Removal of Fluoride, Iron and Arsenic from Drinking water using a combination of electrocoagulation and Microfiltration

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Different parts of the world associated with its adequate presence in the drinking water causes serious damage to health. Different techniques like adsorption, precipitation, membrane separation, ion-exchange, hybrid techniques were reported for the removal of fluoride, iron and arsenic from drinking water. In this work, Electrocoagulation was investigated for the effective removal of fluoride, iron and arsenic from drinking water. Several parameters like initial fluoride, iron and arsenic concentration, current density, electrode connection (monopolar and bipolar), pH, interelectrode distance were found to be dominating in order to remove the above mentioned contaminants from drinking water. Aluminum electrode was considered for the batch mode of electrocoagulation operation. The corrosion of electrodes as well as the sludge formed during the process was estimated. By-products obtained from the electrocoagulation bath were analyzed using SEM, EDAX, FTIR and XRD and explained. Comparative cost estimation for both electrode connections was adopted and presented well. It was found that the drinking water contamination caused by the significant presence of fluoride, iron and arsenic was successfully monitored by the bipolar electrocoagulation for 45 minutes at 625 A m-2 current density and an interelectrode distance of 0.005 m. Electrocoagulation performance was estimated in terms of percentage removal of fluoride, iron and arsenic. Upto 93.2% of fluoride, 99.74% of iron and 95.65% of arsenic removal was achieved. However, electrocoagulated solution was not suitable for the drinking purpose as the solution pH was alkaline along with the agglomerated suspended sludge with size range 10 - 100 Dm. In order to make electrocoagulated solution drinkable, electrocoagulation followed by microfiltration was investigated. In recent times, ceramic microfiltration membranes are being widely used for their better mechanical, thermal and chemical strength compared to the commercial flat-sheet type polymeric membranes. The porous structure of the microporous membranes, mainly composed of ceramic is formed by the process called sintering. In this study ceramic microfiltration membranes were prepared by paste and uni-axial methods. Solid circular ceramic discs of diameter 50 mm and height of 5 mm were prepared and sintered at different temperatures. Five different sintering temperatures were selected (750 DC, 800 DC, 850 DC, 900 DC and 950 DC). The effects of sintering temperature on the structural changes such as porosity, pore-size distribution, average pore radius etc were investigated. All the membranes were characterized using SEM and water permeation test. It was observed that ceramic membranes prepared by both the methods and sintered at 950 DC had sharp pore size distribution. On the other hand, better consolidated microceramic structure was produced by uni-axial cold pressing method. The preparation cost of the ceramic microfiltraton membranes prepared by paste and uni-axial cold pressing methods were 110.62 $/m2 and 135.75 $/m2, respectively...
Supervisor: Mihir Kumar Purkait