Results 1 - 10 of 2224
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[en] In this study,humic acids were produced from coal under controlled conditions by using different oxidation time. This research studies on the behaviour of coal during oxidation process. The coal used as raw material in this research was obtained from Ka Lay Wa, Sagaing Division . The coals were oxidized at the different oxidation times from 76 hr to 380 hr at the temperature 150 5C. The yields of humic acid, the ultimate analysis (percentage of carbon, hydrogen, nitrogen and oxygen) and the proximate analysis (percentage of volatile, ash and moisture) were done in this study. The functional groups and structural entities of the obtained humic acids were identified by using Fourier Transform Infrared Spectrophotometer (FTIR). The yield percentage of prepared humic acid in Ka Lay Wa coal was found to be 3%.
[en] In this research work, experiments were done to study the fouling behavior and performance of lab-made membranes using humic acid solution as feed. These membranes were prepared in lab using polyvinyl chloride membranes and Hydrophilic Bentonite nano particles via a non-solvent induced phase separation method. Membranes were further used in a dead-end filtration setup to filter a synthetic solution of humic acid and water to perform separation and fouling studies. Feed with different concentrations of humic acid was subjected to membrane system and performance was studied in terms of various parameters like flux, fouling ratio, flux recovery, relative flux, and rejection rate. Pure water flux, permeate flux, flux recovery, fouling ratio and rejection of humic acid of membranes increased in the presence of more hydrophilic Bentonite particles because of improved hydrophilicity. Total fouling was also affected, and irreversible fouling decreased in the presence of nano particle. However, agglomeration was observed between inorganic nano particles for 1.5 wt%. So membrane performance started decreasing by adding hydrophilic Bentonite nano particles more than 1%. (paper)
[en] Using physicochemical methods we showed that continuous (15 days) exposure of monazite powder in humic acid (HA) solutions with different acidity gives rise to one to two orders of magnitude growth in the concentration of the monazite' p-, d- and f-elements of Periodic Table (Mg, Al, Si, P, Pb, Ti, Bi, Sc, Ti-Zn, REE, Th, U). The growth in the elements concentration in the humic solutions contacting monazite is shown to depend on the initial concentration of HA in the solutions, pH. It is concluded that these factors should be taken into consideration when inorganic phosphates and alike phases are used as a matrix for the radionuclide wastes solidification. (author)
[en] The properties of various adsorbents for uranium extraction from seawater are measured under standardized experimental conditions. It turns out that fractionated humic acids have exceptionally fast loading kinetics. This property leads to a substantial reduction of capital investments in conventional adsorbent bed techniques as well as in a procedure designed to avoid large adsorbent bed constructions by using carrier bodies in the open sea
[en] The sorption behavior of humic substances (HS) towards iron oxides has been studied as a function of various physico-chemical parameters, such as pH, ionic strength, nature and concentration of humic substances. The selected iron oxide is goethite as a reference mineral studied in the HUMICS project. The results show a strong influence of the different parameters under study: the HS sorption decreases when pH increases, decreases with ionic strength and is higher for humic acids compared to fulvic acids. The surface complexation approach has been applied to describe the retention of humic substances onto the goethite surface. The Kurbatov model (without electrostatic term) successfully describes the HS sorption onto goethite. (orig.)
[en] We explored the effect of the presence or absence of humic acid (HA) on the sorption behaviour of Sr onto soil. We examined three different experimental cases for Sr sorption: (1) sorption in the presence of only colloidal HA, (2) sorption in the presence of only soil and (3) sorption in the presence of both colloidal HA and soil (HS). A batch technique was used to study the influencing factors, including the amount of colloidal HA, solid content, pH, initial concentration of Sr and contact time. The experiments showed that the influencing factors significantly affected the sorption process. For example, in the case of soil and HS, the sorption percentage increased rapidly with increasing solid content at m/V < 20 g/L, changing from 8.35% and 37.54% to 49.09% and 77.03%, respectively. Moreover, scanning electron microscopy and Fourier transform infrared spectroscopy were used to characterize samples. The kinetics and isotherms of Sr were best described by the pseudo-second-order and Langmuir models, which indicated that the process was controlled by chemisorption and uniform monolayer sorption with constant energy on the outer surface. These findings provide valuable information for predicting strontium migration in radioactive waste disposal sites.
[en] This investigation was focused on the role of humic acid-like compounds during the biodegradation of plant mass contaminated with 137Cs. The experiments were set up to distinguish cases of external and internal contamination. The results showed that 137Cs was associated with humic acid-like compounds in eluates from biomass and especially with their lighter fraction. The 137Cs in detritus was markedly mobile and only minor amounts were retained in biomass. These two variants differed in the rate of 137Cs release: while in the internally contaminated biomass the rate decreased during composting, in the externally contaminated biomass the rate increased. (author)
[en] The sorption of Eu(III) on calcareous soil as a function of pH, humic acid (HA), temperature and foreign ions was investigated under ambient conditions. Eu(III) sorption on soil was strongly pH dependent in the observed pH range. The effect of ionic strength was significant at pH < 7, and not obvious at pH > 8. The type of salt cation used had no visible influence on Eu(III) uptake on soil, however at low pH values, the influence of anions was following the order: Cl- ∼ NO3- > ClO4-. In the presence of HA, the sorption edge obviously shifted about two pH units to the lower pH, whilst in range of pH 6-7, the sorption of Eu(III) decreased with increasing pH because a considerable amount of Eu(III) was present as humate complexes in aqueous phase, then increased again at pH > 11. The results indicated that the sorption of Eu(III) on soil mainly formed outer-sphere complexes and/or ion exchange below pH ∼7; whereas inner-sphere complexes and precipitation of Eu(OH)3(s) may play main role above pH ∼8. (author)
[en] Four different sources of humic substances were studied to determine the effects of ozonation on molecular weight distributions, based on dissolved organic carbon (DOC) and trihalomethane formation potential (THMFP). Solutions of two soil-derived fulvic acids and a one soil-derived humic acid, as well as dissolved organic matter (DOM) associated with a natural water source were studied. Both gel permeation chromatography (GPC) and ultrafiltration (UF) were employed to define apparent molecular weight (AMW). Applied ozone doses ranged from 2.0 to 2.5 mg O3/mg DOC. Overall samples of untreated and ozonated waters, as well as individual molecular weight fractions, were characterized according to DOC, uv absorbance, and THMFP. Ozonation resulted in a significant disappearance of higher AMW material with a corresponding increase in lower AMW material. Although little overall reduction in DOC concentration was observed, significant overall reductions in UV absorbance and THMFP levels were observed