الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Water hardness is the traditional measure of the capacity of water to react with soap, hard water requiring considerably more soap to produce a lather. Hard water often produces a noticeable deposit of precipitate (e.g. insoluble metals, soaps or salts) in containers, including “bathtub ring”. It is not caused by a single substance but by a variety of dissolved poly valent metallic ions, predominantly calcium and magnesium cations, although other cations (e.g. aluminum, barium, iron, manganese, strontium and zinc) also contribute. Electrochemical treatment can be characterized as a process that uses simple tools and equipment, short retention time, and simple operation. These characteristics help to decrease the costs of operation in scalable applications. The electrocoagulation (EC) process has been the center of attention compared to other approaches that use electrochemical technology and is now considered one of the widely used techniques for treatment of hard water. The present work is focusing on electrocoagulation as a treatment technique for removal of calcium and magnesium from hard water. An electrocoagulation cell consisting of a square horizontal Al plate cathode had a 9x9 dimensions and placed in the cell bottom; the back of it insulated with epoxy resin. The anode was made of 4 array of separated horizontal cylinders, each cylinder had a length of 1.8cm and 1.2 cm diameter and had a 17 cylinders total. Hard water with high concentrations of calcium and magnesium was used. The effects of different parameters including electrolysis time, initial calcium and magnesium concentration, initial solution pH, NaCl as an electrolyte concentration and stirrer velocity were evaluated. The study found that the percentage removal increase with increasing electrolysis time until an approximately constant removal has been reached after 60 minutes, and then time has no significance. The percentage removal increase with increasing the applied current density as it reached 53.53% calcium removed and 100% magnesium removed at 50.56mA/cm2 .The effect of initial solution pH was maximum in the alkaline range to reach 59.3 % calcium removed and 100% magnesium removed at pH=10. In addition, it was found that the calcium and magnesium removal percentage decreased with increasing initial calcium and magnesium concentration to reach 22.5% calcium removed and 93.44% magnesium removed at 1000 ppm (800ppm ca & 200ppm mg), more over increasing NaCl concentration increased the removal percentage to reach 83.18 % calcium removed and 100% magnesium removed when adding 3 gm. NaCl/L and finally, increasing stirrer velocity increase removal percentage until the optimum stirrer velocity 300 rpm then starts to decrease at 350 rpm. Calculations showed that by increasing current density ,both aluminum consumption and power consumption increased.As opposed to, by increasing NaCl concentration both aluminum consumption and energy consumption decreased. Increasing the initial solution pH, increased the total operating cost. While, increasing the initial solution concentration decrease the total operating cost.