. The synthesis route has a major role of tuning the physical and chemical properties of the nanomaterials, and hence, the membrane morphological parameters can be altered, all of which are summarised in this review. The review surveys different types of nanomaterials used for membrane fabrication, such as single elements, metal oxides and nanotubes. Furthermore, mixed oxide composites and polymer/nanomaterial combinations are also considered for membrane enhancement. A wide application range is investigated for modified membranes in pressure and osmotically driven membrane processes for desalination, including reverse osmosis, forward osmosis, osmotically assisted reverse osmosis and pressure assisted forward osmosis

Thermally induced oxygen related defects in eco-friendly ZnFe2O4 nanoparticles for enhanced wastewater treatment efficiencies

Herein, a simple but highly effective strategy of thermal annealing to modulate oxygen vacancies related defects in ZnFe2O4 (ZFO) nanoparticles for obtaining enhanced wastewater treatment efficiencies is reported. The as-prepared nanoparticles were thermally annealed at three different temperatures (500 °C, 600 °C and 700 °C) and their phase purity was confirmed by X-ray diffraction (XRD). All samples were found to exhibit pure phases of ZFO with different crystallite sizes ranging from 10 nm to 25 nm. The transmission electron microscope (TEM) images showed well dispersed nanoparticles and a strong correlation of grain size growth with annealing temperature was established. The optical absorption and emission characteristics were estimated through UV–visible and Photoluminescence (PL) spectroscopy. Raman spectroscopy and X-ray Photoelectron Spectroscopy (XPS) confirmed the variation of oxygen vacancies in the synthesized samples’ lattice. The photocatalytic activities of all samples were investigated and the highest efficiencies were recorded for the ZFO samples annealed at 500 °C. Under high salinity condition, the organic dye degradation efficiency of the same sample remained the highest among all. The excellent dye degradation abilities in ZFO samples can be attributed to the abundance of oxygen vacancies in the crystal lattice that slow down the recombination rate during the photocatalysis process. Moreover, cytotoxicity tests revealed that all prepared ZFO samples showed insignificant cell structure effects on Picochlorum sp microalgae, as verified by Fourier-transform infrared (FTIR) spectroscopy. On the other hand, no significant changes were detected on the viable cell concentration and Chlorophyll a content. This work presents a systematic way to finely tune the crystal sizes and to modulate oxygen related defects in ZFO through a highly effective annealing approach to signify their potential in industrial wastewater and seawater treatment processes