Halloysite nanoclay was utilized to retain aqueous oxytetracycline (OTC) which is extensively used in the veterinary industry. The micro-structure and functionality of the nanoclay were characterized through spectroscopic techniques before and after adsorption. The OTC removal experiments were performed at different pH conditions (pH 3.0–9.0), ionic strengths (0.001, 0.01, 0.1 M NaNO3) and contact time (up to 32 h) at an initial 25 mg/L OTC concentration with 1.0 g/L halloysite. Oxytetracycline adsorption was pH dependent, and the best pH was observed in the range of pH 3.5–5.5 at a 0.001 M ionic strength. At pH 3.5, the maximum OTC adsorption amount was 21 mg/g which translated to 68% removal of the initial OTC loading. Positively charged inner lumen and negatively charged outer lumen of the tubular halloysite structure led to form inner-sphere complexes with the anionic and cationic forms of OTC, respectively. A rapid adsorption of OTC was observed in the kinetic study where 62% OTC was adsorbed in 90 min.. Pseudo-second order equation obeyed by the kinetic data indicated that the adsorption was governed by chemisorption, whereas Hill isotherm equation was the most fitted with a maximum adsorption capacity of 52.4 mg/g indicating a cooperative adsorption phenomenon.
Seven profiles of intense negative gravity anomaly over the South Western, Southern and South Eastern parts of the continental rise of Sri Lanka have been interpreted two dimensionally. Results of the interpretation of profiles were interpolated and a map of sediment thickness has been compiled. As revealed by the interpretation and the map compiled there are three noticeable sediment distributions with thickness varying from approximately 2.5 km to 3.5 km. Sediment thickness map in this study closely agree with that compiled using seismic studies by previous workers. Results of this study may have applications in the oil and gas exploration activities over the region.
Keywords: gravity anomaly, sediment thickness, Bay of Bengal, Indian Ocean, Sri Lanka
The aim of the study is to identify the wood utilized in the traditional houses built in Uva province of Sri Lanka, constructed using traditional construction technologies. The timber samples were taken out from roof elements such as rafters, wall plates and reapers from three different timber structures located at three different locations constructed during 1960 - 1970 using vernacular timber preservation technics and preservatives. Samples were extracted and adequately prepared for a microscopic investigation to observe the characteristic microscopic anatomical features. Sledge microtome was used for wood sectioning and photomicrographs were obtained by polarized light microscope. The authentic samples and reference microscopic identification keys were employed in order to conclude on the wood species involved. The relative density of the samples was also measured using the maximum moisture content method to verify the identification. Timber samples were identified using vessels, fibers, rays, parenchyma, and other microscopic features. Based on the macro and micro examination of the external and microanatomical features the timber used for rafters, reapers, wall plates were identified as Mango wood which is scientifically known as Mangifera indica. The relative density values were in the range of 0.52 - 0.7