Low fouling ultrathin nanocomposite membranes for efficient removal of manganese

A critical review on ultrasonic-assisted fouling control and cleaning of fouled membranes

Fouling is one of the most challenging problems impacting the performance of membrane-based separation technology. In recent years, ultrasound have been widely applied as an unconventional method to control membrane fouling, as well as to enhance membrane cleaning. The aim of the present work is to review the current literature and the recent developments related to the use of ultrasound as an innovative and alternative approach to improve the fouling behavior of membrane separation processes. The theory underlying ultrasonic-assisted phenomena is reviewed, together with operational factors that influence the effectiveness of the ultrasound treatment, such as frequency, power intensity, pressure, temperature, pH, and operation mode. Ultrasound irradiation effectively aids the cleaning of contaminated surfaces and enhances the permeate flux, owing to cavitation phenomena and powerful convective currents, associated with secondary phenomena, such as microstreamers, shock waves, and heating. However, the lifetime of the membranes should be carefully evaluated when applying ultrasonication as a technique of cleaning or controlling membrane fouling. Indeed, the integrity of membranes after sonication and the control of erosion produced by high ultrasonic intensities are key issues hindering the scale-up of this approach in the membrane industry. This reviews highlights the topics requiring more investigations, specifically to evaluate the economic aspects of ultrasonic assisted fouling control and cleaning in membrane processes.

Evolution of adsorption process for manganese removal in water via agricultural waste adsorbents

Manganese has recently been a topic of interest among researchers, particularly when 1,752 million tonnes of manganese are expected to be produced by the steel industry in 2020. Manganese discharges from industrial effluents have increased manganese contamination in water sources. Its concentrations of more than 0.2 mg/L in the water sources could have negative impacts on human health and the aquatic ecosystem. Thereby, the available water treatment processes face challenges in effectively removing manganese at low cost. In response to these challenges, adsorption has emerged as one of the most practical water treatment processes for manganese removal. In particular, agricultural waste adsorbents received a lot of attention owing to their low cost and high efficiency (99%) in the removal of manganese. Therefore, this paper reviews the removal of manganese by adsorption process using agricultural waste adsorbents. The factors affecting the adsorption process, the mechanisms, and the performances of the adsorbents are elucidated in detail.

The effect of Merpol surfactant on the morphology and performance of PES/PVP membranes: antibiotic separation

The present study used modified nanofiltration (NF) membranes to remove the emerging contaminant of amoxicillin (AMX) from synthetic wastewater. For this purpose, Merpol surfactant and polyvinylpyrrolidone were added to the casting solutions to prepare flat sheet asymmetric polyethersulfone (PES) NF membranes through phase inversion process. Then, the effect of adding Merpol surfactant at different concentrations on the morphology, hydrophilicity, and pure water flux (PWF) of the membranes, as well as the separation of AMX from aqueous solutions was investigated. The characteristics of the prepared membranes were studied by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), contact angle (CA) measurement and performance tests. The obtained results approved the improved hydrophilicity of the PES membranes after adding Merpol surfactant to the casting solution. The findings also revealed a gradual increase in the average size of the membrane pores in sub-layer and thinner top layer, proportional to the increase of surfactant content in the solution. The results also confirmed the increase of PWF under the influence of surfactant increase. As a result, for the membrane containing 8 wt% Merpol additive, the lowest CA (52.08°), the highest PWF (76.31 L/m2 h), and maximum AMX excretion (97%) were achieved.

Multifunctional graphene oxide loaded nanofibrous membrane for removal of dyes and coliform from water

In this study, we fabricated a trifunctional polyurethane (PU)/graphene oxide (GO) electrospun membrane for adsorption of organic dyes such as methylene blue (MB) and rhodamine B (RB). Moreover, the prepared membrane showed antifouling property and inhibition against bacteria. The GO modified PU nanofiber shows a maximum adsorption capacity of 109.88  mg/g and 77.15 mg/g towards MB and RB respectively. Theoretical studies confirmed that the dye adsorption is followed pseudo-second-order kinetics and the Langmuir adsorption isotherm. The superhydrophilic PU/10GO membrane exhibits high water flux of 17,706 lm^-2hr^-1. This membrane also exhibits good antifouling property for separating oil-in-water emulsions with 99.99% separation efficiency. The Mechanism of antifouling was investigated using Hermia model. The results showed that PU/GO membranes also have antibacterial activity against Gram-negative and Gram-positive bacterias. Thus a superhydrophilic nanofibrous antifouling membrane that can reject both organic dye molecule and bacteria from contaminated water is developed using simple electrospinning technique.