No. Registros Solicitud 1 5614 colombia

CC - CATEGORY CODES: 16-Structural-geology; 12-Stratigraphy

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 220; illus. incl. 1 table, geol. sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

IS - ISSN: 0016-7606

CO - CODEN: BUGMAF

UR - URL: (Full text) http://www.gsajournals.org/gsaonline/?request=get-abstract&issn=0016-7606&volume=0113&issue=09&page=01142

AN - ACCESSION NUMBER: 2001-065794

UD - UPDATE CODE: 200120

XURL - URLs, etc : URL; URL-ITEM (UR)

Registro 5172 de 5614 - GeoRef 1997-2001

TI - TITLE: 3-D seismic interpretation of tectonic wrenching and faulting in La Cira-Infantas.

AU - AUTHORS: Gutierrez-Mario-A; Nur-Amos

AF - AUTHOR AFFILIATION: Stanford University, Stanford, CA, United States

BK - BOOK TITLE: In: Geophysics in giant fields.

BA - BOOK AUTHORS: Sternbach-Linda-R (editor)

SO - SOURCE: The Leading Edge (Tulsa, OK). 20; 7, Pages 752-760. 2001.

PB - PUBLISHER: Society of Exploration Geophysicists. Tulsa, OK, United States. 2001.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

DE - DESCRIPTORS: Cenozoic-; Colombia-; faults-; geophysical-methods; geophysical-profiles; geophysical-surveys; giant-fields; La-Cira-Infantas-Field; Magdalena-Valley; oil-and-gas-fields; orientation-; petroleum-; petroleum-engineering; petroleum-exploration; reservoir-properties; seismic-methods; seismic-profiles; South-America; strain-; structural-controls; surveys-; tectonics-; Tertiary-; three-dimensional-methods; thrust-faults; unconformities-; wrench-faults

CC - CATEGORY CODES: 29A-Economic-geology,-geology-of-energy-sources; 20-Applied-geophysics

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: illus. incl. geol. sketch map, strat. col., sects., block diag.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 1070-485X

CO - CODEN: #01738

AN - ACCESSION NUMBER: 2001-057081

UD - UPDATE CODE: 200118

Registro 5173 de 5614 - GeoRef 1997-2001

TI - TITLE: Calibrating spatial and temporal species richness patterns in tropical American marginellid gastropods.

AU - AUTHORS: Nehm-Ross-H

AF - AUTHOR AFFILIATION: Naturhistorisches Museum Basel, Basel, Switzerland

BK - BOOK TITLE: In: Morphology and evolution of the late Cenozoic marine biota of tropical America.

BA - BOOK AUTHORS: Miller-Daniel-J (editor); Budd-Ann-F (editor)

SO - SOURCE: Journal of Paleontology. 75; 3, Pages 680-696. 2001.

PB - PUBLISHER: Paleontological Society. Lawrence, KS, United States. 2001.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: Collectively, studies of the structure of Neogene diversity change in tropical American mollusks have lacked 1) species-level analyses within well-established clades; 2) consideration of abundance and sample size on diversity estimates and comparisons; and 3) geographic comparisons within temporal intervals. This study takes all three factors into consideration and compares Miocene to Recent species richness patterns in tropical American marginellid gastropod species within the clade Prunum+Volvarina. Rarefaction analyses of more than 16,000 specimens from more than 500 samples are used to standardize comparisons of species richness through time and space. Species richness in Prunum+Volvarina from the Miocene to the Recent of the Tropical Western Atlantic (TWA) is compared along a latitudinal gradient from north to south (Florida, the Dominican Republic, and Venezuela). Additionally, temporal patterns of diversity change are compared between the TWA and the Tropical Eastern Pacific (TEP: Peru, Ecuador, Colombia, Panama, and Costa Rica). As is the case with most Neogene lineages, the number of marginellid specimens and samples differ significantly through both time and space. Rarefaction analyses of both specimens and samples indicate that: 1) significant geographic differences in species richness were detected between the Miocene, Pliocene, Pleistocene, and Recent of the TWA; 2) temporal patterns of species richness were similar in the northern and southern TWA; 3) from the Miocene to the Recent, marginellid species richness in the TEP has always been significantly less than TWA diversity; and 4) from the Miocene to the Recent, TWA diversity decreased significantly, whereas TEP diversity was stable and low. Separate rarefaction analyses using the numbers of specimens and samples did not always produce concordant results and indicate that the unit of analysis influences estimates of species richness. Discordant specimen/sample rarefaction results may be a product of sample size. Intrinsic ecological and evolutionary differences do not appear to be primary contributors to differences in marginellid species richness between the TEP and TWA.

DE - DESCRIPTORS: Antilles-; Atlantic-Ocean; biogeography-; biologic-evolution; Caribbean-region; Cenozoic-; Dominican-Republic; ecology-; faunal-list; Florida-; Gastropoda-; Greater-Antilles; Hispaniola-; Invertebrata-; Marginellidae-; Mollusca-; Neogene-; paleoecology-; Prunum-; Quaternary-; South-America; spatial-distribution; statistical-analysis; temporal-distribution; Tertiary-; tropical-environment; United-States; Venezuela-; Volvarina-; West-Atlantic; West-Indies

CC - CATEGORY CODES: 10-Invertebrate-paleontology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

NN - ANNOTATION: Includes appendix.

IL - ILLUSTRATION: Refs: 78; illus.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IS - ISSN: 0022-3360

CO - CODEN: JPALAZ

AN - ACCESSION NUMBER: 2001-055212

UD - UPDATE CODE: 200117

Registro 5174 de 5614 - GeoRef 1997-2001

TI - TITLE: Mid- to late-Holocene pollen-based biome reconstructions for Colombia.

AU - AUTHORS: Marchant-Robert; Behling-Hermann; Berrio-Juan-Carlos; Cleef-Antoine; Duivenvoorden-Joost; Hooghiemstra-Henry; Kuhry-Peter; Melief-Bert; van-Geel-Bas; van-der-Hammen-Thomas; van-Reenen-Guido; Wille-Michael

AF - AUTHOR AFFILIATION: University of Amsterdam, Institute of Biodiversity and Ecosystem Dynamics, Amsterdam, Netherlands

SO - SOURCE: Quaternary Science Reviews. 20; 12, Pages 1289-1308. 2001.

PB - PUBLISHER: Pergamon. Oxford, United Kingdom. 2001.

CP - COUNTRY OF PUBLICATION: United-Kingdom

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: The assignment of Colombian pollen data to biomes allows the data to be synthesised at 10 "time windows" from the present-day to 6000 radiocarbon years before present (BP). The modern reconstructed biomes are compared to a map of modern potential vegetation to check the applicability of the method and the a priori assignment of pollen taxa to plant functional types and ultimately biomes. The reconstructed modern biomes are successful in describing the composition and distribution of modern vegetation. In particular, altitudinal variations in vegetation within the northern Andean Cordilleras are well described. At 6000 BP the biomes are mainly characteristic of warmer environmental conditions relative to those of the present-day. This trend continues until between 4000 and 3000 BP when there is a shift to more mesic vegetation that is thought to equate to an increase in precipitation levels. The period between 2500 and 1000 BP represents little or no change in biome assignment and is interpreted as a period of environmental stability. The influence attributed to human-induced impact on the vegetation is recorded from 5000 BP, but is particularly important from 2000 BP. The extent of this impact increases over the Late-Holocene period, and is recorded at increasingly high altitudes. Despite these changes, a number of sites do not change their biome assignment throughout the analysis. This asynchronous vegetation response is discussed within the context of site location, non-linear response of vegetation to Late-Holocene environmental change, regionally differential signals, localised human impact and methodological artefacts.

DE - DESCRIPTORS: biomes-; Cenozoic-; Colombia-; data-processing; Holocene-; microfossils-; middle-Holocene; miospores-; paleoclimatology-; paleoecology-; paleoenvironment-; palynomorphs-; pollen-; Quaternary-; South-America; upper-Holocene

CC - CATEGORY CODES: 24-Quaternary-geology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 81; illus. incl. 5 tables, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0277-3791

CO - CODEN: #51137

AN - ACCESSION NUMBER: 2001-051229

UD - UPDATE CODE: 200116

Registro 5175 de 5614 - GeoRef 1997-2001

TI - TITLE: An analysis of the feasibility of long-range streamflow forecasting for Colombia using El Nino-Southern Oscillation indicators.

AU - AUTHORS: Gutierrez-Felipe; Dracup-J-A

AF - AUTHOR AFFILIATION: University of California at Los Angeles, Civil and Environmental Engineering Department, Los Angeles, CA, United States

SO - SOURCE: Journal of Hydrology. 246; 1-4, Pages 181-196. 2001.

PB - PUBLISHER: Elsevier. Amsterdam, Netherlands. 2001.

CP - COUNTRY OF PUBLICATION: Netherlands

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: This paper investigates the relationship between El Nino-Southern Oscillation (ENSO) events and the discharge of Colombian rivers and analyzes the possibility of using this relationship to forecast streamflows. Systematic cross-correlations are performed in the exploratory analysis to determine the lag time between ENSO and its effects on Colombian streamflows and the ENSO indicators with the strongest relationship with Colombian streamflows. Several streamflow periods, ENSO indicators, periods for each ENSO indicator, and lag times are considered. The authors demonstrate that long-range streamflow forecasting for Colombia based on ENSO indicators is possible, and that the best ENSO indicators for predicting streamflows in Colombia are the MEI, the SOI, and the Nino 4 sea surface temperature anomalies.

DE - DESCRIPTORS: Colombia-; crosscorrelation-; discharge-; El-Nino; El-Nino-Southern-Oscillation; feasibility-studies; geologic-hazards; hydrology-; indicators-; Pacific-Ocean; prediction-; rivers-and-streams; sea-surface-temperature; South-America; Southern-Oscillation; statistical-analysis; streamflow-; time-series-analysis

CC - CATEGORY CODES: 21-Hydrogeology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 25; illus. incl. 3 tables, sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0022-1694

CO - CODEN: JHYDA7

AN - ACCESSION NUMBER: 2001-043597

UD - UPDATE CODE: 200113

Registro 5176 de 5614 - GeoRef 1997-2001

TI - TITLE: Isotopic evidence for cooler and drier conditions in the tropical Andes during the last glacial stage.

AU - AUTHORS: Mora-German; Pratt-Lisa-M

AF - AUTHOR AFFILIATION: Indiana University, Department of Geological Sciences, Bloomington, IN, United States

SO - SOURCE: Geology (Boulder). 29; 6, Pages 519-522. 2001.

PB - PUBLISHER: Geological Society of America (GSA). Boulder, CO, United States. 2001.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: Documentation of paleoclimatic conditions during the last glacial stage in the tropical Andes is sparse despite the importance of understanding past climate changes in the tropics. To reconstruct paleoenvironmental conditions in the alpine neotropics, we measured the oxygen (delta (super 18) O) and hydrogen (delta D) isotopic composition of authigenic kaolinite within weathering profiles of the Bogota basin (Colombia) because of the strong dependence of isotopic values on both surface temperature and rainfall. While kaolinite isotope data from Holocene soils in the basin reflect modern mean annual temperature and mean weighted rainwater isotopic composition of the basin, kaolinite isotope data from paleosols developed during the last glacial stage suggest 6+ or -2 degrees C cooler temperatures. Moreover, the isotope data indicate higher isotopic values of paleorainwater, interpreted to reflect drier conditions. The combination of reduced rainfall, temperature, and pCO (sub 2) significantly affected the distribution of tropical montane flora during the last glacial stage.

DE - DESCRIPTORS: Andes-; atmospheric-precipitation; Bogota-Basin; Cenozoic-; clay-minerals; climate-change; Colombia-; D-H; Holocene-; hydrogen-; isotope-ratios; isotopes-; kaolinite-; Northern-Andes; O-18-O-16; oxygen-; paleoclimatology-; Paleosols-; Pleistocene-; Quaternary-; reconstruction-; sheet-silicates; silicates-; soil-profiles; South-America; stable-isotopes; temperature-; upper-Pleistocene; weathering-; X-ray-diffraction-data

CC - CATEGORY CODES: 24-Quaternary-geology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

MC - MAP COORDINATES: LAT: N044500; N053000; LONG: W0740000; W0743000.

IL - ILLUSTRATION: Refs: 35; illus. incl. 1 table, sketch map.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States

IS - ISSN: 0091-7613

CO - CODEN: GLGYBA

UR - URL: (Full text) http://www.gsajournals.org/gsaonline/?request=get-abstract&issn=0091-7613&volume=029&issue=06&page=0519

AN - ACCESSION NUMBER: 2001-043124

UD - UPDATE CODE: 200113

XURL - URLs, etc : URL; URL-ITEM (UR)

Registro 5177 de 5614 - GeoRef 1997-2001

BK - BOOK TITLE: The Putumayo-Oriente-Maranon Province of Colombia, Ecuador, and Peru; Mesozoic-Cenozoic and Paleozoic petroleum systems.

BA - BOOK AUTHORS: Higley-Debra-K

BF - BOOK AUTHOR AFFILIATION: U. S. Geological Survey, USA, United States

SO - SOURCE: U. S. Geological Survey Digital Data Series. 2001.

PB - PUBLISHER: U. S. Geological Survey. Reston, VA, United States. Pages: 1 disc. 2001.

RP - RESEARCH PROGRAM: USGS (Publications of the U. S. Geological Survey)

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: This report is an evaluation of oil and gas resources for petroleum systems of the Putumayo-Oriente-Maranon province of Columbia, Ecuador, and Peru. This assessment is a product of the World Energy Project of the U.S. Geological Survey, under the direction of Thomas Ahlbrandt. Described in this explanation of the petroleum geology of the Putumayo-Oriente-Maranon province are thermal maturation of hydrocarbon source rocks, primary reservoir formations, areas and volumes of oil and (or) gas production, and the history of exploration. Complete oil and gas resource assessment results are planned for a later publication, although some data and results are contained in this report.

DE - DESCRIPTORS: CD-ROM; Cenozoic-; Colombia-; digital-data; Ecuador-; lithostratigraphy-; Mesozoic-; natural-gas; oil-and-gas-fields; Paleozoic-; Peru-; petroleum-; petroleum-exploration; production-; Putumayo-Oriente-Maranon-Province; reserves-; reservoir-rocks; resources-; source-rocks; South-America; thermal-maturity; USGS-

CC - CATEGORY CODES: 29A-Economic-geology,-geology-of-energy-sources

DT - DOCUMENT TYPE: Serial; Report

BL - BIB LEVEL: Monograph

NN - ANNOTATION: This CD-ROM was produced in accordance with both the ISO 9660 and Macintosh HFS standards. A CD-ROM drive and associated software are required. Provided graphics are designed for use under NT/Windows on IBM or 100 percent compatible personal computers (PCs), the Apple Macintosh family, and UNIX computers. Minimum requirements for PC NT/Windows Systems: IBM or 100 percent compatible personal computer, i486 or Pentium processor-based. Microsoft Windows 95, Windows 98, or Microsoft Windows NT 4.0 with Service Pack 3 or later. Microsoft compatible mouse. 10 MB available RAM on Windows 95 and Windows 98 (16 MB recommended). 16 MB of available RAM on Windows NT (24 MB recommended). An extended-VGA video board with a minimum screen resolution of 640 by 480 pixels and 256 colors. 10 MB free hard disk space. CD-ROM drive and software supporting ISO 9660 standards. Adobe Acrobat Reader Installer v 4.0 is on this disc and can be loaded onto your computer. Minimum requirements for Macintosh Systems: A Macintosh computer (Macintosh II series with 68020 or greater processor, including all Power Macintosh computers), with MacOS 7.1.2 or later. Minimum of 4.5 MB application RAM; 6.5 MB recommended. 8 MB of available hard disk space. Macintosh with a 13 inch or larger color monitor and CD-ROM drive. Drive and software should support ISO 9660 or HFS standards. Acrobat Reader Installer is included..

IL - ILLUSTRATION: Refs: 55; illus. incl. sect., strat. col., 3 tables, sketch maps.

ME - SOURCE MEDIUM: compact disc

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

CO - CODEN: #03566

RN - REPORT NUMBER: DDS-0063

AV - AVAILABILITY: U. S. Geol. Surv., Denver, CO, United States

UR - URL: (Full text) http://greenwood.cr.usgs.gov/energy/WorldEnergy/DDS-063/

AN - ACCESSION NUMBER: 2001-042996

UD - UPDATE CODE: 200113

XURL - URLs, etc : URL; URL-ITEM (UR)

Registro 5178 de 5614 - GeoRef 1997-2001

TI - TITLE: The hazards of volcanoes.

AU - AUTHORS: Sigurdsson-Haraldur

AF - AUTHOR AFFILIATION: University of Rhode Island, Graduate School of Oceanography, Kingston, RI, United States

BK - BOOK TITLE: In: Earth; inside and out.

BA - BOOK AUTHORS: Mathez-Edmond-A (editor)

CT - COLLECTION TITLE: In the collection: An American Museum of Natural History book. 2001.

SO - SOURCE: Pages 99-104. 2001.

PB - PUBLISHER: New Press. New York, NY, United States. 2001.

CP - COUNTRY OF PUBLICATION: United-States

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

DE - DESCRIPTORS: Colombia-; eruptions-; explosive-eruptions; geologic-hazards; magmas-; Nevado-del-Ruiz; prediction-; risk-assessment; South-America; volcanic-risk; volcanoes-

CC - CATEGORY CODES: 22-Environmental-geology

DT - DOCUMENT TYPE: Book

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: illus.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute.

IB - ISBN: 1-56584-595-1

AN - ACCESSION NUMBER: 2001-042965

UD - UPDATE CODE: 200113

Registro 5179 de 5614 - GeoRef 1997-2001

TI - TITLE: Evidence for Paleoproterozoic, Grenvillian, and Pan-African age Gondwanan crust beneath northeastern Mexico.

AU - AUTHORS: Lopez-Robert; Cameron-K-L; Jones-Norris-W

AF - AUTHOR AFFILIATION: University of California at Santa Cruz, Earth Sciences Department, Santa Cruz, CA, United States

SO - SOURCE: Precambrian Research. 107; 3-4, Pages 195-214. 2001.

PB - PUBLISHER: Elsevier. Amsterdam, International. 2001.

CP - COUNTRY OF PUBLICATION: International

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: A number of previous studies including two recent reconstructions of Rodinia have considered the Grenvillian basement of Mexico to be continuous with the Laurentian basement of Texas. Isotopic studies and U-Pb dating of zircons from Precambrian granitoids that occur as cobbles and boulders in a Paleozoic conglomerate exposed in the state of Coahuila, northeastern Mexico, indicate the region is underlain by Gondwanan rather than Laurentian basement. Essentially nothing was known of the basement before this study because the region is blanketed with Phanerozoic sedimentary and volcanic deposits. Nine out of ten analyzed samples have Grenvillian crystallization ages (1232+ or -7 to 1214+ or -2 Ma). This phase of magmatic activity in northeastern Mexico was coeval with the construction of volcanic arcs in east-central and southern Mexico ( approximately 1220-1150 Ma), but was later than the arc magmatism of Laurentia (e.g., Elzevirian arcs, >1230 Ma, in Texas and the Grenville Province). A subset of the Grenvillian samples contains xenocrystic approximately 1.85 Ga zircons, which are the first evidence of Paleoproterozoic crust south of the Paleozoic Ouachita suture in Mexico. The remaining sample has a Pan-African crystallization age (580+ or -4 Ma), and this is the first sample of Pan-African age basement found in Mexico. The Pan-African orogeny marked the assembly of Gondwana, and Laurentia was unaffected by that event. Two lines of evidence argue that some of the Grenvillian rocks of northeastern Mexico were affected by a Pan-African age event. First, two of the Grenvillian clasts have U-Pb lower intercept ages within error of 580 Ma. Second common Pb and Nd isotopic compositions of the Pan-African granite strongly suggest that it was derived either by melting of Grenvillian basement or by assimilating massive amounts of that basement. Thus far, no other Grenvillian terrane is known to have the exact combination of Nd-Pb isotopic compositions and absolute ages as the Coahuila samples although there are some similarities with the Santa Marta massif of Colombia and the Cordillera de Merida of Venezuela.

DE - DESCRIPTORS: absolute-age; basement-; cathodoluminescence-; clasts-; crust-; crystallization-; dates-; Gondwana-; granites-; Grenvillian-Orogeny; igneous-rocks; Laurentia-; magmatism-; major-elements; mass-spectra; metals-; Mexico-; Neoproterozoic-; nesosilicates-; northeastern-Mexico; orthosilicates-; Paleoproterozoic-; Pan-African-Orogeny; plutonic-rocks; Precambrian-; Proterozoic-; rare-earths; reconstruction-; Rodinia-; silicates-; spectra-; trace-elements; U-Pb; upper-Precambrian; whole-rock; X-ray-fluorescence-spectra; xenocrysts-; zircon-

CC - CATEGORY CODES: 03-Geochronology

DT - DOCUMENT TYPE: Serial

BL - BIB LEVEL: Analytic

IL - ILLUSTRATION: Refs: 64; illus. incl. 2 tables, sketch maps.

RF - REFERENCE SOURCE: GeoRef, Copyright 2002, American Geological Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands

IS - ISSN: 0301-9268

CO - CODEN: PCBRBY

AN - ACCESSION NUMBER: 2001-042132

UD - UPDATE CODE: 200113

Registro 5180 de 5614 - GeoRef 1997-2001

TI - TITLE: Adsorption of sodium dodecylbenzene sulfonate on organophilic bentonites.

AU - AUTHORS: Rodriguez-Sarmiento-David-Christian; Pinzon-Bello-Jorge-Alejo

AF - AUTHOR AFFILIATION: Universidad Nacional de Colombia, Chemistry Department, Santa Fe de Bogota, Colombia

SO - SOURCE: Applied Clay Science. 18; 3-4, Pages 173-181. 2001.

PB - PUBLISHER: Elsevier. Amsterdam, Netherlands. 2001.

CP - COUNTRY OF PUBLICATION: Netherlands

PY - PUBLICATION YEAR: 2001

LA - LANGUAGE: English

AB - ABSTRACT: A bentonite from the Cauca Valley in Colombia was treated with tetramethylammonium bromide (TAB), hexadecyltrimethylammonium bromide (CTAB), hexadecylbenzyldimethylammonium chloride (CDAC), and alkylbenzyldimethylammonium chloride (BTC), in order to obtain organophilic compounds. The treatment was carried out at 50% and 100% of the cationic exchange capacity (CEC) of the natural bentonite (NB). The adsorption of an aqueous solution of sodium dodecylbenzene sulfonate (DBS) over the natural and modified bentonites was studied. The experimental data points were fitted to several equations applicable to adsorption in solution such as: Langmuir, BET and Freundlich. The Langmuir isotherm adequately describes the adsorption process in all cases. The adsorption grade can be quantified by the distribution coefficient, for low concentrations in solution expressed in molality, K (sub dm) . The affinity of organophilic bentonites by DBS can be expressed in terms of the standard adsorption Gibbs energy. The class and structure of the hydrocarbon chains of the quaternary ammonium ions adsorbed over the bentonite determine the DBS adsorption grade.