1,720,965 research outputs found
Cationic starch-enhanced ultrafiltration for Cr(VI) removal
No full textThe feasibility of cationic starch-enhanced ultrafiltration (CSEUF) was investigated to remove chromate from the aqueous stream. Cationic starch is a modified starch with cationic functional groups, which interact with anionic pollutants. For CSEUF, a cationic starch was synthesized, whose degree of substitution was 0.2 and water-insoluble. Chromate was bound spontaneously to cationic starch, after that the binding was saturated. As the concentration of cationic starch increased from 0.5 to 1.0, to 1.5, to 2.0, and to 2.5 g/l, the removal of chromate increased from 33% to 62%, to 82%, to 95% and to 98%, respectively. Based on the high removal, high flux, and biodegradability of cationic starch, CSEUF is a feasible process to remove chromate from the aqueous stream
Biological fixation of CO2 by Chlorella sp HA-1 in a semi-continuous and series reactor system
No full textCharacteristics of biological CO2 fixation by Chlorella sp. HA-1 were investigated in a semi-continuous and series reactor system using an internally illuminated photobioreactor to overcome shortcomings of physicochemical technologies such as adsorption and membrane separation. High CO2 fixation rate was achieved in the semi-continuous reactor system, in which the dilution ratios of the culture medium were controlled. The average CO2 fixation rate was maintained almost constantly when the dilution ratio increased by 0.1 increment from the initial value of 0.5. The total removal efficiency of CO2 was enhanced by employing a series reactor system. The average CO2 fixation rate increased until 4.013 g CO2 day(-1) in a series operation of four reactors, compared to 0.986 g CO2 day(-1) in a batch operation mode. The total CO2 fixation rate was proportional to the number of reactors used in the series reactor system. In the series reactor system of semi-continuous operation. a large amount of CO2 was removed continuously for 30 days. These results showed that the present reactor systems are efficient and economically feasible for a biological CO2 fixation
Removal of chlorinated contaminants form surfactant solution for the reuse of surfactant
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Simultaneous removal of chlorinated contaminants by pervaporation for the reuse of surfactant
No full textSurfactants are widely used for the remediation of groundwater contaminated with chlorinated solvents. The reuse of surfactants is quite important for the economic feasibility of the remediation process. Pervaporation with a polydimethylsiloxane membrane was conducted to simultaneously separate trichloroethylene (TCE) and tetrachloroethylene (PCE) from waste solution of the non-ionic surfactant Tween 80. The effects of key process variables on the removal efficiency were investigated. Membrane thickness between 200 pm and 300 mu m did not affect the pervaporation performance. Organic flux did not increase above the flow rate of 100 mL/min. The increase of feed concentration and temperature led to large organic flux. Selectivity was reduced significantly with temperature due to the increase in thermal motion of polymer. The reduction of flux was small below 1.0 wt% surfactant (Tween 80) in feed solution. Flux and selectivity of TCE were higher than those of PCE because an extramicellar portion of TCE was higher than that of PCE. In simultaneous pervaporation of TCE and PCE, flux and selectivity declined due to the competitive sorption of TCE and PCE. However, the reduction percentage in flux and selectivity was less than 10% with 1:1 ratio of TCE/PCE. With operation during 100 h, over 95% of TCE and 90% of PCE were simultaneously removed from 0.5 wt% of Tween 80 solution with TCE and PCE of 1,000 ppm. From the present results, which gave a high efficiency in the simultaneous removal of chlorinated solvents, this process could be a practical alternative for surfactant reuse
The preparation and characterization of micro-sized emulsion using vegetable oils for the remediation of DNAPL
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