Ion Exchange Equilibrium Prediction for the System Cu2+-Zn2+-Na+

In this work, ion exchange experimental data were obtained in batch operation for the binary systems Cu2+-Na+, Zn2+-Na+, and Zn2+-Cu2+ and for the ternary system Cu2+-Zn2+-Na+. The ionic exchanger employed was the cationic resin Amberlite IR 120. The experimental data for the binary systems and the ternary system were obtained at total concentrations of (1, 3, and 5) mEq.L-1. The total exchange capacity of the Amberlite IR 120 resin was obtained by the column technique. All experiments were carried Out at 25 degrees C. To model the ion exchange equilibrium, the Mass Action Law Was used. The model considered both ideal and nonideal behavior to represent the experimental data. The nonideality in the Solution phase and in the resin phase was described by Bromley's model and by Wilson's model. Wilson's model interaction parameters and the thermodynamic equilibrium constants were obtained from the experimental data for each binary system, from which ternary system ion exchange equilibrium was predicted. Oil the basis of the results obtained to represent the ion exchange equilibrium for the binary systems, a prediction was made using only the nonideal Mass Action Law. Good agreement was obtained between the calculated and Measured values of the resin phase composition.5531333134

Application of the mass action law to describe ion exchange equilibrium in a fixed-bed column

Ion exchange experiments were carried out in a fixed-bed column employing the binary systems Cu(2+)-Na(+) and Zn(2+)-Na(+). Amberlite IR 120 was used as the ion exchange resin. The ion exchange dynamics within the column was described by a model considering the external mass transfer and the diffusion within the particle. A linear driving force model was used to represent the mass transfer within the resin particles. The model considered the thermodynamic equilibrium on the liquid-solid interface, which was described by the Langmuir isotherm and by the mass action law. The results indicate that both models represent well the ion exchange dynamics in all cases. (C) 2011 Elsevier B.V. All rights reserved.172131232

Prediction of the copper (II) ions dynamic removal from a medium by using mathematical models with analytical solution

A copper (II) ions biosorption by Sargassum sp. biomass was studied in a fixed bed column at 30 degrees C and pH 3.5. The experimental curves were obtained for the following feed concentrations -2.08, 4.16, 6.42 and 12.72 mmol/L of the copper ions. The mathematical models developed by Thomas and Bohart-Adams were used for description of ions sorption process in the column. The models principle hypothesis is that the mass transfer controlling stage of the process is the adsorption kinetics between sorbate and adsorbent. The phenomena such as intraparticle diffusion, a mass transfer external resistance and axial dispersion effects were out of considerations. Some of the models parameters were experimentally determined (rho(B), epsilon, u(0), C-0) and the others were evaluated on the bases of the experimental data (k(a1), k(a2)). The unique fitting parameter in all models was the adsorption kinetic constant. The identification procedure was based on the least square statistical method. Simulation results show that the models describe well a copper ions sorption process in a fixed bed column. The used models can be considered as useful tools for adsorption process design and optimization in fixed bed column by using algae biomass of Sargassum sp. as an adsorbent. (c) 2007 Elsevier B.V.. All rights reserved.152136637

Mass Transfer Mechanism of Ion Exchange in Fixed Bed Columns

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)In this Work, the binary ion exchange of Zn(2+)-Na(+) ions has beer Studied by a column technique using a NaY zeolite as the cation exchanger. The experimental data (breakthrough curves) for the system were obtained at total concentrations of (1, 2, and 3) meq.L(-1) The mass action law was used to represent the ion exchange equilibrium. To represent the ion exchange in the column, two models were used. In the first model the rate-controlling step of mass transfer was considered only in the solid phase. The-experimental results were represented by a Linear Driving Force (LDF) model. In the second model, resistance to mass transfer in series in the solid phase and the external liquid film was considered. both models described ion exchange in the fixed-bed column properly, However; in the initial part of the breakthrough curve, the dual resistance model fit better.563375382Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

A qualitative analysis of parental loss and family separation among youth in post-conflict Liberia

Between 1989 and 2003, the Republic of Liberia experienced a brutal civil war. In 2008, the population was approximately 3.5 million people, and there were an estimated 340,000 orphans. Nearly 6000 more children were orphaned by the Ebola epidemic from 2014–2015. The goal of this research was to explore the impact of parental loss, identify moderating factors, and consider interventions that could help vulnerable youth in post-conflict societies following the loss of a parent. Seventy-five young people (age 13–18 years) in Monrovia, the capital city of Liberia, were recruited in 2012. Semi-structured interviews were conducted, and demographic data were collected. Interviews were then transcribed and coded thematically. The loss of a parent or other primary caregiver had a significant impact on psychosocial and emotional health. The timing of the loss, strength of connection with the deceased parent, and relationship with surviving parent or substitute caregiver were all relevant factors. Children separated from living parents were functioning better than those whose parents were deceased. The case of Liberian children underscores the importance of early caregiver relationships and the difficulties children face when such relationships are disrupted. Children who did not experience stable early relationships suffered disconnection from their families and communities

A qualitative analysis of factors impacting resilience among youth in post-conflict Liberia

Background In 2008, 5 years after the Liberian civil war ended, there were an estimated 340,000 orphans in Liberia, 18 % of the total child population of the country. Given that children make up half the population and that these children experienced significant trauma and loss both through direct exposure to the war and then to the Ebola epidemic, and indirectly as a result of the trauma experienced by their parents, the recovery of these children is essential to the recovery of the nation as a whole. The goal of this research was to identify factors contributing to resilience among youth in post-conflict Liberia. Resilience was defined as evidence of adaptive functioning and psychological health. Methods Seventy-five young people (age 13–18) in the capital city of Monrovia, Liberia were recruited in 2012. Semi-structured interviews were conducted, and demographic data were collected. Interviews were then transcribed and coded thematically. Results Forty-six of the participants were attending school, and 29 were not enrolled in school. Youth enrolled in school demonstrated greater adaptive functioning. This was particularly true for boys in any school setting and girls attending private school. Youth not attending school were more likely to have lost family members or become estranged from them, and many were also engaging in substance use. Emotion regulation, cognitive flexibility, agency, social intelligence and, in some cases, meaning-making were found in participants who showed resilient outcomes. Conclusions Caregiver relationships mediate the development of psychological capacities that impact resilience. These findings suggest that youth who have lost a caregiver, many of whom are not attending school, are experiencing a significant ongoing burden in terms of their daily functioning and psychological health in the post-war period and should be the focus of further study and intervention targeting substance use and community reintegration

A qualitative analysis of factors impacting resilience among youth in post-conflict Liberia

Background In 2008, 5 years after the Liberian civil war ended, there were an estimated 340,000 orphans in Liberia, 18 % of the total child population of the country. Given that children make up half the population and that these children experienced significant trauma and loss both through direct exposure to the war and then to the Ebola epidemic, and indirectly as a result of the trauma experienced by their parents, the recovery of these children is essential to the recovery of the nation as a whole. The goal of this research was to identify factors contributing to resilience among youth in post-conflict Liberia. Resilience was defined as evidence of adaptive functioning and psychological health. Methods Seventy-five young people (age 13–18) in the capital city of Monrovia, Liberia were recruited in 2012. Semi-structured interviews were conducted, and demographic data were collected. Interviews were then transcribed and coded thematically. Results Forty-six of the participants were attending school, and 29 were not enrolled in school. Youth enrolled in school demonstrated greater adaptive functioning. This was particularly true for boys in any school setting and girls attending private school. Youth not attending school were more likely to have lost family members or become estranged from them, and many were also engaging in substance use. Emotion regulation, cognitive flexibility, agency, social intelligence and, in some cases, meaning-making were found in participants who showed resilient outcomes. Conclusions Caregiver relationships mediate the development of psychological capacities that impact resilience. These findings suggest that youth who have lost a caregiver, many of whom are not attending school, are experiencing a significant ongoing burden in terms of their daily functioning and psychological health in the post-war period and should be the focus of further study and intervention targeting substance use and community reintegration