As the water flows down and passes over a packing material possessing a large air-liquid inter phase, the volatile organic compounds (VOC) are transferred from the water to the air. It is effective in removing organic as well as inorganic contaminants including hydrogen sulfide. Distillation In this technology, water is heated until it turns to steam, which is then condensed as distilled pure water, free of most dissolved or any solid contaminants including bacteria and viruses. Because distilled water is free of all minerals, it may not be ideal for drinking. Ion Exchange This is a process is used commonly for water softening, by which ions that are dissolved in water are transferred to, and held by, a solid material or exchange resin.
Membrane separation technologies are among the most promising processes in water purification regarding their low energy consumptions. Membrane distillation (MD) is a thermally driven separation process in which liquid feed is evaporated at the feed/membrane interface and is transported through a hydrophobic microporous membrane[1–4]. The hydrophobic character of the membrane allows only volatile components to enter the pores. The differences of the vapour pressures across the membrane is the driving force of the process[5,6]. In comparison with other conventional technologies, membrane distillation benefits from low operational temperature and pressure and therefore low energy requirements.
The most ideal in preparation of sodium alginate is by adding the powder to agitated water rather than vice verso to avoid formation of clumps. Alginic acid can be in two conditions which are water soluble or insoluble. That is relying upon the type of the related salt. The salts of sodium, other alkali metals and ammonia are soluble, though the salts of polyvalent cations such as calcium are water insoluble except for magnesium. The polymer of alginate itself is anionic which is negatively charged.
Water: Water is universal solvent, used to extract plant products with antimicrobial activity. Though traditional healers use primarily water but plant extracts from organic solvents have been found to give more consistent antimicrobial activity compared to water extract. Also water soluble flavonoids (mostly anthocyanins) have no antimicrobial significance and water soluble phenolics only important as antioxidant compound (Das K et al.,2010). 2. Acetone: Acetone dissolves many hydrophilic and lipophilic components, is miscible with water, is volatile and has a low toxicity, it is a very useful extractant, especially for antimicrobial studies where more phenolic compounds are required to be extracted.
They have a relatively high level of hydrophilicity. Conversely, cationic surfactants such as cetyltrimethyl ammonium bromide (CTAB) release a positive charge in an aqueous solution. On the other hand, in alkali pH, amphoteric surfactants act as anionic while in acid pH, it act as cationic. Non-ionic surfactants such as partially hydrolyzed PVA (polyvinyl alcohol) have no charge (Li et al, 2008). Among four types of surfactants, partially hydrolyzed PVA is most frequent used because it gives the smallest microsheres (Jeffrey et al, 1991).
chemical precipitation method , hydrotermal technique [3. 4], emulsion method , and sol-gel process , mechanochemical method . Chemical precipitation process is the most reported method for preparing hydroxyapatite particles. This process is simple, low cost, and suitable for industrial production but difficult to control and resultant particles have a low quality with a large particle size, wide particle size distribution and a lot of agglomerates. The hydrothermal technique usually gives hydroxyapatite powders a high degree of crystallinity.
Non removal of As(III) hence oxidation is required.  3.2.4 Physical removal Some synthetic membranes are permeable to certain dissolved compounds but exclude others. Because of their selective permeability for different compounds, such membranes can act as a molecular filter to remove dissolved arsenic, along with many other dissolved and particulate compounds. High pressures are required to cause water to pass across the membrane from a concentrated to dilute solution. For this reason membrane separation is addressed as a pressure driven process.
CZ Si is free from lattice defects; however, it contains residual impurities such as oxygen, carbon, and transition-metal ions. Oxygen introduced from a quartz crucible is beneficial for microelectronics, because the oxygen strengthens the wafers and can also be used for guttering defects from wafer surfaces. Oxygen reacts with the boron to form an electronically active defect that limits the quality of the material after illumination . Magnetic confinement is used to reduce the amount of oxygen by transferring material from the crucible within the melt. Si grown by the float zone (FZ) process is the preferable method for solar cells of highest efficiencies because it has the lowest recombination losses.
Feedback control system regulates the rate of addition of lime by monitoring pH during addition. Lime is widely used for treating acidic wastes and is least expensive and the solution of excess lime do not reach extremely high pH values as solubility of lime in water is limited. Alkaline wastes could be neutralised by adding inexpensive acid, such as sulphuric acid. Acetic acid is preferable for some applications since it is nontoxic and biodegradable. Alkaline wastes can also be neutralised by bubbling gaseous carbon dioxide to form carbonic acid.