ARSENIC REMOVAL FROM DRINKING WATER USING FLYASH AS AN ADSORBENT
Nowadays water pollution has become a major problem that is being faced by the human kind. Among various pollutants present in water, arsenic is gaining much importance because of the toxicity of its compounds. Hence it is very much necessary to find the best suitable technique for removal of arsenic from drinking water. In the present study, the removal of Arsenic from synthetic sample on coated fly ash has been carried out at room temperature 32 ± 1 o C. Initially raw fly ash was used for the experiment and it was seen that the residual arsenic concentration increased hencebatch tests were conducted for the removal of Arsenic on iron sulphate coated fly ash for optimum parameters such as dosage, pH, time, initial concentration and agitation rate. The maximum removal efficiency was obtained at an optimum dosage of 0.5gms. It was found that 100% removal can be achieved at slightly alkaline pH condition. The optimum time, initial concentration and agitation rate were found to be 15mins, 140µg/l and 150RPM respectively. Arsenic is the 20th most abundant element found in the earth's crust. It occupies nearly 0.00005% of the entire earth's surface (2). Arsenic occurs naturally and sometimes can be produced by anthropogenic sources such as mining, industrial and agricultural activities. It is found naturally in the geologic substrate and also can be produced during volcanic eruptions. Arsenic occurs in organic and in-organic forms. It is present in the organic form in food in small amount which is required for the body. In natural waters, it is present in the in-organic form namely As (III) and As (V). These two ions namely, arsenic trioxide and arsenic pentoxide are either naturally occurring or byproducts of industrial waste. The predominant species for As (III) are H3AsO3 and for As (V) are H2AsO 4- and HAsO4 2-. These chemicals can badly affect human health(10)when they are consumed in large amount. The ground water at various locations in Bangladesh, West Bengal, some parts of Bihar& Karnataka in India, has been noticed to be contaminated with Arsenic (As) in excess of its permissible limit. Recently 14 out of 20 villages at Surpur taluq of Yadgir district, Karnataka state (India) has been found to be affected by Arsenic content.Several incidents have demonstrated that Arsenic in water may be carcinogenic. Acute poisoning by Arsenic involves the central nervous system leading to coma and for doses of 70-80 mg to death. The gastro-intestinal tract, nervous system, the respiratory tract, and the skin can be severely affected (4). It is recommended that, when water is found to contain Arsenic in excess of 0.01 mg/L (W.H.O), the water is considered to be unfit for drinking. Arsenic can be removed by many conventional and non-conventional methods. Adsorption is used widely to remove Arsenic metal from water and industrial wastewater. Adsorption offers significant advantages like low cost, availability, profitability, ease of operation and efficiency, in comparison with conventional methods especially from economical and environmental points of view. Many attempts have been made to remove arsenic from water using various adsorbents. Fly ash is a by-product that is produced by coal fired thermal power plant. From literature review it can be concluded that fly ash has sorptive properties with regard to heavy metals (3).And it was also found that iron containing adsorbents were effective in arsenic removal from aqueous solution hencefly ash coated with iron sulphate was used in the present study (5).
Removal Efficiency of Arsenic by Adsorbents having Different Type of Metal Oxides
In this study, oxidation of As (Ⅲ) as well as removal of total arsenic by adsorbents coated with single oxides or multi-oxides (Fe (Ⅲ), Mn (Ⅳ), Al (Ⅲ)) was investigated. In addition, multi-functional properties of adsorbents coated with multi-oxides were evaluated. Finally, application of activated carbon impregnated with Fe or Mn-oxides on the treatment of As (Ⅲ) or As (Ⅴ) was studied. As (Ⅴ) adsorption results with adsorbents containing Fe and Al shows that adsorbents containing Fe show a greater removal of As (Ⅴ) at pH 4 than at pH 7. In contrast adsorbents containing Al shows a favorable removal of As (Ⅴ) at pH 7 than at pH 4. In case of iron sand, it has a negligible adsorption capacity for As (Ⅴ) although it contains 217.9 g-Fe/kg-adsorbent. Oxidation result shows that manganese coated sand (MCS) has the greatest As (Ⅲ) oxidation capacity among all metal oxides at pH 4. Oxidation efficiency of As (Ⅲ) by IMCS (iron and manganese coated sand) was less than that by MCS. However the total removed amount of arsenic by IMCS was greater than that by MCS.
Diversity of Electrospinning Approach for Vascular Implants: Multilayered Tubular Scaffolds
Abstract The biomimetics of biological structures found in nature remains one of the most promising approaches to engineer functional tissues from natural or synthetic biocompatible materials for the replacement of damaged or injured parts of the human body. Recently, medical therapeutic regimes have advanced into a new era, overcoming the known mechanical and biological variances that occur when using autologous or synthetic grafts. Basically, the core concept of tissue biofabrication, commonly referred to as tissue engineering, is to find out the favorable cellular microenvironments to grow a living tissue prior to clinical uses. In fact, the ability of stem cells to regenerate is controlled via signaling pathways (growth factors) and supporting materials (scaffolds) that guide the cellular activities. After the first successful experiments to fabricate polymer fibers from their solutions, Cooley proposed the use of an electric field a century ago (Cooley (US 692:631, 1902 ). The electrospinning technique has been continually developed as a fruitful polymer processing technique to draw ultrafine nonwoven fibers. Electrospun polymer fibers have been used for a wide range of technical and biotechnical applications such as filtration, organic solar cells, tissue engineering, and drug releasing implants. In this regard, this review begins with an overview about the various spinning approaches for the fabrication of polymer fibers as well as the basic principles of electrospinning process. In addition, this review will highlight vascular bypass surgery and, in particular, the needs for vascular tissue engineering. Finally, the review includes some of the latest attempts to improve the mechanical and biological properties of electrospun polymeric fibers and summarizes the challenges and prospects for the future. Lay Summary However, vascular defects are treated successfully via bypass surgical bypass grafting using autologous or synthetic vessels. The small-diameter vessels (less than 6) are often associated with high failure rate. This review reports some of the recent features that should be highlighted to fabricate an ideal graft for small-diameter vascular grafts. The review introduces multilayered conduits as an alternative approach to overcome the known mechanical and biological mismatches of single layered vascular grafts of electrospun polymers.