Volume 18, Issue 3, 2018 July-September

Volume 18, No 3 Pages:
2018 July-September Articles: 3

Photocatalytic degradation of methylene blue from aqueous solutions using nanopillars-TiO2 thin films: Batch reactor studies

Nanopillars-TiO2 thin films was obtained on a borosilicate glass substrate with (S1) and without (S2) polyethylene glycol as template. The photocatalytic behaviour of S1 and S2 thin films was assessed inthe degradation of methylene blue (MB) dye from aqueous solution under batch reactor operations. The thin films were characterized by the SEM, XRD, FTIR and AFM analytical methods. BET specific surface area and pore sizes were also obtained. The XRD data confirmed that the TiO2 particles are in its anatase mineral phase. The SEM and AFM images indicated the catalyst is composed with nanosized pillars of TiO2, evenly distributed on the surface of the substrate. The BET specific surface area and pore sizes of S1 and S2 catalyst were found to be 5.217 and 1.420 m2/g and 7.77 and 4.16 nm respectively. The photocatalytic degradation of MB was well studied at wide range of physico-chemical parameters. The effect of solution pH (pH 4.0 to 10.0) and MB initial concentration (1.0 to 10.0 mg/L) was extensively studied and the effect of several interfering ions, i.e., cadmium nitrate, copper sulfate, zinc chloride, sodium chloride, sodium nitrate, sodium nitrite, glycine, oxalic acid and EDTA in the photocatalytic degradation of MB was demonstrated. The maximum percent removal of MB was observed at pH 8.0 beyond which it started decreasing and a low initial concentration of the pollutant highly favoured the photocatalytic degradation using thin films and the presence of several interfering ions diminished the photocatalytic activity of thin films to some extent. The overall photocatalytic activity was in the order: S2 > S1 > UV. The photocatalytic degradation of MB was followed the pseudo-first-order rate kinetics. The mineralization of MB was studied with total organic carbon measurement using the TOC (total organic carbon) analysis.

In vitro antioxidant and preliminary phytochemical screening of methanolic extract of Macaranga denticulata (Blume) Müll.Arg.

Macaranga denticulata (Blume) Müll.Arg. (family Euphorbiaceae) is an evergreen tree and a common pioneer species in moist open and secondary forest. It is commonly known as Kharpa in Mizoram. Traditionally, the species of Macaranga are used in the treatment of swelling, cuts, sores, boils and bruises. Preliminary phytochemical screening and evaluation of in vitro antioxidant activity were carried out on the methanolic extract obtained from the bark of M. denticulata. The presence of alkaloids, tannins, flavonoids, saponins, steroids and triterpenoids was indicated by the tests conducted. The in vitro antioxidant activity was evaluated using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, reducing power and hydrogen peroxide radical scavenging activity. Ascorbic acid and butylated hydroxytoluene (BHT) were used as reference standards. The methanolic extract of the plant shows a strong antioxidant activity comparable to that of the reference standards.

Some pharmacognostic studies of the cogon grass Imperata cylindrica from Mizoram, India

Cogon grass Imperata cylindrica is a perennial grass belonging to the family Poaceae, and the rhizome-root portion of which is used for the treatment of bacterial infections, ringworms and other skin infections. Among the Mizo people they are directly consumed or juiced for the treatment of intestinal infection. Its chemical and biological properties are poorly documented. In this study, a methanol extract of the rhizome-root was prepared by hot extraction in a Soxhlet apparatus. Standard chemical tests were conducted. The presence of alkaloids, carbohydrates including reducing sugars, phytosterols, tannins, saponins and proteins were confirmed as the major bio-compounds. Free radical-scavenging activities were also determined. The plant extract indicated concentration-dependent scavenging activity on DPPH with an inhibitory concentration (IC50) of 2.14 µg/ml. H2O2 was similarly scavenged, in which the IC50 was 2.221 µg/ml. Our results suggest that I. cylindrica has important medicinal values.