BACKGROUND: Currently, it is recognized that water polluted with toxic heavy metal ions may cause serious effects on human health. Therefore, the development of new materials for effective removal of heavy metal ions from water is still a widely important area. Melanin is being considered as a potential material for removal of heavy metal from water. METHODS: In this study, we synthesized two melanin-embedded beads from two different melanin powder sources and named IMB (Isolated Melanin Bead originated from squid ink sac) and CMB (Commercial Melanin Bead originated from sesame seeds). These beads were of globular shape and 2-3 mm in diameter. We investigated and compared the sorption abilities of these two bead materials toward hexavalent-chromium (Cr) in water. The isotherm sorption curves were established using Langmuir and Freundlich models in the optimized conditions of pH, sorption time, solid/liquid ratio, and initial concentration of Cr. The FITR analysis was also carried out to show the differences in surface properties of these two beads. RESULTS: The optimized conditions for isotherm sorption of Cr on IMB/CMB were set at pH values of 2/2, sorption times of 90/300 min, and solid-liquid ratios of 10/20 mg/mL. The maximum sorption capacities calculated based on the Langmuir model were 19.60 and 6.24 for IMB and CMB, respectively. However, the adsorption kinetic of Cr on the beads fitted the Freundlich model with R values of 0.992 for IMB and 0.989 for CMB. The deduced Freundlich constant, 1/n, in the range of 0.2-0.8 indicated that these beads are good adsorption materials. In addition, structure analysis data revealed great differences in physical and chemical properties between IMB and CMB. Interestingly, FTIR analysis results showed strong signals of -OH (3295.35 cm) and -C=O (1608.63 cm) groups harboring on the IMB but not CMB. Moreover, loading of Cr on the IMB caused a shift of broad peaks from 3295.35 cm and 1608.63 cm to 3354.21 cm and 1597.06 cm, respectively, due to -OH and -C=O stretching. CONCLUSIONS Taken together, our study suggests that IMB has great potential as a bead material for the elimination of Cr from aqueous solutions and may be highly useful for water treatment applications.
Adsorption ; Chromium ; chemistry ; Kinetics ; Melanins ; chemistry ; Waste Disposal, Fluid ; methods ; Water Pollutants, Chemical ; chemistry ; Water Pollution, Chemical ; prevention & control ; Water Purification ; methods

Background: Shigella-induced diarrhea has been considered a major health problem leading to high morbidity and mortality. This disease can lead to dire consequences; however, the true burden of the disease, including the costs and sequalae associated with shigellosis is not yet known. Objectives: (1) To describe the health seeking behavior and the way of payment of population when suffering Shigella; (2) To identify and analyze the direct household costs associated with the treatment of diarrhea due to Shigella. Subjects and method: 290 patients of all ages with positive Shigella diarrhea admitted to public health facilities in Nha Trang, Khanh Hoa province in the period from August 2002 to January 2004 were included in the study. The subjects were divided into three age groups, the first 0-5, second 5-18 and the last one was over 18 years old. Patients and their relatives were interviewed at three stages - day 7, day 14 and day 90 - to obtain all the required information. Results: 134 of 290 patients (47%) paid for using the other health care services before admission to the study\u2019s facilities. The average direct cost per episode for the patients at group aged 0-5 was 129,000 VND, group aged 6-18 was 59,267 VND and over 18 years old was 173,531 VND; it was 131.960 VND for three groups. Comparison with the average household expenditure for health care, it was higher in the poorer group and it was lower three times than the richest group. The average direct medical cost per episode was higher the average direct non-medical cost per episode for all groups. Conclusions: The average direct cost per episode of Shigellosis treatment was rather high especially the average direct cost for the treatment at the health facility. It was also high compared with the average expenditure for health per capita so that it becomes large economic burden for households.
Direct cost ; Shigella ; treatment