Effective desalination of heavy metal ions from industrial effluents is a challenge mainly due to the existing methods of separation technologies that are energy-intensive, have poor economics of scale, and generate a large amount of sludge. The application of gas hydrate-based technology for the desalination of heavy metals is a promising approach because it generates no sludge and is a relatively green process. In a hydrate-based desalination approach, suitable hydrate-forming guests, a sII hydrate former, interact with water by weak van der Waals forces to produce solid hydrate crystals by excluding the salts and other impurities from an aqueous heavy metal ions solution. As5+, Pb2+, Cd2+, and Cr3+ are common heavy metal ions found in industrial effluents that were individually chosen to prepare a 1000 ppm salt solution. In this work, natural gas was used as the hydrate-forming gas along with cyclopentane (CP) because of its immiscibility in water. The presence of CP also reduces the operating conditions for hydrate formation. CP was used at two different concentrations (6 and 1 mol %), and the kinetics of hydrate formation was further improved by the addition of edible surfactant lecithin to the hydrate-forming solution. The gas uptake kinetics, water to hydrate conversion, and rate of water recovery were studied. Superior kinetics of hydrate growth were observed with 6 mol % CP compared to 1 mol % CP. Also, the addition of a benign additive, lecithin, enhances the kinetics of hydrate formation, resulting in efficient desalination of salt ions. The kinetics of As5+ desalination was the fastest among those of the four selected metal ions.

Zinc oxide (ZnO)-polycarbonate (PC) nanocomposite films were prepared by blade coating method by using pre-synthesized spherical ZnO nanoparticles of 15-20 nm size and pre-dissolved polycarbonate. The blend was homogenized by sonication and the films were dried in an oven at moderate temperature. Various films with different % loading of ZnO nanoparticles in PC were prepared and their effect on antibacterial properties was studied. It is observed that increasing wt-% loading of ZnO nanoparticles in PC leads to enhanced antibacterial properties against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). The freshly prepared ZnO nanoparticles were thoroughly characterized by XRD, SEM, UV-visible and photoluminescence spectroscopy before their use in preparing nanocomposite films. Contact angle measurement of the films was studied to ascertain their hydrophobic behavior. Such nanocomposite films have potential in various packaging applications because of their effective antibacterial and UV-blocking properties and hydrophobic nature.

Simultaneous in situ reduction of hexachloroplatinic acid by the amine group in the pyrrole monomer and oxidation of pyrrole to form polypyrrole (PPy) was examined. The reactions were performed at various temperatures to understand the degree of reduction of platinum precursor as well as doping of polypyrrole with Pt(II) chloro-complex. Spectroscopic images revealed different morphologies for the Pt/PPy nano-composite prepared at various temperatures. The as-prepared Pt/PPy nano-composite samples were tested for their ability to sense liquefied petroleum gas (LPG) which resulted in excellent sensing at relatively low temperature. The porous nature and ohmic contact between the PPy and platinum nanoparticles makes the as-prepared Pt/PPy nano-composite highly useful for sensors as well as electronic applications.

This study investigates the kinetics and morphology of an equimolar CO2–CH4 gas mixture by inducing sI and sH hydrates in gas–water and gas–liquid hydrocarbon (LHC)–water systems using pure water and sH hydrate former cyclooctane (Cyclo-O) at 274 K and 5.0 MPa in a quiescent system. Further, the effect of promoter l-tryptophan in enhancing the kinetics is evaluated for both systems. The visual morphology observations provide mechanistic insights into the hydrate crystal nucleation and growth kinetics in the presence of pure water, 1 wt % tryptophan, 2.86 mol % Cyclo-O, and 1 wt % tryptophan with 2.86 mol % Cyclo-O. Distinct variations in the kinetics and morphology of hydrate crystal growth in aqueous bulk solution depend on the type of additive used. Swordlike elongated polygons were observed in the pure water system at the gas–liquid interface. As time progressed, the smooth polygonal shape was observed in the gas phase, and the evolution of swordlike to larger polygons was observed at the gas–liquid interface. The addition of 1 wt % tryptophan to the gas–liquid system led to significant gas uptake and rapid hydrate formation rate compared to the pure water system and that was evident by morphology study as well. Whereas, in the case of the gas–LHC–water system, the presence of water-insoluble Cyclo-O provides resistance to mass transfer between the gas and the bulk water phase; however, hydrate formation involves only dissolved guest gas molecules that could travel through the Cyclo-O layer in quiescent conditions, showing cloudlike hydrate formation. The addition of 1 wt % tryptophan with 2.86 mol % Cyclo-O aids inducing a growing front by bridging the hydrophobic Cyclo-O layer and enhances gas uptake and hydrate formation rate significantly compared to the water–Cyclo-O system. The significant increase in gas uptake in the presence of tryptophan was assigned to the porous hydrate formation, which enhanced the gas–water contact.