[Removal of excess fluoride from water plants by poly aluminum chloride as a new coagulant]

The fluoride ions are commonly found in water resources. These ions should be in optimum levels for prevention of dental caries. However, the excess value can cause such health problems as fluorosis. The aim of the present study was to investigate the removal of excess fluoride ions by using poly aluminum chloride as a new coagulant that is used in water treatment plants. All experiments were conducted in batch system. Several combinations of parameters such as initial fluoride concentration [1.4, 2 and 2.4 mg/L], pH of solution [3, 7, 9], poly aluminum concentration [10, 20, 30, 40 mg/L], and exposure time [30, 60, 90 minute] were investigated. Various concentrations of poly aluminum chloride solution at different pH levels were added into 200 ml of fluoride solution, and samples were taken in predetermined time intervals and the final concentration of fluoride was determined by spectrophotometer at 570 nm. The results showed that, the highest removal was obtained at pH=7. In addition, it was observed that fluoride removal efficiency was higher in pH=5 than in pH=9. Also the results showed that, removal efficacy can be increased by increasing the poly aluminum chloride and the exposure-time. This study denoted that removal of high levels of fluoride ions can effectively be done by using poly aluminum chloride as a new coagulant. Its use is possible in water treatment facilities without any need for modification in water treatment plans

Biosorption of iron from aqueous solution by dried biomass of activated sludge

This study was conducted to investigate the removal of iron by dried biomass of activated sludge. Dried activated sludge, prepared as a powder, was tested as a sorbent for the removal of iron from aqueous solutions. The effects of various experimental parameters including initial iron concentration, mass of biomass and contact time were examined and optimal experimental conditions were obtained. The equilibrium time for iron adsorption onto biomass was determined as 150 min. The rate of iron removal was directly correlated to biomass amount and contact time. Increasing contact time from 0.5h to 2.5h resulted in 25% improvement in iron removal efficiency. When the weight of the biomass increased from 0.1g to 0.9 g, the iron removal efficiency increased from 62% to 95%. High initial iron concentration had an adverse effect on iron removal efficiency. Increasing initial iron concentration from 2 to 10 [mg/L] caused declining the iron removal efficiency from 70% to 56%. Freundlich, Langmuir, Dubinin-Radushkevich and Temkin isotherm models could describe the adsorption equilibrium of the iron onto the activated sludge. Meanwhile, Freundlich isotherm represented a better correlation compared to other isotherms [R2 > 0.999]. Also Elovich kinetic models fits well with experimental data [R2>0.997]

[ association between vitamin D and bone mineral density in postmenopausal women]

There are inconsistent data regarding the role of vitamin-D in determining bone mineral density [BMD] especially in less severe vitamin-D deficiency. The aim of this study was to investigate the possible association between 25[OH]D and BMD in healthy free-living postmenopausal women in a population-based study. We enrolled 245 postmenopausal women, aged between 40 to 80 years, randomly selected from the Tehran Lipid and Glucose Study. Measurements of BMD were taken at the lumbar spine and upper femur by dual X-ray absorptiometry; additional to demographic and anthropometric data, serum 25[OH]D, PTH, calcium, phosphorus and alkaline phosphatase were measured according to the currently used laboratory methods. Bivariate and multivariate analyses were used to explore the association between 25[OH]D, BMD and other clinical and biochemical variables. Mean age and duration of menopause were 58 +/- 7 and 9.4 +/- 6.8 years, respectively; 25[OH]D [29.3 +/- 24.9 ng/ml] was <10 ng/ml and 11-20 ng/ml in 5.2% [n=13] and 37.6% [n=92] of women, respectively; 25[OH]D correlated inversely with LnPTH [r=-0.25, p<0.01]. However no association was found between 25[OH]D level and BMD at any of the skeletal scanning sites in bivariate analysis or multiple linear regression analyses, after adjusting for age, years since menopause, body mass index [BMI], calcium and LnPTH. In the multivariate analyses, BMD correlated inversely with LnPTH, in addition to age and BMI [R2=20%, p=0.03] only in femoral neck, but not at any other sites. This study showed no association between 25[OH]D and BMD in postmenopausal women