In the first part, an extended version of Solvay method was used for recovery of carbon dioxide through natural and synthetic brine. In the original Solvay method, lime stone was used for carbon dioxide production. However, in the extended Solvay method, the carbon dioxide source is combustion of fossil fuels in power stations and industries. To accelerate carbon dioxide diffusion in brine, bubble column reactor was built. Two products (sodium bicarbonate and sodium carbonate) with more than 98% degree of purity were derived. Brine sample from Kerman was used as natural sample. The efficiency of production of sodium bicarbonate from this sample was 40 gram of dry precipitate with purity of 94%. Indeed, after precipitation, salts were decreased by 48.1%. In another experiment on brine sample from Khour and Biabanak, some products with adequate value were derived including Mg(OH) 2 , NaHCO 3 , Na 2 CO 3 , CaCl 2 , KNO 3. Finally, NH 3 was refined with value of 86.7%. In the second, a feasible method for reducing the original conductivity of the reject of reverse osmosis (RO) unit with the goal of recycling the RO reject water was developed. Due to the high concentration of salts in the RO reject water (TDS=1.42%) the precipitation of impurities was performed and then synthesized composites with ion exchange capabilities were used to further reduce the concentration of ions. For this purpose, bis-phenol epoxy resin synthesized and mixed with bentonite and then sulfonated as a resin to remove ions. In another method used polystyrene cups was recycled and mixed with bentonite as the solid support and the composite was sulfonated. Acidic capacity of bisphenol epoxy composite and sulfonated polystyrene was 2.8 mol.kg -1 and 3.7 mol.kg -1 , respectively. Finally, chitosan was synthesized from natural chitin and loaded on the bentonite as a chitosan-modified bentonite to remove chloride ions. Basic capacity of bentonite composite and chitosan was 0.3 mmol.g -1 . In the optimal condition, using 5 gram of each composite resulted in 58.4% reduction in sample conduction after precipitation.
