Designing biopolymer-based artificial peroxidase for oxidative removal of dibenzothiophene from a model diesel fuel.

Naturally occurring peroxidases are important for living organisms and have manifold utility in industries. However, lack of stability in harsh reaction conditions hinders wide applicability of such enzymes. Thus, suitable alternative is vital which can endure severe reaction conditions. As a substitute of natural peroxidase, herein, biopolymer-based polyelectrolyte complexes (PECs) coordinated with Fen+ is proposed as macromolecular peroxidase mimicking systems. Three PECs were engineered via complexation of protonated chitosan and alginate with Fe2+ (Fe2+-PEC), Fe3+ (Fe3+-PEC), and Fe3O4 (Fe3O4-PEC), respectively. Computational study showed the Fe3+-PEC was highly stable with abundant electrostatic and intramolecular hydrogen bonding interactions. The versatility of the Fe-PECs as artificial peroxidase biocatalysts was probed by two types of peroxidase assays - ABTS oxidation in buffer systems (pH 4.0 and 7.0) and pyrogallol oxidation in organic solvents (acetonitrile, ethyl acetate and toluene). Overall, Fe3+-PEC showed remarkably high peroxidase activity both in aqueous buffers and in organic solvents, whereas, Fe3O4-PEC showed least catalytic activity. Finally, as a proof of concept, the ability of the biocatalyst to carry out deep oxidative desulphurization was demonstrated envisaging removal of dibenzothiophene from model fossil fuel in a sustainable way.

Membrane-based separation of potential emerging pollutants.

The potential emerging pollutants (PEPs) such as hazardous chemicals, toxic metals, bio-wastes, etc., pose a severe threat to human health, hygiene and ecology by way of polluting the environment and water sources. The PEPs are originated from various industrial effluent discharges including pharmaceutical, food and metal processing industries. These PEPs in contact with water may pollute the water and disturb the aquatic life. Innumerable methods have been used for the treatment of effluents and separating the toxic chemicals/metals. Of these methods, membrane-based separation processes (MBSPs) are effective over the conventional techniques for providing clean water from wastewater streams at an affordable cost with minimum energy requirement. Microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), reverse osmosis (RO), and forward osmosis (FO) methods as well as hybrid technologies are discussed citing the published results of the past decade.

Solvent-free production of nano-FeS anchored graphene from Ulva fasciata: A scalable synthesis of super-adsorbent for lead, chromium and dyes.

Here we demonstrate, a simple and solvent-free synthetic route for the production of FeS/Fe(0) functionalized graphene nanocomposite (G-Fe) via a one-step pyrolysis of seaweed biomass (Ulva fasciata). It is proposed that the natural abundance of both inorganic and organic sulfur in the seaweed induces the reduction of exfoliated graphitic sheets at elevated temperatures. FeCl3 was employed both as the iron precursor as well as the templating agent. Iron doping played a dual-faceted role of exfoliating as well as activating agent, producing composite with high adsorption capacity for Pb2+ (645 ±â€¯10 mg/g), CR (970 mg/g), CV(909 mg/g), MO (664 mg/g), MB (402 mg/g) dyes and good recyclability (8 cycles). Pb2+ adsorption was irreversible even at low pH values and the spent composite (G-Fe-Pb) was utilized for efficient Cr(IV) removal (Ì´100 mg/g). The adsorption data followed the pseudo second order kinetics while the equilibrium data fitted perfectly into the Langmuir adsorption equation. Further, a thin layer of composite was deposited on a filter paper by vacuum filtration which was tested under continuous filtration mode for RB5 dye removal. Preliminary results highlight the potential of this composite to be used in pretreatment steps in hybrid membrane processes for filtration of complex wastewater feeds.

Chitosan-Based Aerogel Membrane for Robust Oil-in-Water Emulsion Separation.

Here, we demonstrate direct recovery of water from stable emulsion waste using aerogel membrane. Chitosan-based gel was transformed into highly porous aerogel membrane using bio-origin genipin as cross-linking agent. Aerogel membranes were characterized for their morphology using SEM, chemical composition by FTIR and solid-UV. Further, aerogel was tested for recovery of high quality water from oil spill sample collected from ship breaking yard. High quality (with >99% purity) water was recovered with a flux rate of >600 L·m(-2)·h(-1)·bar(-1). After repeated use, aerogel membranes were tested for greener disposal possibilities by biodegrading membrane in soil.

Distillery wastewater treatment by the membrane-based nanofiltration and reverse osmosis processes.

A hybrid nanofiltration (NF) and reverse osmosis (RO) pilot plant was used to remove the color and contaminants of the distillery spent wash. The feasibility of the membranes for treating wastewater from the distillery industry by varying the feed pressure (0-70 bar) and feed concentration was tested on the separation performance of thin-film composite NF and RO membranes. Color removal by NF and a high rejection of 99.80% total dissolved solids (TDS), 99.90% of chemical oxygen demand (COD) and 99.99% of potassium was achieved from the RO runs, by retaining a significant flux as compared to pure water flux, which shows that membranes were not affected by fouling during wastewater run. The pollutant level in permeates were below the maximum contaminant level as per the guidelines of the World Health Organization and the Central Pollution Control Board specifications for effluent discharge (less than 1,000 ppm of TDS and 500 ppm of COD).