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Effect of modified coal through chemical activation process on performance of heterogeneous reverse osmosis membranes

Thaçi B., Gashi S., Daci N., Daci M., Dylhasi A.

Environment Protection Engineering

2015

Vol. 41, nr 1

53--65

Heterogeneous reverse osmosis (RO) membranes have been prepared from cellulose acetate (CA) and modified coal through chemical activation. Nitric acid of various concentrations, sulfuric and acetic acids used for various time periods have been studied with respect to modification of structure of coal and consequently structure of RO membranes. The effect of these variables on the modification of coal was examined by IR spectroscopy. All membranes prepared in such a way showed improved performance in comparison with standard CA membranes. The volume flux of the best RO membranes at 94% level of solute separation was 3.87×10–2 m3/(m2·h) at 1.76 MPa using aqueous feed solution 400 mg/dm3 of sodium chloride. The performance improvement was related to increases of charge of groups of coal particles in the membrane, affecting their rheology and morphology resulting in better membrane productivity. The SEM of some membranes have also been presented. These membranes were tested also with 1:1, 1:2, 2:2 and 1:3 inorganic salt solutions. The agreement between the calculated and experimental data of solute separation for studied solutes was reasonably good.

Speciation of arsenic in groundwater and technologies for removal of arsenic in drinking water in the spiro tunnel bulkhead, Park City, Utah, USA

Pawlak Z., Rabiega G., Scanlan L., Cartwright P.

Ars Separatoria Acta

2003

No. 2

71-83

Application of an anion exchange resin column was performed to speciate of arsenic (III) and (V) in drinking water. This methodology was used to analyze water samples collectioned from the study of arsenic removal by two technologies, reverse osmosis membrane filtration and chemical coagulation/ filtration in pilot scale in anticipation of EPA=s new arsenic drinking water standard of 10 µg/L takes effect 2006. This EPA treatment technology project was to collect data on the performance of two existing water treatment processes to remove arsenic on pilot scale. Total arsenic concentrations were reduced by reverse osmosis from an average 60 µg/L in the source water to less than 1 µg/L, and chemical coagulation reduced total arsenic from an average 60 µg/L to 4 µg/L. The work reported here will focus on obtaining accurate readings for arsenic valence states (III) and (V), given the Edwards [17] method for arsenic speciation. Separation of arsenic As(III) and As(V) by speciation in field samples, was performed using an anion exchange resin column. The chloride interferences that affect the determination of 75Arsenic from chloride (35 isotope) molecular species (40Ar35Cl), were corrected using chloride measurements in all samples using equation: [75As(corr)] = [75As] - 3.127 × {[40Ar37Cl] - 0.815 [82Se]}. The use of sulfuric acid in the preservation procedure created interferences with ICP-MS in the range one ěg/L of arsenic. The problem of interference in determination of isotope 75As is due to sulfur 34S isotope which is present in sulfate. The (34S isotope, 4.21%) forms the polyatomic species (mass 75) (40Ar34S1H) and species (mass 74) (40Ar34S) which interferes with the determination of 75As isotope. The method detection limit, MDL, for arsenic for ICP-MS was determined to be 0.1 µg/L. Our spiked matrix recoveries, spiked blank samples, and reference materials deviate only a few percents from the listed true values.