Current issues and potential solutions for the electrospinning of major polysaccharides and proteins: A review.

Biopolymers, especially polysaccharides and proteins, are the promising green replacement for petroleum based polymers. Due to their innate properties, they are effectively used in biomedical applications, especially tissue engineering, wound healing, and drug delivery. The fibrous morphology of biopolymers is essentially required for the effectiveness in these biomedical applications. Electrospinning (ES) is the most advanced and robust method to fabricate nanofibers (NFs) and provides a complete solution to the conventional methods issues. However, the major issues regarding fabricating polysaccharides and protein nanofibers using ES include poor electrospinnability, lack of desired fundamental properties for a specific application by a single biopolymer, and insolubility among common solvents. The current review provides the main strategies for effective electrospinning of the major biopolymers. The key strategies include blending major biopolymers with suitable biopolymers and optimizing the solvent system. A systematic literature review was done to provide the optimized solvent system of the major biopolymers along with their best possible biopolymeric blend for ES. The review also highlights the fundamental issues with the commercialization of ES based biomedical products and provides future directions to improve the fabrication of biopolymeric nanofibers.

Interspecies microbial interactions in bioelectrochemical system and biodegradation: A state of the art review.

Microbial mutualistic interaction or synthetic microbiology evolves closely from the concept of cell-cell relations in a complex microbial community, which plays a crucial role in waste degradation, bioremediation, and bioenergy generation. Recently, the application of synthetic microbial consortia has renewed attention in the field of bioelectrochemistry. In the past few years, the influence of microbial mutualistic interaction has been extensively studied in bioelectrochemical systems (BES), especially in microbial fuel cells (MFCs). Nevertheless, synthetic microbial consortia were found to exhibit superior bioremediation performance compared to single strains of microbes for polycyclic aromatic hydrocarbons, synthetic dyes, polychlorinated biphenyls, and other organic pollutants compared to the respective single microbial species. However, a comprehensive understanding of intermicrobial interactions, specifically the metabolic pathways in a mixed-cultured microbial community system, is still lacking. In this study, we have comprehensively reviewed the possible pathways for executing intermicrobial communication within a complex microbial community consortium with various underlying pathways. The influence of mutualistic interactions on the power generation of MFCs and wastewater biodegradation has been widely reviewed. We argue that this study would motivate the design and construction of potential synthetic microbial consortia to stimulate the extraction of bioelectricity and the biodegradation of contaminants.

Performance of Hypersaline Brine Desalination Using Spiral Wound Membrane: A Parametric Study.

Desalination of hypersaline brine is known as one of the methods to cope with the rising global concern on brine disposal in high-salinity water treatment. However, the main problem of hypersaline brine desalination is the high energy usage resulting from the high operating pressure. In this work, we carried out a parametric analysis on a spiral wound membrane (SWM) module to predict the performance of hypersaline brine desalination, in terms of mass transfer and specific energy consumption (SEC). Our analysis shows that at a low inlet pressure of 65 bar, a significantly higher SEC is observed for high feed concentration of brine water compared with seawater (i.e., 0.08 vs. 0.035) due to the very low process recovery ratio (i.e., 1%). Hence, an inlet pressure of at least 75 bar is recommended to minimise energy consumption. A higher feed velocity is also preferred due to its larger productivity when compared with a slightly higher energy requirement. This study found that the SEC reduction is greatly affected by the pressure recovery and the pump efficiencies for brine desalination using SWM, and employing them with high efficiencies (ηR ≥ 95% and ηpump ≥ 50%) can reduce SEC by at least 33% while showing a comparable SEC with SWRO desalination (<5.5 kWh/m3).

Hydrogen production via photoreforming of wastewater under LED light-driven over CuO@exfoliated g-C3N4 nanoheterojunction.

As the global interest heading towards net zero emission by 2050, clean hydrogen production technologies becomes limelight among the research community. Besides, the generation of large quantity of industrial wastewaters creates huge dilemma and needs special attention. In this work, synthetic wastewater using formaldehyde (FA) as a model organic pollutant was utilized to produce hydrogen. The photocatalyst, CuO@exfoliated g-C3N4 nanoheterojunction was synthesized by an acid treatment and facile chemical precipitation technique. XRD results confirmed the successful formation of exfoliated g-C3N4 by expanding the interlayer spacing of the nanosheets via shifting of characteristic peak of graphite towards lower 2θ from 27.97° to 27.04°. Meanwhile, the BET surface area of CuO@exfoliated g-C3N4 (199.3 m2/g) was remarkably enhanced as compared to bulk g-C3N4 (34.5 m2/g) and exfoliated g-C3N4 (104.4 m2/g). The existence of large pores (3.55 cm3/g) in CuO@exfoliated g-C3N4 promotes the accessibility of reactant to the surface active sites, escalating the redox reactions. Study on hydrogen production via photoreforming of aqueous formaldehyde over the prepared photocatalysts were conducted. Interestingly, hydrogen generated using CuO@exfoliated g-C3N4 (3867 µmol/g) was greatly enhanced by 7 times and 13 times than the counterparts catalysts, exfoliated g-C3N4 (532 µmol/g) and pure CuO (271 µmol/g) respectively. By employing the CuO@exfoliated g-C3N4 nanoheterojunction, the optimum hydrogen with apparent quantum efficiency (AQE) of 5664 µmol/g and 22% were obtained respectively. Besides, S-scheme reaction mechanism was proposed based on heterojunction formed between the p-type CuO and n-type exfoliated g-C3N4 nanosheets.

Augmentation of microbial fuel cell and photocatalytic polishing technique for the treatment of hazardous dimethyl phthalate containing wastewater.

In the present paper, the potentiality of integrating microbial fuel cells (MFCs) with a photocatalytic reactor to maximize the wastewater treatment efficiency with concurrent power generation was explored. Dimethyl phthalate (DMP) and acetic acid (AA) were the employed substrate and the co-substrate, respectively, using Pseudomonas aeruginosa as a biocatalyst. MFCs operated by single substrate showed the maximum power generation of 0.75-3.84 W m-3 whereas an addition of AA as the co-substrate yielded 3-12 fold higher power generation. Pseudomonas aeruginosa produced phenazine-1-carboxylic acid in DMP-fed MFC as the metabolite whereas AA along with DMP yielded pyocyanin which reduced the charge transfer resistance. Chemical oxygen demand (COD) removal efficiency in the MFCs was circa 62% after 11 days of operation. Thereafter, it further increased albeit with a drastic reduction in power generation. Subsequently, the MFC anolyte was treated in a photocatalytic reactor under visible light irradiation and catalyzed by CuO-gC3N4. The performance of photocatalytic reactor was evaluated, with COD and total organic carbon (TOC) removal efficiency of 88% and 86% after 200 min of light irradiation. The present work suggests that the MFC can be integrated with photocatalysis as a sustainable wastewater treatment method with concurrent power generation.

Microbial synergistic interactions enhanced power generation in co-culture driven microbial fuel cell.

An understanding of the inter-species relationships, especially their metabolic network in a mixed-culture system, is crucial to design an effective inoculum for enhancing the power generation of wastewater fed microbial fuel cell (MFC). In the present study, the influence of microbial mutualistic interactions on the power generation of palm oil mill effluent fed MFCs has been widely investigated by designing several co-culture and mixed culture inoculums. Among the different inoculum compositions, the highest power density of 14.8 W/m3 was achieved by Pseudomonas aeruginosa and Klebsiella variicola co-culture inoculum due to their synergistic relationships which were inter-linked via fermentation-based metabolites. Besides, the interaction of K. variicola and Bacillus cereus positively influenced the power generation resulting in a maximum power density of 11.8 W/m3 whereas the antagonistic relationship between B. cereus and P. aeruginosa resulted in a lower power generation of 1.9 W/m3. The microbial mutualistic interactions were investigated with polarization, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), as well as by using metabolite and biofilm analysis. It was observed that the synergism between bacteria enhanced power generation through the production of higher electron shuttling mediators and efficient biofilm formation as evidenced by polarization, CV and EIS analysis. In contrast, the antagonistic relationship resulted in production of cell inhibiting metabolites leading to the formation of ineffective biofilm. These findings demonstrate that the synergistic interaction between or within microorganisms is emergent in designing co-culture or mixed-culture inoculum for achieving maximum power generation in MFCs.

Bio-electrochemical power generation in petrochemical wastewater fed microbial fuel cell.

The petrochemical wastewater (PCW) from acrylic acid plants possesses a very high chemical oxygen demand (COD) due to the presence of acrylic acid along with other organic acids. The treatment of PCW by conventional aerobic and anaerobic methods is energy intensive. Therefore, the treatment of PCW with concurrent power generation by employing microbial fuel cell (MFC) could be a potential alternative to solve the energy and environmental issues. This study demonstrates the potentiality of PCW from acrylic acid plant with an initial COD of 45,000 mg L-1 generating maximum power density of 850 mW m-2 at a current density of 1500 mA m-2 using acclimatized anaerobic sludge (AS) as biocatalyst. The predominant microbes present in acclimatized AS were identified using Biolog GEN III analysis, which include the electrogenic genera namely Pseudomonas spp. and Bacillus spp. along with methanogenic archea Methanobacterium spp. The mechanism of electron transfer was elucidated by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) which clearly demonstrated the natural metabolite-based electron transfer across the electrode/biofilm/solution interface. The abundance of the electron shuttle metabolites was increased with the microbial growth in the bulk solution as well as in the biofilm leading to a high power generation. The COD removal efficiency and the coulombic efficiency (CE) were found to be 40% and 21%, respectively after 11 days of operation using initial COD of 45,000 mg L-1. The low COD removal efficiency could drastically be increased to 82% when the initial COD of PCW was 5000 mg L-1 generating a power density of 150 mW m-2. The current work proves the feasibility of the MFC for the treatment of acrylic acid plant PCW using acclimatized anaerobic sludge (AS) as a biocatalyst.

Cellulose Supported Pd(II) Complex Catalyzed Carbon-Carbon Bonds Formation.

Corn-cobs are an agro-industrial waste and composed of cellulose mostly. In this study cellulose was isolated from the waste corn-cobs and modified to polymeric hydroxamic acid palladium complex 1 and characterized by using a variety of spectroscopic methods such as field emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The complex 1 exhibited high catalytic activity towards Suzuki and Heck coupling reactions of activated and deactivated aryl halides to give the respective coupling products with high yield. Moreover, the complex 1 was recovered and recycled five times with no considerable loss of catalytic overall performance.

Adsorption of methylene blue from aqueous solution by jackfruit (Artocarpus heteropyllus) leaf powder: A fixed-bed column study.

Continuous fixed-bed studies were undertaken to evaluate the efficiency of jackfruit leaf powder (JLP) as an adsorbent for the removal of methylene blue (MB) from aqueous solution under the effect of various process parameters like bed depth (5-10cm), flow rate (30-50mL/min) and initial MB concentrations (100-300mg/L). The pH at point of zero charge (pH(PZC)) of the adsorbent was determined by the titration method and a value of 3.9 was obtained. A FTIR of the adsorbent was done before and after the adsorption to find the potential adsorption sites for interaction with methylene blue molecules. The results showed that the total adsorbed quantities and equilibrium uptake decreased with increasing flow rate and increased with increasing initial MB concentration. The longest breakthrough time and maximum MB adsorption were obtained at pH 10. The results showed that the column performed well at low flow rate. Also, breakthrough time and exhaustion time increased with increasing bed depth. The bed-depth service time (BDST) model and the Thomas model were applied to the adsorption of MB at different bed depths, flow rates, influent concentrations and pH to predict the breakthrough curves and to determine the characteristic parameters of the column that are useful for process design. The two model predictions were in very good agreement with the experimental results at all the process parameters studied indicating that they were very suitable for JLP column design.