Mechanisms of chromium(VI) removal from solution by zeolite and vermiculite modified with iron(II).

Mechanisms of Cr(VI) reduction by Fe(II) modified zeolite (clinoptilolite/mordenite) and vermiculite were evaluated. Adsorbents were treated with Fe(SO4)·7H2O to saturate their exchange sites with Fe(II). However, this treatment decreased their CEC and pHPZC, probably due to the dealumination process. Vermiculite (V-Fe) adsorbed more Fe(II) (21.8 mg g-1) than zeolite (Z-Fe) (15.1 mg g-1). Z-Fe and V-Fe were used to remove Cr(VI) from solution in a batch test to evaluate the effect of contact time and the initial concentration of Cr(VI). The Cr(VI) was 100% reduced to Cr(III) by Z-Fe and V-Fe in solution at 18 mg L-1 Cr(VI) after 1 min. Considering that 3 mol of Fe(II) are required to reduce 1 mol of Cr(VI) (3Fe+2 + Cr+6 → 3Fe+3 + Cr+3), the iron content released from Z-Fe and V-Fe was sufficient to reduce 100% of the Cr(VI) in solutions up to 46.8 mg L-1 Cr(VI) and about 90% (V-Fe) and 95% (Z-Fe) at 95.3 mg L-1 Cr(VI). The Fe(II), Cr(III), Cr(VI), and K+ contents of the adsorbents and solutions after the batch tests indicated that the K+ ions from the [Formula: see text] solution were the main cation adsorbed by Z-Fe, while vermiculite did not absorb any of these cations. The H+ of the acidic solution (pH around 5) may have been adsorbed by V-Fe. The release of Fe(II) from Z-Fe and V-Fe involved cation exchange between K+ and H+ ions from solution, respectively. The reduction of Cr(VI) by Fe(II) resulted in the precipitation of Cr(III) and Fe(III) and a decrease in the pH of the solution to < 5. As acidity limits the precipitation of Cr(III) ions, they remained in solution and were not adsorbed by either adsorbent (since they prefer to adsorb K+ and H+). To avoid oxidation, Cr(III) can be removed by precipitation or the adsorption by untreated minerals.

[The "Tortoni effect" in prosopagnosia]. / El "efecto Tortoni" en la prosopagnosia.

Proposapnosia is a type of visual agnosia characterized by the inability to recognize people's faces. There are basically two variants, apperceptive and associative. The "Tortoni effect" is a phenomenon described by Bekinschtein et al a few years ago in waiters from Buenos Aires, who used this tool to remember the orders of each member of a table. We present a case of prosopagnosia associated with bilateral temporo-occipital injury secondary to head trauma, initially manifested by the lack of face recognition with the use of an associative strategy similar to that described in the "Tortoni effect" as compensation, in a 62-year-old female who suffered a severe head injury. A few months after this event, the patient had difficulty in recognizing familiar people, a fact evidenced by her relatives when at a restaurant table, they changed their seats, remained silent momentarily, and right after the patient kept naming them by their previous location. The magnetic resonance imaging of the brain revealed blunt sequelae lesions in the bilateral temporo-occipital region. Acquired prosopagnosia due to focal lesions in the temporo-occipital region, generally bilateral and right, and less frequently left, is a rare condition. The strategy used in the "Tortoni effect" was one of the initial manifestations of the condition in our patient. Carrying out an ecological neuropsychological test that considers this strategy could be useful in the screening and early detection of this entity.

La prosopagnosia es un tipo de agnosia visual caracterizada por la incapacidad de reconocer los rostros de las personas. Existen básicamente dos variantes, aperceptivas y asociativas. El "efecto Tortoni" es un fenómeno descripto por Bekinschtein y col. hace unos años en mozos de café en Buenos Aires, quienes utilizaban esta herramienta para recordar los pedidos de cada integrante de una mesa. Presentamos un caso de prosopagnosia asociada a lesión temporo-occipital bilateral secundaria a traumatismo encefalocraneano, manifestada en forma inicial por la falta de reconocimiento de rostros, con la utilización de una estrategia asociativa similar a la descripta en el efecto "Tortoni" como compensación. Mujer de 62 años que sufrió un traumatismo encefalocraneano grave. Pocos meses después del evento, presentó dificultad para reconocer personas conocidas, hecho evidenciado por sus allegados cuando en una mesa los integrantes cambiaron su asiento, permanecieron callados por unos instantes, y posteriormente la paciente continuó nombrándolos por su ubicación previa. En la resonancia magnética de cerebro se objetivaron lesiones contusas de aspecto secuelar en región temporo-occipital bilateral. La prosopagnosia adquirida secundaria a lesiones focales en la región temporo-occipital generalmente bilateral, derecha, y raramente izquierda, es un cuadro poco frecuente. La estrategia utilizada en el "efecto Tortoni" fue en nuestra paciente una de las manifestaciones iniciales del cuadro. La realización de un test neuropsicológico ecológico que considere esta estrategia podría ser de utilidad en el rastreo y detección precoz de esta entidad.

El "efecto Tortoni" en la prosopagnosia / The "Tortoni effect" in prosopagnosia

Resumen La prosopagnosia es un tipo de agnosia visual caracterizada por la incapacidad de reconocer los rostros de las personas. Existen básicamente dos variantes, aperceptivas y asociativas. El "efecto Tortoni" es un fenómeno descripto por Bekinschtein y col. hace unos años en mozos de café en Buenos Aires, quienes utilizaban esta herramienta para recordar los pedidos de cada integrante de una mesa. Presentamos un caso de prosopagnosia asociada a lesión temporo-occipital bilateral secundaria a traumatismo encefalocra neano, manifestada en forma inicial por la falta de reconocimiento de rostros, con la utilización de una estra tegia asociativa similar a la descripta en el efecto "Tortoni" como compensación. Mujer de 62 años que sufrió un traumatismo encefalocraneano grave. Pocos meses después del evento, presentó dificultad para reconocer personas conocidas, hecho evidenciado por sus allegados cuando en una mesa los integrantes cambiaron su asiento, permanecieron callados por unos instantes, y posteriormente la paciente continuó nombrándolos por su ubicación previa. En la resonancia magnética de cerebro se objetivaron lesiones contusas de aspecto secuelar en región temporo-occipital bilateral. La prosopagnosia adquirida secundaria a lesiones focales en la región temporo-occipital generalmente bilateral, derecha, y raramente izquierda, es un cuadro poco frecuente. La es trategia utilizada en el "efecto Tortoni" fue en nuestra paciente una de las manifestaciones iniciales del cuadro. La realización de un test neuropsicológico ecológico que considere esta estrategia podría ser de utilidad en el rastreo y detección precoz de esta entidad.

Abstract Proposapnosia is a type of visual agnosia characterized by the inability to recognize people's faces. There are basically two variants, apperceptive and associative. The "Tortoni effect" is a phenomenon described by Bekinschtein et al a few years ago in waiters from Buenos Aires, who used this tool to remember the orders of each member of a table. We present a case of prosopagnosia associated with bilateral temporo-occipital injury secondary to head trauma, initially manifested by the lack of face recognition with the use of an associative strategy similar to that described in the "Tortoni effect" as compensation, in a 62-year-old female who suffered a severe head injury. A few months after this event, the patient had difficulty in recognizing familiar people, a fact evidenced by her relatives when at a restaurant table, they changed their seats, remained silent momentarily, and right after the patient kept naming them by their previous location. The magnetic resonance imaging of the brain revealed blunt sequelae lesions in the bilateral temporo-occipital region. Acquired prosopagnosia due to focal lesions in the temporo-occipital region, generally bilateral and right, and less frequently left, is a rare condition. The strategy used in the "Tortoni effect" was one of the initial manifestations of the condition in our patient. Carrying out an ecological neuropsychological test that considers this strategy could be useful in the screening and early detection of this entity.