Microalgae-Enabled Wastewater Remediation and Nutrient Recovery through Membrane Photobioreactors: Recent Achievements and Future Perspective.

The use of microalgae for wastewater remediation and nutrient recovery answers the call for a circular bioeconomy, which involves waste resource utilization and ecosystem protection. The integration of microalgae cultivation and wastewater treatment has been proposed as a promising strategy to tackle the issues of water and energy source depletions. Specifically, microalgae-enabled wastewater treatment offers an opportunity to simultaneously implement wastewater remediation and valuable biomass production. As a versatile technology, membrane-based processes have been increasingly explored for the integration of microalgae-based wastewater remediation. This review provides a literature survey and discussion of recent progressions and achievements made in the development of membrane photobioreactors (MPBRs) for wastewater treatment and nutrient recovery. The opportunities of using microalgae-based wastewater treatment as an interesting option to manage effluents that contain high levels of nutrients are explored. The innovations made in the design of membrane photobioreactors and their performances are evaluated. The achievements pave a way for the effective and practical implementation of membrane technology in large-scale microalgae-enabled wastewater remediation and nutrient recovery processes.

Visible-light-driven photocatalytic PVDF-TiO2/CNT/BiVO4 hybrid nanocomposite ultrafiltration membrane for dairy wastewater treatment.

Enhancing the performance of polymeric membranes by nanomaterials has become of great interest in the field of membrane technology. The present work aimed to fabricate polyvinylidene fluoride (PVDF)-hybrid nanocomposite membranes and modify them with TiO2 and/or BiVO4 nanoparticles and/or carbon nanotubes (CNTs) in various ratios. Their photocatalytic performance under visible light was also investigated. All modified PVDF membranes exhibited higher hydrophilicity (lower contact angle of water droplets) than that of the neat membrane used as a reference. The membranes were characterized by using bovine serum albumin (BSA) as model dairy wastewater. The hybrid membranes had better antifouling properties as they had lower irreversible filtration resistance than that of the neat membrane. Hybrid PVDF membranes containing TiO2/CNT/BiVO4 showed the highest flux and lowest irreversible resistance during the filtration of the BSA solution. PVDF-TiO2/BiVO4 had the highest flux recovery ratio under visible light (70% for the PVDF mixed with 0.5% TiO2 and 0.5% BiVO4). The hydrophilicity of membrane surfaces increased with the incorporation of nanoparticles, preventing BSA to bind to the surface. This resulted in a slight decrease in BSA and chemical oxygen demand rejections, which were still above 97% in all cases.

Statistical Analysis of Synthesis Parameters to Fabricate PVDF/PVP/TiO2 Membranes via Phase-Inversion with Enhanced Filtration Performance and Photocatalytic Properties.

Non-solvent induced phase-inversion is one of the most used methods to fabricate membranes. However, there are only a few studies supported by statistical analysis on how the different fabrication conditions affect the formation and performance of membranes. In this paper, a central composite design was employed to analyze how different fabrication conditions affect the pure water flux, pore size, and photocatalytic activity of polyvinylidene fluoride (PVDF) membranes. Polyvinylpyrrolidone (PVP) was used to form pores, and titanium dioxide (TiO2) to ensure the photocatalytic activity of the membranes. The studied bath temperatures (15 to 25 °C) and evaporation times (0 to 60 s) did not significantly affect the pore size and pure water flux of the membranes. The concentration of PVDF (12.5 to 17.5%) affected the viscosity, formation capability, and pore sizes. PVDF at high concentrations resulted in membranes with small pore sizes. PVP affected the pore size and should be used to a limited extent to avoid possible hole formation. TiO2 contents were responsible for the decolorization of a methyl orange solution (10-5 M) up to 90% over the period studied (30 h). A higher content of TiO2 did not increase the decolorization rate. Acidic conditions increased the photocatalytic activity of the TiO2-membranes.

Intensification of the ultrafiltration of real oil-contaminated (produced) water with pre-ozonation and/or with TiO2, TiO2/CNT nanomaterial-coated membrane surfaces.

In the present study, commercial PES, PVDF, PTFE ultrafilter membranes, and two different nanomaterial (TiO2 and TiO2/CNT composite)-covered PVDF ultrafilter membranes (MWCO = 100 kDa) were used for the purification of an industrial oil-contaminated (produced) wastewater, with and without ozone pretreatment to compare the achievable fouling mitigations by the mentioned surface modifications and/or pre-ozonation. Fluxes, filtration resistances, foulings, and purification efficiencies were compared in detail. Pre-ozonation was able to reduce the total filtration resistance in all cases (up to 50%), independently from the membrane material. During the application of nanomaterial-modified membranes were by far the lowest filtration resistances measured, and in these cases, pre-ozonation resulted in a slight further reduction (11-13%) of the total filtration resistance. The oil removal efficiency was 83-91% in the case of commercial membranes and > 98% in the case of modified membranes. Moreover, the highest fluxes (301-362 L m-2 h-1) were also measured in the case of modified membranes. Overall, the utilization of nanomaterial-modified membranes was more beneficial than pre-ozonation, but with the combination of these methods, slightly higher fluxes, lower filtration resistances, and better antifouling properties were achieved; however, pre-ozonation slightly decreased the oil removal efficiency.

Biomass-Derived Dialdehyde Cellulose Cross-linked Chitosan-Based Nanocomposite Hydrogel with Phytosynthesized Zinc Oxide Nanoparticles for Enhanced Curcumin Delivery and Bioactivity.

A sustainable biomass-based nanocomposite hydrogel was formulated, characterized, and applied for curcumin delivery. Phytosynthesized zinc oxide nanoparticles (ZnO NPs) employing musk melon (Cucumis melo) seed extract was embedded in the hydrogel matrices and cross-linked using Dialdehyde cellulose prepared from sugarcane (Saccharum officinarum) bagasse (SCB). Nanoparticle incorporation enhanced the hydrogel's swelling degree to 4048% at pH 4.0. Also, an improved tensile strength of 14.1 ± 0.32 MPa was exhibited by the nanocomposite hydrogel compared to 9.79 ± 0.76 MPa for the pure chitosan cellulose hydrogel. A curcumin loading efficiency of 89.68% with around 30% increased loading was exhibited for the nanocomposite hydrogel. A Fickian diffusion-controlled curcumin release mechanism with maximum release at pH 7.4 was obtained. The synergistic effect on the antimicrobial activity was exhibited against Staphylococcus aureus and Trichophyton rubrum. The in vitro cytotoxicity studies employing L929 cells and A431 cells demonstrated good biocompatibility and enhanced anticancer activity of the curcumin-loaded green nanocomposite hydrogel compared to pure curcumin.

Nanoparticle- and Nanoporous-Membrane-Mediated Delivery of Therapeutics.

Pharmaceutical particulates and membranes possess promising prospects for delivering drugs and bioactive molecules with the potential to improve drug delivery strategies like sustained and controlled release. For example, inorganic-based nanoparticles such as silica-, titanium-, zirconia-, calcium-, and carbon-based nanomaterials with dimensions smaller than 100 nm have been extensively developed for biomedical applications. Furthermore, inorganic nanoparticles possess magnetic, optical, and electrical properties, which make them suitable for various therapeutic applications including targeting, diagnosis, and drug delivery. Their properties may also be tuned by controlling different parameters, e.g., particle size, shape, surface functionalization, and interactions among them. In a similar fashion, membranes have several functions which are useful in sensing, sorting, imaging, separating, and releasing bioactive or drug molecules. Engineered membranes have been developed for their usage in controlled drug delivery devices. The latest advancement in the technology is therefore made possible to regulate the physico-chemical properties of the membrane pores, which enables the control of drug delivery. The current review aims to highlight the role of both pharmaceutical particulates and membranes over the last fifteen years based on their preparation method, size, shape, surface functionalization, and drug delivery potential.

Enhancement of antibacterial properties of silver nanoparticles-ceftriaxone conjugate through Mukia maderaspatana leaf extract mediated synthesis.

Green synthesis of nanoparticles with low range of toxicity and conjugation to antibiotics has become an attractive area of research for several biomedical applications. Nanoconjugates exhibited notable increase in biological activity compared to free antibiotic molecules. With this perception, we report the biosynthesis of silver nanoparticles using aqueous extract of leaves of Mukia maderaspatana and subsequent conjugation of the silver nanoparticles to antibiotic ceftriaxone. The leaves of this plant are known to be a rich source of phenolic compounds with high antioxidant activity that are used as reducing agents. The size, morphology, crystallinity, composition of the synthesized silver nanoparticles and conjugation of ceftriaxone to silver nanoparticles were studied using analytical techniques. The activity of the conjugates against Bacillus subtilis (MTCC 1790), Klebsiella pneumoniae (MTCC 3384), Staphylococcus aureus (ATCC 25923), and Salmonella typhi (MTCC 3224) was compared to ceftriaxone and unconjugated nanoparticles using disc diffusion method. The effect of silver nanoparticles on the reduction of biofilms of Pseudomonas fluorescens (MTCC 6732) was determined by micro plate assay method. The antioxidant activities of extract, silver nitrate, silver nanoparticles, ceftriaxone and conjugates of nanoparticles were evaluated by radical scavenging 1, 1- diphenyl-2-picrylhydrazyl test. Ultraviolet visible spectroscopy and Fourier transform infrared spectroscopy confirmed the formation of metallic silver nanoparticles and conjugation to ceftriaxone. Atomic force microscopy, transmission electron microscopy and particle size analysis showed that the formed particles were of spherical morphology with appreciable nanosize and the conjugation was confirmed by slight increase in surface roughness. The results thus showed that the conjugation of ceftriaxone with silver nanoparticles has better antioxidant and antimicrobial effects than ceftriaxone and unconjugated nanoparticles. It can be suggested that M. maderaspatana mediated nanoparticle-ceftriaxone conjugate can be used effectively in the production of potential antioxidant and antimicrobial agents. The present study offers a significant overview to the development of novel antimicrobial nanoparticles.