Important properties of anion exchange resins for efficient removal of PFOS and PFOA from groundwater.

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) present in various water sources have raised a serious concern on their health risk worldwide. Anion exchange is known to be one of the effective treatment methods but the resin properties suitable for theses contaminants have not been fully understood. We examined four commercially available anion exchange resins with different properties (DIAION™ PA312, HPA25M, UBA120, and WA30) and one polymer-based adsorbent (HP20), for their PFOA and PFOS removal in the batch experiment. All or a part of the selected resins were further characterized for their functional group, surface morphology and pore size distribution. The 72 h batch experiment with the 100 mg/L PFOA or PFOS in the laboratory pure water matrix showed a superior capacity of the strong base anion exchange resins, the porous-type HPA25M and PA312, and the gel-type UBA120, for PFOA removal (92.6-97.9%). Among those resins, the high porous HPA25M was suggested most effective due to its remarkably high reaction rate and effectiveness to PFOS (99.9%). In the groundwater matrix, however, the performance of the those anion exchange resins was generally suppressed, causing up to 71% decrease in their removal rates. The least matrix impact was observed for PFOS removal by HPA25M, which indicated the resin's high selectivity to the contaminant. The physiochemical analysis indicated that the presence of relatively large pores (1 nm-10 nm) over HPA25M played an important role in the PFAS removal.

The flow, thermal and mass properties of Soret-Dufour model of magnetized Maxwell nanofluid flow over a shrinkage inclined surface.

A mathematical model of 2D-double diffusive layer flow model of boundary in MHD Maxwell fluid created by a sloping slope surface is constructed in this paper. The numerical findings of non-Newtonian fluid are important to the chemical processing industry, mining industry, plastics processing industry, as well as lubrication and biomedical flows. The diversity of regulatory parameters like buoyancy rate, magnetic field, mixed convection, absorption, Brownian motion, thermophoretic diffusion, Deborah number, Lewis number, Prandtl number, Soret number, as well as Dufour number contributes significant impact on the current model. The steps of research methodology are as followed: a) conversion from a separate matrix (PDE) to standard divisive calculations (ODEs), b) Final ODEs are solved in bvp4c program, which developed in MATLAB software, c) The stability analysis part also being developed in bvp4c program, to select the most effective solution in the real liquid state. Lastly, the numerical findings are built on a system of tables and diagrams. As a result, the profiles of velocity, temperature, and concentration are depicted due to the regulatory parameters, as mentioned above. In addition, the characteristics of the local Nusselt, coefficient of skin-friction as well as Sherwood numbers on the Maxwell fluid are described in detail.

Study on adsorption of Congo red onto chemically modified egg shell membrane.

Consumption of eggs leads to generation of huge amount of waste in the form of egg shell, which consists of calcined shell and fibrous membrane. In this study, egg shell membrane (ESM) were chemically modified and used to adsorb congo red from its synthetic aqueous solution. Fourier Transform Infra-red (FTIR) spectra confirmed the presence of hydroxyl, carbonyl and methylene groups in egg shell membrane. Scanning Electron Micrographs (SEM) were also performed to characterize the modified egg shell membrane. Concentration of congo red was measured by using UV spectrophotometer. Effects of various parameters such as initial pH, ESM dosage, contact time and initial congo red concentration were investigated. Highest percentage of adsorption (98%) was obtained at pH 4.5 at a solid to liquid ratio of 1 g-100 ml of congo red solution of concentration of 100 mg/l. Pseudo-second order kinetic model was the best fitted model for this study. The reaction rate constant was found to be 58.04 × 10-3 g mg-1·min-1. The adsorption mechanism was supposed to happen via film diffusion as well as via intraparticle diffusion. Langmuir isotherm gave a better fit for the adsorption compared to the Freundlich isotherm. The maximum monolayer adsorption capacity was determined to be 117.65 mg/g. Thermodynamic parameters (ΔG, ΔH and ΔS) were also studied in this work. The change in enthalpy and change in entropy was found to be 29.217 kJ/mol and 0.124 kJ/mol·K, respectively. The values of ΔG were found to become more negative with increasing temperature.

Symptomatic hyponatremia during treatment of dehydrating diarrheal disease with reduced osmolarity oral rehydration solution.

CONTEXT: In May 2002, the World Health Organization and the United Nations Children's Fund recommended that the formulation of oral rehydration solution (ORS) for treatment of patients with diarrhea be changed to one with a reduced osmolarity and that safety of the new formulation, particularly development of symptomatic hyponatremia, be monitored. OBJECTIVE: To measure the rates of symptomatic hyponatremia during treatment of patients with diarrhea with reduced osmolarity ORS. DESIGN, SETTINGS, AND PATIENTS: A phase 4 trial conducted at the Dhaka hospital (December 1, 2002-November 30, 2003) and Matlab hospital (February 2, 2003-January 31, 2004) of the International Centre for Diarrhoeal Disease Research Bangladesh: Centre for Health and Population Research, Dhaka, Bangladesh. All patients admitted with uncomplicated watery diarrhea were treated with the newly recommended ORS and monitored. Patients developing neurological symptoms (seizure or altered consciousness) were transferred to the special care ward for treatment and investigated to identify the cause of the symptoms. Patient records of the Dhaka hospital were reviewed during the previous year when the old ORS formulation was used. INTERVENTION: Reduced osmolarity ORS. MAIN OUTCOME MEASURE: Incidence rate of symptomatic hyponatremia in a 1-year period. RESULTS: A total of 53,280 patients, including 22,536 children younger than 60 months, were monitored at the Dhaka and Matlab hospitals. Twenty-four patients, none older than 36 months, developed seizures or altered consciousness associated with hyponatremia, with an overall incidence rate of 0.05% (95% confidence interval [CI], 0.03%-0.07%) at the Dhaka hospital and 0.03% (95% CI, 0.01%-0.09%) at the Matlab hospital. During the previous year, 47 patients at the Dhaka hospital had symptoms associated with hyponatremia, for an estimated incidence rate of 0.10% (95% CI, 0.07%-0.13%). The reduction in the rates was statistically significant (odds ratio, 0.50; 95% CI, 0.29-0.85; P = .009). CONCLUSION: The risk of symptoms associated with hyponatremia in patients treated with the reduced osmolarity ORS is minimal and did not increase with the change in formulation.