2 research outputs found
Tratamento de efluentes industriais por processos fĂsico-quĂmicos
Mestrado em Engenharia QuĂmicaA cinĂ©tica da redução de crĂłmio (VI) a crĂłmio (III) pelo bissulfito de
sĂłdio (NaHSO3) foi estudada num reactor batch (regime descontĂnuo), para
uma gama de concentraçÔes de reagentes e temperaturas. Atingiu-se uma
eficiĂȘncia de remoção de Cr(VI) de 99,99% (100%) para uma concentração
de bissulfito igual a 30% (0,3 M), para um tempo de reacção de 18 minutos a
17ÂșC (pH<2,5 e agitação nĂŁo muito vigorosa).
A redução de crómio hexavalente (Cr6+) teve lugar, na presença de
adição de bissulfito de sódio seguindo uma cinética de ordem n=0,35. A
velocidade de redução de Cr(VI) aumentou com o aumento de concentração
de bissulfito de sĂłdio aplicada e com o aumento de temperatura para valores
iguais ou superiores a 45ÂșC.
Os coeficientes de velocidade k (ordem n=0,35) determinados, foram
de 8,36; 2,48 e 1,43 mg0,65.L-0,65.min-1 para dosagens de bissulfito de sĂłdio de
0,3; 0,15; e 0,075 a 17ÂșC, respectivamente (pH <2,5).
Tendo em conta o estudo do efeito da variação de temperatura de operação,
os coeficientes de velocidade k (ordem n=0,35) determinados, foram de 8,36;
8,22 e 9,02 mg0,65.L-0,65.min-1 para as temperaturas de 17, 30 e 45ÂșC
respectivamente (pH <2,5)
Segundo a equação de Arrhenius, a energia de activação de 2,55
kJ/mol e o factor pré-exponencial de 23,7 mg0,65.L-0,65.min-1
foram resultados
obtidos para uma gama de temperaturas situadas entre 290 â 318 K.
A cinética da oxidação de cianetos pelo hipoclorito de sódio (NaOCl)
foi estudada num reactor batch (regime descontĂnuo) para uma gama de
concentraçÔes de reagentes e temperaturas. Atingiu-se uma eficiĂȘncia de
oxidação de CN- de 96,2% para uma concentração de hipoclorito igual a 13%
(0,13 M), sendo o tempo de reacção de 15 minutos a 18ÂșC (pH> 11 e agitação
nĂŁo muito vigorosa).
A oxidação de CN- surge com a adição de hipoclorito de sódio e de
soda cåustica seguindo uma cinética de pseudo - primeira ordem. A
velocidade de oxidação de CN- aumentou com o aumento de concentração de
hipoclorito de sĂłdio, no entanto nĂŁo foi afectada tendo em conta as diferentes
gamas de temperatura aplicadas (18 â 45ÂșC).
Os coeficientes de velocidade kâ (pseudo - primeira ordem)
determinados, foram de 0,227; 0,134 e 0,0907 min-1 para dosagens de
hipoclorito de sĂłdio de 0,13; 0,065 e 0,0325; respectivamente (pH> 11 e T=
18ÂșC).
Relativamente ao resultado do estudo do efeito da variação de temperatura de
operação, os coeficientes de velocidade kâ (pseudo - primeira ordem)
determinados, foram de 0,227; 0,170 e 0.127 min-1 para as temperaturas de
18, 30 e 45ÂșC respectivamente (pH> 11 e NaOCl a 0,13 M)
Tendo em conta a equação de Arrhenius, a energia de activação de
15,1 kJ/mol e o factor prĂ©-exponencial de 2,26Ă10+3 min-1
foram obtidas para
uma gama de temperaturas situadas entre 291 â 318 K.
AtravĂ©s de um conjunto de ensaios de Jar â Test testados ao nĂvel
laboratorial, realizou-se um estudo visando a optimização da remoção de
metais (Fe e Ni) em efluentes com concentraçÔes elevadas dos mesmo (3
000,00 < Fe < 75 000,00 mg/L e 500,00 < Ni < 1 600,00 mg/L).
Para tal, foi testado um conjunto de diferentes tipos de neutralizantes
e coagulantes com o objectivo de determinar e optimizar a dosagem e pH de
operação, bem como determinar a sequĂȘncia Ăłptima de adição de reagentes.
A anålise e caracterização de lamas são um processo fundamental
para futura classificação e possĂvel minimização de alguns aspectos
económicos. Para tal, efectuou-se um estudo quanto à caracterização e
classificação de uma amostra de lama proveniente da zona de processo de
tratamento.
Tendo em conta os valores obtidos da anĂĄlise sobre o resĂduo (ataque
åcido) e o eluato efectuada à amostra de lama e a respectiva comparação
com os valores mĂnimos estipulados por lei, verifica-se que esta se insere na
classe de lamas nĂŁo perigosas.
ABSTRACT: The kinetic of Cr(VI) reduction to Cr(III) by sodium bisulphite was
studied in a batch reactor for a range of temperatures and reagent
concentration. Nearly 99,99% removal efficiency for Cr(VI) was achieved when
bisulphite concentration was 0,3 M, during 18 minutes of reaction time at 17ÂșC
and with a pH < 2,5.
The Cr(VI) reduction followed a n=0,35 order kinetic with addition of redactor
agent (NaHSO3). The Cr(VI) reduction rate increased with the increasing of
sodium bisulphite dosage and with the temperature above 45ÂșC.
The rate coefficients âkâ(n=0,35), were determined as 8,36; 2,48 and 1,43
mg0,65.L-0,65.min-1 when the bisulphite dosages were 0,3; 0,15 and 0,075 M at
17ÂșC and pH< 2,5, respectively. Taking into account the study of the
temperature range effect, the rate coefficients âkâ(n=0,35), were determined as
8,36; 8,22 and 9,02 mg0,65.L-0,65.min-1 for temperature range of 17, 30 and 45ÂșC
at pH< 2,5 and NaHSO3 (0,3 M).
According to the Arrhenius equation, the activation energy of 2,55 kJ/mol and
the pré-exponencial factor 23,7 mg0,65.L-0,65.min-1 were obtained for a
temperature range of 290 â 318 K.
The kinetic of cyanide oxidation by sodium hypochlorite was studied in
a batch reactor for a range of temperatures and reagent concentration. Nearly
96,2% removal efficiency for CN- was achieved when hypochlorite
concentration was 0,13 M, during 15 minutes of reaction time at 18ÂșC and with
a pH > 11.
The cyanide oxidation took place with a overage of sodium hypochlorite and
soda concentrations, following a pseudo-first order kinetic. The cyanide
oxidation rate increased with the increasing of sodium hypochlorite dosage.
However wasnât effected for the temperature range applied.
The pseudo-first order rate coefficients (kâ), were determined as 0,227;
0,134 and 0,0907 min-1 when the hypochlorite dosages were 0,13; 0,065 and
0,0325 M at 18ÂșC and pH > 11, respectively. Taking into account the study of
the temperature range effect, the rate coefficients (kâ), were determined as
0,227; 0,170 and 0,127 min-1 for temperature range of 18, 30 and 45ÂșC at pH >
11 and NaOCl (0,13 M).
According to the Arrhenius equation, the activation energy of 15,1 kJ/mol and
the prĂ©-exponencial factor 2,26Ă10+3 min-1 were obtained for a temperature
range of 291 â 318 K.
According to a group of laboratorial testing (Jar â Test), the
optimization study of removal metals was performed in concentrate effluents
(3000,00 < Fe < 75000,00 mg/L and 500,00 < Ni < 1600,00 mg/L).
Therefore, a group of different sort of neutralizing and coagulants were
tested, in order to determine and optimize the dosage end pH operation, and
determine the optimal sequence of adding reagents.
The analysis and characterization of sludge are the key process for
further classification and possible minimization of some economic aspects. To
this end, a study for characterization and classification of a sample of sludge
from process treatment area was performed.
Taking account the values of the analysis on the residual (acid attack)
and eluate made of sludge, by the comparison with the minimum prescribe by
law, notes that this is classified as non â hazardous sludge
Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries
Background
Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks.
Methods
The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned.
Results
A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31).
Conclusion
Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)