Removal Of Amorphous Material Research Articles

A spectrophotometric method for detection of enzymatic degradation of thin polymer films

An assay method has been developed for monitoring the enzymatic degradation of thin films of translucent polymers. The method was based on the observation that when a solution-cast film of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was exposed to a solution of a depolymerase fromPseudomonas lemoignei, the surface of the film roughened and the film became visibly turbid. This increase in turbidity could be measured spectrophotometrically and was reproducible during the initial stage of degradation. Turbidity correlated very closely with film weight loss early in the degradation but reached a maximum value before extensive degradation had taken place. For a given set of films, this correlation was independent of the concentration of the enzyme used, although it did vary with the mode of enzyme exposure. The turbidity was associated with the exposure of crystalline domains due to the removal of amorphous material from the film surface. The increase in crystallinity at the surface was verified by attenuated total reflectance infrared spectroscopy (ATRIR). In conjunction with SEM, weight loss, and ATRIR, the film turbidity assay provided much semiquantitative insight into the mechanism of the enzymatic degradation reaction. This assay was used to study the enzymatic degradation of films of PHBV solution blended with cellulose acetate esters (CAE). The presence of only 25% of CAE of degree of substitution 2.9 severely hampered the enzymatic degradability of PHBV, a result which is consistent with the environmental degradation of these same samples exposed to activated sludge.

Dissolution of organohetallic complexes and silica from the clay fraction of podzolic soils

Abstract The Ae, Bhf and Bf horizons of two podzolic soils from the Appalachian and Laurentian Highlands were treated with various reagents to remove the amorphous material prior to X‐ray diffraction analysis. Treatments were Na citrate, NaOH, Tiron, DCB and modified DCB, with a lower solid:liquid ratio. Samples treated with NaOH, Tiron and DCB were subsequently extracted with citrate. The latter extraction was necessary to remove Fe2O3 and SiO2 that was not solubilized in the first treatment. The effectiveness of the reagents to extract SiO2, Al203 and Fe2O3 decreased in the following order: DCB 1:1 > Tiron = DCB > citrate > NaOH The total weight loss of the samples represented about 1.8 times the sum of the oxides and reached up to 70% of the Laurentian Bf sample. Organic matter accounted for a part of the weight loss and its removal was more complete in the less crystalline samples of the Laurentian profile. Tiron was the best reagent to improve the X‐ray diffraction patterns, closely followed by DCB 1:1 treatment. Removal of amorphous material and organic matter resulted in a decrease of the cation exchange capacity of the clay fraction, from a maximum of 73.5 meq / 100 g in the Laurentian profile to a minimum of 3.2 meq / 100 g in the Appalachian profile. The results suggested that in the Laurentian profile, very poorly crystallized minerals possibly contributed to a part of the extracted material.

Studies of some soils in the NW Himalayas and the highlands of India

A reconnaissance soil survey of the NW Himalayan mountains and highlands in the Lahul valley (Himachal Pradesh) was undertaken and five soil profiles from different regions and supporting different vegetation, representing both virgin and cultivated lands, were studied, described and classified in two major soil series, viz. Krozing and Shainsha. The clay fraction of these soils consists of illite and chlorite with minor amounts of kaolinite and traces of swelling chlorite and/or montmorillonite. The removal of amorphous material by a dithionite citrate buffer has been found to be imperative. According to the current definitions, these frigid like high mountain soils having an epipedon on limit with mollic qualify for Dystric Eutrochrepts, which does not depict the reality. Therefore, they have been logically classified, by defining new subgroups of Cryic, Mollic and Cryollic within Eutrochrepts, as Dystric Cryic Eutrochrepts (Shainsha series) and Dystric Cryollic Eutrochrepts (Krozing series). The proposed classification is supported by their geographic situation between Eutrochrepts and/or Hapludolls (in lower valleys) and Cryochrepts and/or Haploborolls (on higher hills).