Valorization of Oceanic Waste Biomass: A Catalytic Perspective.

Efficacious waste utilization is vital in context of sustainability. The past decade has witnessed attempts of usage of land biomass and wastes for various applications, contributing towards a sustainable society. Exploitation of the marine biomass, which does not compete with habitation and food production like land biomass has been largely unnoticed and therefore not being utilized judiciously. Researchers have mainly exploited these resources as functional materials having significant potential applications. However, a catalytic perspective for the valorisation of these polymers arising from oceanic waste widens their scope and ameliorates its use. The objective of the present review is to demonstrate the effectiveness of chitin/chitosan as a catalyst and as a feedstock for deriving important fuels and chemicals. It displays all the reactions heterogeneously catalyzed by them along with the strategic methodology. Their important catalytic organic transformations attempted so far, have also been discussed. The future perspectives are also presented which if inculcated would improve the value addition of the waste, paving a way for greener and imperishable world.

Antibacterial activities of Nd doped and Ag coated TiO2 nanoparticles under solar light irradiation.

Nanosized (8-9 nm) Nd doped and Ag coated TiO(2) nanoparticles have been synthesized by sol-gel method. The physicochemical properties of these particles were investigated by X-ray diffraction (XRD), diffuse reflectance UV-visible (DRUV) spectra and Brunauer-Emmett-Teller (BET) surface area analysis. The antibacterial activities of the samples were studied for Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) both, under the light and dark conditions. The results reveal that the extent of activity shows the order as undoped TiO(2)

Silver nanoparticles embedded polymer sorbent for preconcentration of uranium from bio-aggressive aqueous media.

Adsorptive sorbent for bio-aggressive natural aqueous media like seawater was developed by one pot simultaneous synthesis of silver nanoparticles (Ag nps) and poly(ethylene glycol methacrylate phosphate) (PEGMP) by UV-initiator induced photo-polymerization. The photo-polymerization was carried out by irradiating N,N'-dimethylformamide (DMF) solution containing appropriate amounts of the functional monomer (ethylene glycol methacrylate phosphate), UV initiator (α,α'-dimethoxy-α-phenyl acetophenone), and Ag(+) ions with 365 nm UV light in a multilamps photoreactor. To increase mechanical strength, nano-composite sorbent (Ag@PEGMP) was also reinforced with thermally bonded non-woven poly(propylene) fibrous sheet. Transmission electron microscopy (TEM) of the nano-composite sorbent showed uniform distribution of spherical Ag nanoparticles with particles size ranging from 3 to 6 nm. The maximum amount of Ag(0) that could be anchored in the form of nanoparticles were 5±1 and 10±1 wt.% in self-supported PEGMP and poly(propylene) reinforced PEGMP matrices, respectively. Ag@PEGMP sorbent was found to be stable under ambient conditions for a period of six months. Ag@PEGMP composite sorbent did not exhibit growth at all after incubation with pre-grown Escherichia coli cells, and showed non-adherence of this bacteria to the composite. This indicated that composite sorbent has the bio-resistivity due to bacterial repulsion and bactericidal properties of Ag nanoparticles embedded in the PEGMP. Sorption of U(VI) in PEGMP and Ag@PEGMP nano-composite sorbents from well-stirred seawater was studied to explore the possibility of using it for uranium preconcentration from bio-aggressive aqueous streams. The nano-composite sorbent was used to preconcentrate U(VI) from a process aqueous waste stream.

Elucidation of the role of hexamine and other precursors in the formation of magnetite nanorods and their stoichiometry.

Hexamine is known to assist anisotropic growth of metal oxides and the same is also found to be true for magnetite nanosynthesis. In this work we elucidate the role of hexamine and other precursors in the formation of magnetite nanorods by the hydrothermal route and their stoichiometry. Various others hydrolyzing agents such as sodium hydroxide (NaOH), sodium hydroxide + hexamine, ammonia (NH(3)), ammonia + formaldehyde are also studied. The synthesized nanoparticles are characterized with the help of various techniques such as X-ray diffraction (XRD), FT-IR spectroscopy, UV-VIS-NIR spectroscopy, transmission electron microscopy (TEM), Mössbauer spectroscopy and SQUID magnetization measurements. It is found that only when ferric chloride, ferrous ammonium sulfate (FAS) and hexamine are used, well defined nanorods are formed. When sodium hydroxide and hexamine are used as a hydrolyzing system nearly spherical nanoparticles with small size (approximately 13 nm) are formed, as compared to the case of sodium hydroxide alone which leads to bigger cube like nanoparticles. Interestingly the decomposition products of hexamine do not lead to nanorod formation. Thus, slow decomposition of hexamine at elevated temperature and the consequent slow rise in pH is the key to the anisotropic growth of the iron oxide system.

Exchanges of uranium(VI) species in amidoxime-functionalized sorbents.

Amidoxime (AO)-functionalized polymer sorbents used in this study were prepared by two different routes involving UV grafting and electron-beam grafting of acrylonitrile (AN) into poly(propylene) fibrous and microporous sheets, and subsequent conversion of AN to AO groups by reacting the precursor sorbent with hydroxylamine. The values of self-diffusion coefficient (D(s)) of UO(2)(2+) in fibrous and sheet AO sorbents were found to be 1.1 x 10(-6) and 2.3 x 10(-10) cm(2) s(-1), respectively. The higher diffusion mobility of UO(2)(2+) in the fibrous AO sorbent was attributed to its higher free volume as observed in scanning electron microscopic studies. The water content was also found to be maximum in AO-fibrous sorbent (165-200 wt %) and minimum in AO-sheet sorbent (70 wt %). In fibrous AO sorbent, the values of D(s) for Na(+) and Sr(2+) were found to be comparable to their self-diffusion coefficients in the aqueous medium. This indicated that the retardation in diffusion mobility of the ions was a minimum in the fibrous AO sorbent. However, D(s) of UO(2)(2+) in the fibrous membrane was found to be significantly lower than that of Sr(2+), which has a self-diffusion coefficient comparable to that of UO(2)(2+) in aqueous medium. This could be attributed to stronger binding of UO(2)(2+) with AO groups as compared to Sr(2+). To understand the parameters affecting the U(VI) sorption from seawater, the U(VI) exchange rates between fibrous AO sorbent (S) and seawater (aq) involving (H(+)/Na(+))(S) right harpoon over left harpoon ([UO(2)(CO(3))(3)](4-))(aq) and (UO(2)(2+))(S) right harpoon over left harpoon ([UO(2)(CO(3))(3)](4-))(aq) systems were experimentally measured. The exchange profiles thus obtained were found to be non-Fickian and much slower than (H(+))(S) right harpoon over left harpoon (UO(2)(2+))(aq) and (UO(2)(2+))(S) right harpoon over left harpoon (UO(2)(2+))(aq) exchanges. This seems to suggest that the reaction kinetics involved in decomplexation of [UO(2)(CO(3))(3)](4-) into UO(2)(2+), which forms a complex with AO groups, is the rate-determining step in sorption of U(VI) from seawater. The kinetics of U(VI) sorption in AO-gel and AO-fibrous sorbents followed the pseudo-second-order rate equation. The density of AO groups in the sorbents and their conditioning were found to influence the U(VI) sorption from seawater.

Nonaqueous phase synthesis of copper nanoparticles.

Copper nanoparticles were synthesized in a nonaqueous solution of cetyltrimethylammonium bromide with isopropanol as a solvent. Cetyltrimethylammonium bromide in isopropanol is observed to play a role as a catalyst where isopropanol is the reducing agent. The surface plasmon band characteristic for Cu nanoparticles can be observed at approximately 560 nm in the UV-visible spectra at molar ratios for Cu2+: cetyltrimethylammonium bromide of 1:15 and 1:30. On the other hand, at molar ratios of 1:0.25 and 1:1 the presence of peak at approximately 310 nm can be attributed to oligomeric clusters of Cu0. Formation of Cu0 was further confirmed from the X-ray diffraction analysis. The diffractograms exhibited peaks at 2theta = approximately 41.6 degrees, approximately 51.6 degrees, and approximately 74.3 degrees, corresponding to Cu0. At lower concentration of cetyltrimethylammonium bromide (i.e., Cu2+: cetyltrimethylammonium bromide = 1:0.25) higher degree of size dispersity (particles between approximately 5-20 nm) can be noted from transmission electron micrograph. On the other hand, at the highest concentration of cetyltrimethylammonium bromide (i.e., Cu2+: cetyltrimethylammonium bromide = 1:30), formation of finer sized particles with a lower degree of size variation, approximately 2-10 nm, can be observed.