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R S Bowman

Publications and source records attributed to R S Bowman.

5 recordsLinked to original sources
PubMed2001

Regeneration of surfactant-modified zeolite after saturation with chromate and perchloroethylene.

Surfactant-modified zeolites (SMZ) have drawn recent attention as sorbents due to their removal of multiple types of contaminants and low material cost. However, like most sorbents, SMZ has a finite sorption capacity for different contaminants. The potential applications, economics, and efficiency of SMZ as a sorbent are related to the ability to regenerate the material. This paper reports several methods to regenerate chromate- and perchloroethylene-saturated SMZ. Regeneration of chromate-saturated SMZ was achieved by flushing with a sodium carbonate/sodium hydroxide solution. However, this high-pH solution increased the counterion competition for chromate sorption sites and decreased the chromate sorption capacity of the regenerated SMZ. As an alternative regeneration method, chromate sorbed to SMZ was reduced to Cr(III) in situ using sodium dithionite solution. Although reduction with dithionite restored the chromate sorption maximum, the chromate sorption intensity was lowered, possibly due to the competition by sulfate (generated from oxidation of dithionite) for chromate sorption sites. Carbonate-regenerated SMZ showed no loss of sorption affinity for perchloroethylene (PCE) compared to virgin SMZ. Air sparging of PCE-saturated SMZ fully regenerated the SMZ. The results show that it is possible to regenerate and re-use SMZ following saturation with anionic or nonpolar organic contaminants.

Chromates↗
PubMed2001

Retention of inorganic oxyanions by organo-kaolinite.

A natural kaolinite (KGa-1b) was treated with the surfactant hexadecyltrimethylammonium bromide (HDTMA-Br) to a level twice that of the cation exchange capacity (CEC). Sorption of nitrate, arsenate, and chromate by the resultant organo-kaolinite was then quantified. Sorption of each oxyanion was well-described by the Langmuir isotherm. Sorption of nitrate was the greatest, with a Langmuir sorption maximum of 24 mmol/kg, although chromate showed the highest sorption affinity of 20 L/kg. Sorption of nitrate, arsenate, and chromate on organo-kaolinite was at least two orders of magnitude greater than their sorption on unmodified kaolinite. Desorption of the bromide counterion indicated that each of the oxyanions was retained by ion exchange on an HDTMA bilayer formed on the organo-kaolinite. Chromate sorption on the organo-kaolinite was unaffected by solution pH in the range 5-9, but decreased at pH 11 due to competition of OH- for anion exchange sites. Similarly, chromate exchange by organo-kaolinite was reduced in the presence of high background levels of chloride. Chromate was effectively retained when flowing through a packed bed of organo-kaolinite: after an input of more than 40 pore volumes, the effluent concentration of chromate was less than 10% of the input concentration, and 90% of the original HDTMA remained on the organo-kaolinite. The results demonstrate that properly prepared organoclays can remove oxyanions, as well as nonpolar organics, from contaminated waters.

Adsorption↗
PubMed1975

Duration of hospitalization for alcoholism.

On admission to an inpatient alcoholic treatment center, 58 alcoholic men were randomly assigned to two groups. One group was detoxified and after-care services were planned (mean length of stay nine days). The other group, in a-dition to the above, received intensive psychosocial inhospital treatment (mean length of stay 30 days). Posthospital adjustment was measured at five intervals over a 13 month period in the areas of social relationships, financial status, employment record, legal involvement, drinking behavior, use of measures were obtained on psychological change and counseling readiness. No significant difference was found between the two groups on any measure. These results indicate that the hospital has a limited role in the treatment of the alcholic person.

Adaptation, Psychological↗