Adsorption of Cadmium (II) and Chromium (VI) from Aqueous Solution by Waste Marigold Flowers

In this work, waste marigold flowers from Temple were used as adsorbent to remove cadmium (II) and chromium (VI) ions from aqueous solutions. Influences of initial heavy metal concentrations, contact time, adsorbent dose, temperature and initial pH on removal of cadmium (II) and chromium (VI) ions were studied under batch mode of operation. Both the adsorption process of cadmium (II) and chromium (VI) followed pseudo-second order kinetics. Adsorption isotherm parameters of cadmium (II) and chromium (VI) on dried marigold flower were determined using Langmuir and Freundlich models. Thermodynamic parameters depicted that the process was spontaneous and exothermic under experimental conditions. The maximum removal efficiency of cadmium (II) was obtained as 83% at contact time 75 min and pH 5. The maximum removal efficiency of chromium (VI) was found as 96% at contact time 105 min and pH 3. Dried marigold flower showed active reusability characteristics upto three consecutive adsorption-desorption cycles

Formation of micro structured doped and undoped hydrogenated silicon thin films

The microcrystalline hydrogenated-silicon (mu c-Si: H) (also called polymorphous silicon) consisting a two-phase mixture of amorphous and structured silicon is being used for electronic or optoelectronic based thin-film devices. The pc-Si: H thin films are deposited using radio frequency (13.56 MHz) Plasma Enhanced Chemical Vapour Deposition (RF-PECVD) by varying doping gases (diborane (B2H6) and phosphine (PH3)) flow and hydrogen-silane dilution ratio (R = H-2/SiH4) to optimize the crystalline fraction and electrical conductivity. Micro-Raman spectroscopy is used to investigate these effect on the transition fraction regime from amorphous into micro-structured silicon. Qualitative and quantitative properties have been studied by deconvolution of the micro Raman spectra which allows to determine the crystalline fraction in the film and also some investigation regarding the correlation between electrical and structural properties are presented for different annealing temperature (from 300 to 550 degrees C) and various film thickness ranges (10-100 nm). In this work, we present the characterization of thin films (both doped and undoped) deposited at the temperature of 250 degrees C on quartz substrate after annealed at 550 degrees C in N-2-ambient, as a result crystallinity percentage up to 90% for p-type, 96% for n-type and 80% for undoped films are achieved. A detailed characterization of the microcrystalline silicon (mu c-Si: H) has been demonstrated in this paper: structural properties through Raman spectroscopy, electrical properties through Four-point probe station and optical properties using Ellipsometer

PROFITABILITY OF LOW LIFT PUMP AND INCOME INFLUENCING FACTORS OF LLP OWNERS AND USERS IN SOME SELECTED AREAS OF BHOLA DISTRICT

The study examined the profitability of Low Lift Pump (LLPs) and income influencing factors of the owners and users of LLP. A purposive random sampling technique was used for collecting primary data from 74 LLP users and 30 LLP owners from January to March, 2010 through two sets of pre-tested questionnaires. Descriptive as well as statistical techniques were used in the study. Three discounting measures such as: BCR, NPV and IRR were selected for financial analysis taking 11 percent market interest rate (i.e. opportunity cost of the capital). BCR was 1.20, NPV was Tk. 35,673 and IRR was 47 percent from financial point of view which indicate LLP was a profitable business. Sensibility analysis also showed positive results when considering either O&M cost increased or gross return decreased by 10 percent. Crop and LLP machine were found main income source for the farmers and LLP owners respectively. The service, business and other family member’s income were found to be significant factors influencing the farm income

Adsorption-Desorption Surface Bindings, Kinetics, and Mass Transfer Behavior of Thermally and Chemically Treated Great Millet Husk towards Cr(VI) Removal from Synthetic Wastewater

This study reports the efficacy of adsorbents synthesized by thermal (TT-GMH) and chemical (CT-GMH) modification of great millet husk (GMH) for the treatment of synthetic wastewater containing Cr(VI). The chemical modification of raw GMH was done by concentrated H2SO4 to increase the porosity and heterogeneity on the surface. The comparative investigations of physicochemical properties of synthesized adsorbents were examined by point of zero charge (pHpzc), BET surface area, SEM-EDX, FTIR, and XRD analyses. The results revealed that CT-GMH had around three times higher surface area and more porous structure as compared to TT-GMH. The adsorption experiments were executed in batch mode to examine the impact of parameters governing the adsorption process. For Cr(VI) solution of 25 mg/L, adsorbent dose of 4 g/L, temperature of 25°C, and shaking speed of 150 RPM, the maximum removal for TT-GMH was attained at pH 1 and contact time 150 min, while for CT-GMH, maximum removal was attained at pH 2 and contact time 120 min. The experimental results fitted to the rate kinetic equations showed that for both TT-GMH and CT-GMH, adsorbents followed the quasi-second-order kinetic model during the adsorption process. Further, results revealed that the adsorption process was endothermic and Sips isotherm model was followed for both TT-GMH and CT-GMH. Based on the Sips isotherm, maximum uptake capacity for TT-GMH and CT-GMH was noted to be 16 and 22.21 mg/g, respectively. Among the tested mass transfer models, liquid film diffusion model was followed during the adsorption process of both the adsorbents. The desorption study revealed that TT-GMH and CT-GMH give 69.45% and 74.48% removal, respectively, up to six cycles

Absorption of SO2 and NO through an integrative process with a cost-effective aqueous oxidant

Due to the substantial influence on the environment and health, there has been an intensifying environmental concern on sulfur dioxide (SO2) and nitrogen oxide (NO) discharge to the atmosphere all over the world. Flue gas of coal-fired power stations is major leading source for the emission of SO2 and NO. Cost-effective and balanced technologies for the reduction of these pollutants from flue gas have become increasingly essential at the present time. The preliminary experimental attributes were retrieved in a batch scale agitating bubbling reactor for instantaneous absorption of SO2 and NO using aqueous oxidant. The prime conditions for instantaneous absorption examined were including absorbent concentration, reaction temperature, and pH in the fabricated flue gas system. Removal efficiencies of 99% for SO2 and 85% for NO were acquired, respectively under absorbent concentration 5 g/100 ml, reaction temperature 313 K, and pH 5.6